Endocrine Regulation of Reproduction

The functions of the testes and ovaries are regulated by gonadotropic hormones secreted by the anterior pituitary. The gonadotropic hormones stimulate the gonads to secrete their sex steroid hormones, and these steroid hormones, in turn, have an inhibitory effect on the secretion of the gonadotropic hormones. This interaction between the anterior pituitary and the gonads forms a negative feedback loop. The embryonic testes during the first trimester of pregnancy are active endocrine glands,...

Visual Acuity and Sensitivity

While reading or similarly viewing objects in daylight, each eye is oriented so that the image falls within a tiny area of the retina called the fovea centralis. The fovea is a pinhead-sized pit (fovea pit) within a yellow area of the retina called the macula lutea. The pit is formed as a result of the displacement of neural layers around the periphery therefore, light falls directly on photoreceptors in the center (fig. 10.41). Light falling on other areas, by contrast, must pass through...

Sexual Reproduction

Early embryonic gonads can become either testes or ovaries. A particular gene on the Y chromosome induces the embryonic gonads to become testes. Females lack a Y chromosome, and the absence of this gene causes the development of ovaries.The embryonic testes secrete testosterone, which induces the development of male accessory sex organs and external genitalia.The absence of testes (rather than the presence of ovaries) in a female embryo causes the development of the female accessory sex organs....

The Monosynaptic Stretch Reflex

Reflex contraction of skeletal muscles occurs in response to sensory input and does not depend on the activation of upper motor neurons. The reflex arc, which describes the nerve impulse pathway from sensory to motor endings in such reflexes, involves only a few synapses within the CNS. The simplest of all reflexes the muscle stretch reflex consists of only one synapse within the CNS. The sensory neuron directly synapses with the motor neuron, without involving spinal cord interneu-rons. The...

Inhibitors of Prostaglandin Synthesis

Aspirin is the most widely used member of a class of drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs). Other members of this class are indomethacin and ibuprofen. These drugs produce their effects because they specifically inhibit the cyclooxygenase enzyme that is needed for prostaglandin synthesis. Through this action, the drugs inhibit inflammation but produce some unwanted side effects, including gastric bleeding, possible kidney problems, and prolonged clotting time. It is now...

Ionic Bonds

Ionic bonds result when one or more valence electrons from one atom are completely transferred to a second atom. Thus, the electrons are not shared at all. The first atom loses electrons, so that its number of electrons becomes smaller than its number of protons it becomes positively charged. Atoms or molecules that have positive or negative charges are called ions. Positively charged ions are called cations because they move toward the negative pole, or cathode, in an electric field. The...

Endocrine Glands and Hormones

Hormones are regulatory molecules secreted into the blood by endocrine glands. Chemical categories of hormones include steroids, amines, polypeptides, and glycoproteins. Interactions between the various hormones produce effects that may be synergistic, permissive, or antagonistic. Endocrine glands lack the ducts that are present in exocrine glands (chapter 1). The endocrine glands secrete their products, which are biologically active molecules called hormones, into the blood. The blood carries...

Coupled Reactions Oxidation Reduction

When an atom or a molecule gains electrons, it is said to become reduced when it loses electrons, it is said to become oxidized. Reduction and oxidation are always coupled reactions an atom or a molecule cannot become oxidized unless it donates electrons to another, which therefore becomes reduced. The atom or molecule that donates electrons to another is a reducing agent, and the one that accepts electrons from another is an oxidizing agent. It is important to understand that a particular atom...

Osmotic Pressure

Osmosis and the movement of the membrane partition could be prevented by an opposing force. If one compartment contained 180 g L of glucose and the other compartment contained pure water, the osmosis of water into the glucose solution could be prevented by pushing against the membrane with a certain force. This concept is illustrated in figure 6.7. Interactions Between Cells and the Extracellular Environment 131 Figure 6.6 The effects of osmosis. (a) A movable selectively permeable membrane...

Gallbladder

The gallbladder is a saclike organ attached to the inferior surface of the liver. This organ stores and concentrates bile, which drains to it from the liver by way of the bile ducts, hepatic ducts, and cystic duct, respectively. A sphincter valve at the neck of the gallbladder allows a 35- to 100-ml storage capacity. When the gallbladder fills with bile, it expands to the size and shape of a small pear. Bile is a yellowish green fluid containing bile salts, bilirubin, cholesterol, and other...

Acetylcholine in the CNS

There are many cholinergic neurons (those that use ACh as a neurotransmitter) in the CNS, where the axon terminals of one neuron typically synapse with the dendrites or cell body of another. The dendrites and cell body thus serve as the receptive area of the neuron, and it is in these regions that receptor proteins for neurotransmitters and chemically regulated gated channels are located. The first voltage-regulated gated channels are located at the axon hillock, a cone-shaped elevation on the...

Adenylate Cyclase Cyclic AMP Second Messenger System

Cyclic adenosine monophosphate (abbreviated cAMP) was the first second messenger to be discovered and is the best understood. When epinephrine and norepinephrine bind to their P-adrenergic receptors (chapter 9), the effects of these hormones are due to cAMP production within the target cells. It was later discovered that the effects of many (but not all) polypeptide and glycoprotein hormones are also mediated by cAMP. When one of these hormones binds to its receptor protein, it causes the...

Myelin Sheath in CNS

As mentioned earlier, the myelin sheaths of the CNS are formed by oligodendrocytes. This process occurs mostly postnatally (after birth). Unlike a Schwann cell, which forms a myelin sheath around only one axon, each oligodendrocyte has extensions, like the tentacles of an octopus, that form myelin sheaths around several axons (fig. 7.8). The myelin sheaths around axons of the CNS give this tissue a white color areas of the CNS that contain a high concentration of axons thus form the white...

Cross Bridges

Sliding of the filaments is produced by the action of numerous cross bridges that extend out from the myosin toward the actin. These cross bridges are part of the myosin proteins that extend from the axis of the thick filaments to form arms that terminate in globular heads (fig. 12.10). A myosin protein has two globular heads that serve as cross bridges. The orientation of the myosin heads on one side of a sarcomere is opposite to that of Figure 12.9 The sliding filament model of muscle...

Test Your Ability to Analyze and Apply Your Knowledge

A friend, wanting to lose weight, eliminates all fat from her diet. How would this help her to lose weight Could she possibly gain weight on this diet How Discuss the health consequences of such a diet. Suppose a drug is developed that promotes the channeling of H+ out of the intermembrane space into the matrix of the mitochondria of adipose cells. How could this drug affect the production of ATP, body temperature, and body weight For many years, the total number of molecules of ATP produced...

Lung Volumes and Capacities

An example of a spirogram is shown in figure 16.16, and the various lung volumes and capacities are defined in table 16.3. A lung capacity is equal to the sum of two or more lung volumes. During quiet breathing, for example, the amount of air expired in each breath is the tidal volume. The maximum amount of air that can be forcefully exhaled after a maximum inhalation is called the vital capacity, which is equal to the sum of the inspiratory reserve volume, tidal volume, and expiratory reserve...

Effects of Urea

Countercurrent multiplication of the NaCl concentration is the mechanism that contributes most to the hypertonicity of the interstitial fluid in the medulla. However, urea, a waste product of amino acid metabolism (chapter 5 see fig. 5.15), also contributes significantly to the total osmolality of the interstitial fluid. The role of urea was inferred from experimental evidence showing that active transport of Na+ occurs only in the thick segments of the ascending limbs. The thin segments of the...

Law of Specific Nerve Energies

Stimulation of a sensory nerve fiber produces only one sensation touch, cold, pain, and so on. According to the law of specific nerve energies, the sensation characteristic of each sensory neuron is that produced by its normal stimulus, or adequate stimulus (table 10.1). Also, although a variety of different stimuli may activate a receptor, the adequate stimulus requires the least amount of energy to do so. The adequate stimulus for the photoreceptors of the eye, for example, is light, where a...

Coupled Reactions ATP

In order to remain alive, a cell must maintain its highly organized, low-entropy state at the expense of free energy in its environment. Accordingly, the cell contains many enzymes that catalyze exergonic reactions using substrates that come ultimately from the environment. The energy released by these exergonic reactions is used to drive the energy-requiring processes (endergonic reactions) in the cell. Since cells cannot use heat energy to drive energy-requiring processes, the chemical-bond...

Slow and Fast Twitch Fibers

Skeletal muscle fibers can be divided on the basis of their contraction speed (time required to reach maximum tension) into slow-twitch, or type I, fibers, and fast-twitch, or type II, fibers. These differences are associated with different myosin ATPase isoenzymes, which can also be designated as slow and fast. The two fiber types can be distinguished by their ATPase isoenzyme when they are appropriately stained (fig. 12.23). The extraocular muscles that position the eyes, for example, have a...

Bulk Transport

Polypeptides and proteins, as well as many other molecules, are too large to be transported through a membrane by the carriers described in previous sections. Yet many cells do secrete these molecules for example, as hormones or neurotransmitters by the process of exocytosis. As described in chapter 3, this involves the fusion of a membrane-bound vesicle that contains these cellular products with the plasma membrane, so that the membranes become continuous (fig. 6.20). The process of...

Metabolism of Skeletal Muscles

Skeletal muscles respire anaerobically for the first 45 to 90 seconds of moderate-to-heavy exercises because the cardiopulmonary system requires this amount of time to sufficiently increase the oxygen supply to the exercising muscles. If exercise is moderate, aerobic 1. Explain how graded contractions and smooth, sustained contractions can be produced in vitro and in vivo. 2. Distinguish among isotonic, isometric, and eccentric contractions, and describe what factors determine if a contraction...

Hypovolemic Shock

The term hypovolemic shock refers to circulatory shock that is due to low blood volume, as might be caused by hemorrhage (bleeding), dehydration, or burns. This is accompanied by Decreased pulse pressure Increased diastolic pressure Increased pH (alkalosis) due to hyperventilation Decreased pH (acidosis) due to metabolic acids Slight restlessness occasionally warm, dry skin Cold, clammy skin cloudy senses Source From Principles and Techniques of Critical Care, Vol. 1, edited by R. F. Wilson....

Sodium Reabsorption

Although 90 of the filtered sodium is reabsorbed in the early region of the nephron, the amount left in the filtrate delivered to the distal convoluted tubule is still quite large. In the absence of aldosterone, 80 of this remaining amount is reabsorbed through the wall of the tubule into the peritubular blood this represents 8 of the amount filtered. The amount of sodium excreted without aldosterone is thus 2 of the amount filtered. Although this percentage seems small, the actual amount it...

Test Your Knowledge ofTerms and Facts

Which of these offers a nonspecific defense against viral infection Match the cell type with its secretion. 2. killer T cells a. antibodies 4. plasma cells c. lysosomal enzymes 6. Which of these statements about the Fab portion of antibodies is true b. Its amino acid sequences are variable. c. It consists of both H and L chains. 7. Which of these statements about complement proteins C3a and C5a a. They are released during the complement fixation process. b. They stimulate chemotaxis of...

Test Your Understanding of Concepts and Principles

Using the concept of motor units, explain how skeletal muscles in vivo produce graded and sustained contractions.1 2. Describe how an isometric contraction can be converted into an isotonic contraction using the concepts of motor unit recruitment and the series-elastic component of muscles. 3. Trace the sequence of events in which the cross bridges attach to the thin filaments when a muscle is stimulated by a nerve. Why don't the cross bridges attach to the thin filaments when a muscle is...

Length Tension Relationship

The strength of a muscle's contraction is influenced by a variety of factors. These include the number of fibers within the muscle that are stimulated to contract, the frequency of stimulation, the thickness of each muscle fiber (thicker fibers have more myofibrils and thus can exert more power), and the initial length of the muscle fibers when they are at rest. There is an ideal resting length for striated muscle fibers. This is the length at which they can generate maximum force. When the...

Muscle Relaxation

As long as action potentials continue to be produced which is as long as neural simulation of the muscle is maintained the Ca2+ release channels in the sarcoplasmic reticulum will remain open, Ca2+ will passively diffuse out of the sarcoplasmic reticu-lum, and the Ca2+ concentration of the sarcoplasm will remain high. Thus, Ca2+ will remain attached to troponin, and the cross-bridge cycle will continue to maintain contraction. To stop this action, the production of action potentials must cease,...

Ventilation During Exercise

As soon as a person begins to exercise, breathing becomes deeper and more rapid to produce a total minute volume that is many times the resting value. This increased ventilation, particularly in well-trained athletes, is exquisitely matched to the simultaneous increase in oxygen consumption and carbon dioxide production by the exercising muscles. The arterial blood PO2, P 2, and pH thus remain surprisingly constant during exercise (fig. 16.41). It is tempting to suppose that ventilation...

Superior Colliculus and Eye Movements

Neural pathways from the superior colliculus to motor neurons in the spinal cord help mediate the startle response to the sight of an unexpected intruder. Other nerve fibers from the superior colliculus stimulate the extrinsic eye muscles, which are the striated muscles that move the eyes. Figure 10.44 The striate cortex (area 17) and the visual association areas (18 and 19). Neural communication between the striate cortex, the visual association areas, and other brain regions is required for...

Buffers

A buffer is a system of molecules and ions that acts to prevent changes in H+ concentration and thus serves to stabilize the pH of a solution. In blood plasma, for example, the pH is stabilized by the following reversible reaction involving the bicarbonate ion (HCO3-) and carbonic acid (H2CO3) The double arrows indicate that the reaction could go either to the right or to the left the net direction depends on the concentration of molecules and ions on each side. If an acid (such as lactic acid)...

Wwwmhhecomfox8

Summary 278 Review Activities 281 Related Websites 282 Ed is a 45-year-old man who goes to the doctor complaining of severe ear pain and reduced hearing immediately after disembarking from an international flight. It is apparent that Ed has a bad head cold, and the doctor recommends that he take a decon-gestant. He further recommends that Ed come back after the cold is better for an audiology test, if his hearing has not improved by then.While talking to the doctor, Ed complains that he can't...

Regulatory Functions of Adipose Tissue

It is difficult for a person to lose (or gain) weight, many scientists believe, because the body has negative feedback loops that act to defend a particular body weight, or more accurately, the amount of adipose tissue. This regulatory system has been called an adipostat. When a person eats more than is needed to maintain the set point of adipose tissue, the person's metabolic rate increases and hunger decreases, as previously described. Homeostasis of body weight implies negative feedback...

Fetal Hemoglobin

The effects of 2,3-DPG are also important in the transfer of oxygen from maternal to fetal blood. In an adult, hemoglobin molecules are composed of two alpha and two beta chains as previously described, whereas fetal hemoglobin has two gamma chains in place of the beta chains (gamma chains differ from beta chains in thirty-seven of their amino acids). Normal adult hemoglobin in the mother (hemoglobin A) is able to bind to 2,3-DPG. Fetal hemoglobin, or hemoglobin F, by contrast, cannot bind to...

Hindbrain

The rhombencephalon, or hindbrain, is composed of two regions the metencephalon and the myelencephalon. Each of these regions will be discussed separately. The metencephalon is composed of the pons and the cerebellum. The pons can be seen as a rounded bulge on the underside of the brain, between the midbrain and the medulla oblongata (fig. 8.19). Surface fibers in the pons connect to the cerebellum, and deeper fibers are part of motor and sensory tracts that pass from the medulla oblongata,...

Knowledge

Are her symptoms typical of this disorder, and what type of treatment will the doctor most likely prescribe Your friend Bud has the talent to be a star basketball center if only he weren't five foot eight. Since you're a good friend, you start injecting him with growth hormone as he sleeps each night. You think this is a clever strategy, but after a time you notice that he hasn't grown an inch. Instead, his jaw and forehead seem to have 15. Human chorionic gonadotropin (hCG) is secreted by 16....

Review Activities

Test Your Knowledge of Terms and Facts 1. Which of these statements about the precentral gyrus is true a. It is involved in motor control. b. It is involved in sensory 6 perception. It is located in the frontal lobe. Both a and c are true. Both b and c are true. In most people, the right hemisphere controls movement of a. the right side of the body primarily. b. the left side of the body primarily. c. both the right and left sides of the body equally. 3. Which of these statements about the...

And Growth Hormone

Epinephrine,the glucocorticoids, thyroxine, and growth hormone stimulate the catabolism of carbohydrates and lipids.These hormones are thus antagonistic to insulin in their regulation of carbohydrate and lipid metabolism.Thyroxine and growth hormone promote protein synthesis, however, and are needed for body growth and proper development of the central nervous system.The stimulatory effect of these hormones on protein synthesis is complementary to that of insulin. The anabolic effects of...

Transport Process Affecting Renal Clearance

Reneal clearance refers to the ability of the kidneys to remove molecules from the blood plasma by excreting them in the urine. Molecules and ions dissolved in the plasma can be filtered through the glomerular capillaries and enter the glomerular capsules. Then, those that are not reabsorbed will be eliminated in the urine they will be cleared from the blood. The process of filtration, a type of bulk transport through capillaries, promotes renal clearance. The process of reabsorption involving...

Cerebral Cortex

The cerebrum consists of an outer cerebral cortex, composed of 2 to 4 mm of gray matter and underlying white matter. The cerebral cortex is characterized by numerous folds and grooves called convolutions. The elevated folds of the convolutions are called gyri, and the depressed grooves are the sulci. Each cerebral hemisphere is subdivided by deep sulci, or fissures, into five lobes, four of which are visible from the surface (fig. 8.6). These lobes are the frontal, parietal, temporal, and...

Summary

Skeletal muscles are attached to bones by tendons. A. Skeletal muscles are composed of separate cells, or fibers, that are attached in parallel to the tendons. B. Individual muscle fibers are covered by the endomysium bundles of fibers, called fascicles, are covered by the perimysium and the entire muscle is covered by the epimysium. C. Skeletal muscle fibers are striated. 1. The dark striations are called A bands, and the light regions are called I bands. 2. Z lines are located in the...

Disorders Caused by High Partial Pressures of Gases

The total atmospheric pressure increases by one atmosphere (760 mmHg) for every 10 m (33 ft) below sea level. If a diver descends 10 meters below sea level, therefore, the partial pressures and amounts of dissolved gases in the plasma will be twice those values at sea level. At 20 meters, they are three times, and at 30 meters they are four times the values at sea level. The increased amounts of nitrogen and oxygen dissolved in the blood plasma under these conditions can have serious effects on...

Calculation of PO2

With increasing altitude, the total atmospheric pressure and the partial pressure of the constituent gases decrease (table 16.5). At Denver, for example (5,000 feet above sea level), the atmospheric pressure is decreased to 619 mmHg, and the PO2 is therefore reduced to 619 x 0.21 130 mmHg. At the peak of Mount Everest (at 29,000 feet), the PO2 is only 42 mmHg. As one descends below sea level, as in ocean diving, the total pressure increases by one atmosphere for every 33 feet. At 33 feet...

Blood Gas Measurements

Measurement of the oxygen content of blood (in ml O2 per 100 ml blood) is a laborious procedure. Fortunately, an oxygen electrode that produces an electric current in proportion to the concentration of dissolved oxygen has been developed. If this electrode is placed in a fluid while oxygen is artificially bubbled into it, the current produced by the oxygen electrode will in Effect of Altitude on Partial Oxygen Pressure (Po2) Figure 16.21 The relationship between alveoli and blood vessels. The...

Venous Return

Length of muscle (as percent of optimum at 100 ) Length of muscle (as percent of optimum at 100 ) Figure 14.4 The effect of muscle length and epinephrine on contraction strength. In this schematic comparison, all three curves demonstrate that each muscle contracts with its maximum force (100 relative tension) at its own optimum length (100 optimum length). As the length is decreased from optimum, each curve demonstrates a decreased contraction strength. Notice that the decline is steeper for...

Endergonic and Exergonic Reactions

Chemical reactions that require an input of energy are known as endergonic reactions. Since energy is added to make these reactions go, the products of endergonic reactions must contain more free energy than the reactants. A portion of the energy added, in other words, is contained within the product molecules. This follows from the fact that energy cannot be created or destroyed (first law of thermodynamics) and from the fact that a more-organized state of matter contains more free energy, or...

Glycolysis and the Lactic Acid Pathway

In cellular respiration, energy is released by the stepwise breakdown of glucose and other molecules, and some of this energy is used to produce ATP The complete combustion of glucose requires the presence of oxygen and yields thirty ATP for each molecule of glucose. However, some energy can be obtained in the absence of oxygen by the pathway that leads to the production of lactic acid. This process results in a net gain of two ATP per glucose. All of the reactions in the body that involve...

Red Blood Cell Antigens and Blood Typing

There are certain molecules on the surfaces of all cells in the body that can be recognized as foreign by the immune system of another individual. These molecules are known as antigens. As part of the immune response, particular lymphocytes secrete a class of proteins called antibodies that bond in a specific fashion with antigens. The specificity of antibodies for antigens is analogous to the specificity of enzymes for their substrates, and of receptor proteins for neurotransmitters and...

The Sodium Potassium Pump

Primary active transport carriers are often referred to as pumps. Although some of these carriers transport only one molecule or ion at a time, others exchange one molecule or ion for another. The most important of the latter type of carrier is the Na+ K+ pump. This carrier protein, which is also an ATPase enzyme that converts ATP to ADP and Pi, actively extrudes three sodium ions (Na+) from the cell as it transports two potassium ions (K+) into the cell. This transport is energy dependent...

Hematopoiesis

Blood cells are constantly formed through a process called hematopoiesis (also called hemopoiesis). The hematopoietic stem cells those that give rise to blood cells originate in the yolk sac of the human embryo and then migrate to the liver. Hematopoiesis thus occurs in the liver of the fetus. The stem cells then migrate to the bone marrow, and shortly after birth the liver ceases to be a source of blood cell production. The term erythropoiesis refers to the formation of erythrocytes, and...

Cardiac and Smooth Muscles

Cardiac muscle, like skeletal muscle, is striated and contains sarcomeres that shorten by sliding of thin and thick filaments. But while skeletal muscle requires nervous stimulation to contract, cardiac muscle can produce impulses and contract spontaneously. Smooth muscles lack sarcomeres, but they do contain actin and myosin that produce contractions in response to a unique regulatory mechanism. Figure 12.31 Myocardial cells are interconnected by gap junctions. The gap junctions are...

Test Your Knowledge ofTerms and I

The movement of water across a plasma membrane occurs by 2. Which of these statements about the facilitated diffusion of glucose is true a There is a net movement from the region of lower to the region of higher concentration. b. Carrier proteins in the cell membrane are required for this transport. c. This transport requires energy obtained from ATP. d. It is an example of cotransport. 3. If a poison such as cyanide stopped the production of ATP, which of the following transport processes...

Lymphatic System

Lymphatic vessels absorb excess interstitial fluid and transport this fluid now called lymph to ducts that drain into veins. Lymph nodes, and lymphoid tissue in the thymus, spleen, and tonsils produce lymphocytes, which are white blood cells involved in immunity. The lymphatic system has three basic functions (1) it transports interstitial (tissue) fluid, initially formed as a blood filtrate, back to the blood (2) it transports absorbed fat from the small intestine to the blood and (3) its...

Intrapulmonary and Intrapleural Pressures

The visceral and parietal pleurae are normally flush against each other, so that the lungs are stuck to the chest wall in the same manner as two wet pieces of glass sticking to each other. The in-trapleural space contains only a film of fluid secreted by the two membranes. The pleural cavity in a healthy person is thus potential rather than real it can become real only in abnormal situations when air enters the intrapleural space. Since the lungs normally remain in contact with the chest wall,...

Digestion of Lipids

The emulsification of fat aids digestion because the smaller and more numerous emulsification droplets present a greater surface area than the unemulsified fat droplets that originally entered the duodenum. Fat digestion occurs at the surface of the droplets through the enzymatic action of pancreatic lipase, which is aided in its action by a protein called colipase (also secreted by the pancreas) that coats the emulsification droplets and anchors the lipase enzyme to them. Through hydrolysis,...

Medulla Oblongata and Pons

A loose aggregation of neurons in the reticular formation of the medulla oblongata forms the rhythmicity center that controls automatic breathing. The rhythmicity center consists of interacting pools of neurons that fire either during inspiration (inspira-tory, or I, neurons) or expiration (expiratory, or E, neurons). The I neurons project to and stimulate spinal motoneurons that innervate the respiratory muscles. Expiration is a passive process that occurs when the I neurons are inhibited,...

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Cable properties, of neurons, 164 165 Caffeine, as phosphodiesterase inhibitor, 296 Cajal, interstitial cells of, 571, 572 balance, regulation of, 623-628, 623t channels for blockers of, 357 for hypertension, 437t in excitation-contraction coupling, 336 fast, 385 slow, 385 voltage-regulated, 168-169 in hormone action, 296, 297 , 298t in muscle contraction skeletal, 336, 337 smooth, 356, 357 and muscle relaxation, 338 as plasma clotting factor, 375t recommended dietary allowance for, 601 t...

Renal Blood Vessels

Arterial blood enters the kidney through the renal artery, which divides into interlobar arteries (fig. 17.4) that pass between the pyramids through the renal columns. Arcuate arteries branch from the interlobar arteries at the boundary of the cortex and medulla. A number of interlobular arteries radiate from the arcuate arteries into the cortex and subdivide into numerous afferent arterioles (fig. 17.5), which are microscopic. The afferent arterioles deliver blood into glomeruli capillary...

Hypothalamus and Pituitary Gland

The hypothalamus is the most inferior portion of the dien-cephalon. Located below the thalamus, it forms the floor and part of the lateral walls of the third ventricle. This small but extremely important brain region contains neural centers for hunger and thirst and for the regulation of body temperature and hormone secretion from the pituitary gland (fig. 8.17). In addition, centers in the hypothalamus contribute to the regulation of sleep, wakefulness, sexual arousal and performance, and such...

Inspiration and Expiration

Between the bony portions of the rib cage are two layers of intercostal muscles the external intercostal muscles and the internal intercostal muscles (fig. 16.14). Between the costal cartilages, however, there is only one muscle layer, and its fibers are oriented in a manner similar to those of the internal inter-costals. These muscles are therefore called the interchondral part of the internal intercostals. Another name for them is the parasternal intercostals. An unforced, or quiet,...

Muscle Spindle Apparatus

In order for the nervous system to control skeletal movements properly, it must receive continuous sensory feedback information concerning the effects of its actions. This sensory information includes (1) the tension that the muscle exerts on its tendons, provided by the Golgi tendon organs, and (2) muscle length, provided by the muscle spindle apparatus. The spindle apparatus, so called because it is wider in the center and tapers toward the ends, functions as a length detector. Muscles that...

Molarity and Molality

Glucose is a monosaccharide with a molecular weight of 180 (the sum of its atomic weights). Sucrose is a disaccharide of glucose and fructose, which have molecular weights of 180 each. When glucose and fructose join together by dehydration synthesis to form sucrose, a molecule of water (molecular weight 18) is split off. Therefore, sucrose has a molecular weight of 342 (180 + 180 - 18). Since the molecular weights of sucrose and glucose are in a ratio of 342 180, it follows that 342 grams of...

Small Intestine

The mucosa of the small intestine is folded into villi that project into the lumen. In addition, the cells that line these villi have foldings of their plasma membrane called microvilli. This arrangement greatly increases the surface area for absorption. It also improves digestion, since the digestive enzymes of the small intestine are embedded within the plasma membrane of the microvilli. The small intestine (fig. 18.10) is that portion of the GI tract between the pyloric sphincter of the...

Twitch Summation and Tetanus

When the muscle is stimulated with a single electric shock of sufficient voltage, it quickly contracts and relaxes. This response is called a twitch. Increasing the stimulus voltage increases the strength of the twitch, up to a maximum. The strength of a muscle contraction can thus be graded, or varied an obvious requirement for the proper control of skeletal movements. If a second electric shock is delivered immediately after the first, it will produce a second twitch that may partially ride...

Spiral Organ Organ of Corti

The sensory hair cells are located on the basilar membrane, with their hairs (actually stereocilia) projecting into the endolymph of the cochlear duct. These hair cells are arranged to form one row of inner cells, which extends the length of the basilar membrane, and multiple rows of outer hair cells three rows in the basal turn, four in the middle turn, and five in the apical turn of the cochlea (fig. 10.21). The stereocilia of the outer hair cells are embedded in a gelatinous tectorial...

Pressure Changes During the Cardiac Cycle

When the heart is in diastole, pressure in the systemic arteries averages about 80 mmHg (millimeters of mercury). These events in the cardiac cycle then occur 1. As the ventricles begin their contraction, the intraventricular pressure rises, causing the AV valves to snap shut. At this time, the ventricles are neither being filled with blood (because the AV valves are closed) nor ejecting blood (because the intraventricular pressure has not risen sufficiently to open the semilunar valves). This...

Aerobic Respiration

In the aerobic respiration of glucose, pyruvic acid is formed by glycolysis and then converted into acetyl coenzyme A. This begins a cyclic metabolic pathway called the Krebs cycle. As a result of these pathways, a large amount of reduced NAD and FAD (NADH and FADH2) is generated. These reduced coenzymes provide electrons for an energy-generating process that drives the formation of ATP Aerobic respiration is equivalent to combustion in terms of its final products (CO2 and H2O) and in terms of...

Pepsin and Hydrochloric Acid Secretion

The parietal cells secrete H+, at a pH as low as 0.8, into the gastric lumen by primary active transport (involving carriers that function as an ATPase). These carriers, known as H+ K+ ATPase pumps, transport H+ uphill against a million-to-one concentration gradient into the lumen of the stomach while they transport K+ in the opposite direction (fig. 18.8). At the same time, the parietal cell's basolateral membrane (facing the blood in capillaries of the lamina propria) take in Cl-against its...

D

See Diacylglycerol Dale, Henry, 7t Dalton's law, 493 Dark adaptation, 269-270 Dark current, 271, 271 Data, reproducible, 4 Deacetylation, 62, 63 Dead space, anatomical, 491 Deafness conduction, 257, 260-261 sensorineural, 260 Deamination, oxidative, 117-118, 118 Decidua basalis, 670 Decidual reaction, 670 Decompression sickness, 499 Decussation, 197 Dedifferentiation, 468 Defecation, 574 Defecation reflex, 574 Defense mechanisms, 446-453. See also Immunity...

Electrical Activity of the Heart and the Electrocardiogram

The pacemaker region of the heart (SA node) exhibits a spontaneous depolarization that causes action potentials, resulting in the automatic beating of the heart.Electrical impulses are conducted by myocardial cells in the atria and are transmitted to the ventricles by specialized conducting tissue.Electrocardiogram waves correspond to the electrical events in the heart as follows P wave (depolarization of the atria) QRS wave (depolarization of the ventricles) and T wave (repolarization of the...

Categories of Transport Across the Plasma Membrane

The plasma (cell) membrane separates the intracellular environment from the extracellular environment. Molecules that move from the blood to the interstitial fluid, or molecules that move within the interstitial fluid between different cells, must eventually come into contact with the plasma membrane surrounding the cells. Some of these molecules may be able to penetrate the membrane, while others may not. Similarly, some intracellular molecules can penetrate, or permeate, the plasma membrane...

Take Advantage of the Technology

Visit the Online Learning Center for these additional study resources. Summary 554 Review Activities 555 Related Websites 557 Summary 554 Review Activities 555 Related Websites 557 Fox Human Physiology, I 17. Physiology of the I Text I I The McGraw-Hill Eighth Edition Kidneys Companies, 2003 Emily, a high school senior, visits her family physician complaining of pain in her lower back, somewhere between the twelfth rib and the lumbar vertebrae. Her urine is noticeably discolored, and urinalysis...

Test Your Knowledge of Terms and Facts

Which of these statements about the 7 a. They are located in the medulla. c. They contain collecting ducts. d. They empty urine into the calyces. Match these 8 proximal tubule descending limb of loop ascending limb of loop distal tubule medullary collecting duct 2. Active transport of sodium water follows passively 3. Active transport sodium water impermeable to water 4. Passively permeable to water only 5. Passively permeable to water and urea 6. Antidiuretic hormone promotes the retention of...

T

After studying this chapter, you should be able to . 1. define cardiac output and explain how it is calculated. 2. explain how autonomic nerves regulate cardiac rate and the strength of ventricular contraction. 3. explain the intrinsic regulation of stroke volume (the Frank-Starling Law of the Heart). 4. list the factors that affect the venous return of blood to the heart. 5. explain how interstitial fluid is formed and how it is returned to the capillary blood. 6. describe the conditions that...

Accommodation

Ciliary Muscle

When a normal eye views an object, parallel rays of light are refracted to a point, or focus, on the retina (see fig. 10.34). If the degree of refraction remained constant, movement of the object closer to or farther from the eye would cause corresponding movement of the focal point, so that the focus would either be behind or in front of the retina. The ability of the eyes to keep the image focused on the retina as the distance between the eyes and object varies is called accommodation....

Astigmatism

Because the curvature of the cornea and lens is not perfectly symmetrical, light passing through some parts of these structures may be refracted to a different degree than light passing through other parts. When the asymmetry of the cornea and or lens is significant, the person is said to have astigmatism. If a person with astigmatism views a circle of lines radiating from the center, like the spokes of a wheel, the image of these lines will not appear clear in all 360 degrees. The parts of the...

Chapter at a Glance

Structure of Skeletal Muscles Motor Units 328 Sliding Filament Theory of Contraction 331 Cross Bridges 333 Regulation of Contraction 335 Role of Ca2+ in Muscle Contraction 336 Excitation-Contraction Coupling 336 Muscle Relaxation 338 Contractions of Skeletal Muscles 340 Treppe 340 Isotonic, Isometric, and Eccentric Contractions 340 Series-Elastic Component 341 Length-Tension Relationship 341 Energy Requirements of Skeletal Muscles 342 Metabolism of Skeletal Muscles 342 Maximal Oxygen Uptake 343...

Lactic Acid Pathway

In order for glycolysis to continue, there must be adequate amounts of NAD available to accept hydrogen atoms. Therefore, the NADH produced in glycolysis must become oxidized by donating its electrons to another molecule. (In aerobic respiration this other molecule is located in the mitochondria and ultimately passes its electrons to oxygen.) When oxygen is not available in sufficient amounts, the NADH (+ H+) produced in glycolysis is oxidized in the cytoplasm by donating its electrons to...

Immunotherapy for Cancer

The production of human interferons by genetically engineered bacteria has made large amounts of these substances available for the experimental treatment of cancer. Thus far, interferons have proven to be a useful addition to the treatment of particular forms of cancer, including some types of lymphomas, renal carcinoma, melanoma, Kaposi's sarcoma, and breast cancer. They have not, however, proved to be the magic bullet against cancer (a term coined by Paul Ehrlich) as had previously been...

Ion Gating in Axons

The changes in membrane potential just described depolarization, repolarization, and hyperpolarization are caused by changes in the net flow of ions through ion channels in the membrane. Ions such as Na+, K+, and others pass through ion channels in the plasma membrane that are said to be gated channels. The gates are part of the proteins that comprise the channels, and can open or close the ion channels in response to particular changes. When ion channels are closed, the plasma membrane is less...

Female Reproductive System

Vulva Woman External Sex Organs

The ovaries contain a large number of follicles, each of which encloses an ovum. Some of these follicles mature during the ovarian cycle, and the ova they contain progress to the secondary oocyte stage of meiosis. At ovulation, the largest follicle breaks open to extrude a secondary oocyte from the ovary. The empty follicle then becomes a corpus luteum, which ultimately degenerates at the end of a nonfertile cycle. The two ovaries (fig. 20.25), about the size and shape of large almonds, are...

Menstrual Cycle

Cyclic changes in the secretion of gonadotropic hormones from the anterior pituitary cause the ovarian changes during a monthly cycle. The ovarian cycle is accompanied by cyclic changes in the secretion of estradiol and progesterone, which interact with the hypothalamus and pituitary to regulate gonadotropin secretion.The cyclic changes in ovarian hormone secretion also cause changes in the endometrium of the uterus during a menstrual cycle. Humans, apes, and Old-World monkeys have cycles of...

P

Pacemaker The group of cells that has the fastest spontaneous rate of depolarization and contraction in a mass of electrically coupled cells in the heart, this is the sinoatrial, or SA, node. pacesetter potentials Changes in membrane potential produced spontaneously by pacemaker cells of single-unit smooth muscles. pacinian corpuscle (pa-sin' e-an kor'pus'l) A cutaneous sensory receptor sensitive to pressure. It is characterized by an onionlike layering of cells around a central sensory...

Myopia and Hyperopia

When a person with normal visual acuity stands 20 feet from a Snellen eye chart (so that accommodation is not a factor influencing acuity), the line of letters marked 20 20 can be read. If a person has myopia (nearsightedness), this line will appear blurred because the image will be brought to a focus in front of the retina. This is usually due to the fact that the eyeball is too long. Myopia is corrected by glasses with concave lenses that cause the light rays to diverge, so that the point of...

Functions of the Endoplasmic Reticulum and Golgi Complex

Proteins that are to be used within the cell are likely to be produced by polyribosomes that float freely in the cytoplasm, unattached to other organelles. If the protein is to be secreted by the cell, however, it is made by mRNA-ribosome complexes that are located on the granular endoplasmic reticulum. The membranes of this system enclose fluid-filled spaces called cis-ternae, into which the newly formed proteins may enter. Once in the cisternae, the structure of these proteins is modified in...

Nephron Tubules

The tubular portion of a nephron consists of a glomerular capsule, a proximal convoluted tubule, a descending limb of the loop of Henle, an ascending limb of the loop of Henle, and a distal convoluted tubule (fig. 17.5). The glomerular (Bowman's) capsule surrounds the glomerulus. The glomerular capsule and its associated glomerulus are located in the cortex of the kidney and together constitute the renal corpuscle. The glomerular capsule contains an inner visceral layer of epithelium around the...

Electron Transport and Oxidative Phosphorylation

Built into the foldings, or cristae, of the inner mitochondrial membrane are a series of molecules that serve as an electron-transport system during aerobic respiration. This electron-transport chain of molecules consists of a protein containing flavin mononucleotide (abbreviated FMN and derived from the vitamin riboflavin), coenzyme Q, and a group of iron-containing pigments called cytochromes. The last of these cytochromes is cytochrome a3, which donates electrons to oxygen in the final...

Principles

Explain how the structure of the 8. epithelial wall of the proximal tubule and the distribution of Na+ K+ pumps contribute to the ability of the proximal 9. Describe how the thiazide diuretics, loop diuretics, and osmotic diuretics work. How do these substances cause 10. Which diuretic drugs do not produce hypokalemia How do these drugs work What happens to urinary bicarbonate excretion when a person hyperventilates How might this response be helpful Describe the location of the macula densa...

Chapter Review Pages Summarize and Challenge

At the end of each chapter, the material is summarized in outline form. This outline summary is organized by major section headings with page references, followed by the key points in the section. Students may read the summary after studying the chapter to be sure that they haven't missed any points, and can use the chapter summaries to help review for examinations. I. Physiology is the study of how cells, tissues, and organs function. A. In the study of physiology, cause-and-effect sequences...

Congestive Heart Failure

Cardiac failure occurs when the cardiac output is insufficient to maintain the blood flow required by the body. This may be due to heart disease resulting from myocardial infarction or congenital defects or to hypertension, which increases the after-load of the heart. The most common causes of left ventricular heart failure are myocardial infarction, aortic valve stenosis, and incompetence of the aortic and bicuspid (mitral) valves. Failure of the right ventricle is usually caused by prior...

Hormonal Regulation of Metabolism

The absorption of energy carriers from the intestine is not continuous it rises to high levels over a 4-hour period following each meal (the absorptive state) and tapers toward zero between meals, after each absorptive state has ended (the postabsorptive, or fasting, state). Despite this fluctuation, the plasma concentration of glucose and other energy substrates does not remain high during periods of absorption, nor it does normally fall below a certain level during periods of fasting. During...

Pulmonary Circulation and Ventilation Perfusion Ratios

In a fetus, the pulmonary circulation has a high vascular resistance because the lungs are partially collapsed. This high vascular resistance helps to shunt blood from the right to the left atrium through the foramen ovale, and from the pulmonary ar tery to the aorta through the ductus arteriosus (described in chapter 13). After birth, the foramen ovale and ductus arteriosus close, and the vascular resistance of the pulmonary circulation falls sharply. This fall in vascular resistance at birth...

Negative Feedback Loops

The concept of homeostasis has been of immense value in the study of physiology because it allows diverse regulatory mechanisms to be understood in terms of their why as well as their how. The concept of homeostasis also provides a major foundation for medical diagnostic procedures. When a particular measurement of the internal environment, such as a blood measurement (table 1.2), deviates significantly from the normal range of values, it can be concluded that homeostasis is not being...

Gastritis and Peptic Ulcers

Peptic ulcers are erosions of the mucous membranes of the stomach or duodenum produced by the action of HCl. In Zollinger-Ellison syndrome, ulcers of the duodenum are produced by excessive gastric acid secretion in response to very high levels of the hormone gastrin. Gastrin is normally produced by the stomach but, in this case, it may be secreted by a pancreatic tumor. This is a rare condition, but it does demonstrate that excessive gastric acid can cause ulcers of the duodenum. Ulcers of the...

Killer Helper and Suppressor T Lymphocytes

The killer, or cytotoxic, T lymphocytes can be identified in the laboratory by a surface molecule called CD8. Their function is to destroy body cells that harbor foreign molecules. These are usually molecules from an invading microorganism, but they can also be molecules produced by the cell's genome because of a malignant transformation, or they may simply be body molecules that had never been presented before to the immune system. In contrast to the action of B lymphocytes, which kill at a...

Caloric Expenditures

The caloric energy expenditure of the body has three components 1. Basal metabolic rate (BMR) is the energy expenditure of a relaxed, resting person who is at a neutral ambient temperature (about 28 C) and who has not eaten in 8 to 12 hours. This comprises the majority (about 60 ) of the total calorie expenditure in an average adult. 2. Adaptive thermogenesis is the heat energy expended in response to (a) changes in ambient temperature and (b) the digestion and absorption of food. This...

E

Eccentric (ek-sen trik) contraction A muscle contraction in which the muscle lengthens despite its contraction, due to a greater external stretching force applied to it. The contraction in this case can serve a shock absorbing function, for example, when the quadriceps muscles of the leg contract eccentrically upon landing when a person jumps from a heighth. ECG Electrocardiogram (e-lekk'tro-ka de-o-gram) (also abbreviated EKG).A recording of electrical currents produced by the heart. E. coli...

Solutions to Clinical Investigations

Since our enzymes can recognize only Lamino acids and D-sugars, the opposite stereoisomers that George was eating could not be used by his body. He was weak because he was literally starving. The ketonuria also may have contributed to his malaise. Since he was starving, his stored fat was being rapidly hydrolyzed into glycerol and fatty acids for use as energy sources. The excessive release of fatty acids from his adipose tissue resulted in the excessive production of ketone bodies by his liver...

Cutaneous Blood Flow

The skin is the outer covering of the body and as such serves as the first line of defense against invasion by disease-causing organisms. The skin, as the interface between the internal and external environments, also helps to maintain a constant deep-body temperature despite changes in the ambient (external) temperature a process called thermoregulation. The thinness and large area of the skin (1.0 to 1.5 mm thick 1.7 to 1. Describe blood flow and oxygen delivery to the myocardium during...

Urinary Buffers

When a person has a blood pH of less than 7.35 (acidosis), the urine pH almost always falls below 5.5. The nephron, however, cannot produce a urine pH that is significantly less than 4.5. In order for more H+ to be excreted, the acid must be buffered. (Actually, even in normal urine, most of the H+ excreted is in a buffered form.) Bicarbonate cannot serve this buffering function because it is normally completely reabsorbed. Instead, the buffering action of phosphates (mainly HPO42-) and ammonia...