G

See Gamma-aminobutyric acid G-actin, 335 G1 phase, 71, 71 G2 phase, 71, 71 , 72 G-CSF. See Granulocyte colony-stimulating factor Gage, Phineas P., 201 Galactose, 32 Galen, 6 Gallbladder, 580-581, 580 as accessory digestive organ, 561 , 562 regulation of, 587 structure of, 580 Gallstones, 580, 581 Gametes (germ cells), 634 Gamma globulin, 453 Gamma motoneurons, 349-350 coactivation of, 350 Gamma-aminobutyric acid (GABA), as neurotransmitter, 179, 180 , 182 Gamma-carboxyglutamate, 377...

Hypertension

Approximately 20 of all adults in the United States have hypertension blood pressure in excess of the normal range for a person's age and sex. Hypertension that is a result of (secondary to) known disease processes is logically called secondary hypertension. Of the hypertensive population, secondary hypertension accounts for only about 5 . Hypertension that is the result of complex and poorly understood processes is not so logically called primary, or essential, hypertension. Hypertension in...

Summary

Alveoli are microscopic thin-walled air sacs that provide an enormous surface area for gas diffusion. A. The region of the lungs where gas exchange with the blood occurs is known as the respiratory zone. B. The trachea, bronchi, and bronchioles that deliver air to the respiratory zone constitute the conducting zone. II. The thoracic cavity is delimited by the chest wall and diaphragm. A. The structures of the thoracic cavity are covered by thin, wet pleurae. B. The lungs are covered by a...

The Laboratory Guide to Human Physiology Concepts

And Clinical Applications, Tenth Edition, by Stuart I. Fox, is self-contained so students can prepare for laboratory exercises and quizzes without having to bring the textbook to the laboratory. The introduction to each exercise contains cross-references to the pages in this textbook where related information can be found. Similarly, those figures in the lab manual that correspond to full-color figures in the textbook are also cross-referenced. Both of these mechanisms help students better...

Obesity

Obesity is a risk factor for cardiovascular diseases, diabetes mel-litus, gallbladder disease, and some malignancies (particularly endometrial and breast cancer). The distribution of fat in the body is also important there is a greater risk of cardiovascular disease when the distribution of fat produces a high waist-to-hip ratio, or an apple shape, as compared to a pear shape. This is because the amount of intra-abdominal fat in the mesenteries and greater omentum is a better predictor of a...

Treatment of Hypertension

The first form of treatment that is usually attempted is modification of lifestyle. This modification includes cessation of smoking, moderation of alcohol intake, and weight reduction, if applicable. It can also include programmed exercise and a reduction in sodium intake. People with essential hypertension may have a potassium deficiency, and there is evidence that eating food that is rich in potassium may help to lower blood pressure. There is also evidence that supplementing the diet with...

Acute Renal Failure

In acute renal failure, the ability of the kidneys to excrete wastes and regulate the homeostasis of blood volume, pH, and electrolytes deteriorates over a relatively short period of time (hours to days). There is a rise in blood creatinine concentration and a decrease in the renal plasma clearance of creatinine. This may be due to a reduced blood flow through the kidneys, perhaps as a result of atherosclerosis or inflammation of the renal tubules. The compromised kidney function may be the...

Energy Regulation by the Islets of Langerhans

Insulin secretion is stimulated by a rise in the blood glucose concentration, and insulin promotes the entry of blood glucose into tissue cells. Insulin thus increases the storage of glycogen and fat while causing the blood glucose concentration to fall. Glucagon secretion is stimulated by a fall in blood glucose, and glucagon acts to raise the blood glucose concentration by promoting glycogenolysis in the liver Scattered within a sea of pancreatic exocrine tissue (the acini) are islands of...

Test Yourself Before You Continue

Describe the effects of epinephrine and the glucocorticoids on the metabolism of carbohydrates and lipids. What is the significance of these effects as a response to stress 2. Explain the actions of thyroxine on the basal metabolic rate. Why do people who are hypothyroid have a tendency to gain weight and why are they less resistant to cold stress 3. Describe the effects of growth hormone on the metabolism of lipids, glucose, and amino acids. 4. Explain how growth hormone stimulates skeletal...

Per Links Establish Connections

Interactions page can be found at the end of each chapter or group of chapters relating to a particular body system, and also at the ends of chapters 3,5, and 6. These resource pages list the many ways a major concept applies to the study of different body systems, and the ways that a given system interacts with other body systems. Each application or interaction includes a page reference to related material in the textbook. The term HPer Links is a hybrid of hyperlinks and the initials of...

Regulatory Functions of Adipocytes

In addition to storing fat (triglyceride, or triacylglycerol), adipocytes produce and secrete regulatory molecules. One of the most important of these is leptin (Greek leptos thin), a hormone that signals the hypothalamus to indicate the level of fat storage. This hormone is involved in long-term regulation of eating and metabolism, as described in the next section. Another regulatory molecule produced by adipocytes is tumor necrosis factor-alpha (TNFa). TNFa is a cytokine that is also produced...

Info

The decline in physical strength of older people is associated with a reduced muscle mass, which is due to a loss of muscle fibers and to a decrease in the size of fast-twitch muscle fibers. Aging is also associated with a reduced density of blood capillaries surrounding the muscle fibers, leading to a decrease in oxidative capacity. Resistance training can cause the surviving muscle fibers to hypertrophy and become stronger, partially compensating for the decline in the number of muscle fibers...

Insulin and Glucagon Absorptive State

The lowering of plasma glucose by insulin is, in a sense, a side effect of the primary action of this hormone. Insulin is the major hormone that promotes anabolism in the body. During absorption of the products of digestion and the subsequent rise in the plasma concentrations of circulating energy substrates, insulin promotes the cellular uptake of plasma glucose and its incorporation into energy-reserve molecules of glycogen in the liver and muscles, and of triglycerides in adipose cells...

Type 2 Diabetes Mellitus

Insulin Resistance Symptoms Weight Gain

The effects produced by insulin, or any hormone, depend on the concentration of that hormone in the blood and on the sensitivity of the target tissue to given amounts of the hormone. Tissue responsiveness to insulin, for example, varies under normal conditions. Exercise increases insulin sensitivity and obesity decreases insulin sensitivity of the target tissues. The islets of a nondiabetic obese person must therefore secrete high amounts of insulin to maintain the blood glucose concentration...

Chapter at a Glance

Human Physiology

Neural Control of Involuntary Effectors 220 Autonomic Neurons 220 Visceral Effector Organs 221 Divisions of the Autonomic Nervous System 222 Sympathetic Division 222 Collateral Ganglia 222 Adrenal Glands 223 Parasympathetic Division 223 Functions of the Autonomic Nervous System 227 Transmission 228 Responses to Adrenergic Stimulation 230 Responses to Cholinergic Stimulation 232 Other Autonomic Neurotransmitters 233 Organs with Dual Innervation 234 Antagonistic Effects 234 Complementary and...

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...

Diseases Caused by the Immune System

Immune mechanisms that normally protect the body are very complex and subject to errors that can result in diseases. Autoimmune diseases and allergies are two categories of disease that are not caused by an invading pathogen, but rather by a derangement in the normal functions of the immune system. The ability of the normal immune system to tolerate self-antigens while it identifies and attacks foreign antigens provides a specific defense against invading pathogens. In every individual,...

S

Saccadic sa-kad'ik eye movements Very rapid eye movements that occur constantly and that change the focus on the retina from one point to another. saltatory sal tai-tor-e conduction The rapid passage of action potentials from one node of Ranvier to another in myelinated axons. sarcolemma saZ'co-lem'a The cell membrane of striated muscle cells. sarcomere sar'ko-mer The structural subunit of a myofibril in a striated muscle equal to the distance between two successive Z lines. sarcoplasm sa...

Cranial and Spinal Nerves

The central nervous system communicates with the body by means of nerves that exit the CNS from the brain cranial nerves and spinal cord spinal nerves . These nerves, together with aggregations of cell bodies located outside the CNS, constitute the peripheral nervous system. As mentioned in chapter 7, the peripheral nervous system PNS consists of nerves collections of axons and their associated ganglia collections of cell bodies . Although this chapter is devoted to the CNS, the CNS cannot...

Dangers of Hypertension

If other factors remain constant, blood flow increases as arterial blood pressure increases. The organs of people with hypertension are thus adequately perfused with blood until the excessively high pressure causes vascular damage. Because most patients are asymptomatic without symptoms until substantial vascular damage has occurred, hypertension is often referred to as a silent killer. Hypertension is dangerous for a number of reasons. First, high arterial pressure increases the afterload,...

Vitamins and Minerals

Vitamins are small organic molecules that serve as coenzymes in metabolic reactions or that have other highly specific functions. They must be obtained in the diet because the body either doesn't produce them, or it produces them in insufficient quantities. Vitamin D is produced in limited quantities by the skin, and the B vitamins and vitamin K are produced by intestinal bacteria. There are two classes of vitamins fat-soluble and water-soluble. The fat-soluble vitamins include vitamins A, D,...

Adrenal Glands

The adrenal cortex and adrenal medulla are structurally and functionally differentThe adrenal medulla secretes catecholamine hormones, which complement the sympathetic nervous system in the fight-or-flight reaction.The adrenal cortex secretes steroid hormones that participate in the regulation of mineral and energy balance. The adrenal glands are paired organs that cap the superior borders of the kidneys fig. 11.18 . Each adrenal consists of an outer cortex and inner medulla that function as...

Plasma

Blood Plasma And Buffy Coat Chart

Plasma is a straw-colored liquid consisting of water and dissolved solutes. The major solute of the plasma in terms of its concentration is Na . In addition to Na , plasma contains many other ions, as well as organic molecules such as metabolites, hormones, 1. State the components of the circulatory system that function in oxygen transport, in the transport of nutrients from the digestive system, and in protection. 2. Describe the functions of arteries, veins, and capillaries. 3. Define the...

Norepinephrine as a Neurotransmitter

Norepinephrine, like ACh, is used as a neurotransmitter in both the PNS and the CNS. Sympathetic neurons of the PNS use nor-epinephrine as a neurotransmitter at their synapse with smooth muscles, cardiac muscle, and glands. Some neurons in the CNS also use norepinephrine as a neurotransmitter these neurons seem to be involved in general behavioral arousal. This would help to explain the mental arousal elicited by amphetamines, which stimulate pathways in which norepinephrine is used as a...

Enterohepatic Circulation

Enterohepatic Circulation Urobilinogen

Conjugated bilirubin bilirubin glucuronide Conjugated bilirubin bilirubin glucuronide Figure 18.24 The enterohepatic circulation of urobilinogen. Bacteria in the intestine convert bilirubin bile pigment into urobilinogen. Some of this pigment leaves the body in the feces some is absorbed by the intestine and is recycled through the liver. A portion of the urobilinogen that is absorbed enters the general circulation and is filtered by the kidneys into the urine. Figure 18.25 The two major bile...

Regulation of Energy Metabolism

The blood plasma contains circulating glucose,fatty acids, amino acids, and other molecules that can be used by the body tissues for cell respiration. These circulating molecules may be derived from food or from the breakdown of the body's own glycogen, fat, and protein. The building of the body's energy reserves following a meal and the utilization of these reserves between meals are regulated by the action of a number of hormones that act to promote either anabolism or catabolism. The...

Absorption of Lipids

Free fatty acids, monoglycerides, and lysolecithin can leave the micelles and pass through the membrane of the microvilli to enter the intestinal epithelial cells. There is also some evidence that the micelles may be transported intact into the epithelial cells and that the lipid digestion products may be removed intra-cellularly from the micelles. In either event, these products are used to resynthesize triglycerides and phospholipids within the epithelial cells. This process is different from...

Essential Hypertension

The vast majority of people with hypertension have essential hypertension. An increased total peripheral resistance is a universal characteristic of this condition. Cardiac rate and the cardiac output are elevated in many, but not all, of these cases. The secretion of renin, which is correlated with an-giotensin II production and aldosterone secretion, is likewise variable. Although some people with essential hypertension have low renin secretion, most have either normal or elevated levels of...

Thyroid and Parathyroid Glands

Photomicrograph The Thyroid Gland

The thyroid secretes thyroxine T4 and triiodothyronine T3 , which are needed for proper growth and development and which are primarily responsible for determining the basal metabolic rate BMR . The parathyroid glands secrete parathyroid hormone, which helps to raise the blood Ca2 concentration. The thyroid gland is located just below the larynx fig. 11.21 . Its two lobes are positioned on either side of the trachea and are connected anteriorly by a medial mass of thyroid tissue called the...

Lactate Threshold and Endurance Training

The ability of the cardiopulmonary system to deliver adequate amounts of oxygen to the exercising muscles at the beginning of exercise may be insufficient because of the time lag required to make proper cardiovascular adjustments. During this time, therefore, the muscles respire anaerobically and a stitch in the side possibly due to hypoxia of the diaphragm may develop. After numerous cardiovascular and pulmonary adjustments have been made, a person may experience a second wind when the muscles...

Regulation of Renin Secretion

An inadequate dietary intake of salt NaCl is always accompanied by a fall in blood volume. This is because the decreased plasma concentration osmolality inhibits ADH secretion. With Figure 17.25 The juxtaglomerular apparatus. a The location of the juxtaglomerular apparatus. This structure includes the region of contact of the afferent arteriole with the last portion of the thick ascending limb of the loop. The afferent arterioles in this region contain granular cells that secrete renin, and the...

Active Immunity

The development of a secondary response provides active immunity against the specific pathogens. The development of active immunity requires prior exposure to the specific antigens, at which time the sluggishness of the primary response may cause the person to develop the disease. Some parents, for example, deliberately expose their children to others who have measles, chickenpox, or mumps so that their children will be immune to these diseases in later life, when the diseases are potentially...

Digital Content Manager

Physiology Carbohydrate Metabolism

This multimedia collection of visual resources allows instructors to utilize artwork from the text in multiple formats to create customized classroom presentations, visually based tests and quizzes, dynamic course website content, or attractive printed support materials. The digital assets on this cross-platform CD-ROM are grouped by chapter within easy-to-use folders. Art Library Full-color digital files of all illustrations in the book, plus grayscale versions of the same artwork, are housed...

Asthma

The dyspnea, wheezing, and other symptoms of asthma are produced by an obstruction of air flow through the bronchioles that occurs in episodes, or attacks. This obstruction is caused by inflammation, mucous secretion, and bronchoconstriction. Inflammation of the airways is characteristic of asthma, and itself contributes to increased airway responsiveness to agents that promote bronchiolar constriction. Bronchoconstriction further increases airway resistance and makes breathing difficult. The...

Regulation of Glomerular Filtration Rate

Vasoconstriction or dilation of afferent arterioles affects the rate of blood flow to the glomerulus, and thus affects the glomerular filtration rate. Changes in the diameter of the afferent arterioles result from both extrinsic regulatory mechanisms produced by sympathetic nerve innervation , and intrinsic regulatory mechanisms those within the kidneys, also termed renal autoregulation . These mechanisms are needed to ensure that the GFR will be high enough to allow the kidneys to eliminate...

Potassium Secretion

Destal Hyperkalemia

About 90 of the filtered potassium is reabsorbed in the early regions of the nephron mainly from the proximal tubule . In order for potassium to appear in the urine, it must be secreted into later regions of the nephron tubule. Secretion of potassium occurs in the parts of the nephron that are sensitive to aldosterone that is, in the late distal tubule and cortical collecting duct fig. 17.24 . As Na is reabsorbed in these regions of the nephron, the lumen of the tubule becomes more negatively...

Maximal Oxygen Uptake

Whether exercise is light, moderate, or heavy for a given person depends on that person's maximal capacity for aerobic exercise. The maximum rate of oxygen consumption by aerobic respiration in the body is called the maximal oxygen uptake, or the aero.bic capacity, and is often expressed in abbreviated form as the VO2 max. The maximal oxygen uptake is determined primarily by a person's age, size, and sex. It is from 15 to 20 higher for males than for females and highest at age 20 for both...

Mechanisms of Contraction

Cross Section Myofibril Sarcomere

The A bands within each muscle fiber are composed of thick filaments and the I bands contain thin filaments. Movement of cross bridges that extend from the thick to the thin filaments causes sliding of the filaments, and thus muscle tension and shortening.The activity of the cross bridges is regulated by the availability of Ca2 , which is increased by electrical stimulation of the muscle fiber. Electrical stimulation produces contraction of the muscle through the binding of Ca2 to regulatory...

Ovarian Cycle

Ovarian Cycle Follicle

The germ cells that migrate into the ovaries during early embryonic development multiply, so that by about 5 months of gestation prenatal life the ovaries contain approximately 6 million Figure 20.27 The external female genitalia. The labia majora and clitoris in a female are homologous to the scrotum and penis, respectively, in a male. Figure 20.28 Photomicrographs of the ovary. a Primary follicles and one secondary follicle and b a graafian follicle are visible in these sections. to 7 million...

Production and Action of Thyroid Hormones

The thyroid follicles actively accumulate iodide I- from the blood and secrete it into the colloid. Once the iodide has entered the colloid, it is oxidized to iodine and attached to a specific amino acid tyrosine within the polypeptide chain of a protein called thyroglobulin. The attachment of one iodine to tyrosine produces monoiodotyrosine MIT the attachment of two iodines produces diiodotyrosine DIT . Within the colloid, enzymes modify the structure of MIT and DIT and couple them together....

The Onset of Puberty

Physiology Puberty

Secretion of FSH and LH is high in the newborn, but falls to very low levels a few weeks after birth. Gonadotropin secretion remains low until the beginning of puberty, which is marked by rising levels of FSH followed by LH secretion. Experimental Table 20.2 Development of Secondary Sex Characteristics and Other Changes That Occur During Puberty in Girls Estrogen, progesterone, growth hormone, thyroxine, insulin, cortisol Menarche first menstrual flow Axillary underarm hair Eccrine sweat glands...

Digestion and Absorption in the Stomach

Proteins are only partially digested in the stomach by the action of pepsin, while carbohydrates and fats are not digested at all by pepsin. Digestion of starch begins in the mouth with the action of salivary amylase and continues for a time when the food enters the stomach, but amylase soon becomes inactivated by the strong acidity of gastric juice. The complete digestion of food molecules occurs later, when chyme enters the small intestine. Therefore, people who have had partial gastric...

Nutritional Requirements

The body's energy requirements must be met by the caloric value of food to prevent catabolism of the body's own fat, carbohydrates, and protein.Additionally,food molecules particularly the essential amino acids and fatty acids are needed for replacement of molecules in the body that are continuously degraded. Vitamins and minerals do not directly provide energy but instead are required for diverse enzymatic reactions. Living tissue is maintained by the constant expenditure of energy. This...

The Sodium Potassium Pump

Physiology 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 because Na...

Role of Ca2 in Muscle Contraction

In a relaxed muscle, when tropomyosin blocks the attachment of cross bridges to actin, the concentration of Ca2 in the sar-coplasm cytoplasm of muscle cells is very low. When the muscle cell is stimulated to contract, mechanisms that will be discussed shortly cause the concentration of Ca2 in the sar-coplasm to quickly rise. Some of this Ca2 attaches to troponin, causing a conformational change that moves the troponin complex and its attached tropomyosin out of the way so that the cross bridges...

Cranial Nerves

Of the twelve pairs of cranial nerves, two pairs arise from neuron cell bodies located in the forebrain and ten pairs arise from the midbrain and hindbrain. The cranial nerves are designated by Roman numerals and by names. The Roman numerals refer to the order in which the nerves are positioned from the front of the brain to the back. The names indicate the structures innervated by these nerves e.g., facial or the principal function of the nerves e.g., oculomotor . A summary of the cranial...

Characteristics of Sensory Receptors

Each type of sensory receptor responds to a particular modality of environmental stimulus by causing the production of action potentials in a sensory neuron.These impulses are conducted to parts of the brain that provide the proper interpretation of the sensory information when that particular neural pathway is activated. Our perceptions of the world its textures, colors, and sounds its warmth, smells, and tastes are created by the brain from electrochemical nerve impulses delivered to it from...

Functions of Proteins

Because of their tremendous structural diversity, proteins can serve a wider variety of functions than any other type of molecule in the body. Many proteins, for example, contribute significantly to the structure of different tissues and in this way play a passive role in the functions of these tissues. Examples of such structural proteins include collagen fig. 2.28 and keratin. Collagen is a fibrous protein that provides tensile strength to connective tissues, such as tendons and ligaments....

Descending Limb of the Loop of Henle

The deeper regions of the medulla, around the tips of the loops of juxtamedullary nephrons, reach a concentration of 1,200 to 1,400 mOsm. In order to reach this high a concentration, the salt pumped out of the ascending limb must accumulate in the interstitial fluid of the medulla. This occurs because of the properties of the descending limb, to be discussed next, and because blood vessels around the loop do not carry back all of the extruded salt to the general circulation. The capillaries in...

Changes in Ventilation

Starting at altitudes as low as 1,500 meters 5,000 feet , the decreased arterial Po2 stimulates an increase in ventilation. This hypoxic ventilatory response produces hyperventilation, which lowers the arterial PCO2 table 16.12 and thus produces a respiratory alkalosis. The rise in arterial pH helps to blunt the hyperventilation, and within a few days the total minute volume becomes stabilized at a level 2.5 L min higher than that at sea level. Hyperventilation at high altitude increases tidal...

Interferons

Alpha Interferon Kaposi

In 1957, researchers demonstrated that cells infected with a virus produced polypeptides that interfered with the ability of a second, unrelated strain of virus to infect other cells in the same culture. These interferons, as they were called, thus produced a nonspecific, short-acting resistance to viral infection. Although this discovery generated a great deal of excitement, further research was hindered by the fact that human interferons could be obtained only in very small quantities...

Related Websites

Proximal Tubule And Vessels

Check out the Links Library at www.mhhe.com fox8 for links to sites containing resources related to respiratory physiology. These links are monitored to ensure current URLs. explain how the vasa recta function in countercurrent exchange. describe the role of the kidneys in the regulation of acid-base balance. describe active transport and osmosis in the loop of Henle and explain how these processes produce a countercurrent multiplier system. explain how the vasa recta function in countercurrent...

Digestion and Absorption of Carbohydrates

Most carbohydrates are ingested as starch, which is a long poly-saccharide of glucose in the form of straight chains with occasional branchings. The most commonly ingested sugars are sucrose table sugar, a disaccharide consisting of glucose and fructose and lactose milk sugar, a disaccharide consisting of glucose and galactose . The digestion of starch begins in the mouth with the action of salivary amylase. This enzyme cleaves some of the bonds between adjacent glucose molecules, but most...

And Growth Hormone

Growth Hormone Adipose

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...

Carbon Dioxide Transport and Acid Base Balance

Carbon dioxide is transported in the blood primarily in the form of bicarbonate HCO3- ,which is released when carbonic acid dissociates. Bicarbonate can buffer H , and thus helps to maintain a normal arterial pH. Hypoventilation raises, and hyperventilation lowers, the carbonic acid concentration of the blood. Carbon dioxide is carried by the blood in three forms 1 as dissolved CO2 carbon dioxide is about twenty-one times more soluble than oxygen in water, and about one-tenth of the total blood...

Hypertension Shock and Congestive Heart Failure

An understanding of the normal physiology of the cardiovascular system is prerequisite to the study of its pathophysiology, or mechanisms of abnormal function. Since the mechanisms that regulate cardiac output, blood flow, and blood pressure are highlighted in particular disease states, a study of pathophysiology at this time can augment your understanding of the mechanisms involved in normal function. Blood Pressure Classification in Adults Evaluate immediately or within 1 week based on...

Cardiac Muscle

Muscle Contraction Steps With Pictures

Like skeletal muscle cells, cardiac heart muscle cells, or myo-cardial cells, are striated they contain actin and myosin filaments arranged in the form of sarcomeres, and they contract by means of the sliding filament mechanism. The long, fibrous skeletal muscle cells, however, are structurally and functionally separated from each other, whereas the myocardial cells are short, branched, and interconnected. Each myocardial cell is tubular in structure and joined to adjacent myocardial cells by...

Electrical Activity in Axons

Depolarazation Axon

The permeability of the axon membrane to Na and K is regulated by gates, which open in response to stimulation. Net diffusion of these ions occurs in two stages first Na moves into the axon, then K moves out. This flow of ions,and the changes in the membrane potential that result, constitute an event called an action potential. All cells in the body maintain a potential difference voltage across the membrane, or resting membrane potential, in which the inside of the cell is negatively charged...

Describe The Sequence Of Events That Occurs From The Time The Patellar Tendon

Figure 12.30 The crossed-extensor reflex. This complex reflex demonstrates double reciprocal innervation. Table 12.8 Symptoms of Upper Motor Neuron Damage Babinski's reflex Extension of the great toe when the sole of the foot is stroked along the lateral border Spastic paralysis High muscle tone and hyperactive stretch reflexes flexion of arms and extension of legs Hemiplegia Paralysis of upper and lower limbs on one side commonly produced by damage to motor tracts as they pass through...

Clinical Content Adds Interest

Clinical information is presented throughout the text to underscore the real-life importance of understanding human physiology and to provide concrete examples that demonstrate the application of complex physiological concepts. Clinical Investigations are diagnostic puzzles provided at the very beginning of each chapter. These thought-provoking cases are designed to engage students' interest and motivate them to delve into the content of each chapter. Students must read the chapter, understand...

Antigens

Agglutination Latex Particles

Antigens are molecules that stimulate the production of specific antibodies and combine specifically with the antibodies produced. Most antigens are large molecules such as proteins with a molecular weight greater than about 10,000, although there are important exceptions. Also, most antigens are foreign to the blood and other body fluids. This is because the immune system can distinguish its own self molecules from those of any other organism nonself and normally mounts an immune response only...

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 hoped....

Effect of pH and Temperature on Oxygen Transport

In addition to changes in PO2, the loading and unloading reactions are influenced by changes in the affinity of hemoglobin for oxygen. Such changes ensure that active skeletal muscles will receive more oxygen from the blood than they do at rest. This occurs as a result of the lowered pH and increased temperature in exercising muscles. The affinity is decreased when the pH is lowered and increased when the pH is raised this is called the Bohr effect. When the affinity of hemoglobin for oxygen is...

Excitation Contraction Coupling in Smooth Muscles

Excitation Contraction Coupling Steps

As in striated muscles, the contraction of smooth muscles is triggered by a sharp rise in the Ca2 concentration within the cytoplasm of the muscle cells. However, the sarcoplasmic reticu-lum of smooth muscles is less developed than that of skeletal muscles, and Ca2 released from this organelle may account for Myosin thick filament Actin thin filament Figure 12.33 Smooth muscle and its contractile apparatus. a A photomicrograph of smooth muscle cells in the wall of a blood vessel. b Arrangement...

D

Dalton's law The statement that the total pressure of a gas mixture is equal to the sum that each individual gas in the mixture would exert independently. The part contributed by each gas is known as the partial pressure of the gas. dark adaptation The ability of the eyes to increase their sensitivity to low light levels over a period of time. Part of this adaptation involves increased amounts of visual pigment in the photoreceptors. dark current The steady inward diffusion of Na into the rods...

Adrenal Hormones

As described in chapter 11, the adrenal gland consists of two parts that function as separate glands. The two parts secrete different hormones and are regulated by different control systems. The adrenal medulla secretes catecholamine hormones epinephrine and lesser amounts of norepinephrine in response to sympathetic nerve stimulation. The adrenal cortex secretes corticosteroid hormones. These are grouped into two functional categories mineralocorti-coids, such as aldosterone, which act on the...

Reabsorption of Bicarbonate in the Proximal Tubule

The apical membranes of the tubule cells facing the lumen are impermeable to bicarbonate. The reabsorption of bicarbonate must therefore occur indirectly. When the urine is acidic, HCO3-combines with H to form carbonic acid. Carbonic acid in the filtrate is then converted to CO2 and H2O in a reaction catalyzed by carbonic anhydrase. This enzyme is located in the apical cell membrane of the proximal tubule in contact with the filtrate. Notice that the reaction that occurs in the filtrate is the...

Digestion and Absorption of Carbohydrates Lipids and Proteins

Polysaccharides and polypeptides are hydrolyzed into their subunits. These subunits enter the epithelial cells of the intestinal villi and are secreted into blood capillaries. Fat is emulsified by the action of bile salts, hydrolyzed into fatty acids and monoglycerides,and absorbed into the intestinal epithelial cells. Once inside the cells, triglycerides are resynthesized and combined with proteins to form particles that are secreted into the lymphatic fluid. The caloric energy value of food...

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 for...

Small Intestine

Plica Circularis Jejunum

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...

Digestion of Lipids

Triglyceride Pancreatic Lipase

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,...

Body Fluid Compartments

Tissues, organs, and systems can all be divided into two major parts, or compartments. The intracellular compartment is that part inside the cells the extracellular compartment is that part outside the cells. Both compartments consist primarily of water they are said to be aqueous. The two compartments are separated by the cell membrane surrounding each cell see chapter 3 . The extracellular compartment is subdivided into two parts. One part is the blood plasma, the fluid portion of the blood....

Autocrine and Paracrine Regulation

Many regulatory molecules produced throughout the body act within the organs that produce them.These molecules may regulate different cells within one tissue, or they may be produced within one tissue and regulate a different tissue within the same organ. Thus far in this text, two types of regulatory molecules have been considered neurotransmitters in chapter 7 and hormones in the present chapter. These two classes of regulatory molecules cannot be defined simply by differences in chemical...

Serotonin as a Neurotransmitter

Zoloft Serotonin Transmission

Serotonin, or 5-hydroxytryptamine 5-HT , is used as a neuro-transmitter by neurons with cell bodies in what are called the raphe nuclei that are located along the midline of the brain stem see chapter 8 . Serotonin is derived from the amino acid L-tryptophan, and variations in the amount of this amino acid in the diet tryptophan-rich foods include milk and turkey can affect the amount of serotonin produced by the neurons. Physiological functions attributed to serotonin include a role in the...

Local Inflammation

Antibodies Antigens Bacteria

Aspects of the innate and adaptive immune responses and their interactions are well illustrated by the events that occur when bacteria enter a break in the skin and produce a local inflammation table 15.5 . The inflammatory reaction is initiated by the nonspecific mechanisms of phagocytosis and complement activation. Complement proteins are activated during humoral immunity by B lymphocytes, as described in a later section. Activated complement further increases this nonspecific response by...

Stress and the Adrenal Gland

List Glands And Its Secretions

In 1936, a Canadian physiologist, Hans Selye, discovered that injections of a cattle ovary extract into rats 1 stimulated growth of the adrenal cortex 2 caused atrophy of the lym-phoid tissue of the spleen, lymph nodes, and thymus and 3 produced bleeding peptic ulcers. At first he attributed these effects to the action of a specific hormone in the extract. However subsequent experiments revealed that injections of a variety of substances including foreign chemicals such as formaldehyde could...

Ligand Operated Channels

Nicotinic Receptor

This is the most direct mechanism by which chemically regulated gates can be opened. In this case, the ion channel runs through the receptor itself. The ion channel is opened by the binding of the receptor to the neurotransmitter ligand. Such is the case when ACh binds to its nicotinic ACh receptor. This receptor consists of five polypeptide subunits that enclose the ion channel. Two of these subunits contain ACh-binding sites, and the channel opens when both sites bind to ACh fig. 7.23 . The...

Antibody Structure

Cell Pathogen

All antibody molecules consist of four interconnected polypep-tide chains. Two long, heavy chains the H chains are joined to two shorter, lighter L chains. Research has shown that these four 1. List the phagocytic cells found in blood and lymph, and indicate which organs contain fixed phagocytes. 2. Describe the actions of interferons. 3. Distinguish between innate and adaptive immunity, and describe the properties of antigens. 4. Distinguish between B and T lymphocytes in terms of their...

Mechanism of Thyroid Hormone Action

Mechanisms Hormones Action

As previously discussed, the major hormone secreted by the thyroid gland is thyroxine, or tetraiodothyronine T4 . Like steroid hormones, thyroxine travels in the blood attached to carrier proteins primarily to thyroxine-binding globulin, or TBG . The thyroid also secretes a small amount of triiodothyronine, or T3. The carrier proteins have a higher affinity for T4 than for T3, however, and, as a result, the amount of unbound or free T3 in the plasma is about ten times greater than the amount of...

Blood Gas Measurements

Terminal Bronchioles

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...

Hormones That Bind to Nuclear Receptor Proteins

Hormones Receptors Target Cells

Unlike the water-soluble hormones, the lipophilic steroid and thyroid hormones do not travel dissolved in the aqueous portion of the plasma rather, they are transported to their target cells attached to plasma carrier proteins. These hormones must then dissociate from their carrier proteins in the blood in order to pass through the lipid component of the plasma membrane and enter the target cell, within which their receptor proteins are located fig 11.4 . The receptors for the lipophilic...

Electron Transport and Oxidative Phosphorylation

Oxidative Phorylation

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...

Regulation of Hunger

The possibility that adipose tissue secretes a hormonal satiety factor a circulating chemical that decreases appetite has been suspected for years on the basis of physiological evidence. According to this view, secretion of the satiety factor would increase following meals and decrease during fasting. Such a satiety factor could act through its regulation of the hunger centers in the hypothalamus. The satiety factor secreted by adipose tissue has recently been identified. It is the product of a...

The Respiratory System

Alveolar Walls And Alveolar Cell

The respiratory system is divided into a respiratory zone, which is the site of gas exchange between air and blood, and a conducting zone, which conducts the air to the respiratory zone. The exchange of gases between air and blood occurs across the walls of respiratory alveoli. These tiny air sacs,only a single cell layer thick,permit rapid rates of gas diffusion. The term respiration includes three separate but related functions 1 ventilation breathing 2 gas exchange, which occurs between the...

Regulation of Gastric Function

Gastric motility and secretion are, to some extent, automatic. Waves of contraction that serve to push chyme through the py-loric sphincter, for example, are initiated spontaneously by pacesetter cells in the greater curvature of the stomach. Likewise, the secretion of HCl from parietal cells and pepsinogen from chief cells can be stimulated in the absence of neural and hormonal influences by the presence of cooked or partially digested protein in the stomach. This action involves other cells...

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 comprises about 10...

Adaptations of Muscles to Exercise Training

The maximal oxygen uptake, obtained during very strenuous exercise, averages 50 ml of O2 per minute per kilogram body weight in males between the ages of 20 and 25 females average 25 lower . For trained endurance athletes such as swimmers and long-distance runners , maximal oxygen uptakes can be as high as 86 ml of O2 per minute per kilogram. These considerable differences affect the lactate threshold, and thus the amount of exercise that can be performed before lactic acid production...

Pancreas

Exocrine Portion The Pancreas

Figure 18.27 Gallstones. a A radiograph of a gallbladder that contains gallstones biliary calculi . b A posterior view of a gallbladder that has been surgically removed cholecystectomy and cut open to reveal its gallstones. Note their size relative to that of a dime. The pancreas is a soft, glandular organ that has both exocrine and endocrine functions fig. 18.28 . The endocrine function is performed by clusters of cells called the pancreatic islets, or islets of Langerhans fig. 18.28a , that...

Regulation of Cardiac Rate

In the complete absence of neural influences, the heart will continue to beat according to the rhythm set by the SA node. This automatic rhythm is produced by the spontaneous depolarization of the resting membrane potential to a threshold level, at which point voltage-regulated membrane gates are opened and action potentials are produced. As described in chapter 13, Ca2 enters the myocardial cytoplasm during the action potential, attaches to troponin, and causes contraction. Normally, however,...

Superior Colliculus and Eye Movements

Visual Association Area

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...

Liver Lobules

Hepatocytes Sinusoids

The hepatic plates are arranged into functional units called liver lobules figs. 18.20 and 18.21 . In the middle of each lobule is a central vein, and at the periphery of each lobule are branches of the hepatic portal vein and of the hepatic artery, which open into the sinusoids between hepatic plates. Arterial blood and portal venous blood, containing molecules absorbed in the GI tract, thus mix as the blood flows within the sinusoids from the periphery of the lobule to the central vein. The...

Hypoglycemia

A person with type 1 diabetes mellitus depends on insulin injections to prevent hyperglycemia and ketoacidosis. If inadequate insulin is injected, the person may enter a coma as a result of the ketoacidosis, electrolyte imbalance, and dehydration that develop. An overdose of insulin, however, can also produce a coma as a result of the hypoglycemia abnormally low blood glucose levels produced. The physical signs and symptoms of diabetic and hypoglycemic coma are sufficiently different to allow...

Gallbladder

Pancreas Secretion Pancreatic Juice

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...

Cutaneous Blood Flow

Increased Blood Flow The Brain

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 systole...

For Somatesthetic Sensations

The conduction pathways for the somatesthetic senses a term that includes sensations from cutaneous receptors and proprioceptors are shown in chapter 8 fig. 8.20 . These pathways involve three orders of neurons in series. Sensory information from proprioceptors and pressure receptors is first carried by large, myelinated nerve fibers that ascend in the dorsal columns of the spinal cord on the same ipsilateral side. These fibers do not synapse until they reach the medulla oblongata of the brain...

Enzymes as Catalysts

Enzymes are biological catalysts that increase the rate of chemical reactions. Most enzymes are proteins,and their catalytic action results from their complex structure. The great diversity of protein structure allows different enzymes to be specialized in their action. The ability of yeast cells to make alcohol from glucose a process called fermentation had been known since antiquity, yet even as late as the mid-nineteenth century no scientist had been able to duplicate this process in the...

Test Your Knowledge ofTerms and I

Which of these statements about hypothalamic-releasing hormones is true a. They are secreted into capillaries in the median eminence. b. They are transported by portal veins to the anterior pituitary. c. They stimulate the secretion of specific hormones from the anterior pituitary. 2. The hormone primarily responsible for setting the basal metabolic rate and for promoting the maturation of the brain is 3. Which of these statements about the a. It is not innervated by nerve fibers. c. The...

Review Activities

Test Your Knowledge ofTerms and Facts 1. When a visceral organ is denervated, 2. Parasympathetic ganglia are located 3. The neurotransmitter of preganglionic Test Your Knowledge ofTerms and Facts 1. When a visceral organ is denervated, 2. Parasympathetic ganglia are located 3. The neurotransmitter of preganglionic in the dorsal roots of spinal nerves. 4. Which of these results from stimulation of alpha-adrenergic receptors a. constriction of blood vessels 5. Which of these fibers release...

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...

Cephalic Phase

The cephalic phase of gastric regulation refers to control by the brain via the vagus nerve. As previously discussed, various conditioned stimuli can evoke gastric secretion. This conditioning in humans is, of course, more subtle than that exhibited by Pavlov's dogs in response to a bell. In fact, just talking about appetizing food is sometimes a more potent stimulus for gastric acid secretion than the actual sight and smell of food Activation of the vagus nerve 1 stimulates the chief cells to...