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O-A-B blood types, 451-453, 452f, 452t Oat bran, 851 Obesity, 846, 872-874 cortisol and, 952 diabetes mellitus and, 974, 975 hyperplastic, 872 Obesity (Continued) hypertrophic, 872 leptin and, 871 renal failure in, 407-408 sympathetic nervous system in, 887-888 treatment of, 873-874 Obligatory urine volume, 350, 356-357 Oblique muscles, of eye, 645, 645f Obstructive sleep apnea, 523 Occipital cortex, in eye movement, 645-646, 646f Oddi, sphincter of, 803, 803f Odontoblasts, 992 Odor blindness,...

Info

CHAPTER 38 Pulmonary Circulation, Pulmonary Edema, Pleural Fluid Physiologic Anatomy of the Pulmonary Circulatory System Pressures in the Pulmonary System Blood Volume of the Lungs Blood Flow Through the Lungs and Its Distribution Effect of Hydrostatic Pressure Gradients in the Lungs on Regional Pulmonary Blood Flow Zones 1, 2, and 3 of Pulmonary Blood Flow Effect of Increased Cardiac Output on Pulmonary Blood Flow and Pulmonary Arterial Pressure During Heavy Exercise Function of the Pulmonary...

Placental Hormone From Euroform Healthcare

Maturation and Fertilization of the Ovum 1027 Transport of the Fertilized Ovum in the Implantation of the Blastocyst in the Uterus 1029 Early Nutrition of the Embryo 1029 Function of the Placenta 1029 Developmental and Physiologic Anatomy Hormonal Factors in Pregnancy 1031 Human Chorionic Gonadotropin and Its Effect to Cause Persistence of the Corpus Luteum and to Prevent Secretion of Estrogens by the Placenta 1032 Secretion of Progesterone by the Placenta 1033 Human Chorionic Somatomammotropin...

Slow Wave Sleep

Most of us can understand the characteristics of deep slow-wave sleep by remembering the last time we were kept awake for more than 24 hours and then the deep sleep that occurred during the first hour after going to sleep. This sleep is exceedingly restful and is associated with decrease in both peripheral vascular tone and many other vegetative functions of the body. For instance, there are 10 to 30 per cent decreases in blood pressure, respiratory rate, and basal metabolic rate. Although...

Sleep

Sleep is defined as unconsciousness from which the person can be aroused by sensory or other stimuli. It is to be distinguished from coma, which is unconsciousness from which the person cannot be aroused. There are multiple stages of sleep, from very light sleep to very deep sleep sleep researchers also divide sleep into two entirely different types of sleep that have different qualities, as follows. Two Types of Sleep. During each night, a person goes through stages of two types of sleep that...

Exchange of Fluid Volume Through the Capillary Membrane

Now that the different factors affecting fluid movement through the capillary membrane have been discussed, it is possible to put all these together to see how the capillary system maintains normal fluid volume distribution between the plasma and the interstitial fluid. The average capillary pressure at the arterial ends of the capillaries is 15 to 25 mm Hg greater than at the venous ends. Because of this difference, fluid filters out of the capillaries at their arterial ends, but at their...

Circulatory Arrest

A condition closely allied to circulatory shock is circulatory arrest, in which all blood flow stops. This occurs frequently on the surgical operating table as a result of cardiac arrest or ventricular fibrillation. Ventricular fibrillation can usually be stopped by strong electroshock of the heart, the basic principles of which are described in Chapter 13. Cardiac arrest often results from too little oxygen in the anesthetic gaseous mixture or from a depressant effect of the anesthesia itself....

Physiologic Anatomy of the Gastrointestinal Wall

Figure 62-2 shows a typical cross section of the intestinal wall, including the following layers from outer surface inward (1) the serosa, (2) a longitudinal muscle layer, (3) a circular muscle layer, (4) the submucosa, and (5) the mucosa. In addition, sparse bundles of smooth muscle fibers, the mucosal muscle, lie in the deeper layers of the mucosa. The motor functions of the gut are performed by the different layers of smooth muscle. The general characteristics of smooth muscle and its...

Cerebellum and Its Motor Functions

The cerebellum, illustrated in Figures 56-1 and 56-2, has long been called a silent area of the brain, principally because electrical excitation of the cerebellum does not cause any conscious sensation and rarely causes any motor movement. Removal of the cerebellum, however, does cause body movements to become highly abnormal. The cerebellum is especially vital during rapid muscular activities such as running, typing, playing the piano, and even talking. Loss of this area of the brain can cause...

Does Sodium Pass Easily Through Hydrated Channels

Transport of sodium and potassium ions through protein channels. Also shown are conformational changes in the protein molecules to open or close gates guarding the channels. molecules that hydrate them. The hydrated form of the potassium ion is considerably smaller than the hydrated form of sodium because the sodium ion attracts far more water molecules than does potassium. Therefore, the smaller hydrated potassium ions can pass easily through this small channel, whereas the larger hydrated...

Unit Ix

General Principles and Sensory Physiology CHAPTER 45 Organization of the Nervous System, Basic Functions of Synapses, Transmitter Substances 555 General Design of the Nervous System 555 Central Nervous System Neuron The Basic Sensory Part of the Nervous System Processing of Function of the Nervous System 556 Storage of Information Memory 557 Major Levels of Central Nervous System Function 557 Lower Brain or Subcortical Level 558 Higher Brain or Cortical Level 558 Central...

Figure 294

Effect of plasma aldosterone concentration (red line) and extracellular potassium ion concentration (black line) on the rate of urinary potassium excretion. These factors stimulate potassium secretion by the principal cells of the cortical collecting tubules. (Drawn from data in Young DB, Paulsen AW Interrelated effects of aldosterone and plasma potassium on potassium excretion. Am J Physiol 244 F28, 1983.) Aldosterone Stimulates Potassium Secretion. In Chapter 27, we discuss the fact that...

Regulation of Respiration During Exercise

In strenuous exercise, oxygen consumption and carbon dioxide formation can increase as much as 20-fold.Yet, as illustrated in Figure 41-8, in the healthy athlete, alveolar ventilation ordinarily increases almost exactly in step with the increased level of oxygen metabolism. The arterial Po2, Pco2, and pH remain almost exactly normal. In trying to analyze what causes the increased ventilation during exercise, one is tempted to ascribe this to increases in blood carbon dioxide and hydrogen ions,...

D

Effect of concentration difference (A), electrical potential difference affecting negative ions (B), and pressure difference (C) to cause diffusion of molecules and ions through a cell membrane. right, creating the condition shown in the right panel of Figure 4-85, in which a concentration difference of the ions has developed in the direction opposite to the electrical potential difference. The concentration difference now tends to move the ions to the left, while the electrical difference...

Diffusion Through the Capillary Membrane

By far the most important means by which substances are transferred between the plasma and the interstitial fluid is diffusion. Figure 16-3 demonstrates this process, showing that as the blood flows along the lumen of the capillary, tremendous numbers of water molecules and dissolved particles diffuse back and forth through the capillary wall, providing continual mixing between the interstitial fluid and the plasma. Diffusion results from thermal motion of the water molecules and dissolved...

Secretion of Bile by the Liver Functions of the Biliary Tree

One of the many functions of the liver is to secrete bile, normally between 600 and 1000 ml day. Bile serves two important functions First, bile plays an important role in fat digestion and absorption, not because of any enzymes in the bile that cause fat digestion, but because bile acids in the bile do two things (1) they help to emulsify the large fat particles of the food into many minute particles, the surface of which can then be attacked by lipase enzymes secreted in pancreatic juice, and...

Control of Extracellular Fluid Osmolarity and Sodium Concentration

Regulation of extracellular fluid osmolarity and sodium concentration are closely linked because sodium is the most abundant ion in the extracellular compartment. Plasma sodium concentration is normally regulated within close limits of 140 to 145 mEq L, with an average concentration of about 142 mEq L. Osmolarity averages about 300 mOsm L (about 282 mOsm L when corrected for interionic attraction) and seldom changes more than 2 to 3 per cent. As discussed in Chapter 25, these variables must be...

Respiratory Alkalosis Results from Increased Ventilation and Decreased Pco2

Respiratory alkalosis is caused by overventilation by the lungs. Rarely does this occur because of physical pathological conditions. However, a psychoneurosis can occasionally cause overbreathing to the extent that a person becomes alkalotic. A physiologic type of respiratory alkalosis occurs when a person ascends to high altitude. The low oxygen content of the air stimulates respiration, which causes excess loss of CO2 and development of mild respiratory alkalosis. Again, the major means for...

CO2 Concentration and Partial Pressure in the Alveoli

Carbon dioxide is continually being formed in the body and then carried in the blood to the alveoli it is continually being removed from the alveoli by ventilation. Figure 39-5 shows the effects on the alveolar partial pressure of carbon dioxide (Pco2) of both alveolar ventilation and two rates of carbon dioxide excretion, 200 and 800 ml min. One curve represents a normal rate of carbon dioxide excretion of 200 ml min. At the normal rate of alveolar ventilation of 4.2 L min, the operating point...

Pancreatic Secretion

The pancreas, which lies parallel to and beneath the stomach (illustrated in Figure 64-10), is a large compound gland with most of its internal structure similar to that of the salivary glands shown in Figure 64-2. The pancreatic digestive enzymes are secreted by pancreatic acini, and large volumes of sodium bicarbonate solution are secreted by the small ductules and larger ducts leading from the acini. The combined product of enzymes and sodium bicarbonate then flows through a long pancreatic...

Normal Heart Sounds

Listening with a stethoscope to a normal heart, one hears a sound usually described as lub, dub, lub, dub. The lub is associated with closure of the atrioventricular (A-V) valves at the beginning of systole, and the dub is associated with closure of the semilunar (aortic and pulmonary) valves at the end of systole. The lub sound is called the first heart sound, and the dub is called the second heart sound, because the normal pumping cycle of the heart is considered to start when the A-V valves...

Control of Calcium Excretion by the Kidneys

Because calcium is both filtered and reabsorbed in the kidneys but not secreted, the rate of renal calcium excretion is calculated as Renal calcium excretion Calcium filtered - Calcium reabsorbed Only about 50 per cent of the plasma calcium is ionized, with the remainder being bound to the plasma proteins or complexed with anions such as phosphate. Therefore, only about 50 per cent of the plasma calcium can be filtered at the glomerulus. Normally, about 99 per cent of the filtered calcium is...

Transport of Substances Through the Cell Membrane

1 Figure 4-1 gives the approximate concentrations of important electrolytes and other substances in the J ' extracellular fluid and intracellular fluid. Note that the extracellular fluid contains a large amount of sodium but only a small amount of potassium. Exactly the opposite is true of the intracellular fluid. Also, the extracellular fluid contains a large amount of chloride ions, whereas the intracellular fluid contains very little. But the concentrations of phosphates and proteins in the...

Interstitial Fluid Colloid Osmotic Pressure

Although the size of the usual capillary pore is smaller than the molecular sizes of the plasma proteins, this is not true of all the pores. Therefore, small amounts of plasma proteins do leak through the pores into the interstitial spaces. The total quantity of protein in the entire 12 liters of interstitial fluid of the body is slightly greater than the total quantity of protein in the plasma itself, but because this volume is four times the volume of plasma, the average protein concentration...

Prolonged QRS Complex Resulting from Purkinje System Blocks

When the Purkinje fibers are blocked, the cardiac impulse must then be conducted by the ventricular muscle instead of by way of the Purkinje system. This decreases the velocity of impulse conduction to about one third of normal. Therefore, if complete block of one of the bundle branches occurs, the duration of the QRS complex usually is increased to 0.14 second or greater. In general, a QRS complex is considered to be abnormally long when it lasts more than 0.09 second when it lasts more than...

Spread of the Action Potential to the Interior of the Muscle Fiber by Way of Transverse Tubules

The skeletal muscle fiber is so large that action potentials spreading along its surface membrane cause almost no current flow deep within the fiber. Yet, to cause maximum muscle contraction, current must penetrate deeply into the muscle fiber to the vicinity of the separate myofibrils. This is achieved by transmission of action potentials along transverse tubules (T tubules) that penetrate all the way through the muscle fiber from one side of the fiber to the other, as illustrated in Figure...

Figure 282

Formation of a dilute urine when antidiuretic hormone (ADH) levels are very low. Note that in the ascending loop of Henle, the tubular fluid becomes very dilute. In the distal tubules and collecting tubules, the tubular fluid is further diluted by the reabsorption of sodium chloride and the failure to reabsorb water when ADH levels are very low. The failure to reabsorb water and continued reabsorption of solutes lead to a large volume of dilute urine. (Numerical values are in milliosmoles per...

Measurement of Cardiac Output Using the Oxygen Fick Principle

The Fick principle is explained by Figure 20-18. This figure shows that 200 milliliters of oxygen are being absorbed from the lungs into the pulmonary blood each minute. It also shows that the blood entering the right heart has an oxygen concentration of 160 milliliters per liter of blood, whereas that leaving the left heart has an oxygen concentration of 200 milliliters per liter of blood. From these data, one can calculate that each liter of blood passing through the lungs absorbs 40...

Long Term Mechanisms for Arterial Pressure Regulation

Goal of this chapter has been to explain the role of the kidneys in long-term control of arterial pressure. To the far right in Figure 19-15 is shown the renal-blood volume pressure control mechanism (which is the same as the renal-body fluid pressure control mechanism), demonstrating that it takes a few hours to begin showing significant response. Yet it eventually develops a feedback gain for control of arterial pressure equal to infinity. This means that this mechanism can eventually return...

Transport of Oxygen in the Dissolved State

At the normal arterial Po2 of 95 mm Hg, about 0.29 milliliter of oxygen is dissolved in every 100 milliliters of water in the blood, and when the Po2 of the blood falls to the normal 40 mm Hg in the tissue capillaries, only 0.12 milliliter of oxygen remains dissolved. In other words, 0.17 milliliter of oxygen is normally transported in the dissolved state to the tissues by each 100 milliliters of arterial blood flow. This compares with almost 5 milliliters of oxygen transported by the red cell...

Sense of Taste

Taste is mainly a function of the taste buds in the mouth, but it is common experience that one's sense of smell also contributes strongly to taste perception. In addition, the texture of food, as detected by tactual senses of the mouth, and the presence of substances in the food that stimulate pain endings, such as pepper, greatly alter the taste experience. The importance of taste lies in the fact that it allows a person to select food in accord with desires and often in accord with the body...

Myg

Effect of Rate of Tissue Metabolism and Tissue Blood Flow on Interstitial PCO2. Tissue capillary blood flow and tissue metabolism affect the Pco2 in ways exactly opposite to their effect on tissue Po2. Figure 40-7 shows these effects, as follows 1. A decrease in blood flow from normal (point A) to one quarter normal (point B) increases peripheral tissue Pco2 from the normal value of 45 mm Hg to an elevated level of 60 mm Hg. Conversely, increasing the blood flow to six times normal (point C)...

Pain in Coronary Heart Disease

Normally, a person cannot feel his or her heart, but ischemic cardiac muscle often does cause pain sensa-tion sometimes severe pain. Exactly what causes this pain is not known, but it is believed that ischemia causes the muscle to release acidic substances, such as lactic acid, or other pain-promoting products, such as histamine, kinins, or cellular proteolytic enzymes, that are not removed rapidly enough by the slowly moving coronary blood flow. The high concentrations of these abnormal...

Pregnancy and Lactation

In Chapters 80 and 81, the sexual functions of the male and female are described to the point of fertilization of the ovum. If the ovum becomes fertilized, a new sequence of events called gestation, or pregnancy, takes place, and the fertilized ovum eventually develops into a full-term fetus. The purpose of this chapter is to discuss the early stages of ovum development after fertilization and then to discuss the physiology of pregnancy. In Chapter 83, some special aspects of fetal and early...

I I I I I Ii

Retinal image Cortical stimulation Pattern of excitation that occurs in the visual cortex in response to a retinal image of a dark cross. of each line or border that is, whether it is vertical or horizontal or lies at some degree of inclination. This is believed to result from linear organizations of mutually inhibiting cells that excite second-order neurons when inhibition occurs all along a line of cells where there is a contrast edge. Thus, for each such orientation of a line, specific...

Diffusion of Gases Through Tissues

The gases that are of respiratory importance are all highly soluble in lipids and, consequently, are highly soluble in cell membranes. Because of this, the major limitation to the movement of gases in tissues is the rate at which the gases can diffuse through the tissue water instead of through the cell membranes. Therefore, diffusion of gases through the tissues, including through the respiratory membrane, is almost equal to the diffusion of gases in water, as given in the preceding list.

Figure 293

Mechanisms of potassium secretion and sodium reabsorption by the principal cells of the late distal and collecting tubules. and make up about 90 per cent of the epithelial cells in these regions. Figure 29-3 shows the basic cellular mechanisms of potassium secretion by the principal cells. Secretion of potassium from the blood into the tubular lumen is a two-step process, beginning with uptake from the interstitium into the cell by the sodium-potassium ATPase pump in the basolateral membrane of...

Sodium Excretion Is Precisely Matched to Intake Under Steady State Conditions

An important consideration in overall control of sodium excretion or excretion of any electrolyte, for that matter is that under steady-state conditions, excretion by the kidneys is determined by intake. To maintain life, a person must, over the long term, excrete almost precisely the amount of sodium ingested. Therefore, even with disturbances that cause major changes in kidney function, balance between intake and output of sodium usually is restored within a few days. If disturbances of...

Figure 372

Contraction and expansion of the thoracic cage during expiration and inspiration, demonstrating diaphragmatic contraction, function of the intercostal muscles, and elevation and depression of the rib cage. Figure 37-1 also shows the mechanism by which the external and internal intercostals act to cause inspiration and expiration. To the left, the ribs during expiration are angled downward, and the external intercostals are elongated forward and downward. As they contract, they pull the upper...

The Cardiac Cycle

The cardiac events that occur from the beginning of one heartbeat to the beginning of the next are called the cardiac cycle. Each cycle is initiated by spontaneous generation of an action potential in the sinus node, as explained in Chapter l0. This node is located in the superior lateral wall of the right atrium near the opening of the superior vena cava, and the action potential travels from here rapidly through both atria and then through the A-V bundle into the ventricles. Because of this...

Increase in Arterial Pressure During Muscle Exercise and Other Types of Stress

An important example of the ability of the nervous system to increase the arterial pressure is the increase in pressure that occurs during muscle exercise. During heavy exercise, the muscles require greatly increased blood flow. Part of this increase results from local vasodilation of the muscle vasculature caused by increased metabolism of the muscle cells, as explained in Chapter 17. Additional increase results from simultaneous elevation of arterial pressure caused by sympathetic stimulation...

G

The baroreceptors respond extremely rapidly to changes in arterial pressure in fact, the rate of impulse firing increases in the fraction of a second during each systole and decreases again during diastole. Furthermore, the baroreceptors respond much more to a rapidly changing pressure than to a stationary pressure. That is, if the mean arterial pressure is 150 mm Hg but at that moment is rising rapidly, the rate of impulse transmission may be as much as twice that when the pressure is...

Control of Overall Respiratory Center Activity

Up to this point, we have discussed the basic mechanisms for causing inspiration and expiration, but it is also important to know how the intensity of the respiratory control signals is increased or decreased to match the ventilatory needs of the body. For example, during heavy exercise, the rates of oxygen usage and carbon dioxide formation are often increased to as much as 20 times normal, requiring commensurate increases in pulmonary ventilation.The major purpose of the remainder of this...

Overview of Renal Potassium Excretion

Potassium excretion is determined by the sum of three renal processes (1) the rate of potassium filtration (GFR multiplied by the plasma potassium concentration), (2) the rate of potassium reabsorption by the tubules, and (3) the rate of potassium secretion by the tubules. The normal rate of potassium filtration is about 756 mEq day (GFR, 180 L day multiplied by plasma potassium, 4.2 mEq L) this rate of filtration is usually relatively constant because of the autoregula-tory mechanisms for GFR...

Visual Pathways

Figure 51-1 shows the principal visual pathways from the two retinas to the visual cortex. The visual nerve signals leave the retinas through the optic nerves. At the optic chiasm, the optic nerve fibers from the nasal halves of the retinas cross to the opposite sides, where they join the fibers from the opposite temporal retinas to form the optic tracts. The fibers of each optic tract then synapse in the dorsal lateral geniculate nucleus of the thalamus, and from there, geniculocalcarine...

Stomach Emptying

Stomach emptying is promoted by intense peristaltic contractions in the stomach antrum. At the same time, emptying is opposed by varying degrees of resistance to passage of chyme at the pylorus. Intense Antral Peristaltic Contractions During Stomach Emptying Pyloric Pump. Most of the time, the rhythmical stomach contractions are weak and function mainly to cause mixing of food and gastric secretions. However, for about 20 per cent of the time while food is in the stomach, the contractions...

Feedback Effect of Thyroid Hormone to Decrease Anterior Pituitary Secretion of TSH

Increased thyroid hormone in the body fluids decreases secretion of TSH by the anterior pituitary. When the rate of thyroid hormone secretion rises to about 1.75 times normal, the rate of TSH secretion falls essentially to zero. Almost all this feedback depressant effect occurs even when the anterior pituitary has been separated from the hypothalamus. Therefore, as shown in Figure 76-7, it is probable that increased thyroid hormone inhibits anterior pituitary secretion of TSH mainly by a direct...

Figure 305

Cellular mechanisms for (1) active secretion of hydrogen ions into the renal tubule (2) tubular reabsorption of bicarbonate ions by combination with hydrogen ions to form carbonic acid, which dissociates to form carbon dioxide and water and (3) sodium ion reabsorption in exchange for hydrogen ions secreted. This pattern of hydrogen ion secretion occurs in the proximal tubule, the thick ascending segment of the loop of Henle, and the early distal tubule. process begins when CO2 either diffuses...

Figure 205

Experiment in a dog to demonstrate the importance of nervous maintenance of the arterial pressure as a prerequisite for cardiac output control. Note that with pressure control, the metabolic stimulant dinitrophenol increases cardiac output greatly without pressure control, the arterial pressure falls and the cardiac output rises very little. (Drawn from experiments by Dr. M. Banet.) However, after autonomic control of the nervous system had been blocked, none of the normal circulatory reflexes...

References

Adair TH, Gay WJ, Montani JP Growth regulation of the vascular system evidence for a metabolic hypothesis. Am J Physiol 259 R393,1990. Campbell WB, Gauthier KM What is new in endothelium-derived hyperpolarizing factors Curr Opin Nephrol Hypertens 11 177,2002. Chang L, Kaipainen A, Folkman J Lymphangiogenesis new mechanisms. Ann N Y Acad Sci 979 111, 2002. Cowley AW Jr, Mori T, Mattson D, Zou AP Role of renal NO production in the regulation of medullary blood flow. Am J Physiol Regul Integr Comp...

Figure 199

Renin-angiotensin vasoconstrictor mechanism for arterial pressure control. arterioles immediately proximal to the glomeruli. When the arterial pressure falls, intrinsic reactions in the kidneys themselves cause many of the prorenin molecules in the JG cells to split and release renin. Most of the renin enters the renal blood and then passes out of the kidneys to circulate throughout the entire body. However, small amounts of the renin do remain in the local fluids of the kidney and initiate...

Combination of Hemoglobin with Carbon Monoxide Displacement of Oxygen

Carbon monoxide combines with hemoglobin at the same point on the hemoglobin molecule as does oxygen it can therefore displace oxygen from the hemoglobin, thereby decreasing the oxygen carrying capacity of blood. Further, it binds with about 250 times as much tenacity as oxygen, which is demonstrated by the carbon monoxide-hemoglobin dissociation curve in Figure 40-12. This curve is almost identical to the oxygen-hemoglobin dissociation curve, except that the carbon monoxide partial pressures,...

Figure 167

Effect of Abnormal Imbalance of Forces at the Capillary Membrane If the mean capillary pressure rises above 17 mm Hg, the net force tending to cause filtration of fluid into the tissue spaces rises. Thus, a 20 mm Hg rise in mean capillary pressure causes an increase in net filtration pressure from 0.3 mm Hg to 20.3 mm Hg, which results in 68 times as much net filtration of fluid into the interstitial spaces as normally occurs. To prevent accumulation of excess fluid in these spaces would...

Nervous Regulation of the Circulation

As discussed in Chapter 17, adjustment of blood flow tissue by tissue is mainly the function of local tissue blood flow control mechanisms. We shall see in this chapter that nervous control of the circulation has more global functions, such as redistributing blood flow to different areas of the body, increasing or decreasing pumping activity by the heart, and, especially, providing very rapid control of systemic arterial pressure. The nervous system controls the circulation almost entirely...

Hmb

The 10 essential amino acids cannot be synthesized in sufficient quantities in the body these essential amino acids must be obtained, already formed, from food. by other linkages, often by hydrogen bonding between the CO and NH radicals of the peptides, as follows

Diffusion of Gases Through the Respiratory Membrane

Figure 39-7 shows the respiratory unit (also called respiratory lobule), which is composed of a respiratory bronchiole, alveolar ducts, atria, and alveoli. There are about 300 million alveoli in the two lungs, and each alveolus has an average diameter of about 0.2 millimeter. The alveolar walls are extremely thin, and between the alveoli is an almost solid network of interconnecting capillaries, shown in Figure 39-8. Indeed, because of the extensiveness of the capillary...

Figure 653

Hydrolysis of neutral fat catalyzed by lipase. are digested to the final stage to form single amino acids these then pass on through to the other side of the enterocyte and thence into the blood. More than 99 per cent of the final protein digestive products that are absorbed are individual amino acids, with only rare absorption of peptides and very, very rare absorption of whole protein molecules. Even these very few absorbed molecules of whole protein can sometimes cause serious allergic or...

Cortical and Brain Stem Control of Motor Function

In this chapter, we discuss control of body movements by the cerebral cortex and brain stem. Most voluntary movements initiated by the cerebral cortex are achieved when the cortex activates patterns of function stored in lower brain areas the cord, brain stem, basal ganglia, and cerebellum. These lower centers, in turn, send specific control signals to the muscles. For a few types of movements, however, the cortex has almost a direct pathway to the anterior motor neurons of the cord, bypassing...

Digestion of Triglycerides by Pancreatic Lipase By far the

Most important enzyme for digestion of the triglycerides is pancreatic lipase, present in enormous quantities in pancreatic juice, enough to digest within 1 minute all triglycerides that it can reach. In addition, the enterocytes of the small intestine contain still more lipase, known as enteric lipase, but this is usually not needed. End Products of Fat Digestion. Most of the triglycerides of the diet are split by pancreatic lipase into (Bile + Agitation) Fat--- Emulsified fat

Hydrolysis of Disaccharides and Small Glucose Polymers into Monosaccharides by Intestinal Epithelial Enzymes

Enterocytes lining the villi of the small intestine contain four enzymes (lactase, sucrase, maltase, and a-dextrinase), which are capable of splitting the disac-charides lactose, sucrose, and maltose, plus other small glucose polymers, into their constituent monosaccha-rides.These enzymes are located in the enterocytes covering the intestinal microvilli brush border, so that the disaccharides are digested as they come in contact with these enterocytes. Lactose splits into a molecule of...

Work of Breathing

We have already pointed out that during normal quiet breathing, all respiratory muscle contraction occurs during inspiration expiration is almost entirely a passive process caused by elastic recoil of the lungs and chest cage. Thus, under resting conditions, the respiratory muscles normally perform work to cause inspiration but not to cause expiration. The work of inspiration can be divided into three fractions (1) that required to expand the lungs against the lung and chest elastic forces,...

Diq

Changes in the average direction of the electrical potential from the heart. The so-called vectorcardiogram depicts these changes at different times during the cardiac cycle, as shown in Figure 12-10. In the large vectorcardiogram of Figure 12-10, point 5 is the zero reference point, and this point is the negative end of all the successive vectors. While the heart muscle is polarized between heartbeats, the positive end of the vector remains at the zero point because there is no vectorial...

Nadh

This reaction will not occur without intermediation of the specific dehydrogenase or without the availability of NAD+ to act as a hydrogen carrier. Both the free hydrogen ion and the hydrogen bound with NAD+ subsequently enter into multiple oxidative chemical reactions that form tremendous quantities of ATP, as discussed later. The remaining four hydrogen atoms released during the breakdown of glucose the four released during the citric acid cycle between the succinic and fumaric acid stages...

Physiologic Anatomy of the Sympathetic Nervous System

Figure 60-1 shows the general organization of the peripheral portions of the sympathetic nervous system. Shown specifically in the figure are (1) one of the two paravertebral sympathetic chains of ganglia that are interconnected with the spinal nerves on the side of the vertebral column, (2) two prevertebral ganglia (the celiac and hypogastric), and (3) nerves extending from the ganglia to the different internal organs. The sympathetic nerve fibers originate in the spinal cord along with spinal...

Vestibular Mechanisms for Stabilizing the Eyes

When a person changes his or her direction of movement rapidly or even leans the head sideways, forward, or backward, it would be impossible to maintain a stable image on the retinas unless the person had some automatic control mechanism to stabilize the direction of the eyes' gaze. In addition, the eyes would be of little use in detecting an image unless they remained fixed on each object long enough to gain a clear image. Fortunately, each time the head is suddenly rotated, signals from the...

Figure 583

Multiple centers in the brain stem, the neurons of which secrete different transmitter substances (specified in parentheses). These neurons send control signals upward into the diencephalon and cerebrum and downward into the spinal cord. JCingulate cortex Caudate nucleus

Figure 158

Changes in systolic, diastolic, and mean arterial pressures with age. The shaded areas show the approximate normal ranges. by millisecond over a period of time. It is not equal to the average of systolic and diastolic pressure because the arterial pressure remains nearer to diastolic pressure than to systolic pressure during the greater part of the cardiac cycle. Therefore, the mean arterial pressure is determined about 60 per cent by the diastolic pressure and 40 per cent by the systolic...

Hemophilia

Hemophilia is a bleeding disease that occurs almost exclusively in males. In 85 per cent of cases, it is caused by an abnormality or deficiency of Factor VIII this type of hemophilia is called hemophilia A or classic hemophilia. About 1 of every 10,000 males in the United States has classic hemophilia. In the other 15 per cent of hemophilia patients, the bleeding tendency is caused by deficiency of Factor IX. Both of these factors are transmitted genetically by way of the female chromosome....

Low Output Cardiac Failure Cardiogenic Shock

In many instances after acute heart attacks and often after prolonged periods of slow progressive cardiac deterioration, the heart becomes incapable of pumping even the minimal amount of blood flow required to keep the body alive. Consequently, all the body tissues begin to suffer and even to deteriorate, often leading to death within a few hours to a few days. The picture then is one of circulatory shock, as explained in Chapter 24. Even the cardiovascular system suffers from lack of...

Increased Voltage in the Standard Bipolar Limb Leads

Normally, the voltages in the three standard bipolar limb leads, as measured from the peak of the R wave to the bottom of the S wave, vary between 0.5 and 2.0 millivolts, with lead III usually recording the lowest voltage and lead II the highest. However, these relations are not invariable, even for the normal heart. In general, when the sum of the voltages of all the QRS complexes of the three standard leads is greater than 4 millivolts, the patient is considered to have a highvoltage...

Figure 752

Metabolic functions of the anterior pituitary hormones. ACH, adrenal corticosteroid hormones. anterior pituitary gland. With special stains attached to high-affinity antibodies that bind with the distinctive hormones, at least five cell types can be differentiated (Figure 75-3). Table 75-1 provides a summary of these cell types, the hormones they produce, and their physiological actions. These five cell types are 1. Somatotropes human growth hormone (hGH) (ACTH) hormone (TSH) 4. Gonadotropes...

Distribution of Extracellular Fluid Between the Interstitial Spaces and Vascular System

From Figure 29-12 it is apparent that blood volume and extracellular fluid volume are usually controlled in parallel with each other. Ingested fluid initially goes into the blood, but it rapidly becomes distributed between the interstitial spaces and the plasma. Therefore, blood volume and extracellular fluid volume usually are controlled simultaneously. There are circumstances, however, in which the distribution of extracellular fluid between the interstitial spaces and blood can vary greatly....

Figure 376

Diagram showing respiratory excursions during normal breathing and during maximal inspiration and maximal expiration. expiring to the maximum extent (about 4600 milliliters). 4. The total lung capacity is the maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 milliliters) it is equal to the vital capacity plus the residual volume. All pulmonary volumes and capacities are about 20 to 25 per cent less in women than in men, and they are greater in large...

Moderate Fluid Retention in Cardiac Failure Can Be Beneficial

Many cardiologists formerly considered fluid retention always to have a detrimental effect in cardiac failure. But it is now known that a moderate increase in body fluid and blood volume is an important factor in helping to compensate for the diminished pumping ability of the heart by increasing the venous return. The increased blood volume increases venous return in two ways First, it increases the mean systemic filling pressure, which increases the pressure gradient for causing venous flow of...

Visual Acuity

Theoretically, light from a distant point source, when focused on the retina, should be infinitely small. However, because the lens system of the eye is never perfect, such a retinal spot ordinarily has a total diameter of about 11 micrometers, even with maximal resolution of the normal eye optical system. The spot is brightest in its center and shades off gradually toward the edges, as shown by the two-point images in Figure 49-16. The average diameter of the cones in the fovea of the retina...

Physiology of Treatment in Shock

If a person is in shock caused by hemorrhage, the best possible therapy is usually transfusion of whole blood. If the shock is caused by plasma loss, the best therapy is administration of plasma when dehydration is the cause, administration of an appropriate electrolyte solution can correct the shock. Whole blood is not always available, such as under battlefield conditions. Plasma can usually substitute adequately for whole blood because it increases the blood...

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By HCO3-, which is then converted into dissolved CO2, decreasing the ratio of HCO3- to CO2 and decreasing the pH of the extracellular fluid. Buffer Power Is Determined by the Amount and Relative Concentrations of the Buffer Components. From the titration curve in Figure 30-1, several points are apparent. First, the pH of the system is the same as the pK when each of the components (HCO3- and CO2) constitutes 50 per cent of the total concentration of the buffer system. Second, the buffer system...

Cardiac Reserve

The maximum percentage that the cardiac output can increase above normal is called the cardiac reserve. Thus, in the healthy young adult, the cardiac reserve is 300 to 400 per cent. In athletically trained persons, it is occasionally 500 to 600 per cent. But in heart failure, there is no cardiac reserve. As an example of normal reserve, during severe exercise the cardiac output of a healthy young adult can rise to about five times normal this is an increase above normal of 400 per cent that is,...

Puberty and Menarche

Puberty means the onset of adult sexual life, and menarche means the beginning of the cycle of Total rates of secretion of gonadotropic hormones throughout the sexual lives of female and male human beings, showing an especially abrupt increase in gonadotropic hormones at menopause in the female. menstruation. The period of puberty is caused by a gradual increase in gonadotropic hormone secretion by the pituitary, beginning in about the eighth year of life, as shown in Figure 81-9, and usually...

Specific Areas in the Hypothalamus Control Secretion of Specific Hypothalamic Releasing and Inhibitory Hormones All or

Most of the hypothalamic hormones are secreted at nerve endings in the median eminence before being transported to the anterior pituitary gland. Electrical stimulation of this region excites these nerve endings and, therefore, causes release of essentially all the hypothalamic hormones. However, the neuronal cell bodies that give rise to these median eminence nerve endings are located in other discrete areas of the hypothalamus or in closely related areas of the basal brain. The specific loci...

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Macula densa feedback mechanism for autoregulation of glomerular hydrostatic pressure and glomerular filtration rate (GFR) during decreased renal arterial pressure. Blockade of Angiotensin II Formation Further Reduces GFR During Renal Hypoperfusion. As discussed earlier, a preferential constrictor action of angiotensin II on efferent arteri-oles helps prevent serious reductions in glomerular hydrostatic pressure and GFR when renal perfusion pressure falls below normal. The administration of...

Excretion of Excess Hydrogen Ions and Generation of New Bicarbonate by the Ammonia Buffer System

A second buffer system in the tubular fluid that is even more important quantitatively than the phosphate buffer system is composed of ammonia (NH3) and the ammonium ion (NH4+). Ammonium ion is synthesized from glutamine, which comes mainly from the metabolism of amino acids in the liver. The glutamine delivered to the kidneys is transported into the epithelial cells of the proximal tubules, thick ascending limb of the loop of Henle, and distal tubules (Figure 30-8). Once inside the cell, each...

Transport of Carbon Dioxide in the Blood

Transport of carbon dioxide by the blood is not nearly as problematical as transport of oxygen is, because even in the most abnormal conditions, carbon dioxide can usually be transported in far greater quantities than oxygen can be. However, the amount of carbon dioxide in the blood has a lot to do with the acid-base balance of the body fluids, which is discussed in Chapter 30. Under normal resting conditions, an average of 4 milliliters of carbon dioxide is transported from the tissues to the...

Theoretical Function of the Hippocampus in Learning

Hippocampus originated as part of the olfactory cortex. In many lower animals, this cortex plays essential roles in determining whether the animal will eat a particular food, whether the smell of a particular object suggests danger, or whether the odor is sexually inviting, thus making decisions that are of life-or-death importance.Very early in evolutionary development of the brain, the hippocampus presumably became a critical decision-making neuronal mechanism, determining the importance of...

Blood Volume

Blood contains both extracellular fluid (the fluid in plasma) and intracellular fluid (the fluid in the red blood cells). However, blood is considered to be a separate fluid compartment because it is contained in a chamber of its own, the circulatory system. The blood volume is especially important in the control of cardiovascular dynamics. The average blood volume of adults is about 7 per cent of body weight, or about 5 liters. About 60 per cent of the blood is plasma and 40 per cent is red...

Synthesis and Secretion of the Thyroid Metabolic Hormones

About 93 per cent of the metabolically active hormones secreted by the thyroid gland is thyroxine, and 7 per cent triiodothyronine. However, almost all the thy-roxine is eventually converted to triiodothyronine in the tissues, so that both are functionally important. The functions of these two hormones are qualitatively the same, but they differ in rapidity and intensity of action. Triiodothy-ronine is about four times as potent as thyroxine, but it is present in the blood in much smaller...

Control of Pupillary Diameter

Stimulation of the parasympathetic nerves also excites the pupillary sphincter muscle, thereby decreasing the pupillary aperture this is called miosis. Conversely, stimulation of the sympathetic nerves excites the radial fibers of the iris and causes pupillary dilation, called mydriasis. Pupillary Light Reflex. When light is shone into the eyes, the pupils constrict, a reaction called the pupillary light reflex. The neuronal pathway for this reflex is demonstrated by the upper two black traces...

Renal Interstitial Hydrostatic and Colloid Osmotic Pressures

Ultimately, changes in peritubular capillary physical forces influence tubular reabsorption by changing the physical forces in the renal interstitium surrounding the tubules. For example, a decrease in the reabsorp-tive force across the peritubular capillary membranes, caused by either increased peritubular capillary hydrostatic pressure or decreased peritubular capillary colloid osmotic pressure, reduces the uptake of fluid and solutes from the interstitium into the peritubular capillaries....

Some Hormones That Use the Adenylyl CyclasecAMP Second Messenger System

Adrenocorticotropic hormone (ACTH) Angiotensin II (epithelial cells) Calcitonin Catecholamines ( receptors) Corticotropin-releasing hormone (CRH) Follicle-stimulating hormone (FSH) Glucagon Human chorionic gonadotropin (HCG) Luteinizing hormone (LH) Parathyroid hormone (PTH) Secretin Somatostatin Thyroid-stimulating hormone (TSH) Vasopressin (V2 receptor, epithelial cells) cAMP is not the only second messenger used by the different hormones. Two other especially important ones are (1) calcium...

Basilar Membrane and Resonance in the Cochlea

Basilar membrane is a fibrous membrane that separates the scala media from the scala tympani. It contains 20,000 to 30,000 basilar fibers that project from the bony center of the cochlea, the modiolus, toward the outer wall. These fibers are stiff, elastic, reedlike structures that are fixed at their basal ends in the central bony structure of the cochlea (the modi-olus) but are not fixed at their distal ends, except that the distal ends are embedded in the loose basilar membrane. Because the...

Figure 418

To transmit at the same time collateral impulses into the brain stem to excite the respiratory center. This is analogous to the stimulation of the vasomotor center of the brain stem during exercise that causes a simultaneous increase in arterial pressure. Actually, when a person begins to exercise, a large share of the total increase in ventilation begins immediately on initiation of the exercise, before any blood chemicals have had time to change. It is likely that most of the increase in...

Pituitary Gland and Its Relation to the Hypothalamus

Pituitary Gland Two Distinct Parts-The Anterior and Posterior Lobes. The pituitary gland (Figure 75-1), also called the hypophysis, is a small gland about 1 centimeter in diameter and 0.5 to 1 gram in weight that lies in the sella turcica, a bony cavity at the base of the brain, and is connected to the hypothalamus by the pituitary (or hypophysial) stalk. Physiologically, the pituitary gland is divisible into two distinct portions the anterior pituitary, also known as the adenohypophysis, and...

Absorption and Secretion of Electrolytes and Water

Mucosa of the large intestine, like that of the small intestine, has a high capability for active absorption of sodium, and the electrical potential gradient created by absorption of the sodium causes chloride absorption as well. The tight junctions between the epithelial cells of the large intestinal epithelium are much tighter than those of the small intestine. This prevents significant amounts of back-diffusion of ions through these junctions, thus allowing the large intestinal mucosa to...

Implantation of the Blastocyst in the Uterus

After reaching the uterus, the developing blastocyst usually remains in the uterine cavity an additional 1 to 3 days before it implants in the endometrium thus, implantation ordinarily occurs on about the fifth to seventh day after ovulation. Before implantation, the blastocyst obtains its nutrition from the uterine endometrial secretions, called uterine milk. Implantation results from the action of trophoblast cells that develop over the surface of the blastocyst. These cells secrete...

Figure 5612

Caudate circuit through the basal ganglia for cognitive planning of sequential and parallel motor patterns to achieve specific conscious goals. ventroanterior and ventrolateral thalamus, and finally back to the prefrontal, premotor, and supplementary motor areas of the cerebral cortex, but with almost none of the returning signals passing directly to the primary motor cortex. Instead, the returning signals go to those accessory motor regions in the premotor and supplementary motor areas that...

Regulation of Stomach Emptying

The rate at which the stomach empties is regulated by signals from both the stomach and the duodenum. However, the duodenum provides by far the more potent of the signals, controlling the emptying of chyme into the duodenum at a rate no greater than the rate at which the chyme can be digested and absorbed in the small intestine. Gastric Factors That Promote Emptying Effect of Gastric Food Volume on Rate of Emptying. Increased food volume in the stomach promotes increased emptying from the...

Extracellular Fluid Compartment

All the fluids outside the cells are collectively called the extracellular fluid. Together these fluids account for about 20 per cent of the body weight, or about 14 liters in a normal 70-kilogram adult. The two largest compartments of the extracellular fluid are the interstitial fluid, which makes up more than three fourths of the extracellular fluid, and the plasma, which makes up almost one fourth of the extracellular fluid, or about 3 liters. The plasma is the noncellular part of the blood...

Figure 148

Principles of three types of electronic transducers for recording rapidly changing blood pressures (explained in the text). In Figure 14-8A, a simple metal plate is placed a few hundredths of a centimeter above the membrane.When the membrane bulges, the membrane comes closer to the plate, which increases the electrical capacitance between these two, and this change in capacitance can be recorded using an appropriate electronic system. In Figure 14-85, a small iron slug rests on the membrane,...

Figure 141

Distribution of blood (in percentage of total blood) in the different parts of the circulatory system. in major segments of the circulation. For instance, about 84 per cent of the entire blood volume of the body is in the systemic circulation, and 16 per cent in heart and lungs. Of the 84 per cent in the systemic circulation, 64 per cent is in the veins, 13 per cent in the arteries, and 7 per cent in the systemic arterioles and capillaries. The heart contains 7 per cent of the blood, and the...

Medullary Collecting Duct

Although the medullary collecting ducts reabsorb less than 10 per cent of the filtered water and sodium, they are the final site for processing the urine and, therefore, play an extremely important role in determining the final urine output of water and solutes. The epithelial cells of the collecting ducts are nearly cuboidal in shape with smooth surfaces and relatively Cellular ultrastructure and transport characteristics of the medullary collecting duct. The medullary collecting ducts...