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Articles

Ventilation and Acid Base Balance

The basic concepts and terminology relating to the acid-base balance of the blood were introduced in chapter 13. In brief review, acidosis refers to an arterial pH below 7.35, and alkalosis refers to an arterial pH above 7.45. There are two components of each respiratory and metabolic. The respiratory component refers to the carbon dioxide concentration of the blood, as measured by the PCO2. As implied by its name, the respiratory component is regulated by the respiratory system. The metabolic...

Hormone Metabolism and Excretion

A hormone's concentration in the plasma depends not only upon its rate of secretion by the endocrine gland but also upon its rate of removal from the blood, either by excretion or by metabolic transformation. The liver and the kidneys are the major organs that excrete or metabolize hormones. The liver and kidneys, however, are not the only routes for eliminating hormones. Sometimes the hormone is metabolized by the cells upon which it acts. Very importantly, in the case of peptide hormones,...

Synergistic and Permissive Effects

When two or more hormones work together to produce a particular result, their effects are said to be synergistic. These effects may be additive or complementary. The action of epinephrine and norepinephrine on the heart is a good example of an additive effect. Each of these hormones separately produces an increase in cardiac rate acting together in the same concentrations, they stimulate an even greater increase in car- diac rate. The synergistic action of FSH and testosterone is an example of...

The Global Biotechnology Industry

Biotechnology is an enabling technology and therefore has been embraced by governments to drive economic growth and improve quality of human life. The global biotechnology sector is currently undergoing change. The recent market downturn in the global economy is impacting on the current biotechnology landscape. The biotechnology sector is moving towards an alliance network of specialty companies (Ernst & Young 2003a). A company's activities do not have to span the full breadth of the...

Exchange of Fluid Between Capillaries and Tissues

The distribution of extracellular fluid between the plasma and interstitial compartments is in a state of dynamic equilibrium. Tissue fluid is not normally a stagnant pond rather, it is a continuously circulating medium, formed from and returning to the vascular system. In this way, the tissue cells receive a continuously fresh supply of glucose and other plasma solutes that are filtered through tiny endothelial channels in the capillary walls. Filtration results from blood pressure within the...

Balance in the Homeostasis of Chemicals

Many homeostatic systems are concerned with the balance between the addition to and removal from the body of a chemical substance. Figure 7-8 is a generalized schema of the possible pathways involved in such balance. The pool occupies a position of central importance in the balance sheet. It is the body's readily available quantity of the particular substance and is frequently identical to the amount present in the extracellular fluid. The pool receives substances from and contributes them to...

Regulation of Blood Volume by the Kidneys

The formation of urine begins in the same manner as the formation of tissue fluid by filtration of plasma through capillary pores. These capillaries are known as glomeruli, and the filtrate they produce enters a system of tubules that transports and modifies the filtrate by mechanisms discussed in chapter 17 . The kidneys produce about 180 L per day of blood filtrate, but since there is only 5.5 L of blood in the body, it is clear that most of this filtrate must be returned to the vascular...

Maintenance of Upright Posture and Balance

The skeleton supporting the body is a system of long bones and a many-jointed spine that cannot stand erect against the forces of gravity without the support given by coordinated muscle activity. The muscles that maintain upright posture that is, support the body's weight against gravity are controlled by the brain and by reflex mechanisms that are wired into the neural networks of the brainstem and spinal cord. Many of the reflex pathways previously introduced for example, the stretch and...

Renal Clearance of Inulin Measurement of GFR

If a substance is neither reabsorbed nor secreted by the tubules, the amount excreted in the urine per minute will be equal to the amount that is filtered out of the glomeruli per minute. There does not seem to be a single substance produced by the body, however, that is not reabsorbed or secreted to some degree. Plants such as artichokes, dahlias, onions, and garlic, fortunately, do produce such a compound. This compound, a polymer of the monosaccharide fructose, is inulin. Once injected into...

The Internal Environment and Homeostasis

An amoeba and a human liver cell both obtain their energy by breaking down certain organic nutrients. The chemical reactions involved in this intracellular process are remarkably similar in the two types of cells and involve the utilization of oxygen and the production of carbon dioxide. The amoeba picks up oxygen directly from the fluid surrounding it its external environment and eliminates carbon dioxide into the same fluid. But how can the liver cell and all other internal parts of the body...

Transport of Lipids in the Blood

Once the chylomicrons are in the blood, their triglyceride content is removed by the enzyme lipoprotein lipase, which is attached to the endothelium of blood vessels. This enzyme hydrolyzes triglycerides and thus provides free fatty acids and Step 1 Emulsification of fat droplets by bile salts Step 2 Hydrolysis of triglycerides in emulsified fat droplets into fatty acid and monoglycerides Step 3 Dissolving of fatty acids and monoglycerides into micelles to produce mixed micelles Figure 18.35...

Pressure Changes During the Cardiac Cycle

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

Mechanism of Thyroid Hormone Action

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

Bone Deposition and Resorption

The skeleton, in addition to providing support for the body, serves as a large store of calcium and phosphate in the form of crystals called hydroxyapatite, which has the formula Cajo PO4 6 OH 2. The calcium phosphate in these hydroxyap-atite crystals is derived from the blood by the action of bone-forming cells, or osteoblasts. The osteoblasts secrete an organic matrix composed largely of collagen protein, which becomes hardened by deposits of hydroxyapatite. This process is called bone...

Adrenergic and Cholinergic Synaptic Transmission

Acetylcholine ACh is the neurotransmitter of all preganglionic fibers both sympathetic and parasympathetic . Acetylcholine is also the transmitter released by most parasympathetic post- ganglionic fibers at their synapses with effector cells fig. 9.7 . Transmission at these synapses is thus said to be cholinergic. The neurotransmitter released by most postganglionic sympathetic nerve fibers is norepinephrine noradrenaline . Transmission at these synapses is thus said to be adrenergic. There are...

Intrapulmonary and Intrapleural Pressures

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

Belsey Fundoplication Technique

The total Nissen fundoplication is a 360-degree wrap of gastric fundus around the distal esophagus. After complete distal esophageal and proximal gastric mobilization including division of the proximal short gastric vessels left panel , the crura are approximated to close the hiatus to a normal caliber center panel . The proximal fundus is wrapped posteriorly around the esophagus and a portion of the fundus is brought anterior to the esophagus.The two edges are sutured together to...

Digestion and Absorption in the Stomach

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

Refractory Period of the Heart

Ventricular muscle, unlike skeletal muscle, is incapable of any significant degree of summation of contractions, and this is a very good thing. Imagine that cardiac muscle were able to undergo a prolonged tetanic contraction. During this period, no ventricular filling could occur since filling can occur only when the ventricular muscle is relaxed, and the heart would therefore cease to function as a pump. The inability of the heart to generate tetanic contractions is the result of the long...

Organs with Dual Innervation

Most visceral organs receive dual innervation they are innervated by both sympathetic and parasympathetic fibers. In this condition, the effects of the two divisions of the autonomic system may be antagonistic, complementary, or cooperative table 9.7 . The effects of sympathetic and parasympathetic innervation of the pacemaker region of the heart is the best example of the antagonism of these two systems. In this case, sympathetic and parasympathetic fibers innervate the same cells. Adrenergic...

Significance of Blood PO and PCO2 Measurements

Since blood PO2 measurements are not directly affected by the oxygen in red blood cells, the PO2 does not provide a measurement of the total oxygen content of whole blood. It does, however, provide a good index of lung function. If the inspired air had a normal PO2 but the arterial PO2 was below normal, for example, you could conclude that gas exchange in the lungs was impaired. Measurements of arterial PO2 thus provide valuable information in treating people with pulmonary diseases, in...

What Is Traditional Entrepreneurship

The word 'entrepreneur' is derived from the French word 'entreprendre' meaning 'to undertake' (Ronstadt 1985, p. 28). The traditional entrepreneur is one who undertakes to control, coordinate and assume the risk of a business in a competitive marketplace. Today's entrepreneurs possess those same features and have to be versatile in facing the challenges of a dynamic environment. Today's entrepreneur is an innovator and developer of ideas he or she seizes opportunities and converts them into...

Effects of Blood PO2 on Ventilation

Under normal conditions, blood Po2 affects breathing only indirectly, by influencing the chemoreceptor sensitivity to changes in PcO2- Chemoreceptor sensitivity to PCO gt 2 is augmented by a low PO2 so ventilation is increased at a high altitude, for example and is decreased by a high PO2. If the blood PO2 is raised by breathing 100 oxygen, therefore, the breath can be held longer because the response to increased PCO2 is blunted. When the blood PCO2 is held constant by experimental techniques,...

Circulatory Changes During Exercise

While the vascular resistance in skeletal muscles decreases during exercise, the resistance to flow through the visceral organs and skin increases. This increased resistance occurs because of vasoconstriction stimulated by adrenergic sympathetic fibers, and it results in decreased rates of blood flow through these organs. During exercise, therefore, the blood flow to skeletal muscles increases because of three simultaneous changes 1 increased total blood flow cardiac output 2 metabolic...

Herbivores have special adaptations for digesting cellulose

Cellulose is the principal organic compound in the diets of herbivores. Most herbivores, however, cannot produce cellu-lases, the enzymes that hydrolyze cellulose. Exceptions include silverfish insects well known for eating books and stored papers , earthworms, and shipworms. Other herbivores, from termites to cattle, rely on microorganisms living in their digestive tracts to digest cellulose for them. The digestive tracts of ruminants cud chewers such as cattle, goats, and sheep are...

Tests for nerve root compression

Prolapse of intervertebral discs occurs most frequently at the L4 5 or L5 SI level, producing compression of the L5 and SI nerve roots respectively. Tension can be applied to these nerve roots by flexing the hip with the knee straight -the so-called straight leg raising test. Normally, about 90 degrees of hip flexion should be possible but this varies considerably 70-120 degrees . When the root is stretched over a prolapsed disc, straight leg raising will be restricted and pain will usually be...

The Formed Elements of Blood

The formed elements of blood include two types of blood cells erythrocytes, or red blood cells, and leukocytes, or white blood cells. Erythrocytes are by far the more numerous of the two. A cubic millimeter of blood contains 5.1 million to 5.8 million erythrocytes in males and 4.3 million to 5.2 million erythrocytes in females. The same volume of blood, by contrast, contains only 5,000 to 9,000 leukocytes. Erythrocytes are flattened, biconcave discs, about 7 im in diameter and 2.2 im thick....

Atrial Stretch Reflexes

In addition to the baroreceptor reflex, several other reflexes help to regulate blood pressure. The reflex control of ADH release by osmoreceptors in the hypothalamus and the control of an-giotensin II production and aldosterone secretion by the juxta- glomerular apparatus of the kidneys have been previously discussed. Antidiuretic hormone and aldosterone increase blood pressure by increasing blood volume, and angiotensin II stimulates vasoconstriction to cause an increase in blood pressure....

Chemical Classification of Hormones

Hormones secreted by different endocrine glands vary widely in chemical structure. All hormones, however, can be divided into a few chemical classes. 1. Amines. These are hormones derived from the amino acids tyrosine and tryptophan. They include the hormones secreted by the adrenal medulla, thyroid, and pineal glands. 2. Polypeptides and proteins. Polypeptide hormones generally contain less than 100 amino acids an example is antidiuretic hormone table 11.2 . Protein hormones are polypeptides...

Inspiration and Expiration

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

Skeletal Muscle Action Potential

Brane potential to change after a stimulus is applied is called the time constant or t, and its relationship to capacitance C and resistance R is defined by the following equation In the absence of an action potential, a stimulus applied to the neuronal membrane results in a local potential change that decreases with distance away from the point of stimulation. The voltage change at any point is a function of current and resistance as defined by Ohm's law. If a lig-and-gated channel opens...

Hormones That Use Second Messengers

Hormones that are catecholamines epinephrine and norepineph-rine , polypeptides, and glycoproteins cannot pass through the lipid barrier of the target cell's plasma membrane. Although some of these hormones may enter the cell by pinocytosis, most of their effects result from their binding to receptor proteins on the outer surface of the target cell membrane. Since they exert their effects without entering the target cells, the actions of these hormones must be mediated by other molecules within...

Visual Acuity and Sensitivity

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

Abnormalities in the shape of the chest

Those of clinical importance are as follows. Increase in anteroposterior diameter. In some patients with emphysema, the posterior AP diameter is increased and the two measurements may approximate barrel chest . The degree of chest deformity in emphysema is not a reliable guide to the severity of the functional defect. An increase in anteroposterior diameter may also be due to thoracic kyphosis unrelated to respiratory disease Fig. 4.12 . Thoracic kyphoscoliosis. This ranges in degree from the...

Lung Volumes Affect Pulmonary Vascular Resistance

Pulmonary vascular resistance is also significantly affected by lung volume. Because pulmonary capillaries have little , Measuring pulmonary wedge pressure. A catheter is threaded through a peripheral vein in the systemic circulation, through the right heart, and into the pulmonary artery. The wedged catheter temporarily occludes blood flow in a part of the vascular bed. The wedge pressure is a measure of downstream pressure, which is pulmonary venous pressure. Pulmonary venous pressure...

Physiology Of Cortisol Metabolism

The principal metabolites of cortisol are shown in Figure 18.2. The enzymes directly metabolizing cor tisol include the A-ring reductases 5a- and 5P-reductases , 6 -hydroxylase, 20-reductase, and 11 -hydroxysteroid dehydrogenases. In rats and mice, which lack 17-hydroxylase in their adrenal cortex, the principal glucocorticoid is corticosterone, which is subject to analogous metabolism. 11 P-Hydroxysteroid Dehydrogenases 1ip-HSDs These enzymes catalyse the interconversion of cortisol or...

Female sex organs produce eggs receive sperm and nurture the embryo

When a mammalian egg matures, it is released from the ovary directly into the body cavity. But the egg does not go far. Each ovary is enveloped by the undulating, fringed opening of an oviduct also known as a Fallopian tube , which sweeps the egg into that tube Figure 43.11 . Fertilization takes place in the oviduct. Whether or not the egg is fertilized, cilia lining the oviduct propel it slowly toward the uterus, a muscular, thick-walled cavity shaped in humans like an upside-down pear. The...

Spiral Organ Organ of Corti

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

Control of the Autonomic Nervous System by Higher Brain Centers

Visceral functions are largely regulated by autonomic reflexes. In most autonomic reflexes, sensory input is transmitted to brain centers that integrate this information and respond by modifying the activity of preganglionic autonomic neurons. The neural centers that directly control the activity of autonomic nerves are influenced by higher brain areas, as well as by sensory input. The medulla oblongata of the brain stem is the area that most directly controls the activity of the autonomic...

Acute and Chronic Exercise Increases Insulin Sensitivity Insulin Receptor Density and Glucose Transport into Muscle

Though skeletal muscle is omnivorous, its work intensity and duration, training status, inherent metabolic capacities, and substrate availability determine its energy sources. For very short-term exercise, stored phosphagens ATP and creatine phosphate are sufficient for crossbridge interaction between actin and myosin, even maximal efforts lasting 5 to 10 seconds require little or no glycolytic or oxidative energy production. When work to exhaustion is paced to be somewhat longer in duration,...

Bowel Obstruction In The Elderly

Causes of bowel obstruction usually specific to the elderly include sigmoid volvulus, Ogilvie's Syndrome, colon carcinoma, and gallstone ileus. These conditions in the elderly patient can lead to gangrene with resulting perforation. Sigmoid volvulus is 20 times more likely in the patient age 60 yr and greater 19 . This age association may be due to acquired redundancy of the sigmoid colon. High-residue diets are believed to be the causative factor in developing a redundant sigmoid 20 . Other...

Fluid Movement In Capillaries

Hypoxia-Induced Pulmonary Hypertension Hypoxia has opposite effects on the pulmonary and systemic circulations. Hypoxia relaxes vascular smooth muscle in systemic vessels and elicits vasoconstriction in the pulmonary vasculature. Hypoxic pulmonary vasoconstriction is the major mechanism regulating the matching of regional blood flow to regional ventilation in the lungs. With regional hypoxia, the matching mechanism automatically adjusts regional pulmonary capillary blood flow in response to...

Transport of Oxygen in Blood

Table 15-7 summarizes the oxygen content of systemic arterial blood we shall henceforth refer to systemic arterial blood simply as arterial blood . Each liter normally contains the number of oxygen molecules equivalent to 200 ml of pure gaseous oxygen at atmospheric pressure. The oxygen is present in two forms 1 dissolved in the plasma and erythrocyte water and 2 re-versibly combined with hemoglobin molecules in the erythrocytes. As predicted by Henry's law, the amount of oxygen dissolved in...

Feedback Control of the Anterior Pituitary

In view of its secretion of releasing and inhibiting hormones, the hypothalamus might be considered the master gland. The chain of command, however, is not linear the hypothalamus and anterior pituitary are controlled by the effects of their own actions. In the endocrine system, to use an analogy, the general takes orders from the private. The hypothalamus and anterior pituitary are not master glands because their secretions are controlled by the target glands they regulate. Anterior pituitary...

The Liver Plays an Important Role in the Metabolism of Lipids

The liver plays a pivotal role in lipid metabolism Fig. 28.4 . It takes up free fatty acids and lipoproteins complexes of lipid and protein from the plasma. Lipid is circulated in the plasma as lipoproteins because lipid and water are not mis- The Metabolism of Monosaccharides. Monosaccharides are first phosphorylated by a reaction catalyzed by the enzyme hexokinase. In the liver but not in the muscle , there is a specific enzyme glucokinase for the phosphorylation of glucose to form glucose...

Autonomic Nervous System

The efferent innervation of all tissues other than skeletal muscle is by way of the autonomic nervous system. A special case occurs in the gastrointestinal tract, where autonomic neurons innervate a nerve network in the wall of the intestinal tract. This network, termed the enteric nervous system, will be described in Chapter 17. In the autonomic nervous system, parallel chains, each with two neurons, connect the central nervous system and the effector cells Figure 8-43 . This is in contrast to...

Chemoreceptors in the Medulla

The chemoreceptors most sensitive to changes in the arterial PCO2 are located in the ventral area of the medulla oblongata, near the exit of the ninth and tenth cranial nerves. These chemoreceptor neurons are anatomically separate from, but synaptically communicate with, the neurons of the respiratory control center in the medulla. An increase in arterial PCO2 causes a rise in the H concentration of the blood as a result of increased carbonic acid concentrations. The H in the blood, however,...

Effects of Blood PCO2 and pH on Ventilation

Chemoreceptor input to the brain stem modifies the rate and depth of breathing so that, under normal conditions, arterial PCo2, pH, and Po2 remain relatively constant. If hypoventilation inadequate ventilation occurs, PCO2 quickly rises and pH falls. The fall in pH is due to the fact that carbon dioxide can combine Sensory nerve fibers in vagus nerve Sensory nerve fibers in vagus nerve Figure 16.26 Sensory input from the aortic and carotid bodies. The peripheral chemoreceptors aortic and...

Transport of Carbon Dioxide in Blood

In a resting person, metabolism generates about 200 ml of carbon dioxide per minute. When arterial blood flows through tissue capillaries, this volume of carbon dioxide diffuses from the tissues into the blood Figure 15-27 . Carbon dioxide is much more soluble in water than is oxygen, and so more dissolved carbon dioxide than dissolved oxygen is carried in blood. Even so, only a relatively small amount of blood carbon dioxide is transported in this way only 10 percent of the carbon dioxide...

The Challenges Of Working In The Transference

Not untypically, those new to the practice of psychoanalytic therapy are hesitant about making transference interpretations. When patients are encouraged to work directly with transference reactions, conflictual issues are identified and the patient's anxiety is heightened. The patient may perceive our behaviour as critical, attacking or intrusive. In these situations, we may find it difficult to be experienced as the bad, persecuting object. The interpersonal strain that is generated when...

Regulation of Insulin and Glucagon Secretion

Insulin and glucagon secretion is largely regulated by the plasma concentrations of glucose and, to a lesser degree, of amino acids. The alpha and beta cells, therefore, act as both the sensors and effectors in this control system. Since the plasma concentration of glucose and amino acids rises during the absorption of a meal and falls during fasting, the secretion of insulin and glucagon likewise fluctuates between the absorptive and postabsorptive states. These changes in insulin and...

Endothelial Cells Can Release Chemicals That Cause Relaxation or Constriction of Arterioles

An important contributor to local vascular regulation is released by endothelial cells. This substance, endothelium-derived relaxing factor EDRF , is released from all arteries, microvessels, veins, and lymphatic endothelial cells. EDRF is nitric oxide NO , which is formed by the action of nitric oxide synthase on the amino acid arginine. NO causes the relaxation of vascular smooth muscle by inducing an increase in cyclic guanosine monophosphate cGMP . When cGMP is increased, the smooth muscle...

The Primary Neurotransmitters of the ANS Are Acetylcholine and Norepinephrine

In the somatic nervous system, neurotransmitter is released from specialized nerve endings that make intimate contact with the target structure. The mammalian motor endplate, with one nerve terminal to one skeletal muscle fiber, illustrates this principle. This arrangement contrasts with the ANS, where postganglionic axons terminate in varicosities, swellings enriched in synaptic vesicles, which release the transmitter into the extracellular space surrounding the effector cells see Fig. 6.1 ....

Extrinsic Regulation of Blood Flow

The term extrinsic regulation refers to control by the autonomic nervous system and endocrine system. Angiotensin II, for example, directly stimulates vascular smooth muscle to produce generalized vasoconstriction. Antidiuretic hormone ADH also has a vasoconstrictor effect at high concentrations this is why it is also called vasopressin. This vasopressor effect of ADH is not believed to be significant under physiological conditions in humans. Stimulation of the sympathoadrenal system produces...

Functional Neuroanatomy Of Penile Function

Parasympathetic and Nonadrenergic and Noncholinergic Outflow Parasympathetic preganglionic input to the human penis originates in the sacral S2-S4 spinal cord 30 . In most men, S3 is the main source of erectogenic fibers, with a smaller supply provided by either S2 or S4. These preganglionic neurons are situated in the intermediolateral cell column and send dendritic projections to laminae V, VII, IX, and X of the spinal cord. These distributions for axonal processes imply that sacral...

Types of Skeletal Muscle Fibers

All skeletal-muscle fibers do not have the same mechanical and metabolic characteristics. Different types of fibers can be identified on the basis of 1 their maximal velocities of shortening fast and slow fibers and 2 the major pathway used to form ATP oxida-tive and glycolytic fibers. Fast and slow fibers contain myosin isozymes that differ in the maximal rates at which they split ATP, which in turn determine the maximal rate of cross-bridge cycling and hence the fibers' maximal shortening...

Length Tension Relationship

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

Considerations for Esophageal Lengthening Procedures

It is essential that the gastroesophageal junction lie tension free in the abdomen before creating a fundic wrap. The length of tension-free intraabdominal esophagus should be measured after closing the crural defect. When the crura are closed from the caudal condensation of the crural fibers toward the anterior margin of the hiatus, the hiatal orifice is effectively displaced cephalad. This transposition of the hiatal orifice lengthens the intraabdominal segment of esophagus because the...

Intrinsic Regulation of Blood Flow

Intrinsic, or built-in, mechanisms within individual organs provide a localized regulation of vascular resistance and blood flow. Intrinsic mechanisms are classified as myogenic or metabolic. Some organs, the brain and kidneys in particular, utilize these intrinsic mechanisms to maintain relatively constant flow rates despite wide fluctuations in blood pressure. This ability is termed autoregulation. If the arterial blood pressure and flow through an organ are inadequate if the organ is...

Pulse Pressure and Mean Arterial Pressure

When someone takes a pulse, he or she palpates an artery for example, the radial artery and feels the expansion of the artery occur in response to the beating of the heart the pulse rate is thus a measure of the cardiac rate. The expansion of the artery with each pulse occurs as a result of the rise in blood pressure within the artery as the artery receives the volume of blood ejected by a stroke of the left ventricle. Since the pulse is produced by the rise in pressure from dia-stolic to...

Muscle Cells Obtain ATP From Several Sources

Although ATP is the immediate fuel for the contraction process, its concentration in the muscle cell is never high enough to sustain a long series of contractions. Most of the immediate energy supply is held in an energy pool of the compound creatine phosphate or phosphocreatine PCr , which is in chemical equilibrium with ATP. After a molecule of ATP has been split and yielded its energy, the resulting ADP molecule is readily rephosphorylated to ATP by the high-energy phosphate group from a...

Responses to Adrenergic Stimulation

Adrenergic stimulation by epinephrine in the blood and by norepinephrine released from sympathetic nerve endings has both excitatory and inhibitory effects. The heart, dilatory muscles of the iris, and the smooth muscles of many blood vessels are stimulated to contract. The smooth muscles of the bronchioles and of some blood vessels, however, are inhibited from contracting adrenergic chemicals, therefore, cause these structures to dilate. Since excitatory and inhibitory effects can be produced...

Monoamines as Neurotransmitters

A variety of chemicals in the CNS function as neurotransmitters. Among these are the monoamines,a chemical family that includes dopamine,norepinephrine,and serotonin. Although these molecules have similar mechanisms of action, they are used by different neurons for different functions. The regulatory molecules epinephrine, norepinephrine, dopamine, and serotonin are in the chemical family known as monoamines. Serotonin is derived from the amino acid tryptophan. Epinephrine, norepinephrine, and...

Localized Inflammatory Response

The hallmarks of a localized acute inflammatory response, first described almost 2000 years ago, are swelling tumor , redness rubor , heat calor , pain dolor , and loss of function. Within minutes after tissue injury, there is an increase in vascular diameter vasodilation , resulting in an increase in the volume of blood in the area and a reduction in the flow of blood. The increased blood volume heats the tissue and causes it to redden. Vascular permeability also increases, leading to leakage...

The Complement System Clears Immune Complexes from Circulation

The importance of the complement system in clearing immune complexes is seen in patients with the autoimmune disease systemic lupus erythematosus SLE . These individuals produce large quantities of immune complexes and suffer tissue damage as a result of complement-mediated lysis and the induction of type II or type III hypersensitivity see Chapter 16 . Although complement plays a significant role in the development of tissue damage in SLE, the paradoxical finding is that deficiencies in C1,...

Slow and Fast Twitch Fibers

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

Herpes Simplex Virus Type Ii Hsv2

Genital herpes simplex virus HSV infection is not a reportable disease but is considered to be extremely common in the U.S. with approximately 45 million adults approx 22 of the population aged 15-74 yr estimated to be infected in 1990, based on the serologic results of a random sampling of civilian adults examined as part of the National Health and Nutrition Examination Survey NHANES III 12 . This represents a 32 increase compared to 1978, when the seroprevalence of HSV-2 was 16 among the...

Clinical Aspects of the Urinary System Infections

Organisms that infect the urinary tract generally enter through the urethra and ascend toward the bladder. Although urinary tract infections UTIs do occur in males, they appear more commonly in females. Infection of the urinary bladder produces cystitis. The infecting organisms are usually colon bacteria carried in feces, particularly Escherichia coli. Cystitis is more common in females than in males because the female urethra is shorter than the male urethra and the opening is closer to the...

Potential Causes of Failure

Regardless of the surgical nuances, failed antireflux operations can be analyzed and subdivided into three distinct anatomic regions. Failure can occur at the esophageal, wrap, or crural level, although there may be overlapping or concurrent issues. Before the wide adoption of laparoscopic techniques,wrap disruption was the most common mode of failure. In the laparoscopic era, the most common cause of failure is herniation of the wrap through the diaphragmatic hiatus. The construction of a...

The Loading and Unloading Reactions

Deoxyhemoglobin and oxygen combine to form oxyhemoglo-bin this is called the loading reaction. Oxyhemoglobin, in turn, dissociates to yield deoxyhemoglobin and free oxygen molecules this is the unloading reaction. The loading reaction occurs in the lungs and the unloading reaction occurs in the systemic capillaries. Loading and unloading can thus be shown as a reversible reaction Deoxyhemoglobin O2 lt z gt Oxyhemoglobin tissues The extent to which the reaction will go in each direction depends...

Types of Endocrine Disorders

Most endocrine disorders fall into one of four categories 1 too little hormone hyposecretion 2 too much hormone hypersecretion 3 reduced response of the target cells hyporesponsiveness and 4 increased response of the target cells hyperresponsive-ness . In the first two categories, the phrases too little hormone and too much hormone here mean too little or too much for any given physiological situation. For example, as we shall see, insulin secretion decreases during fasting, and this decrease...

Structure of the Respiratory System

Gas exchange in the lungs occurs across an estimated 300 million tiny 0.25 to 0.50 mm in diameter air sacs, known as alveoli. Their enormous number provides a large surface area 60 to 80 square meters, or about 760 square feet for diffusion of gases. The diffusion rate is further increased by the fact that each alveolus is only one cell-layer thick, so that the total air-blood barrier is only two cells across an alveolar cell and a capillary endothelial cell , or about 2 im. This is an average...

Reciprocal Innervation and the Crossed Extensor Reflex

In the knee-jerk and other stretch reflexes, the sensory neuron that stimulates the motor neuron of a muscle also stimulates interneu-rons within the spinal cord via collateral branches. These interneu-rons inhibit the motor neurons of antagonist muscles via inhibitory postsynaptic potentials IPSPs . This dual stimulatory and inhibitory activity is called reciprocal innervation fig. 12.29 . When a limb is flexed, for example, the antagonistic extensor muscles are passively stretched. Extension...

Pepsin and Hydrochloric Acid Secretion

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

How To Prepare A Wet Mount

Using a pipette bulb, aspirate a small amount of the Proteus culture with a capillary pipette and place a small drop on a clean microscope slide fig. 3.2, step 1 . 2. Carefully place a clean cover glass see Experiment 3.1, procedure 1 over the drop, trying to avoid bubble formation fig. 3.2, step 2 . The fluid should not leak out from under the edges of the cover glass. If it does, wait until it dries before sealing. 3. If you examine the slide immediately, you need not seal the coverslip....

Problems with luminal stenosis

Although luminal stenosis percentage is the most commonly used clinical measure of plaque risk, it is not at all clear how to measure it in the first place, as evidenced by the two different systems adopted by the two major clinical trials in this area, ECST and NASCET. ECST determined the fractional stenosis by using the luminal diameter at the point of maximal stenosis at angiography as the numerator and the projected diameter of the artery at that same Fig. 1. Diagram showing the problems...

Neural Control of Skeletal Muscles

Skeletal muscles contain stretch receptors called muscle spindles that stimulate the production of impulses in sensory neurons when a muscle is stretched.These sensory neurons can synapse with alpha motoneurons, which stimulate the muscle to contract in response to the stretch. Other motor neurons, called gamma motoneurons, stimulate the tightening of the spindles and thus increase their sensitivity. Motor neurons in the spinal cord, or lower motor neurons often shortened to motoneurons , are...

Rupture Of The Patellar Tendon

Rupture of the patellar tendon after total knee replacement is a rare and typically devastating problem Fig. 13.1 . Unfortunately, the results of several methods of acute repair are almost uniformly Numerous theories have been postulated to explain the etiology of late rupture of the patellar tendon following TKA. As mentioned previously, improper surgical technique that malaligns the knee or the position of any single component can play a contributory role. Some authors have found its...

Organs without Dual Innervation

Although most organs are innervated by both sympathetic and parasympathetic nerves, some including the adrenal medulla, ar-rector pili muscles, sweat glands, and most blood vessels receive only sympathetic innervation. In these cases, regulation is achieved by increases or decreases in the tone firing rate of the sympathetic fibers. Constriction of cutaneous blood vessels, for example, is produced by increased sympathetic activity that stimulates alpha-adrenergic receptors, and vasodilation...

Lung Volumes and Capacities

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

Anterior Tibial Artery Palpation

The anatomy of he radial, brachial and carotid pulses have been described I p. 83 . Femoral artery. The I'emoral artery is situated just below the inguinal ligament, midway between the anterior superior iliac spine and the pubic symphysis mid-inguinal point . It is immediately lateral to the femoral vein and medial to the femoral nerve. In the obese it can be difficult to feel. Popliteal artery. At the level of the knee crease, the artery lies deep in the popliteal fossa and the pulse is...

Proposed Mechanisms for Induction of Autoimmunity

A variety of mechanisms have been proposed to account for the T-cell-mediated generation of autoimmune diseases Figure 20-8 . Evidence exists for each of these mechanisms, Inappropriate MHC expression on non-APCs Inappropriate MHC expression on non-APCs TH cell B cell Plasma cell TH cell B cell Plasma cell Proposed mechanisms for inducing autoimmune responses. Normal thymic selection appears to generate some self-reactive TH cells abnormalities in this process may generate even more...

Endocrine Functions of the Placenta

The placenta secretes both steroid hormones and protein hormones. The protein hormones include chorionic gonadotropin hCG and chorionic somatomammotropin hCS , both of which have actions similar to those of some anterior pituitary hormones table 20.7 . Chorionic gonadotropin has LH-like effects, as previously described it also has thyroid-stimulating ability, like pituitary TSH. Chorionic somatomammotropin likewise has actions that are similar to two pituitary hormones growth hormone and...

Clinical Significance Of Transverse Pericardial

Chapter 2 FUNCTIONAL ANATOMY OF THE HEART CORRELATIVE ANATOMY This section in this chapter is an illustrated review of applied cardiac anatomy. The clinical significance of the anatomy described is highlighted in italics. The fibrous parietal pericardium is a resilient sac that envelops the heart and attaches onto the great vessels. 5 Almost the entire ascending aorta and main pulmonary artery and portions of both venae cavae and all four pulmonary veins are intrapericardial Fig. 2-19 . These...

Extracellular Osmolarity and Cell Volume

We can now apply the principles learned about osmosis to cells, which meet all the criteria necessary to produce an osmotic flow of water across a membrane. Both the intracellular and extracellular fluids contain water, and cells are surrounded by a membrane that is very permeable to water but impermeable to many substances nonpenetrating solutes . About 85 percent of the extracellular solute particles are sodium and chloride ions, which can diffuse into the cell through protein channels in the...

Effects Of Powerfull Magnet On Humanbeings

The Influence of Magnetic Fields on Man The human body is composed of atoms of different elements surrounded by water molecules. These atoms react to magnetic and electric forces and fields, and this may lead to, for example, a net-nuclear magnetization of a person when placed in a clinical MRI machine. It is therefore easy to imagine that magnetic and electromagnetic forces could alter physiologic functions, induce effects, or influence the organism in either a positive or negative way....

Stress Reaction Femur

Stress fractures of the femur in runners may occur in the femoral neck, trochan-teric and subtrochanteric region, and femoral shaft. These injuries are often not considered in the initial presentation, and a high index of suspicion must be maintained. Patients commonly present with hip, groin, gluteal, thigh, or knee pain, depending on the location of the injury 18,72,73 . In a study by Clement and colleagues 72 , 71 patients who had 74 stress fractures of the femur were studied. Nearly 95 were...

Carrier Mediated Transport

Molecules such as glucose are transported across plasma membranes by special protein carriers. Carrier-mediated transport in which the net movement is down a concentration gradient, and which is therefore passive, is called facilitated diffusion. Carrier-mediated transport that occurs against a concentration gradient, and which therefore requires metabolic energy, is called active transport. In order to sustain metabolism, cells must take up glucose, amino acids, and other organic molecules...

Feedback Control of Hormone Secretion

The nature of the endocrine glands, the interaction of the nervous and endocrine systems, and the actions of hormones will be discussed in detail in later chapters. For now, it is sufficient to describe the regulation of hormone secretion very broadly, since it so superbly illustrates the principles of homeostasis and negative feedback regulation. Hormones are secreted in response to specific chemical stimuli. A rise in the plasma glucose concentration, for example, stimulates insulin secretion...

Endocrine Functions of the Testes

Testosterone is by far the major androgen secreted by the adult testis. This hormone and its derivatives the 5a-reduced androgens are responsible for initiation and maintenance of the body changes associated with puberty in males. Androgens are sometimes called anabolic steroids because they stimulate the growth of muscles and other structures table 20.4 . Increased testosterone secretion during puberty is also required for growth of the accessory sex organs primarily the seminal vesicles and...

Cleavage and Blastocyst Formation

At about 30 to 36 hours after fertilization, the zygote divides by mitosis a process called cleavage into two smaller cells. The rate of cleavage is thereafter accelerated. A second cleavage, which occurs about 40 hours after fertilization, produces four cells. A third cleavage about 50 to 60 hours after fertilization produces a ball of eight cells called a morula mulberry . This very early embryo enters the uterus 3 days after ovulation has occurred fig. 20.43 . Continued cleavage produces a...

Cellular Distribution of MHC Molecules

In general, the classical class I MHC molecules are expressed on most nucleated cells, but the level of expression differs among different cell types. The highest levels of class I molecules are expressed by lymphocytes, where they constitute approximately 1 of the total plasma-membrane proteins, or some 5 X 105 molecules per cell. In contrast, fibroblasts, muscle cells, liver hepatocytes, and neural cells express very low levels of class I MHC molecules. The low level on liver cells may...

Organization of the Respiratory System

There are two lungs, the right and left, each divided into several lobes. Pulmonary is the adjective referring to lungs. The lungs consist mainly of tiny air-containing sacs called alveoli singular, alveolus , which number approximately 300 million in the adult. The alveoli are the sites of gas exchange with the blood. The airways are all the tubes through which air flows between the external environment and the alveoli. Inspiration inhalation is the movement of air from the external...

Natural History Of Cervical Hpv Infection And Csil

There are more than 100 anogenital HPV types and these are generally divided into oncogenic and nononcogenic types by virtue of the frequency of their association with invasive cervical cancer see Chapter 14 . Of the oncogenic types, HPV-16 is the most important because it is the most common type found in cervical cancer, followed by HPV types 18, 31, and 45. HPV 16 alone counts for about 50 of all cervical cancers worldwide 4 . HPV types 18, 31, and 45 are associated with an additional 20 of...

Negative Feedback Control of Calcium and Phosphate Balance

The secretion of parathyroid hormone is controlled by the plasma calcium concentrations. Its secretion is stimulated by low calcium concentrations and inhibited by high calcium concentrations. Since parathyroid hormone stimulates the final hy-droxylation step in the formation of 1,25-dihydroxyvitamin D3, a rise in parathyroid hormone results in an increase in production of 1,25-dihydroxyvitamin D3. Low blood calcium can thus be corrected by the effects of increased parathyroid hormone and...

Methods for the Synthesis of Cannabinergic Ligands

Nikas, Richard I. Duclos, Jr., and Alexandros Makriyannis During the last decade, numerous cannabinergic ligands with high affinity and selectivity profiles for cannabinoid receptors CB1 and CB2 emerged from rigorously pursued structure-activity relationship studies. This chapter focuses on the synthetic aspects of key cannabi-noid receptor probes representing the different classes of cannabinergic ligands that encompasses classical cannabinoids CCs including some...

Palpation during inspiration

The liver, gallbladder, spleen and kidneys should be examined in turn during deep inspiration. The key to success is to keep the examining hand still and wait for the organ to descend. One common error is to begin palpation of the liver too close to the costal margin, thereby missing Place the hand flat on the abdomen with the lingers pointing upwards and position the sensing fingers index and middle lateral to the rectus muscle so that the fingertips lie on a line parallel to lhe expected...

Anterolateral Pain Pathway

A stimulus that causes or is on the verge of causing tissue damage usually elicits a sensation of pain. Receptors for such stimuli are known as nociceptors. They respond to intense mechanical deformation, excessive heat, and many chemicals, including neuropeptide transmitters, bradykinin, histamine, cytokines, and prostaglandins, several of which are released by damaged cells. These substances act by combining with specific ligand-sensitive ion channels on the nociceptor plasma membrane. Vander...

Review Activities

Test Your Knowledge ofTerms and Facts Match the vestibular organ on the left 9. with its correct component on the right. 1. utricle and saccule a. cupula 2. semicircular canals b. ciliary body 4. The dissociation of rhodopsin in the rods in response to light causes a. the Na channels to become blocked. b. the rods to secrete less neurotransmitter. c. the bipolar cells to become either stimulated or inhibited. b. do not fire continuously to a sustained stimulus. c. produce action potentials at a...

Labor and Parturition

Powerful contractions of the uterus are needed to expel the fetus in the sequence of events called labor. These uterine contractions are known to be stimulated by two agents 1 oxytocin, a polypeptide hormone produced in the hypothalamus and released by the posterior pituitary and also produced by the uterus itself , and 2 prostaglandins, a class of cyclic fatty acids with paracrine functions produced within the uterus. The particular prostaglandins PGs involved are PGF2a and PGE2. Labor can...