Secretion of Saliva

Salivary Glands Characteristics of Saliva. The principal glands of salivation are the parotid, submandibular, and sublingual glands in addition, there are many very small buccal glands. Daily secretion of saliva normally ranges between 800 and 1500 milliliters, as shown by the average value of 1000 milliliters in Table 64-1. Saliva contains two major types of protein secretion (1) a serous secretion that contains ptyalin (an a-amylase), which is an enzyme for digesting starches, and (2) mucus...

Regulation of Growth Hormone Secretion

For many years it was believed that growth hormone was secreted primarily during the period of growth but then disappeared from the blood at adolescence. This has proved to be untrue. After adolescence, secretion decreases slowly with aging, finally falling to about 25 per cent of the adolescent level in very old age. Growth hormone is secreted in a pulsatile pattern, increasing and decreasing. The precise mechanisms that control secretion of growth hormone are not fully understood, but several...

H2o

Transport of carbon dioxide in the blood. Carbon monoxide-hemoglobin dissociation curve. Note the extremely low carbon monoxide pressures at which carbon monoxide combines with hemoglobin. 0.6 mm Hg (a volume concentration of less than one part per thousand in air) can be lethal. Even though the oxygen content of blood is greatly reduced in carbon monoxide poisoning, the Po2 of the blood may be normal. This makes exposure to carbon monoxide especially dangerous, because the blood is bright red...

Info

Responses of a ganglion cell to light in (1) an area excited by a spot of light and (2) an area adjacent to the excited spot the ganglion cell in this area is inhibited by the mechanism of lateral inhibition. (Modified from Granit R Receptors and Sensory Perception A Discussion of Aims, Means, and Results of Electro-physiological Research into the Process of Reception. New Haven, Conn Yale University Press, 1955.) Responses of a ganglion cell to light in (1) an area excited by a spot of light...

Figure 584

Anatomy of the limbic system, shown in the dark pink area. (Redrawn from Warwick R, Williams PL Gray's Anatomy, 35th Br. ed. London Longman Group Ltd, 1973.) Limbic system, showing the key position of the hypothalamus. Limbic system, showing the key position of the hypothalamus. forebrain bundle, which extends from the septal and orbitofrontal regions of the cerebral cortex downward through the middle of the hypothalamus to the brain stem reticular formation. This bundle carries fibers in both...

Extrapyramidal System

The term extrapyramidal motor system is widely used in clinical circles to denote all those portions of the brain and brain stem that contribute to motor control but are not part of the direct corticospinal-pyramidal system. These include pathways through the basal ganglia, the reticular formation of the brain stem, the vestibular nuclei, and often the red nuclei. This is such an all-inclusive and diverse group of motor control areas that it is difficult to ascribe specific neurophysiologic...

Prolonged QRS Complex as a Result of Cardiac Hypertrophy or Dilatation

The QRS complex lasts as long as depolarization continues to spread through the ventricles that is, as long as part of the ventricles is depolarized and part is still polarized. Therefore, prolonged conduction of the impulse through the ventricles always causes a prolonged QRS complex. Such prolongation often occurs when one or both ventricles are hypertrophied or dilated, owing to the longer pathway that the impulse must then travel. The normal QRS complex lasts 0.06 to 0.08 second, whereas in...

Anterior Pituitary Secretion of TSH Is Regulated by Thyrotropin Releasing Hormone from the Hypothalamus

Anterior pituitary secretion of TSH is controlled by a hypothalamic hormone, thyrotropin-releasing hormone (TRH), which is secreted by nerve endings in the median eminence of the hypothalamus. From the median eminence, the TRH is then transported to the anterior pituitary by way of the hypothalamic-hypophysial portal blood, as explained in Chapter 74. TRH has been obtained in pure form. It is a simple substance, a tripeptide TRH directly affects the anterior pituitary gland cells to increase...

References

Andresen MC, Doyle MW, Jin YH, Bailey TW Cellular mechanisms of baroreceptor integration at the nucleus tractus solitarius. Ann N Y Acad Sci 940 132, 2001 Chang HY, Mashimo H, Goyal RK Musings on the wanderer what's new in our understanding of vago-vagal reflex IV. Current concepts of vagal efferent projections to the gut. Am J Physiol Gastrointest Liver Physiol 284 G357, 2003. Dajas-Bailador F, Wonnacott S Nicotinic acetylcholine receptors and the regulation of neuronal signalling. Trends...

Unit Viii

Aviation, Space, and Deep-Sea Diving Physiology CHAPTER 43 Aviation, High-Altitude, and Space Physiology Effects of Low Oxygen Pressure on the Body Alveolar Po2 at Different Elevations Effect of Breathing Pure Oxygen on Alveolar Po2 at Different Altitudes Acute Effects of Hypoxia Acclimatization to Low Po2 Natural Acclimatization of Native Human Beings Living at High Altitudes Reduced Work Capacity at High Altitudes and Positive Effect of Acclimatization Acute Mountain Sickness and...

Figure 198

Progressive changes in important circulatory system variables during the first few weeks of volume-loading hypertension. Note especially the initial increase in cardiac output as the basic cause of the hypertension. Subsequently, the autoregulation mechanism returns the cardiac output almost to normal while simultaneously causing a secondary increase in total peripheral resistance. (Modified from Guyton AC Arterial Pressure and Hypertension. Philadelphia WB Saunders Co, 1980.)

Dietary Balances

The energy liberated from each gram of carbohydrate as it is oxidized to carbon dioxide and water is 4.1 Calories (1 Calorie equals 1 kilocalorie), and that liberated from fat is 9.3 Calories.The energy liberated from metabolism of the average dietary protein as each gram is oxidized to carbon dioxide, water, and urea is 4.35 Calories. Also, these substances vary in the average percentages that are absorbed from the gastrointestinal tract about 98 per cent of carbohydrate, 95 per cent of fat,...

Chapter

Resistance of the Body to Infection I. Leukocytes, Granulocytes, the Monocyte-Macrophage System, and Inflammation Our bodies are exposed continually to bacteria, viruses, fungi, and parasites, all of which occur normally and to varying degrees in the skin, the mouth, the respiratory passageways, the intestinal tract, the lining membranes of the eyes, and even the urinary tract. Many of these infectious agents are capable of causing serious abnormal physiologic function or even death if they...

Transport of Oxygen in the Arterial Blood

About 98 per cent of the blood that enters the left atrium from the lungs has just passed through the alveolar capillaries and has become oxygenated up to a Po2 of about 104 mm Hg. Another 2 per cent of the blood has passed from the aorta through the bronchial circulation, which supplies mainly the deep tissues of the lungs and is not exposed to lung air. This blood flow is called shunt flow, meaning that blood is shunted past the gas exchange areas. On leaving the lungs, the Po2 of the shunt...

Bas

See also Infection. colonic, 817 Bactericidal agents of lysosomes, 20 of saliva, 794 of white blood cells, 432 Bainbridge reflex, 212, 233 Baldness, 1005 Baroreceptor(s), 6-7,209-212,757 activation of, 209-210,209f, 210f anatomy of, 209, 209f buffer function of, 210, 211f, 230, 230f denervation of, 210, 211f, 228 in antidiuretic hormone secretion, 360 in cardiac failure, 258-259 in extracellular volume control, 377 in hemorrhagic shock, 281 oscillation of, 214,214f postural...

Control of Blood Flow Through the Skeletal Muscles

Local Regulation Decreased Oxygen in Muscle Greatly Enhances Flow. The tremendous increase in muscle blood flow that occurs during skeletal muscle activity is caused primarily by chemical effects acting directly on the muscle arterioles to cause dilation. One of the most important chemical effects is reduction of oxygen in the muscle tissues. That is, during muscle activity, the muscle uses oxygen rapidly, thereby decreasing the oxygen concentration in the tissue fluids. This in turn causes...

Cells and Hormones of the Anterior Pituitary Gland and Their Physiological Functions

Lactotropes, Mammotropes IGF, insulin-like growth factor Adrenocorticotropic hormone (ACTH corticotropin) Thyroid-stimulating hormone (TSH thyrotropin) Single chain of 191 amino acids Single chain of 39 amino acids Glycoprotein of two subunits, a (89 amino acids) and b (112 amino acids) Glycoprotein of two subunits, a (89 amino acids) and b (112 amino acids) Glycoprotein of two subunits, a (89 amino acids) and b (115 amino acids) Stimulates body growth stimulates secretion of IGF-1 stimulates...

Figure 231

Chest areas from which sound from each valve is best heard. Amplitude of different-frequency vibrations in the heart sounds and heart murmurs in relation to the threshold of audibility, showing that the range of sounds that can be heard is between 40 and 520 cycles sec. (Modified from Butterworth JS, Chassin JL, McGrath JJ Cardiac Auscultation, 2nd ed. New York Grune & Stratton, 1960.) Chest areas from which sound from each valve is best heard.

Cooh

Synthesis of alanine from pyruvic acid by transamination. which are the precursors of the respective amino acids. For instance, pyruvic acid, which is formed in large quantities during the glycolytic breakdown of glucose, is the keto acid precursor of the amino acid alanine. Then, by the process of transamination, an amino radical is transferred to the a-keto acid, and the keto oxygen is transferred to the donor of the amino radical. This reaction is shown in Figure 69-3. Note in this figure...

Control of Cerebral Activity by Continuous Excitatory Signals from the Brain Stem

Reticular Excitatory Area of the Brain Stem Figure 58-1 shows a general system for controlling the level of activity of the brain. The central driving component of this system is an excitatory area located in the reticular substance of the pons and mesencephalon. This area is also known by the name bulboreticular facilitory area. We also discuss this area in Chapter 55 because it is the same brain stem reticular area that transmits facilitory signals downward to the spinal cord to maintain tone...

Movements of the Colon

The principal functions of the colon are (1) absorption of water and electrolytes from the chyme to form solid feces and (2) storage of fecal matter until it can be expelled. The proximal half of the colon, shown in Figure 63-5, is concerned principally with absorption, and the distal half with storage. Because intense colon wall movements are not required for these functions, the movements of the colon are normally very sluggish. Yet in a sluggish manner, the movements still have...

Control of Brain Stem Autonomic Centers by Higher Areas

Signals from the hypothalamus and even from the cerebrum can affect the activities of almost all the brain stem autonomic control centers. For instance, stimulation in appropriate areas mainly of the posterior hypothalamus can activate the medullary cardiovascular control centers strongly enough to increase arterial pressure to more than twice normal. Likewise, other hypothalamic centers control body temperature, increase or decrease salivation and gastrointestinal activity, and cause bladder...

Clc

Wall collagen alters two important clotting factors in the blood Factor XII and the platelets. When Factor XII is disturbed, such as by coming into contact with collagen or with a wettable surface such as glass, it takes on a new molecular configuration that converts it into a proteolytic enzyme called activated Factor XII. Simultaneously, the blood trauma also damages the platelets because of adherence to either collagen or a wettable surface (or by damage in other ways), and this releases...

Thyroid Hormones Increase the Transcription of Large Numbers of Genes

The general effect of thyroid hormone is to activate nuclear transcription of large numbers of genes (Figure 76-5). Therefore, in virtually all cells of the body, great numbers of protein enzymes, structural proteins, transport proteins, and other substances are synthesized. The net result is generalized increase in functional activity throughout the body. Most of the Thyroxine Secreted by the Thyroid Is Converted to Triiodothyronine. Before acting on the genes to increase genetic...

The Liver as an Organ

The liver performs many different functions yet is also a discrete organ, and many of its functions interrelate with one another. This becomes especially evident in abnormalities of the liver, because many of its functions are disturbed simultaneously. The purpose of this chapter is to summarize the liver's different functions, including (1) filtration and storage of blood (2) metabolism of carbohydrates, proteins, fats, hormones, and foreign chemicals (3) formation of bile (4) storage of...

Possible Nongenomic Actions of Aldosterone and Other Steroid Hormones

Recent studies suggest that many steroids, including aldosterone, elicit not only slowly developing genomic effects that have a latency of 60 to 90 minutes and require gene transcription and synthesis of new proteins, but also rapid nongenomic effects that take place in a few seconds or minutes. These nongenomic actions are believed to be mediated by binding of steroids to cell membrane receptors that are coupled to second messenger systems, similar to those used for peptide hormone signal...

Stm

And the functional cellular systems, but it can transfer energy interchangeably with ATP. When extra amounts of ATP are available in the cell, much of its energy is used to synthesize phosphocreatine, thus building up this storehouse of energy. Then, when the ATP begins to be used up, the energy in the phosphocreatine is transferred rapidly back to ATP and then to the functional systems of the cells. This reversible interrelation between ATP and phosphocreatine is demonstrated by the following...

Figure 306

Primary active secretion of hydrogen ions through the luminal membrane of the intercalated epithelial cells of the late distal and collecting tubules. Note that one bicarbonate ion is absorbed for each hydrogen ion secreted, and a chloride ion is passively secreted along with the hydrogen ion. instead of by counter-transport, as occurs in the early parts of the nephron. Although the secretion of H+ in the late distal tubule and collecting tubules accounts for only about 5 per cent of the total...

Figure 397

Respiratory unit. (Redrawn from Miller WS The Lung. Springfield, Ill Charles C Thomas, 1947.) and the pulmonary blood occurs through the membranes of all the terminal portions of the lungs, not merely in the alveoli themselves. All these membranes are collectively known as the respiratory membrane, also called the pulmonary membrane. Oxygen and carbon dioxide partial pressures in the various portions of normal expired air.

Normal Values for Plasma Colloid Osmotic Pressure

Colloid osmotic pressure of normal human plasma averages about 28 mm Hg 19 mm of this is caused by molecular effects of the dissolved protein and 9 mm by the Donnan effect that is, extra osmotic pressure caused by sodium, potassium, and the other cations held in the plasma by the proteins. Effect of the Different Plasma Proteins on Colloid Osmotic Pressure. The plasma proteins are a mixture that contains albumin, with an average molecular weight of 69,000 globulins, 140,000 and fibrinogen,...

Figure 417

Composite diagram showing the interrelated effects of Pco2, Po2, and pH on alveolar ventilation. (Drawn from data in Cunningham DJC, Lloyd BB The Regulation of Human Respiration. Oxford Blackwell Scientific Publications, 1963.) family of red curves represents the combined effects of alveolar Pco2 and Po2 on ventilation. Now observe the green curves. The red curves were measured at a blood pH of 7.4 the green curves were measured at a pH of 7.3. We now have two families of curves representing...

J

Mechanisms by which water, chloride, and urea reabsorption are coupled with sodium reabsorption. Cellular ultrastructure and primary transport characteristics of the proximal tubule. The proximal tubules reabsorb about 65 per cent of the filtered sodium, chloride, bicarbonate, and potassium and essentially all the filtered glucose and amino acids. The proximal tubules also secrete organic acids, bases, and hydrogen ions into the tubular lumen. Chloride ions can also be reabsorbed by secondary...

Use of Extracorporeal Circulation During Cardiac Surgery

It is almost impossible to repair intracardiac defects surgically while the heart is still pumping. Therefore, many types of artificial heart-lung machines have been developed to take the place of the heart and lungs during the course of operation. Such a system is called extracorporeal circulation. The system consists principally of a pump and an oxygenating device. Almost any type of pump that does not cause hemolysis of the blood seems to be suitable. Methods used for oxygenating blood...

Physiological Functions of ADH

The injection of extremely minute quantities of ADH as small as 2 nanograms can cause decreased excretion of water by the kidneys (antidiuresis). This antidiuretic effect is discussed in detail in Chapter 28. Briefly, in the absence of ADH, the collecting tubules and ducts become almost impermeable to water, which prevents significant reabsorption of water and therefore allows extreme loss of water into the urine, also causing extreme dilution of the urine. Conversely, in the presence of ADH,...

Vestibular Apparatus

The vestibular apparatus, shown in Figure 55-9, is the sensory organ for detecting sensations of equilibrium. It is encased in a system of bony tubes and chambers Membranous labyrinth, and organization of the crista ampullaris and the macula. Hair cell of the equilibrium apparatus and its synapses with the vestibular nerve. Membranous labyrinth, and organization of the crista ampullaris and the macula. located in the petrous portion of the temporal bone, called the bony labyrinth. Within this...

Primary Sensations of Taste

The identities of the specific chemicals that excite different taste receptors are not all known. Even so, psychophysiologic and neurophysiologic studies have identified at least 13 possible or probable chemical receptors in the taste cells, as follows 2 sodium receptors, 2 potassium receptors, 1 chloride receptor, 1 adenosine receptor, 1 inosine receptor, 2 sweet receptors, 2 bitter receptors, 1 glutamate receptor, and 1 hydrogen ion receptor. For practical analysis of taste, the...

Initiation of Lactation Function of Prolactin

Although estrogen and progesterone are essential for the physical development of the breasts during pregnancy, a specific effect of both these hormones is to inhibit the actual secretion of milk. Conversely, the hormone prolactin has exactly the opposite effect on milk secretion promoting it. This hormone is secreted by the mother's anterior pituitary gland, and its concentration in her blood rises steadily from the fifth week of pregnancy until birth of the baby, at which time it has risen to...

Detection of Vibration

All tactile receptors are involved in detection of vibration, although different receptors detect different frequencies of vibration. Pacinian corpuscles can detect signal vibrations from 30 to 800 cycles per second because they respond extremely rapidly to minute and rapid deformations of the tissues, and they also transmit their signals over type Ab nerve fibers, which can transmit as many as 1000 impulses per second. Low-frequency vibrations from 2 up to 80 cycles per second, in contrast,...

H

The DNA-Genetic System Also Controls Cell Reproduction Cell reproduction is another example of the ubiquitous role that the DNA-genetic system plays in all life processes. The genes and their regulatory mechanisms determine the growth characteristics of the cells and also when or whether these cells will divide to form new cells. In this way, the all-important genetic system controls each stage in the development of the human being, from the single-cell fertilized ovum to the whole functioning...

O

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,...

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...

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...

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

Hemoglobin And Carbon Monoxide

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...