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. A...
The Respiratory System
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...
Lymphocytes and Lymphoid Organs
Leukocytes, erythrocytes, and blood platelets are all ultimately derived from stem from unspecialized cells in the bone marrow. These stem cells produce the specialized blood cells, and they replace themselves by cell division so that the stem cell population is not exhausted. Lymphocytes produced in this manner seed the thymus, spleen, and lymph nodes, producing self-replacing lymphocyte colonies in these organs. The lymphocytes that seed the thymus become T lymphocytes, or T cells the letter...
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...
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...
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...
Gas Exchange in the Lungs
Gas exchange between the alveolar air and the blood in pulmonary capillaries results in an increased oxygen concentration and a decreased carbon dioxide concentration in the blood leaving the lungs. This blood enters the systemic arteries,where blood gas measurements are taken to assess the effectiveness of lung function. The atmosphere is an ocean of gas that exerts pressure on all objects within it. This pressure can be measured with a glass U-tube filled with fluid. One end of the U-tube is...
Production of Plasma Proteins
Plasma albumin and most of the plasma globulins with the exception of immunoglobulins, or antibodies are produced by the liver. Albumin constitutes about 70 of the total plasma protein and contributes most to the colloid osmotic pressure of the blood chapter 14 . The globulins produced by the liver have a wide variety of functions, including transport of cholesterol and triglycerides, transport of steroid and thyroid hormones, inhibition of trypsin activity, and blood clotting. Clotting factors...
Regulation of Calcium and Phosphate Balance
A normal blood Ca2 concentration is critically important for contraction of muscles and maintenance of proper membrane permeability. Parathyroid hormone promotes an elevation in blood Ca2 by stimulating resorption of the calcium phosphate crystals from bone and renal excretion of phosphate. A derivative of vitamin D produced in the body, 1,25-dihydroxyvitamin D3, promotes the intestinal absorption of calcium and phosphate. The calcium and phosphate concentrations of plasma are affected by bone...
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...
Acetylcholinesterase AChE
The bond between ACh and its receptor protein exists for only a brief instant. The ACh-receptor complex quickly dissociates but can be quickly re-formed as long as free ACh is in the vicinity. In order for activity in the postsynaptic cell to be stopped, free ACh must be inactivated very soon after it is released. The inactivation of ACh is achieved by means of an enzyme called acetyl-cholinesterase, or AChE, which is present on the postsynaptic membrane or immediately outside the membrane,...
EndProduct Inhibition
The activities of enzymes at the branch points of metabolic pathways are often regulated by a process called end-product inhibition, which is a form of negative feedback inhibition. In this process, one of the final products of a divergent pathway inhibits the activity of the branch-point enzyme that began the path toward the production of this inhibitor. This inhibition prevents that final product from accumulating excessively and results in a shift toward the final product of the alternate...
Liver Gallbladder and Pancreas
The liver regulates the chemical composition of the blood in numerous ways. In addition, the liver produces and secretes bile, which is stored and concentrated in the gallbladder prior to its discharge into the duodenum.The pancreas produces pancreatic juice, an exocrine secretion containing bicarbonate and important digestive enzymes, which is passed into the duodenum via the pancreatic duct. The liver is positioned immediately beneath the diaphragm in the abdominal cavity. It is the largest...
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,...
Autonomic Innervation of Smooth Muscles
The neural control of skeletal muscles differs significantly from that of smooth muscles. A skeletal muscle fiber has only one junction with a somatic nerve fiber, and the receptors for the neu-rotransmitter are located only at the neuromuscular junction. By contrast, the entire surface of smooth muscle cells contains neu-rotransmitter receptor proteins. Neurotransmitter molecules are released along a stretch of an autonomic nerve fiber that is located some distance from the smooth muscle...
Summary Vxr
Glycolysis and the Lactic Acid Pathway 104 I. Glycolysis refers to the conversion of glucose to two molecules of pyruvic acid. A. In the process, two molecules of ATP are consumed and four molecules of ATP are formed. Thus, there is a net gain of two ATP. B. In the steps of glycolysis, two pairs of hydrogens are released. Electrons from these hydrogens reduce two molecules of NAD. II. When respiration is anaerobic, reduced NAD is oxidized by pyruvic acid, which accepts two hydrogen atoms and is...
Neural Pathways for Hearing
Sensory neurons in the vestibulocochlear nerve VIII synapse with neurons in the medulla oblongata that project to the inferior colliculus of the midbrain fig. 10.23 . Neurons in this area, in turn, project to the thalamus, which sends axons to the auditory cortex of the temporal lobe. By means of this pathway, neurons in different regions of the basilar membrane stimulate neurons in corresponding areas of the auditory cortex. Each area of this cortex thus represents a different part of the...
Boyles Law
Changes in intrapulmonary pressure occur as a result of changes in lung volume. This follows from Boyle's law, which states that the pressure of a given quantity of gas is inversely proportional to its volume. An increase in lung volume during inspiration decreases intrapulmonary pressure to subatmospheric levels air therefore goes in. A decrease in lung volume, conversely, raises the intrapulmonary pressure above that of the atmosphere, expelling air from the lungs. These changes in lung...
Take Advantage of the Technology Idn
Visit the Online Learning Center for these additional study resources. Crossword puzzles Vocabulary flashcards Labeling activities Crossword puzzles Vocabulary flashcards Labeling activities Tom is a 77-year-old man who was brought to the hospital because of severe chest pain. He also complained that he had difficulty urinating and that he got the runs when he ate ice cream. Laboratory tests were performed and demonstrated an abnormally high plasma concentration of the MB isoform of creatine...
Dihydroxyvitamin D3
The production of 1,25-dihydroxyvitamin D3 begins in the skin, where vitamin D3 is produced from its precursor molecule 7-dehydrocholesterol under the influence of sunlight. In equatorial regions of the globe, exposure to sunlight can allow sufficient cutaneous production of vitamin D3. In more northerly or southerly latitudes, however, exposure to the winter sun may not allow sufficient production of vitamin D3. When the skin does not make sufficient amounts of vitamin D3, this compound must...
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...
Refresh Your Memory
Structural Organization of the Brain 190 Cerebral Cortex 193 Visualizing the Brain 194 Electroencephalogram 194 Basal Nuclei 197 Cerebral Lateralization 197 Language 199 Emotion and Motivation 200 Memory 201 Brain Regions in Memory 201 Synaptic Changes in Memory 202 Neural Stem Cells in Learning and Memory 203 Thalamus and Epithalamus 204 Hypothalamus and Pituitary Gland 205 Metencephalon 206 Myelencephalon 208 Reticular Formation 208 Ascending Tracts 209 Descending Tracts 209 Cranial Nerves...
Test Yourself Before You Continue Rwf
1. Compare the structure and contents of a primary follicle, secondary follicle, and graafian follicle. 2. Define ovulation and describe the changes that occur in the ovary following ovulation in a nonfertile cycle. 3. Describe oogenesis and explain why only one mature ovum is produced by this process. 4. Compare the hormonal secretions of the ovarian follicles with those of a corpus luteum. Figure 20.32 Oogenesis. During meiosis, each primary oocyte produces a single haploid gamete. If the...
Liver Lobules
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...
Regulation of Coronary Blood Flow
The coronary arterioles contain both alpha and beta adrenergic receptors, which promote vasoconstriction and vasodilation, respectively. Norepinephrine released by sympathetic nerve fibers stimulates alpha-adrenergic receptors to raise vascular resistance at rest. Epinephrine released by the adrenal medulla can stimulate the beta-adrenergic receptors to produce vasodilation when the sympa-thoadrenal system is activated during the fight-or-flight reaction. Most of the vasodilation that occurs...
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...
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 systole...
Review Activities Qrd
Test Your Knowledge ofTerms and Facts Match the vestibular organ on the left 9. with its correct component on the right. 1. utricle and saccule a. cupula 2. semicircular canals b. ciliary body 4. The dissociation of rhodopsin in the rods in response to light causes a. the Na channels to become blocked. b. the rods to secrete less neurotransmitter. c. the bipolar cells to become either stimulated or inhibited. b. do not fire continuously to a sustained stimulus. c. produce action potentials at a...
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...
Test Your Knowledge of Terms and Facts
1. 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...
Atrioventricular and Semilunar Valves
Although adjacent myocardial cells are joined together mechanically and electrically by intercalated discs chapter 12 see figs. 12.31 and 12.32 , the atria and ventricles are separated into two functional units by a sheet of connective tissue the fibrous skeleton previously mentioned. Embedded within this sheet of tissue are one-way atrioventricular AV valves. The AV valve located between the right atrium and right ventricle 1. Using a flow diagram arrows , describe the pathway of the pulmonary...
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...
Cytoplasm and Cytoskeleton
The jellylike matrix within a cell exclusive of that within the nucleus is known as cytoplasm. Cytoplasm includes structures called organelles that are visible under the microscope, and the fluidlike cytosol that surrounds the organelles. When viewed in a microscope without special techniques, the cytoplasm appears to be uniform and unstructured. According to modern evidence, however, the cytosol is not a homogenous solution it is, rather, a highly organized structure in which protein fibers in...
TestYour Knowledge ofTerms and I
1. 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...
Regulation of the Gastrointestinal Tract
The GI tract is innervated by the sympathetic and parasympa-thetic divisions of the autonomic nervous system. As discussed in chapter 9, parasympathetic nerves in general stimulate motility and secretions of the gastrointestinal tract. The vagus nerve is the source of parasympathetic activity in the esophagus, stomach, pancreas, gallbladder, small intestine, and upper portion of the large intestine. The lower portion of the large intestine receives parasympathetic innervation from spinal nerves...
Review Activities Sgj
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...
Hemoglobin and Oxygen Transport
Hemoglobin without oxygen, or deoxyhemoglobin, can bond with oxygen to form oxyhemoglobin.This loading reaction occurs in the capillaries of the lungs.The dissociation of oxyhemoglobin, or unloading reaction, occurs in the tissue capillaries.The bond strength between hemoglobin and oxygen, and thus the extent of the unloading reaction, is adjusted by various factors to ensure an adequate delivery of oxygen to the tissues. If the lungs are functioning properly, blood leaving in the pulmonary...
Stereoisomers
Two molecules may have exactly the same atoms arranged in exactly the same sequence yet differ with respect to the spatial orientation of a key functional group. Such molecules are called stereoisomers of each other. Depending upon the direction in Carbonyl CO C C C C C Amino nh2 C C C C C Figure 2.10 Various functional groups of organic molecules. The general symbol for a functional group is R. Figure 2.11 Categories of organic molecules based on functional groups. Acids, alcohols, and other...
Objectives
After studying this chapter, you should be able to . 1. describe the composition of the extracellular environment. 2. describe diffusion and explain its physical basis. 3. explain how nonpolar molecules, inorganic ions, and water can diffuse through a cell membrane. 4. state the factors that influence the rate of diffusion through cell membranes. 5. define the term osmosis and describe the conditions required for osmosis to occur. 6. define the terms osmolality and osmotic pressure and explain...
Related Websites Vml
Check out the Links Library at www.mhhe.com fox8 for links to sites containing resources related to the central nervous system. These links are monitored to ensure current URLs. lNote This question is answered in the chapter 8 Study Guide found on the Online Learning Center at www.mhhe.com fox8. compare the structures and pathways of the autonomic system with those involved in the control of skeletal muscle. explain how autonomic innervation of involuntary effectors differs from the innervation...
Test Yourself Before You Continue
1. Describe how the secretions of insulin and glucagon change during periods of absorption and periods of fasting. How are these changes in hormone secretion produced 2. Explain how the synthesis of fat in adipose cells is regulated by insulin. Also, explain how fat metabolism is regulated by insulin and glucagon during periods of absorption and fasting. 3. Define the following terms glycogenolysis, gluconeogenesis, and ketogenesis. How do insulin and glucagon affect each of these processes...
Categories of Sensory Receptors
Sensory receptors can be categorized on the basis of structure or various functional criteria. Structurally, the sensory receptors may be the dendritic endings of sensory neurons. These dendritic endings may be free such as those that respond to pain and temperature or encapsulated within nonneural structures such as those that respond to pressure see fig. 10.4 . The photoreceptors in the retina of the eyes rods and cones are highly specialized neurons that synapse with other neurons in 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...
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...
Structure and Function of the Kidneys
Each kidney contains many tiny tubules that empty into a cavity drained by the ureter. Each of the tubules receives a blood filtrate from a capillary bed called the glomerulus. The filtrate is similar to interstitial fluid, but it is modified as it passes through different regions of the tubule and is thereby changed into urine. The tubules and associated blood vessels thus form the functioning units of the kidneys, known as nephrons. The primary function of the kidneys is regulation of the...
Atoms Ions and Chemical Bonds 24
I. Covalent bonds are formed by atoms that share electrons. They are the strongest type of chemical bond. A. Electrons are equally shared in nonpolar covalent bonds and unequally shared in polar covalent bonds. B. Atoms of oxygen, nitrogen, and phosphorus strongly attract electrons and become electrically negative compared to the other atoms sharing electrons with them. II. Ionic bonds are formed by atoms that transfer electrons. These weak bonds join atoms together in an ionic compound. A. If...
Diabetes Mellitus and Hypoglycemia
Inadequate secretion of insulin, or defects in the action of insulin, produce metabolic disturbances that are characteristic of diabetes mellitus. A person with type 1 diabetes requires injections of insulin a person with type 2 diabetes can control this condition by other methods. In both types, hyperglycemia and glycosuria result from a deficiency and or inadequate action of insulin. A person with reactive hypoglycemia, by contrast, secretes excessive amounts of insulin and thus experiences...
Alpha and Gamma Motoneurons
In the spinal cord, two types of lower motor neurons innervate skeletal muscles. The motor neurons that innervate the extrafusal muscle fibers are called alpha motoneurons those that innervate the intrafusal fibers are called gamma motoneurons fig. 12.26 . The alpha motoneurons are faster conducting 60 to 90 meters per second than the thinner gamma motoneurons 10 to 40 meters per second . Since only the extrafusal muscle fibers are sufficiently strong and numerous to cause a muscle to shorten,...