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Usually arthritis magazine generic 400mg etodolac with visa, body weight remains fairly constant over a prolonged period of time (except during growth), because food intake is adjusted to match energy expenditure on a long-term basis. Food intake is controlled primarily by the hypothalamus by means of complex regulatory mechanisms in which hunger and satiety are important components. Feeding or appetite signals give rise to the sensation of hunger and promote eating, whereas satiety signals lead to the sensation of fullness and suppress eating. The skin exchanges heat energy with the external environment, with the direction and amount of heat transfer depending on the environmental temperature and the momentary insulating capacity of the shell. The four physical means by which heat is exchanged between the body and external environment are (1) radiation (net movement of heat energy via electromagnetic waves); (2) conduction (exchange of heat energy by direct contact); (3) convection (transfer of heat energy by means of air currents); and (4) evaporation (extraction of heat energy from the body by the heat-requiring conversion of liquid H2O to H2O vapour). Because heat energy moves from warmer to cooler objects, radiation, conduction, and convection can be channels for either heat loss or heat gain, depending on whether surrounding objects are cooler or warmer, respectively, than the body surface. Normally, they are avenues for heat loss, along with evaporation resulting from sweating. Peripheral thermoreceptors inform the hypothalamus of the skin temperature, and central thermoreceptors-the most important of which are located in the hypothalamus itself- inform the hypothalamus of the core temperature. The primary means of heat gain is heat production by metabolic activity; the biggest contributor is skeletal muscle contraction. Heat loss is adjusted by sweating and by controlling to the greatest extent possible the temperature gradient between the skin and surrounding environment. The layer of cool skin between the core and environment increases the insulating barrier between the warm core and the external air. On exposure to cool surroundings, the core temperature starts to fall as heat loss increases, because of the larger-thannormal skin-to-air temperature gradient. The hypothalamus responds to reduce the heat loss by inducing skin vasoconstriction, while simultaneously increasing heat production through heat-generating shivering. A fever occurs when endogenous pyrogen released from macrophages in response to infection raises the hypothalamic set point. An elevated core temperature develops as the hypothalamus initiates cold-response mechanisms to raise the core temperature to the new set point. Testosterone stimulates the mitotic and meiotic divisions required to transform the undifferentiated diploid germ cells, the spermatogonia, into undifferentiated haploid spermatids. The epididymis and ductus deferens store and concentrate the sperm and increase their motility and fertility prior to ejaculation. Prostaglandins are produced throughout the body, not just in the reproductive tract. These ubiquitous chemical messengers are derived from arachidonic acid, a component of the plasma membrane. By acting as paracrines, specific prostaglandins exert a variety of local effects. Union of a sperm and an ovum at fertilization results in the beginning of a new individual that has 23 complete pairs of chromosomes, half from the father and half from the mother. The externally visible portions of the reproductive system constitute the external genitalia. In the presence of masculinizing factors, a male reproductive system develops; in their absence, a female system develops. The cooler temperature in the scrotum than in the abdominal cavity is essential for spermatogenesis. Testosterone is responsible for maturation and maintenance of the entire male reproductive tract, for development of secondary sexual characteristics, and for stimulating libido. It consists of two stages: (1) emission, the emptying of semen (sperm and accessory sex gland secretions) into the urethra; and (2) expulsion of semen from the penis. The latter is accompanied by a set of characteristic systemic responses and intense pleasure referred to as orgasm. During the female sexual response, the outer portion of the vagina constricts to grip the penis, whereas the inner part expands to create space for sperm deposition. The same steps in chromosome replication and division take place in oogenesis as in spermatogenesis, but the timing and end result are markedly different. Spermatogenesis is accomplished within two months, whereas the similar steps in oogenesis take anywhere from 12 to 50 years to complete on a cyclic basis from the onset of puberty until menopause. A female is born with a limited, largely nonrenewable supply of germ cells, whereas postpubertal males can produce several hundred million sperm each day. Each primary oocyte yields only one cytoplasm-rich ovum along with three doomed cytoplasm-poor polar bodies that disintegrate, whereas each primary spermatocyte yields four equally viable spermatozoa. This endocrine unit prepares the uterus for implantation if the released ovum is fertilized. The consequent withdrawal of hormonal support for the highly developed uterine lining causes it to disintegrate and slough, producing menstrual flow. Within a week it grows and differentiates into a blastocyst capable of implantation. These enzymes digest the nutrient-rich endometrial tissue, accomplishing the dual function of carving a hole in the endometrium for implantation of the blastocyst while simultaneously releasing nutrients from the endometrial cells for use by the developing embryo. The placenta is the organ of exchange between the maternal and fetal blood and also acts as a transient, complex endocrine organ that secretes a number of hormones essential for pregnancy. Human chorionic gonadotropin, estrogen, and progesterone are the most important of these hormones. High levels of estrogen and progesterone are essential for maintaining a normal pregnancy. Once the contractions are initiated at the onset of labour, a positive-feedback cycle is established that progressively increases their force. As contractions push the fetus against the cervix, secretion of oxytocin, a powerful uterine muscle stimulant, is reflexly increased. The extra oxytocin causes stronger contractions, giving rise to even more oxytocin release, and so on. This positive-feedback cycle progressively intensifies until cervical dilation and delivery are complete. However, the high gestational level of estrogen and progesterone prevents prolactin from promoting milk production. Lactation is sustained by suckling, which triggers the release of oxytocin and prolactin. Oxytocin causes milk ejection by stimulating the myoepithelial cells surrounding the alveoli to squeeze the secreted milk out through the ducts. Prolactin stimulates the secretion of more milk to replace the milk ejected as the baby nurses. In subsequent chapters, you will learn how energy is used to transport molecules across cell membranes and to create movement. That search still had 46 million results but on the first page was a link to the American Diabetes Association, diabetes. Q2: What kinds of websites should Jimmy be looking for in his results list, and how can he recognize them Cell-to-cell communication uses chemical signals, electrical signals, or a combination of both. Information may go from one cell to its neighbors (local communication) or from one part of the body to another (long-distance communication). When chemical signals reach their target cells, they must get their information into the cell. Some molecules are able to pass through the barrier of the cell membrane, but signal molecules that cannot enter the cell must pass their message across the cell membrane. Homeostasis and regulation of the internal environment are key principles of physiology and underlying themes in each chapter of this book. The next section looks in detail at the key elements Play BioFlix Animation of this important @Mastering Anatomy & Physiology theme. During his studies of experimental medicine, Bernard noted the stability of various physiological functions, such as body temperature, heart rate, and blood pressure. Cannon divided his variables into what he described as environmental factors that affect cells (osmolarity, temperature, and pH) and "materials for cell needs" (nutrients, water, sodium, calcium, other inorganic ions, oxygen, as well as "internal secretions having general and continuous effects").

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Even for the first few years after puberty arthritis in fingers diet purchase etodolac on line, many of the cycles are anovulatory. This limited gamete potential in females is in sharp contrast to the continual process of spermatogenesis in males, who have the potential to produce several hundred million sperm in a single day. Furthermore, considerable chromosome wastage occurs in oogenesis compared with spermatogenesis. The undifferentiated primordial germ cells in the fetal ovaries, the oogonia (comparable to the spermatogonia), divide mitotically to give rise to 6 million to 7 million oogonia by the fifth month of gestation, when mitotic proliferation ceases. The primary oocyte within a primary follicle is still a diploid cell that contains 46 doubled chromosomes. From puberty until menopause, a portion of the resting pool of follicles starts developing into secondary (antral) follicles on a cyclic basis. The mechanisms determining which follicles in the pool will develop during a given cycle are unknown. Development of a secondary follicle is characterized by growth of the primary oocyte and by expansion and differentiation of the surrounding cell layers. This oocyte enlargement is caused by a buildup of cytoplasmic materials that are needed by the early embryo. Just before ovulation, the primary oocyte, whose nucleus has been in meiotic arrest for years, completes its first meiotic division. However, almost all the cytoplasm remains with one of the daughter cells, now called the secondary oocyte, which is destined to become the ovum. The chromosomes of the other daughter cell together with a small share of cytoplasm form the first polar body. In this way, the ovum-to-be loses half of its chromosomes to form a haploid gamete but retains all of its nutrient-rich cytoplasm. Sperm entry into the secondary oocyte is needed to trigger the second meiotic division. During this division, a half set of chromosomes and a thin layer of cytoplasm is extruded as the second polar body. The other half set of 23 unpaired chromosomes remains behind in what is now the mature ovum. These 23 maternal chromosomes unite with the 23 paternal chromosomes of the penetrating sperm to complete fertilization. If the first polar body has not already degenerated, it too undergoes the second meiotic division at the same time the fertilized secondary oocyte is dividing its chromosomes. In spermatogenesis, each daughter cell develops into a highly specialized, motile spermatozoon unencumbered by unessential cytoplasm and organelles; its only destiny is to supply half the genes for a new individual. In oogenesis, however, of the four daughter cells only the one destined to become the ovum receives cytoplasm. This uneven distribution of cytoplasm is important, because the ovum, in addition to providing half the genes, provides all the cytoplasmic components needed to support early development of the fertilized ovum. The large, relatively undifferentiated ovum contains numerous nutrients, organelles, and structural and enzymatic proteins. The three other cytoplasm-scarce daughter cells, the polar bodies, rapidly degenerate-their chromosomes deliberately wasted. Note also the considerable difference in time to complete spermatogenesis and oogenesis. It takes about two months for a spermatogonium to develop into fully remodelled spermatozoa. In contrast, development of an oogonium (present before birth) to a mature ovum requires anywhere from 11 years (beginning of ovulation at onset of puberty) to 50 years (end of ovulation at onset of menopause). The actual length of the active steps in meiosis is the same in both males and females, but in females the developing eggs remain in meiotic arrest for a variable number of years. The older age of ova released by women in their late 30s and 40s is believed to account for the higher incidence of genetic abnormalities, such as Down syndrome, in children born to women in this age range. These granulosa cells and the oocyte secrete several glycoproteins that form a thick extracellular matrix that covers the oocyte and separates it from the surrounding granulosa cells. Scientists have recently discovered gap junctions that penetrate the zona pellucida and extend between the oocyte and the surrounding granulosa cells in a developing follicle. Recall that gap junctions between excitable cells permit the spread of action potentials from one cell to the next as chargecarrying ions pass through these connecting tunnels (p. The cells in a developing follicle are not excitable, so gap junctions here serve a role other than transfer of electrical activity. Glucose, amino acids, and other important molecules are delivered to the oocyte from the granulosa cells through these tunnels, enabling the egg to stockpile these critical nutrients. Also, signalling molecules pass through the gap junctions in both directions, helping coordinate the changes that take place in the oocyte and the surrounding cells as both mature and prepare for ovulation. Normally, this cycle is interrupted only if pregnancy occurs and is finally terminated by menopause. The average ovarian cycle lasts 28 days, but this varies among women and among cycles in any particular woman. The follicle operates in the first half of the cycle to produce a mature egg ready for ovulation at midcycle. The corpus luteum takes over during the last half of the cycle to prepare the female reproductive tract for pregnancy if fertilization of the released egg occurs. At the same time as the oocyte enlarges and the granulosa cells proliferate, specialized ovarian connective tissue cells in contact with the expanding granulosa cells both proliferate and differentiate to form an outer layer of thecal cells. The thecal and granulosa cells, collectively known as follicular cells, function as a unit to secrete estrogen. Of the three physiologically important estrogens-estradiol, estrone, and estriol-estradiol is the principal ovarian estrogen. However, only those that do so during the follicular phase, when the hormonal environment is right to promote their maturation, continue beyond the early stages of development. The follicular fluid originates partially from plasma that passes through capillary pores and partially from follicular cell secretions. As the follicular cells start producing estrogen, some of this hormone is secreted into the blood for distribution throughout the body. Part of the follicular growth is due to continued proliferation of the granulosa and thecal cells, but most is due to a dramatic expansion of the antrum. A recruited follicle develops into an antral, or secondary, oocyte, resulting in ovulation and ending the follicular phase. Antrum Thecal cells that completely divides into two separate, genetically identical embryos at a very early stage in development. Rupture of the follicle at ovulation signals the end of the follicular phase and ushers in the luteal phase. The luteal phase the ruptured follicle left behind in the ovary after release of the ovum changes rapidly. The granulosa and thecal cells remaining in the remnant follicle first collapse into the emptied antral space that has been partially filled by clotted blood. The oocyte, surrounded by the zona pellucida and a single layer of granulosa cells, is displaced asymmetrically at one side of the growing follicle, in a little mound that protrudes into the antrum. The greatly expanded mature ovarian follicle bulges on the ovarian surface, creating a thin area that ruptures to release the oocyte at ovulation. Rupture of the follicle is facilitated by the release from the follicular cells of enzymes that digest the connective tissue in the follicular wall. The bulging wall is thus weakened so that it balloons out even farther, to the point that it can no longer contain the rapidly expanding follicular contents. The released ovum is quickly drawn into the oviduct, where fertilization may or may not take place. The other developing follicles that failed to reach maturation and ovulate undergo degeneration, never to be reactivated. Occasionally, two (or perhaps more) follicles reach maturation and ovulate at about the same time. Because fraternal twins arise from separate ova fertilized by separate sperm, they share no more in common than any other two siblings except for the same birth date.

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Our eyes are hollow fluid-filled spheres subdivided into two compartments best arthritis pain pills order 300mg etodolac with mastercard, the aqueous and vitreous humors. George Papanicolaou has saved the lives of millions of women by popularizing the Pap test, a cervical cytology screening method that detects early signs of cancer in the uterine cervix. In the past 50 years, deaths from cervical cancer have dropped dramatically in countries that routinely use the Pap test. In contrast, cervical cancer is a leading cause of death in regions where Pap test screening is not routine, such as Africa and Central America. The results will determine whether she needs to undergo further testing for cervical cancer. Pleural sac Pericardial sac Thoracic cavity Interstitial fluid surrounds most cells. Cell Heart Dense connective tissue Seen magnified, the pericardial membrane is a layer of flattened cells supported by connective tissue. Cancerous cells that originate in one tissue can escape from that tissue and spread to other organs through the circulatory system and the lymph vessels, a process known as metastasis. An interesting illustration of this distinction between the internal environment and the external environment in a lumen involves the bacterium Escherichia coli. This organism normally lives and reproduces inside the large intestine, an internalized compartment whose lumen is continuous with the external environment. By the 1890s, scientists had concluded that the outer surface of cells, the cell membrane, was a thin layer of lipids that separated the aqueous fluids of the interior and outside environment. We now know that cell membranes consist of microscopic double layers, or bilayers, of phospholipids with protein molecules inserted in them. One source of confusion is that tissue membranes are often depicted in book illustrations as a single line, leading students to think of them as if they were similar in structure to the cell membrane. In this section, you will learn more about the phospholipid membranes that create compartments for cells. We will use the term cell membrane in this book rather than plasma membrane or plasmalemma to avoid confusion with the term blood plasma. The cell membrane is a physical barrier that separates intracellular fluid inside the cell from the surrounding extracellular fluid. The cell membrane controls the entry of ions and nutrients into the cell, the elimination of cellular wastes, and the release of products from the cell. The cell membrane contains proteins that enable the cell to recognize and respond to molecules or to changes in its external environment. Membrane proteins also create specialized junctions between adjacent cells or between cells and the extracellular matrix extra-, outside, which is extracellular material that is synthesized and secreted by the cells. Functionally, the Body Has Three Fluid Compartments In physiology, we are often more interested in functional compartments than in anatomical compartments. The extracellular fluid subdivides further into plasma, the fluid portion of the blood, and interstitial fluid inter-, between + stare, to stand, which surrounds most cells of the body. Before the invention of microscopes in the sixteenth century, a membrane always described a tissue that lined a cavity or separated two compartments. Even today, we speak of mucous membranes in the mouth and vagina, the peritoneal membrane that lines the inside of the abdomen, the pleural membrane that covers the surface of the lungs, and the pericardial membrane that surrounds the heart. Membranes Are Mostly Lipid and Protein In the early decades of the twentieth century, researchers trying to decipher membrane structure ground up cells and analyzed their composition. However, a simple and uniform structure did not account for the highly variable properties of membranes found in different types of cells. How could water cross the cell membrane to enter a red blood cell but not be able to enter certain cells of the kidney tubule The explanation had to lie in the molecular arrangement of the proteins and lipids in the various membranes. Generally, the more metabolically active a membrane is, the more proteins it contains. This chemical analysis of membranes was useful, but it did not explain the structural arrangement of lipids and proteins in a membrane. Studies in the 1920s suggested that there was enough lipid in a given area of membrane to create a double layer. The bilayer model was further modified in the 1930s to account for the presence of proteins. With the introduction of electron microscopy, scientists saw the cell membrane for the first time. The 1960s model of the membrane, as seen in electron micrographs, was a "butter sandwich"-a clear layer of lipids sandwiched between two dark layers of protein. By the early 1970s, freeze-fracture electron micrographs had revealed the actual three-dimensional arrangement of lipids and proteins within cell membranes. The cell membrane is studded with protein molecules, like raisins in a slice of bread, and the extracellular surface has glycoproteins and glycolipids. Micelles are small droplets with a single layer of phospholipids arranged so that the interior of the micelle is filled with hydrophobic fatty acid tails. Micelles are important in the digestion and absorption of fats in the digestive tract. This arrangement leaves a hollow center with an aqueous core that can be filled with water-soluble molecules. Biologists think that a liposome-like structure was the precursor of the first living cell. To make drug delivery more specific, researchers can make immunoliposomes that use antibodies to recognize specific types of cancer cells. By targeting drugs to the cells they are treating, researchers hope to increase the effectiveness of the drugs and decrease unwanted side effects. Phospholipids are the major lipid of membranes, but some membranes also have significant amounts of sphingolipids. Sphingolipids also have fatty acid tails, but their heads may be either phospholipids or glycolipids. Cholesterol helps make membranes impermeable to small watersoluble molecules and keeps membranes flexible over a wide range of temperatures. Each cell has between 10 and 50 different types of proteins inserted into its membranes. Peripheral proteins peripheria, circumference attach to other membrane proteins by noncovalent interactions [p. Phospholipids are made of a glycerol backbone with two fatty acid chains extending to one side and a phosphate group extending to the other [p. They arrange themselves so that their nonpolar tails are not in contact with aqueous solutions such as extracellular fluid. Polar head (hydrophilic) Stylized model Nonpolar fatty acid tail (hydrophobic) can arrange themselves as Phospholipid bilayer forms a sheet. Carbohydrate Phospholipid heads face the aqueous intracellular and extracellular compartments. When a protein crosses the membrane more than once, loops of the amino acid chain protrude into the cytoplasm and the extracellular fluid. Carbohydrates may attach to the extracellular loops, and phosphate groups may attach to the intracellular loops. Phosphorylation or dephosphorylation of proteins is one way cells alter protein function [p. Transmembrane proteins are classified into families according to how many transmembrane segments they have. Membrane-spanning proteins are integral proteins, tightly but not covalently bound to the membrane. This allows those amino acids to create strong noncovalent interactions with the lipid tails of the membrane phospholipids, holding them tightly in place. Some of these proteins are covalently bound to lipid tails that insert themselves into the bilayer. The longer tails of the sphingolipids elevate the lipid rafts over their phospholipid neighbors. According to the original fluid mosaic model of the cell membrane, membrane proteins could move laterally from location to location, directed by protein fibers that run just under the membrane surface. The ability of the cytoskeleton to restrict the movement of integral proteins allows cells to develop polarity, in which different faces of the cell have different proteins and therefore different properties.

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Male gametes must be produced in abundance for two reasons: (1) Only a small percentage of them survive the hazardous journey through the female reproductive tract to the site of fertilization; and (2) the cooperative effort of many spermatozoa is required to 17 Breastfeeding is also advantageous for the mother arthritis diet paleo buy 200 mg etodolac with mastercard. Lactation, therefore, tends to prevent ovulation, decreasing the likelihood of another pregnancy (although it is not a reliable means of contraception). The female reproductive system undergoes complex changes on a cyclic monthly basis. During the first half of the cycle, a single nonmotile ovum is prepared for release. During the second half, the reproductive system is geared toward preparing a suitable environment for supporting the ovum if fertilization (union with a spermatozoon) occurs. If fertilization does not occur, the prepared supportive environment within the uterus sloughs off, and the cycle starts over again as a new ovum is prepared for release. If fertilization occurs, the female reproductive system adjusts to support growth and development of the new individual until it can survive on its own on the outside. There are three important parallels in the male and female reproductive systems, even though they differ considerably in structure and function. First, the same set of undifferentiated reproductive tissues in the embryo can develop into either a male or a female system, depending on the presence or absence, respectively, of male-determining factors. In both cases, gonadal steroids and inhibin act in negative-feedback fashion to control hypothalamic and anterior pituitary output. If a follicle does not reach maturity during one ovarian cycle, it can finish maturing during the next cycle. Spermatogenesis takes place within the of the testes, stimulated by the hormones and. During estrogen production by the follicle, the cells under the influence of the hormone produce androgens, and the cells under the influence of the hormone convert these androgens into estrogens. The source of estrogen and progesterone during the first 10 weeks of gestation is the. All human somatic cells contain 23 chromosomal pairs for a total diploid number of 46 chromosomes. The sex chromosome content of the fertilizing sperm determines the sex of the offspring. What are the primary reproductive organs, gametes, sex hormones, reproductive tract, accessory sex glands, external genitalia, and secondary sexual characteristics in males and in females Discuss the differences between males and females with regard to genetic, gonadal, and phenotypic sex. Using the answer code on the right, indicate when each event takes place during the ovarian cycle: 1. Occasionally, testicular tumours composed of interstitial cells of Leydig may secrete up to 100 times the normal amount of testosterone. When such a tumour develops in young children, they grow up much shorter than their genetic potential. What type of sexual dysfunction might arise in men taking drugs that inhibit sympathetic nervous system activity as part of the treatment for high blood pressure Explain the physiological basis for administering a posterior pituitary extract to induce or facilitate labour. The symptoms of menopause are sometimes treated with supplemental estrogen and progesterone. Her physician has diagnosed her condition as a tubal pregnancy: the developing embryo is implanted in the oviduct instead of in the uterine endometrium. These particles are too small to be seen individually, even with the most powerful electron microscopes available today. Although atoms are extremely small, they consist of three types of even smaller subatomic particles. Different types of atoms vary in the number of these various subatomic particles they contain. Protons and neutrons are particles of nearly identical mass: protons carry a positive charge and neutrons have no charge. Electrons have a much smaller mass than protons and neutrons and are negatively charged. The magnitude of the charge of a proton exactly matches that of an electron, but it is opposite in sign, being positive. In all atoms, the number of protons in the nucleus is equal to the number of electrons moving around the nucleus, so their charges balance, and the atoms are neutral. Surrounding the nucleus is the electron cloud, where the electrons move rapidly around the nucleus. Compounds and molecules Pure substances composed of more than one type of atom are known as compounds. Pure water, for example, is a compound that contains atoms of hydrogen and atoms of oxygen in a 2-to-1 ratio, regardless of whether the water is in the form of liquid, solid (ice), or vapour (steam). A molecule is the smallest unit of a pure substance that has the properties of that substance and is capable of a stable, independent existence. For example, a molecule of water consists of two atoms of hydrogen and one atom of oxygen, held together by chemical bonds. Elements and atomic symbols A pure substance composed of only one type of atom is called an element. A pure sample of the element carbon contains only carbon atoms, even though the atoms might be arranged in the form of diamond or in the form of graphite (pencil lead). Usually these symbols are easy to follow, because they are derived from the English name for the element. In a few cases, the atomic symbol is based on Atomic number Exactly what are we talking about when we refer to a "type" of atom An astronaut has the same mass whether on Earth or in space, but is weightless in the zero gravity of space. Of course, these numbers also represent the number of electrons moving around each nucleus, because the number of electrons and number of protons in an atom are equal. The number of protons in the nucleus of an atom of an element is called the atomic number of the element. These very small numbers are inconvenient to work with in calculations, so a system of relative masses has been developed. These relative masses simply compare the actual masses of the atoms with each other. Their relative masses are then determined by dividing each mass by the smaller mass of the two: 45. The relative masses of atoms are called atomic masses, or atomic weights, and are given in atomic mass units (amu). In this system, hydrogen atoms, the least massive of all atoms, have an atomic weight of 1. Table B-1 gives the atomic weights and some other characteristics of the elements that are most important physiologically. Because all matter is made up of atoms, atoms must somehow be held together to form matter. Not all chemical bonds are formed in the same way, but all involve the electrons of atoms. Whether one atom will bond with another depends on the number and arrangement of its electrons. The orbitals, or pathways, travelled by electrons around the nucleus, are arranged in an orderly series of concentric layers known as electron shells, which consecutively surround the nucleus. The first (innermost) shell closest to the nucleus can contain a maximum of only two electrons, no matter what the element is. The third, fourth, and fifth shells can hold 18, 32, and 50 electrons, respectively.

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Whenever you see reference to "adrenergic control" of a function rheumatoid arthritis cure zone generic etodolac 200mg visa, you must make the connection to a neuron secreting norepinephrine. Adrenergic receptors are divided into two classes: a (alpha) and b (beta), with multiple subtypes of each. McKhann decided to perform nerve conduction tests on some of the paralyzed children in Beijing Hospital. Q4: Is the paralytic illness that affected the Chinese children a demyelinating condition Peptides the nervous system secretes a variety of peptides that act as neurotransmitters and neuromodulators in addition to functioning as neurohormones. These peptides include substance P, involved in some pain pathways, and the opioid peptides (enkephalins and endorphins) that mediate pain relief, or analgesia an-, without algos, pain. Nitric oxide acting as a neurotransmitter diffuses freely into a target cell rather than binding to a membrane receptor [p. McKhann then asked to see autopsy reports on some of the children who had died of their paralysis at Beijing Hospital. In the reports, pathologists noted that the patients had normal myelin but damaged axons. In some cases, the axon had been completely destroyed, leaving only a hollow shell of myelin. It is also released from cells other than neurons and often acts as a paracrine signal. Some vesicles are "docked" at active zones along the membrane closest to the synaptic cleft, waiting for a signal to release their contents. In this section, we discuss general patterns of neurotransmitter synthesis, storage, release, and termination of action. Neurotransmitter Synthesis Neurotransmitter synthesis takes place both in the nerve cell body and in the axon terminal. Polypeptides must be made in the cell body because axon terminals do not have the organelles needed for protein synthesis. The large propeptide that results is packaged into vesicles along with the enzymes needed to modify it. The vesicles then move from the cell body to the axon terminal by fast axonal transport. Inside the vesicle, the propeptide is broken down into smaller active peptides-a pattern similar to the preprohormone-prohormone-active hormone process in endocrine cells [p. Smaller neurotransmitters, such as acetylcholine, amines, and purines, are synthesized and packaged into vesicles in the axon terminal. They all provide neuroscientists with compounds for studying synaptic transmission, extracted from the neurotoxic venoms these creatures use to kill their prey. The Asian snake Bungarus multicinctus provides us with a@bungarotoxin, a long-lasting poison that binds tightly to nicotinic acetylcholine receptors. The fish-hunting cone snail, Conus geographus, and the funnel web spider, Agelenopsis aperta, use toxins that block different types of voltage-gated Ca2+ channels. One of the most potent poisons known, however, comes from the Japanese puffer fish, a highly prized delicacy whose flesh is consumed as sushi. This neurotoxin blocks Na+ channels on axons and prevents the transmission of action potentials, so ingestion of only a tiny amount can be fatal. The dissolved enzymes are then brought to axon terminals by slow axonal transport. Neurotransmitter Release Neurotransmitters in the axon terminal are stored in vesicles, so their release into the synaptic cleft takes place by exocytosis [p. From what we can tell, exocytosis in neurons is similar to exocytosis in other types of cells, but much faster. When the depolarization of an action potential reaches the axon terminal, the change in membrane potential sets off a sequence of events 1. The axon terminal membrane has voltage-gated Ca2+ channels that open in response to depolarization 2. Calcium ions are more concentrated in the extracellular fluid than in the cytosol, and so they move into the cell down their electrochemical gradient. The membrane of the synaptic vesicle fuses with the cell membrane, aided by multiple membrane proteins. The fused area opens, and neurotransmitter inside the synaptic vesicle moves into the synaptic cleft 4. The neurotransmitter molecules diffuse across the gap to bind with membrane receptors on the postsynaptic cell. When neurotransmitters bind to their receptors, a response is initiated in the postsynaptic cell 5. Each synaptic vesicle contains the same amount of neurotransmitter, so measuring the magnitude of the target cell response is an indication of how many vesicles released their content. The transporters that concentrate neurotransmitter into vesicles are H+@dependent antiporters (p. The postsynaptic membrane has receptors for neurotransmitter that diffuses across the synaptic cleft. In an experiment on synaptic transmission, a synapse was bathed in a Ca2+@free medium that was otherwise equivalent to extracellular fluid. Although the action potential reached the axon terminal at the synapse, the usual response of the postsynaptic cell did not occur. Classify the H+@neurotransmitter exchange as facilitated diffusion, primary active transport, or secondary active transport. Which organelles are needed to synthesize proteins and package them into vesicles In this model, called the kiss-and-run pathway, synaptic vesicles fuse to the presynaptic membrane at a complex called the fusion pore. This fusion opens a small channel that is just large enough for neurotransmitter to pass through. Then, instead of opening the fused area wider and incorporating the vesicle membrane into the cell membrane, the vesicle pulls back from the fusion pore and returns to the pool of vesicles in the cytoplasm. Termination of Neurotransmitter Activity A key feature of neural signaling is its short duration, due to the rapid removal or inactivation of neurotransmitter in the synaptic cleft. Recall that ligand binding to a protein is reversible and goes to a state of equilibrium, with a constant ratio of unbound to bound ligand [p. If unbound neurotransmitter is removed from the synapse, the receptors release bound neurotransmitter, terminating its activity, to keep the ratio of unbound/bound transmitter constant. Synaptic vesicle with neurotransmitter molecules 2 the depolarization opens voltagegated Ca2+ channels, and Ca2+ enters the cell. Blood vessel Axon terminal of presynaptic cell 1 Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells. Many neurotransmitters are removed from the extracellular fluid by transport back into the presynaptic cell or into adjacent neurons or glia. For example, norepinephrine action is terminated when the intact neurotransmitter is transported back into the presynaptic axon terminal. Neurotransmitters and their components can be recycled to refill empty synaptic vesicles. Stronger Stimuli Release More Neurotransmitter A single action potential arriving at the axon terminal releases a constant amount of neurotransmitter. Neurons therefore can use the frequency of action potentials to transmit information about the duration and strength of the stimuli that activated them. Duration of a stimulus is coded by the duration of a series of repeated action potentials. A stronger stimulus causes more action potentials per second to arrive at the axon terminal, which in turn may result in more neurotransmitter release. An above-threshold graded potential reaching the trigger zone of the sensory neuron does not trigger just one action potential. Brain neurons show different electrical personalities by firing action potentials in a variety of patterns, sometimes spontaneously, without an external stimulus to bring them to threshold. Other neurons exhibit bursting, bursts of action potentials rhythmically alternating with intervals of quiet (rhythmic pacemakers).

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In positive feedback loops arthritis in hands fingers symptoms cheap etodolac 200 mg on-line, the response reinforces the stimulus rather than decreasing or removing it. This destabilizes the system until some intervention or event outside the loop stops the response. In scientific experimentation, the factor manipulated by the investigator is the independent variable, and the observed factor is the dependent variable. All well-designed experiments have controls to ensure that observed changes are due to the experimental manipulation and not to some outside factor. Data, the information collected during an experiment, are analyzed and presented, often as a graph. When new evidence does not support a theory or a model, the theory or model must be revised. Animal experimentation is important because of the tremendous variability within human populations and because it is difficult to control human experiments. In addition, ethical questions may arise when using humans as experimental subjects. To control many experiments, some subjects take an inactive substance known as a placebo. Placebo and nocebo effects, in which changes take place even if the treatment is inactive, may affect experimental outcomes. In a blind study, the subjects do not know whether they are receiving the experimental treatment or a placebo. In a doubleblind study, a third party removed from the experiment is the only one who knows which group is the experimental group and which is the control. In a crossover study, the control group in the first half of the experiment becomes the experimental group in the second half, and vice versa. Put the following parts of a reflex in the correct order for a physiological response loop: input signal, integrating center, output signal, response, sensor, stimulus, target. The name for daily fluctuations of body functions such as blood pressure, temperature, and metabolic processes is a(n). Try to include functions of all components on the map and remember that some structures may share functions. Name as many organs or body structures that connect directly with the external environment as you can. Which systems exchange material with the external environment, and what do they exchange Explain the differences among positive feedback, negative feedback, and feedforward mechanisms. At the end of the semester, researchers measured an intermediatelevel class of 25 male weight lifters for aerobic fitness and midarm muscle circumference. A group of biology majors went to a mall and asked passersby, "Why does blood flow Although dehydration is one of the most serious physiological obstacles that land animals must overcome, there are others. Think of as many as you can, and think of various strategies that different terrestrial animals have to overcome these obstacles. In one sentence, summarize the relationship between the two variables plotted on the graph. A study7 was carried out on human volunteers to see whether two procedures performed during arthroscopic surgery arthro-, joint + scopium, to look at are effective in relieving knee pain associated with osteoarthritis, or degenerative joint disease osteon, bone + arthro@, joint + @itis, inflammation. The volunteers were up to 75 years old and were recruited from a Veterans Affairs Medical Center. One-third of the subjects had placebo operations-that is, they were given anesthesia and their knees were cut open, but the remainder of the treatment procedure was not done. The other two-thirds of the subjects had one of the two treatment procedures performed. They answered questions about their knee pain and function and were given an objective walking and stairclimbing test. At the end of the study, the results showed no significant difference in knee function or perception of pain between subjects getting one of the standard treatments and those getting the placebo operation. Do you think it is ethical to perform placebo surgeries on humans who are suffering from a painful condition, even if the subjects are informed that they might receive the placebo operation and not the standard treatment Give two possible explanations for the decreased pain reported by the placebo operation subjects. Why do you think the investigators felt it was necessary to include a placebo operation in this study A group of students wanted to see what effect a diet deficient in vitamin D would have on the growth of baby guppies. They fed the guppies a diet low in vitamin D and measured fish body length every third day for three weeks. What was the dependent variable and what was the independent variable in this experiment You performed an experiment in which you measured the volumes of nine slices of potato, then soaked the slices in solutions of different salinities for 30 minutes. The changes you found were: Percent Change in Volume after 30 Minutes Solution Sample 1 Sample 2 Sample 3 Distilled water 1% salt (NaCl) 9% salt (NaCl) 10% 0% - 8% 8% - 0. Can you tell from the information given whether or not there was a control in this experiment Their theories were put to the test in 1953, when a 23-year-old scientist named Stanley Miller combined these molecules in a closed flask and boiled them for a week while periodically discharging flashes of electricity through them, simulating lightning. With this simple experiment, he had shown that it was possible to create organic molecules, usually associated with living creatures, from nonliving inorganic precursors. Numerous scientific theories have been proposed, ranging from life arriving by meteor from outer space to molecules forming in deep ocean hydrothermal vents. No matter what their origin, the molecules associated with living organisms have the ability to organize themselves into compartments, replicate themselves, and act as catalysts to speed up reactions that would otherwise proceed too slowly to be useful. The human body is far removed from the earliest life forms, but we are still a collection of chemicals-dilute solutions of dissolved and suspended molecules enclosed in compartments with lipid-protein walls. Strong links between atoms, known as chemical bonds, store and transfer energy to support life functions. Weaker interactions between and within molecules create distinctive molecular shapes and allow biological molecules to interact reversibly with each other. This article introduces some of the fundamental principles of molecular interactions that you will encounter repeatedly in your study of physiology. The human body is more than 50% water, and because most of its molecules are dissolved in this water, we will review the properties of aqueous solutions. If you would like to refresh your understanding of the key features of atoms, chemical bonds, and biomolecules, you will find a series of oneand two-page review features that encapsulate biochemistry as it pertains to physiology. You can test your knowledge of basic chemistry and biochemistry with a special review quiz at the end of the chapter. These three plus eight additional elements are considered major essential elements. Some additional minor essential elements (trace elements) are required in minute amounts, but there is no universal agreement on which trace elements are essential for cell function in humans. A periodic table showing the major and commonly accepted minor essential elements is located inside the back cover of the book. There are four major groups of biomolecules: carbohydrates, lipids, proteins, and nucleotides. The body uses carbohydrates, lipids, and proteins for energy and as the building blocks of cellular components. Each group of biomolecules has a characteristic composition and molecular structure. Conjugated proteins are protein molecules combined with another kind of biomolecule. Lipoproteins are found in cell membranes and in the blood, where they act as carriers for less soluble molecules, such as cholesterol.

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Recent findings suggest lakota arthritis relief discount etodolac 300 mg without prescription, however, that the higher incidence of these self-destructive conditions in females may be a legacy of pregnancy. The major histocompatibility (histo means "tissue"; compatibility means "ability to get along") complex was so named because these genes and the self-antigens they encode were first discerned in relation to tissue typing (similar to blood typing), which is done to obtain the most compatible matches for tissue grafting and transplantation. However, the transfer of tissue from one individual to another does not normally occur in nature. Thus, T-cell receptors bind only with body cells, making the statement-by bearing both self- and nonself antigens on their surface-"I, one of your own kind, have been invaded. It would be futile for T cells to bind with free, extracellular antigens; they cannot defend against foreign material unless it is intracellular. A foreign protein first must be enzymatically broken down within a body cell into small fragments known as peptides. Once displayed at the cell surface, the combined presence of these self- and nonself antigens alerts the immune system to the presence of an undesirable agent within the cell. In the case of cytotoxic T cells, the outcome of this binding is the destruction of the infected body cell. Specific binding requirements for the two types of T cells ensure that these cells bind only with the targets that they can influence. This requirement is met when a virus invades a body cell, whereupon the cell is destroyed by the cytotoxic T cells. That is, a helper T cell can bind with foreign antigen only when it is found on the surfaces of immune cells with which the helper T cell interacts. These include the macrophages, which present antigen to helper T cells, as well as B cells and cytotoxic T cells, whose activities are enhanced by cytokines secreted by helper T cells. The capabilities of helper T cells would be squandered if these cells were able to bind with body cells other than these special immune cells. In this way, the specific binding requirements for the two types of T cells help ensure the appropriate T-cell responses. At least once a day, on average, your immune system destroys a mutated cell that could potentially become cancerous. Any normal cell may be transformed into a cancer cell if mutations occur within its genes that govern cell division and growth. Such mutations may occur by chance alone or, more frequently, by exposure to carcinogenic (cancer-causing) factors such as ionizing radiation, certain environmental chemicals, or physical irritants. Alternatively, a few cancers are caused by tumour viruses, which turn the cells they invade into cancer cells. Cell multiplication and growth are normally under strict control, but the regulatory mechanisms are largely unknown. If a cell that has transformed into a tumour cell manages to escape immune destruction, however, it defies the normal controls on its proliferation and position. Unrestricted multiplication of a single cancer cell results in a tumour that consists of a clone of cells identical to the original mutated cell. If the mass is slow growing, stays put in its original location, and does not infiltrate the surrounding tissue, it is considered a benign tumour. In contrast, the transformed cell may multiply rapidly and form an invasive mass that lacks the "altruistic" behaviour characteristic of normal cells. Malignant tumour cells usually do not adhere well to the neighbouring normal cells, so often some of the cancer cells break away from the parent tumour. These "emigrant" cancer cells are transported through the blood to new territories, where they continue to proliferate, forming multiple malignant tumours. The term metastasis is applied to this spreading of cancer to other parts of the body. If a malignant tumour is detected early, before it has metastasized, it can be removed surgically. Once cancer cells have dispersed and seeded multiple cancerous sites, surgical elimination of the malignancy is impossible. In this case, agents that interfere with rapidly dividing and growing cells, such as certain chemotherapeutic drugs, are used in an attempt to destroy the malignant cells. Unfortunately, these agents also harm normal body cells, especially rapidly proliferating cells, such as blood cells and the cells lining the digestive tract. Untreated cancer is eventually fatal in most cases, for several interrelated reasons. The uncontrollably growing malignant mass crowds out normal cells by vigorously competing with them for space and nutrients, yet the cancer cells cannot take over the functions of the cells they are destroying. The ensuing destruction of the transplanted cells triggers the rejection of transplanted or grafted tissues. In the past, the primary immunosuppressive tools included radiation therapy and drugs aimed at destroying the actively multiplying lymphocyte populations, plus anti-inflammatory drugs that suppressed growth of all lymphoid tissue. However, these measures not only suppressed the T cells that were primarily responsible for rejecting transplanted tissue but also depleted the antibody-secreting B cells. Unfortunately, the treated individual was left with little specific immune protection against bacterial and viral infections. In recent years, new therapeutic agents have become extremely useful in selectively depressing T-cell-mediated immune activity while leaving B-cell humoural immunity essentially intact. For example, cyclosporin blocks interleukin 2, the cytokine secreted by helper T cells that is required for expansion of the selected cytotoxic T-cell clone. Furthermore, a new technique under investigation may completely prevent rejection of transplanted tissues even from an unmatched donor. This technique involves the use of tailor-made antibodies that block specific facets of the rejection process. If proven safe and effective, the technique will have a tremendous impact on tissue transplantation. The normal cells display specialized cilia, which constantly contract in whiplike motion to sweep debris and microorganisms from the respiratory airways so they do not gain entrance to the deeper portions of the lungs. The cancerous cells are not ciliated, so they are unable to perform this specialized defence task. Affected organs gradually become disrupted to the point that they can no longer perform their life-sustaining functions, and the person dies. On contacting a cancer cell, both these killer cells release perforin and other toxic chemicals that destroy the targeted mutant cell. Macrophages, in addition to clearing away the remains of the dead victim cell, can engulf and destroy cancer cells intracellularly. The fact that cancer does sometimes occur means that cancer cells occasionally escape these immune mechanisms. Some cancer cells are believed to survive by evading immune detection, for example, by failing to display identifying antigens on their surface or by being surrounded by counterproductive blocking antibodies that interfere with T-cell function. Although B cells and antibodies are not believed to play a direct role in cancer defence, B cells may produce antibodies against a mutant cancer cell when they recognize it is not a normal self-cell. These antibodies, for unknown reasons, do not activate the complement system, which could destroy the cancer cells. Instead, the antibodies bind with the antigenic sites on the cancer cell, thereby hiding these sites from recognition by cytotoxic T cells. The coating of a tumour cell by blocking antibodies thus protects the harmful cell from attack by deadly T cells. A new finding reveals that still other successful cancer cells thwart immune attack by turning on their pursuers. A cell usually becomes cancerous only after an accumulation of multiple independent mutations. This requirement contributes at least in part to the much higher incidence of cancer in older individuals, in whom mutations have had more time to accumulate in a single-cell lineage. Potentially cancerous cells that do arise are usually destroyed by the immune system early in their development. Regulatory loops From the preceding discussion, it is obvious that complex controlling factors operate within the immune system itself. Until recently, the immune system was believed to function independently of other control systems in the body. Investigations now indicate, however, that the immune system both influences and is influenced by the two major regulatory systems-the nervous and endocrine systems.

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During sexual arousal arthritis juvenile purchase etodolac 200mg otc, these arterioles reflexly dilate and the erectile tissue fills with blood, causing the penis to enlarge both in length and width and to become more rigid. More than 50 percent of men between ages 40 and 70 experience some impotence, climbing to nearly 70 percent by age 70. No wonder, then, that more prescriptions were written for the much-publicized drug sildenafil (Viagra) during its first year on the market Stimulation of mechanoreceptors after its approval in 1998 for treating erectile in glans penis dysfunction than for any other new drug in history. Sildenafil does not produce an erecor tion, but it amplifies and prolongs an erectile response triggered by usual means of stimulaor Parasympathetic supply Parasympathetic Sympathetic tion. Just as pushing a pedal on a piano does not cause a note to numerous regions throughout the brain that can influence be played but does prolong a played note, sildenafil cannot cause the male sexual response. The work to either facilitate or inhibit the basic spinal erection reflex, drug has no benefit for those who do not have erectile dysfuncdepending on the momentary circumstances. As an example of tion, but its success rate has been high among sufferers of the facilitation, psychic stimuli, such as viewing something sexucondition. In contrast, failure to achieve an Ejaculation erection despite appropriate stimulation may result from inhibition of the erection reflex by higher brain centres. The overall A pattern of failing to achieve or maintain an erection ejaculatory response occurs in two phases: emission and expulsuitable for sexual intercourse-erectile dysfunction sion (see Table 17-4). Heavy breathing, a heart rate of up to 180 beats per minute, marked generalized skeletal muscle contraction, and heightened emotions are characteristic. These pelvic and overall systemic responses that culminate the sex act are associated with an intense pleasure characterized by a feeling of release and complete gratification, an experience known as orgasm. Muscle tone returns to normal, while the cardiovascular and respiratory systems return to their prearousal level of activity. Once ejaculation has occurred, a temporary refractory period of variable duration ensues before sexual stimulation can trigger another erection. Males therefore cannot experience multiple orgasms within a matter of minutes, as females sometimes do. An average human ejaculate contains about 180 million sperm (66 million/mL), but some ejaculates contain as many as 400 million sperm. A man is considered clinically infertile if his sperm concentration falls below 20 million/mL of semen. The quality of sperm also must be taken into account when assessing the fertility potential of a semen sample. The presence of substantial numbers of sperm with abnormal motility or structure, such as sperm with distorted tails, reduces the chances of fertilization. The excitement phase in females can be initiated by either physical or psychological stimuli. Tactile stimulation of the clitoris and surrounding perineal area is an especially powerful sexual stimulus. These stimuli trigger spinal reflexes that bring about parasympathetically induced vasodilation of arterioles throughout the vagina and external genitalia, especially the clitoris. The resultant inflow of blood becomes evident as the swelling of the labia and the erection of the clitoris. The latter- like its male homologue, the penis-is composed largely of erectile tissue. Vasocongestion of the vaginal capillaries forces fluid out of the vessels into the vaginal lumen. This fluid, which is the first positive indication of sexual arousal, serves as the primary lubricant for intercourse. Also during the excitement phase in the female, the nipples become erect and the breasts enlarge as a result of vasocongestion. In addition, the majority of women show a sex flush during this time, which is caused by increased blood flow through the skin. During the plateau phase, the changes initiated during the excitement phase intensify, while systemic responses similar to those in the male (such as increased heart rate, blood pressure, respiratory rate, and muscle tension) occur. Further vasocongestion of the lower third of the vagina during this time reduces its inner capacity so that it tightens around the thrusting penis, heightening tactile sensation for both the female and the male. Simultaneously, the uterus raises upward, lifting the cervix and enlarging the upper two-thirds of the vagina. If erotic stimulation continues, the sexual response culminates in orgasm as sympathetic impulses trigger rhythmic contractions of the pelvic musculature at 0. The contractions occur most intensely in the engorged lower third of the vaginal canal. In fact, the orgasmic experience in females parallels that of males with two exceptions. Second, females do not become refractory following an orgasm, so they can respond immediately to continued erotic stimulation and achieve multiple orgasms. If stimulation continues, the sexual intensity only diminishes to the plateau level following orgasm and can quickly be brought to a peak again. During resolution, pelvic vasocongestion and the systemic manifestations gradually subside. Furthermore, the physiologic mechanisms responsible for orgasm are fundamentally the same in males and females. Complex cycling Unlike the continuous sperm production and essentially constant testosterone secretion characteristic of the male, release of ova is intermittent, and secretion of female sex hormones displays wide cyclic swings. The tissues influenced by these sex hormones also undergo cyclic changes, the most obvious of which is the monthly menstrual cycle. If fertilization does occur, the cycles are interrupted while the female system adapts to nurture and protect the newly conceived human being until it has developed into an individual capable of living outside the maternal environment. Thus, the female reproductive system is characterized by complex cycles that are interrupted by even more complex changes when pregnancy occurs. The ovaries are the primary female reproductive organs, performing the dual function of producing ova (oogenesis) and secreting estrogen and progesterone. These hormones act together to promote fertilization of the ovum and to prepare the female reproductive system for pregnancy. Estrogen in the female governs many functions similar to those carried out by testosterone in the male, such as maturation and maintenance of the entire female reproductive system and establishment of female secondary sexual characteristics. Estrogen is essential for ova maturation and release, development of physical characteristics that are sexually attractive to males, and transport of sperm from the vagina to the site of fertilization in the oviduct. Furthermore, estrogen contributes to breast development in anticipation of lactation. As in males, reproductive capability begins at puberty in females, but unlike males, who have reproductive potential throughout life, female reproductive potential ceases during middle age at menopause. During the last part of fetal life, the oogonia begin the early steps of the first meiotic division, but do not complete it. Known now as primary oocytes, they contain the diploid number of 46 replicated chromosomes, which are gathered into homologous pairs, but do not separate. The primary oocytes remain in this state of meiotic arrest for years until they are prepared for ovulation. Before birth, each primary oocyte is surrounded by a single layer of flat granulosa cells. Together, an oocyte and surrounding granulosa cells make up a primordial follicle. At birth, only about 2 million primary follicles remain, each containing a single primary oocyte capable of producing a single ovum. The traditional view is that no new oocytes or follicles appear after birth, with the follicles already present in the ovaries at birth serving as a reservoir from which all ova throughout the reproductive life of a female must arise. However, researchers recently discovered, in mice at least, that new oocytes and follicles are produced after birth from previously unknown ovarian stem cells capable of generating primordial germ cells (oogonia). Despite the potential for similar egg-generating stem cells in humans, the follicular pool gradually dwindles away as a result of processes that deplete the oocyte-containing follicles. The pool of primordial follicles gives rise to an ongoing trickle of developing follicles. During this development phase, the granulosa cells become cuboidal, and the follicles are now referred to as primary follicles.

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Also note that the values used in these examples represent hypothetical situations proliferative arthritis definition buy genuine etodolac. Deviations in pH actually occur over a wide range, and the degree to which compensation can be accomplished varies considerably. This effect tends to limit the extent to which a nonrespiratory factor, such as fever or anxiety, can cause hyperventilation. The serum is uncharged or electro-neutral, meaning that the number of anions and number of cations are equal. The anion gap is a mathematical way of determining the difference in laboratory-measured anions (negatively charged ions) and laboratory-measured cations (positively charged ions) in serum. Therefore, to determine the anion gap, look at the ions that are measured in the serum, and this gives you an idea of the amount of unmeasured anions. When the anion gap increases, this generally indicates there is an excess of one or more of these unmeasured anions. It can also mean that other anions, such as lactate or keto acids, have been added to the plasma. Some diseases, extreme exercise, alcohol abuse, or even septic shock can cause unmeasured anions to increase. These anions are generally acidic and, as such, cause a decrease in serum bicarbonate by the action of chemical buffering. In cases of a normal anion-gap metabolic acidosis, the disturbance is often due to a loss of bicarbonate. To maintain an electrically neutral serum, the loss in bicarbonate is generally countered by an increase in serum chloride. Other stresses to the body, including pregnancy or high altitude, can cause respiratory alkalosis. When kidney disease causes metabolic acidosis, complete compensation is not possible because the renal mechanism is not available for pH regulation. Recall that the respiratory system can compensate only up to 75 percent of the way toward normal. Uraemic acidosis is very serious because the kidneys cannot help restore pH all the way to normal. This leads to the breakdown of lipids and proteins and induces an overall energy deficient state, increasing hunger and food intake (polyphagia). Although caloric intake increases, it is usually insufficient to counterbalance the overall catabolic state, and weight loss ensues. These two metabolically produced compounds are acidic, which leads to a decrease in the plasma pH and a state of metabolic acidosis. Furthermore, these compounds are anionic and increase the number of unmeasured anions in the plasma, thereby elevating the plasma anion gap. The absence of insulin results in an inability for cells to use glucose for metabolic processes. As a result, abnormal fat metabolism leads to the formation of excess keto acids whose dissociation increases plasma [H1]. When muscles resort to anaerobic glycolysis during strenuous exercise, excess lactic acid is produced, raising plasma [H1] (p. In severe kidney failure (uraemia), the kidneys cannot rid the body of normal amounts of metabolically generated H1 from noncarbonic acid sources. Vomiting causes abnormal loss of [H1] from the body as a result of lost acidic gastric juices. Hydrochloric acid is secreted into the stomach lumen in preparation for and during digestion. In these instances, vomiting can result in a metabolic acidosis instead of metabolic alkalosis. The procedures for making these distinctions are beyond the scope of this textbook. Salt balance is maintained by constantly adjusting salt output in the urine to match unregulated, variable salt intake. Such shifts of H2O into or out of the cells cause the cells to swell or shrink, respectively. Cells, especially brain neurons, do not function normally when swollen or shrunken. Water balance is largely maintained by controlling the volume of free H2O (H2O not accompanied by solute) lost in the urine to compensate for 4 uncontrolled losses of variable volumes of H2O from other avenues, 0 such as through sweating or diar7. These effects are fatal if the pH falls outside the range of of the three lines of defence against this change in [H1]. Like salt and water balance, control of H1 output by the kidneys is the main regulatory factor in achieving H1 balance. Regulation of fluid balance systems can take up or liberate H1, transiently keeping its concentrainvolves two separate components: control of salt balance and contion constant within the body until its output can be brought into line trol of water balance. Such a mechanism is not available for salt or water in the long-term regulation of arterial blood pressure, because the balance. Salt balance in humans is poorly regulated because of our hedonistic salt appetite. Compare the ionic composition of plasma, interstitial fluid, and intracellular fluid. Outline the sources of input and output in a daily salt balance and a daily H 2 O balance. Describe the three lines of defence against changes in [H1] in terms of their mechanisms and speed of action. Which solution would be better at expanding plasma volume in a patient who has just haemorrhaged Explain why a person still feels thirsty after excessive consumption of alcoholic beverages. If a person loses 1500 mL of salt-rich sweat and drinks 1000 mL of water during the same time period, what will happen to vasopressin secretion Explain why it is safer to treat gastric hyperacidity with antacids that are poorly absorbed from the digestive tract than with baking soda, which is a good buffer for acid but is readily absorbed. Integration of Human Physiology Altitude Adaptation the Physiological Response to Altitude: Adaptation and Performance Enhancement chemoreceptor sensitivity to hypoxia. This is based on findings (primarily in research on goats) that the acclimatization occurs even when only the carotid bodies, not the rest of the body (including the brain), are exposed to hypoxic blood. In humans, acclimatization still occurs even if hypocapnia and respiratory alkalosis are prevented through the addition of carbon dioxide to the inspired gas. The arterial O2 content also increases rapidly at altitude because of a decrease in plasma volume, which is increased urine production and/or a shift of fluid to the interstitial and intracellular compartments. The arterial hypoxaemia associated with altitude also stimulates, via activation of hypoxia-inducible factor, the release of erythropoietin, the protein that controls the production of red blood cells. Although the red blood cells that are released may be immature, the haematocrit increases, thereby increasing the O2-carrying capacity of the blood. Increases in arterial O2 content are, however, ineffective in maintaining O2 delivery if perfusion to tissues is inadequate. Many vascular beds of the systemic vasculature, especially those in the brain and heart, are sensitive to the prevailing blood gases. This effect, however, is blunted by the hypocapnia resulting from altitude-induced hyperventilation; as a result, vascular resistance depends on the net effect of the opposing vasodilator and vasoconstrictor stimuli. Many factors derived from the endothelium affect vascular smooth muscle, including nitric oxide and prostaglandins (vasodilators) and endothelin-1 and superoxides (vasoconstrictors). To these must be added the mechanical effects of changes in blood pressure and viscosity. Research to determine how all these factors interact- and change over time as the cardiorespiratory system responds- to control vascular resistance at altitude is in the early stages.

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In an oxidation-reduction reaction arthritis in the knee and running buy cheapest etodolac, in which electrons are moved between molecules, the molecule that gains an electron is said to be, and the one that loses an electron is said to be. Transfer of an amino group from one molecule to the carbon skeleton of another molecule (to form a different amino acid) is called. In metabolism, reactions release energy and result in the breakdown of large biomolecules, and reactions require a net input of energy and result in the synthesis of large biomolecules. Metabolic regulation in which the last product of a metabolic pathway (the end product) accumulates and slows or stops reactions earlier in the pathway is called. List two carrier molecules that deliver high-energy electrons to the electron transport system. Explain why it is advantageous for a cell to store or secrete an enzyme in an inactive form. When bonds are broken during a chemical reaction, what are the three possible fates for the potential energy found in those bonds Match the metabolic processes with the letter of the biological theme that best describes the process: (a) biological energy use (b) compartmentation (c) molecular interactions 1. Glycolysis takes place in the cytosol; oxidative phosphorylation takes place in mitochondria. The electron transport system traps energy in a hydrogen ion concentration gradient. For two days, the patient received a slow drip of fluid into his veins directly from young coconuts suspended next to his bed. A salty taste meant that the child was destined to die of a mysterious disease that withered the flesh and robbed the breath. Today, a similar "sweat test" will be performed in a major hospital-this time, with state-of-the-art techniques-on Daniel Biller, an 18-month-old with a history of weight loss and respiratory problems. Water is essentially the only molecule that moves freely between cells and the extracellular fluid. Because of this free movement of water, the extracellular and intracellular compartments reach a state of osmotic equilibrium 5 osmos, push or thrust 6, in which the fluid concentrations are equal on the two sides of the cell membrane. Calcium (not shown in the figure) is more concentrated in the extracellular fluid than in the cytosol, although many cells store Ca2+ inside organelles such as the endoplasmic reticulum and mitochondria. Proteins and other large anions are concentrated in the plasma but cannot cross the leaky exchange epithelium of blood vessels [p. On the other hand, smaller molecules and ions such as Na+ and Cl- are small enough to pass freely between the endothelial cells and therefore have the same concentrations in plasma and interstitial fluid. The concentration differences of chemical disequilibrium are a hallmark of a living organism, as only the continual input of energy keeps the body in this state. If solutes leak across the cell membranes dividing the intracellular and extracellular compartments, energy is required to return them to the compartment they left. When cells die and cannot use energy, they obey the second law of thermodynamics [p. Many body solutes mentioned so far are ions, and for this reason we must also consider the distribution of electrical charge between the intracellular and extracellular compartments. The body as a whole is electrically neutral, but a few extra negative ions are found in the intracellular fluid, while their matching positive ions are located in the extracellular fluid. As a result, the inside of cells is slightly negative relative to the extracellular fluid. The intracellular and extracellular compartments of the body are in osmotic equilibrium, but in chemical and electrical disequilibrium. Furthermore, osmotic equilibrium and the two disequilibria are dynamic steady states. In the remainder of this chapter, we discuss these three steady states, and the role transport mechanisms and the selective permeability of cell membranes play in maintaining these states. Substances moving between the plasma and interstitial fluid must cross the leaky exchange epithelium of the capillary wall. Use your answers from the two questions above to calculate the percentage of total body water in the plasma and interstitial fluid. In clinical situations, we monitor homeostasis of various substances such as ions, blood gases, and organic solutes by taking a blood sample and analyzing its plasma. In this section, we examine the relationship between solute movement and water movement across cell membranes. Infants have relatively more water than adults, and water content decreases as people grow older than 60. In clinical practice, it is necessary to allow for the variability of body water content when prescribing drugs. Because women and older people have less body water, they will have a higher concentration of a drug in the plasma than will young men if all are given an equal dose per kilogram of body mass. The remaining third (33%) is split between the interstitial fluid (which contains about 75% of the extracellular water) and the plasma (which contains about 25% of the extracellular water). The Body Is in Osmotic Equilibrium Water is able to move freely between cells and the extracellular fluid and distributes itself until water concentrations are equal throughout the body-in other words, until the body is in a state of osmotic equilibrium. The movement of water across a membrane in response to a solute concentration gradient is called osmosis. As we look for life in distant parts of the solar system, one of the first questions scientists ask about a planet is, "Does it have water However, in human physiology we often speak of standard values for physiological functions based on "the 70-kg man. Each kilogram of water has a volume of 1 liter, so his total body water is 42 liters. Adult women have less water per kilogram of body mass than men because women have more adipose tissue. Selectively permeable membrane Glucose molecules the osmotic movement of water into compartment B is known as the osmotic pressure of solution B. The units for osmotic pressure, just as with other pressures in physiology, are atmospheres (atm) or millimeters of mercury (mm Hg). A pressure of 1 mm Hg is equivalent to the pressure exerted on a 1@cm2 area by a 1-mm-high column of mercury. In chemistry, concentrathe more concentrated increased tions are often expressed as molarity (M), which is defined solution. H2O However, using molarity to describe biological concentrations can be misleading. Because some molecules dissociate into ions when they dissolve in a solution, the number of 3 Compartment A is pure water, and compartment B is a particles in solution is not always the same as the numForce is applied to glucose solution. Water moves by osmosis in response to the total Pure water concentration of all particles in the solution. The membrane is permeable to water but does not allow (osmol/L or OsM) or, for very dilute physiological solutions, milglucose to cross. Compartment B has more solute larity, use the following equation: (glucose) per volume of solution and therefore is the more conmolarity (mol/L) * particles>molecule (osmol/mol) centrated solution. A concentration gradient across the membrane = osmolarity (osmol>L) exists for glucose. However, because the membrane is not permeable to glucose, glucose cannot move to equalize its distribution. It will move Let us look at two examples, glucose and sodium chloride, and by osmosis from compartment A, which contains the dilute glucose compare their molarities with their osmolarities. Thus, water moves to dilute the more concencreate 1 liter of solution yields a 1 molar solution (1 M). The solution to be mea1 M glucose * 1 osmole>mole glucose = 1 OsM glucose sured is placed in compartment B with pure water in compartment A. Because compartment B has a higher solute concentration than compartment A, water will flow from A to B. The pressure on the piston that exactly opposes of 2 ions per NaCl, the dissociation factor is about 1. A 1 OsM solution could be composed of pure glucose or pure Na+ and Clor a mixture of all three solutes. The normal osmolarity of the human body ranges from 280 to 296 milliosmoles per liter (mOsM). In this book, to simplify calculations, we will round that number up slightly to 300 mOsM. Because biological solutions are dilute and little of their weight comes from solute, physiologists often use the terms osmolarity and osmolality interchangeably. Because 1 liter of pure water weighs 1 kilogram, a decrease in body weight of 1 kg (or 2.