However, action potential vary from slow to fast type in different tissues of the heart. An elastic tissue once stretched recoils back to its unstretched position like a spring. In all virilizing forms of adrenal hyperplasia, glucocorticoid therapy is preferred. Neuromuscular diseases Myasthenia gravis Paralysis of diaphragm Muscular dystrophy Conditions that Decrease Static Lung Compliance Pulmonary edema Chronic pulmonary congestion Kyphoscoliosis Fibrothorax Interstitial fibrosis Atelectasis Patients with decreased compliance have to put in more respiratory muscular effort to achieve adequate alveolar ventilation. Hyperventilation induced by hypoxia is not In Second Stage In second stage, ventilation increases slowly in 8 to 10 hours and then remains sustained. Second messengers are formed depending on the hormone signaling of the effector cells. Parasympathetic stimulation decreases heart rate by slowly raising the pacemaker potential so that slope of prepotential reaches threshold later. Evacuation of bladder and bowel, those occur partly due to increased abdominal pressure. This is the initial and important step of urine formation as it considerably contributes to the volumes and composi tion of urine. Tissue suffers from hypoxia due to decreased oxygen content inspite of normal oxygen saturation. Primary Motor Cortex Primary motor cortex (area 4) is present in the precentral gyrus. Con sequently, whenever vagotomy is performed for the treatment of peptic ulcer, usually a drainage procedure like pyloroplasty or gastrojejunostomy is also performed to ensure proper passage of food from the stomach into the duodenum (Clinical Box 48. Fall in blood pressure below 60 mm Hg, with or without change in PaO2 stimulates chemoreceptor activity. The epithelial cells of collecting duct are modified to participate in transport of ions and water. S Wave the last parts to be depolarized are the posterobasal portion of the left ventricle and the pulmonary conus. It is important for circulatory system to perform efficiently to meet the usual challenges of day-to-day activities imposed by exercise, exposure to hot or cold environment, change in posture, emotional reactions, and other stressors. The rate of coronary blood flow is the second highest in the body, next to the renal blood flow, which is 420 mL per 100 g of tissue per minute. Basal gangliathalamic cortical projection to brainstem influences descending pathways that control posture. The right coronary artery principally supplies the right ventricle and the right atrium, and the left coronary artery supplies the left ventricle and the left atrium. Thus, these tracts are involved in the regulation of skilled voluntary movements as lateral group of motor neurons innervate the distal limb muscles. Cell Types Parathyroid glands contain two types of cells: chief cells and oxyphil cells. Various metabolic effects of catecholamines mediated though different receptors are summarized in Table 58. Hair Follicle Endings the endings of the afferent fibers are often present adjacent to the hair follicles. However, readers are advised to check the most current information available on procedures included and check information from the manufacturer of each product to be administered, to verify the recommended dose, formula, method and duration of administration, adverse effects and contraindications. Therefore, the excretion of this organic compound in urine via their secretion by the tubular cells (rather than through filtration), constitutes an important mechanism for their elimination from the body. Chapter 85: Functional Anatomy of Heart, Cardiac Muscle, Conducting System, and Cardiac Innervation 745. Thus, if ovulation occurs on 14th day of the cycle, for conception to occur the coitus should take place on 12th, 13th, 14th, and 15th days (the fertile period) of the menstrual cycle). He also studied the functions of secretory and trophic nerves of glands and promoted the intracellular theory of secretory phenomena. Gate Control Theory of Pain According to this theory, pain can be modulated by the peripheral mechanisms, especially by gating the impulses in the spinal cord. Wilhelm and Eduard completed the full study of locomotion and demonstrated that vagal stimulation stops heart.
This division results in production of two structures: one is the daughter cell, called secondary oocyte containing 23 chromosomes, and the other is the first polar body. Sometimes, the stages of development of sperms are collectively called as spermatogenic cycle. Arginine, leucine, lysine and alanine are potent stimulator of insulin release: 1. This is a medical emergency that requires immediate fluid replacement and steroid therapy with antithyroid drugs. Ventricular Systole the phase of ventricular systole is divided into two parts: the phase of isovolumetric contraction, and the phase of ejection. This is mainly due to the myogenic theory and theory of tubuloglomerular feedback. However, secretion of mucus increases proportionately, permitting lubrication of the mouth despite increased ventilation and reduced salivation. Function this is a rapidly adapting mechanoreceptor capable of receiving high frequency vibration. Braggpaul Method this consists of a hollow elastic rubber bag, which is wrapped round the chest. Constitutional amenorrhea: Though menstrual cycle starts normally by the age of 16 years, sometimes it may not occur even at the age of 18 years or more, without there being any abnormality. Etiocholanolone, a metabolite of adrenal androgens and testosterone, forms 17-ketosteroid. T cells that are activated against fetal proteins are destroyed (undergo apoptosis) by Fas, a placental surface ligand. This is usually seen in restrictive cardiomyopathy as seen in amyloidosis in which the heart muscle is infiltrated by amyloid proteins. This is called triple response as it has three components: red reaction, wheal, and flare. Development of Secondary Sex Characteristics Testosterone is primarily responsible for changes in males that occur at puberty. Bubbles in the pulmonary vessels produce dyspnea and a feeling of respiratory compression, and bubbles in the coronary vessels produce myocardial ischemia. This plays an important role counter-current mechanism and makes the urine concentrated. Note the expulsion of the fetus by uterine contraction, of fetus facilitated by increased abdominal pressure. For example, the heart and the inner aspect of the arm develop from the same embryonic segment. The tubes should be in close proximity to each other and should be selectively permeable. It usually occurs in elderly and may be due to degeneration of peripheral autonomic nerves. Urea transported in collecting duct also greatly helps in generating osmotic gradient in the medullary pyramid. The afferent limb of the reflex pathway is somatic fibers whereas the efferent pathway is the sympathetic fibers. Specific Pain Syndromes Terminologies Hyperalgesia: Hyperalgesia refers to increased sensitivity and lowered threshold to painful stimuli. Proteins in Urine Normally, glomerulus is not permeable to substances with molecular weight more than 69000. Septic shock (following septicemia) Types Shock is classified broadly into four categories based on the mechanisms that decrease cardiac output. Note: In ischemia and compression, elimination of touchsensationoccursfirst and then the pain sensation, Demyelination Demyelination occurs in many neuropathies. Some amount of cartilage is present up to 10th generation, up to which the airways are referred to as bronchi (Clinical Box 103. It occurs either due to decreased cardiac output or decreased blood flow secondary to some other causes.
Responses Responses consist of movement of body parts (motor activities), change in visceral functions (autonomic responses) or even the change in behavior of the individual. Glycogenolysis increases plasma glucose concentration and lipolysis promotes plasma free fatty acid level. In examinations, "Composition, mechanism and regulation of salivary secretion" may sometimes come as a Long Question. If stomach is allowed to remain empty for a longer duration, contractions become vigorous. The vasocompression during systole is more marked in the left ventricle than right ventricle, as the pressure generated by left ventricle is significantly more. These membrane enzymes are adext rinase that causes hydrolysis of a-1,6 linkage, maltase that causes hydrolysis of maltotriose and maltose, lactase that causes hydrolysis of lactose into glucose and galactose, glucoamylase that splits malto-oligosachharides into single glucose molecules and sucrase that causes hydrolysis of sucrose into fructose and glucose. Chapter 83: Physiology of Micturition and Bladder Dysfunctions 725 of neuraxis above pons promotes activity of micturition reflex in which less filling of bladder triggers its reflex evac uation, and section above midbrain does not affect it. Activation of 2 receptors increases bronchial secretion and 2 receptors inhibits secretion. There are two sets of neurons in the efferent pathway: preganglionic and postganglionic neurons. Vasoconstriction decreases the blood flow and returns blood flow to the previous levels. Hypokalemia, hypernatremia and low renin in plasma, and metabolic alkalosis are usual laboratory findings. Granule cell also stimulates the Golgi cells (the interneurons in granular cell layer), which, in turn, inhibit the activity of granule cells. Therefore, in case of incompetent pyloric sphincter, regurgitation of duodenal content (containing bile acids) into the stomach usually results in gastric ulcer. Decreased frequency (cycle more than 35 days) of menstrual cycle is called oligomenorrhea. Drugs that are administered rectally include purgatives, sedatives, anesthetics, and tranquilizers. Therefore, quality and degree of filtration are different through the filtration barrier. The Rab family regulates rate of vesicle movement between cell organelles and the cell membrane. Fullness of bladder is sensed by afferents in pelvic nerve and parasympathetic efferents also travel in pelvic nerve. The arterial blood gas tension is primarily affected by the relationship of ventilation with perfusion. About 99% of calcium, 86% of phosphate, 80% of carbonate and 50% of magnesium of their total body content are present in bones (Table 61. The proposed explanation is that when spermatocytes attempt to penetrate the barrier, the tight junction in front of them dislocate and give way for them, and immediately after the spermatocytes pass through the tight junctions the new tight junctions are concomitantly formed behind them. In human, it is produced by Paneth cells (endocrine cells located in the crypts of Lieberkuhn of small intestine). For example, a patient on mechanical ventilator, alveolar ventilation decreases due to increased dead space volume (by tubing etc. However, albuminuria is seen in diseases in which: - There is increase in the size of the pores in the glo merular membrane, or, - There is disruption of electrostatic force of glomeru lar membrane proteins. They are broadly divided into two categories: Upper motor neurons and lower motor neurons. It is a congenital disease characterized by failure of development of Auerbach (myenteric) plexus with absence of postganglionic parasympa thetic neurons in the wall of distal part of colon. What are the mechanisms for ventilator acclimatization at high altitude, What are the respiratory changes as acclimatization to high altitude, What are the hematological changes as acclimatization to high altitude, What are the cardiovascular changes as acclimatization to high altitude, What are the tissue changes as acclimatization to high altitude, What are the features of acute mountain sickness, What are the features of chronic mountain sickness, What is the mechanism of pulmonary hypertension and edema, What is the mechanism of cerebral edema, What is the physiological basis of treatment of high altitude illness. For example, if heart is stimulated following the sympathetic activation, the magnitude of contraction increases. These tests are usually employed to diagnose pancreatic deficiencies as in pancreatitis, cystic fibrosis, etc. Mechanism of Pain Recognition and Perception Pain Recognition Nociceptive stimuli damage the tissues, which are recogn ized by the body as sensation of pain.
The main specialty of male reproduction is that the male gametes are produced in millions and after puberty the process of production is a continuous phenomenon. About 70% norepinephrine and epinephrine, and 90% of dopamine are conjugated to sulfate. Rather, they modulate the sensitivity of muscle spindle and thereby regulate muscle length and muscle tone. Within one hour of ejaculation in the vagina, the sperms reach fallopian tube where they fertilize the ovum. Uric acid is increased in urine in conditions that are associated with increased purine catabolism. Pulmonary capillary blood flow Alveolar-Capillary Membrane Alveolar-capillary membrane (also called respiratory membrane) forms the blood-gas interface that separates blood in the pulmonary capillaries from the gas in the alveoli. Therefore, plasma glucose level determines the transport maximum for glucose (TmG). Effects on Intermediary Metabolism Thyroid hormones by increasing oxygen consumption of tissues increase oxidation of substrates in general. The receptors in the autonomic ganglia usually contains 3 subunits in addition to other subunits. Firstly, it increases calcium influx by opening the calcium channels on the cell membranes, and secondly, it increases calcium release from the sarcoplasmic reticulum. When they accumulate in blood, they cause episodic fever known as etiocholanolone fever. Effects of Lesions Lesion of lateral corticospinal tract results in impairment of skilled voluntary activities like writing, painting, etc. Sometimes, exercise induces bronchoconstriction, which could be due to entry of cool air into bronchial tree due to hypoventilation that occurs during exercise. Thus, when blood passes through tissue capillaries, the acidic environment facilitates release of oxygen from Hb into the tissues. Botulinum toxin C acts on syntaxin and prevents its attachment with synaptobrevin. These changes are Acrosome Reaction the binding sperm to the zona pellucida triggers acrosome reaction in the bound sperm, which is required for 636 Section 7: Reproductive System sperm penetration: the steps of acrosome reaction and penetration of the sperm are as follows: 1. By osmotic effect, solutes hold water in the tubule (prevents reabsorption of water) that causes diuresis. Usually, functions of many viscera can be altered by changing the basal level of sympathetic discharge to the organs. Once placenta is fully formed and starts secreting hormones (usually after sixth weeks of pregnancy), functions of corpus luteum slowly decline. The chromosomes of these fetal cells can also be examined for diagnosis of certain disorders and determination of fetal sex. Details of dwarfisms are discussed in the chapter "Physiology of Growth and Development" in Section 13. Usually cholesterol stones are big and may be one or two stones are present in gallbladder. Vasodilators: Nitrates like nitroglycerin produce prompt improvement, as they are potent vasodilators. The extent to which ventricle is distended (stretched) depends on the degree of end-diastolic filling of the ventricle. This makes the intrapleural pressure more negative that helps in expan sion of the lungs due to which the air is sucked in. Epinephrine potentiates sympathetic effects with greater efficacy than norepinephrine as it is more effective in stimulating both and -adrenergic receptors (though in general, epinephrine is a better receptor agonist and norepinephrine is a better receptor agonist). The ratio of the thickness of the wall to the diameter of the vessel is high in arterioles. They stimulate the neural pathways that activate sympathetic fibers to release norepinephrine and adrenal medulla to release mainly epinephrine.
In the brain stem on their way to thalamus, fibers project to three major nuclear groups forming three subsystems: 1. A flap of smooth muscle called precapillary sphincter is present at the end of the metarterioles or arterioles. Follistatin Follistatin is a single chain protein having molecular weight of about 40,000. Therefore, red cells just squeeze through the lumen of the capillaries in single file. Every effort has been made where necessary to contact holders of copyright to obtain permission to reproduce copyright material. Movement is defined as displacement of the body parts that results in change in position of the body as a whole or a part of the body. Rhabdomyolysis (break down of the skeletal muscle) due to muscle crushing is another cause of shock. Spinal Segmental Circuit Sensory signals arising from muscle enter the spinal cord through muscle afferents. Systemic illness: Amenorrhea occurs in chronic illnesses like chronic hypothyroidism, chronic renal failure and cirrhosis of liver. Primary function of gastrin is the stimulation of gastric acid and pepsin secretion. A Motor unit constitutes a motor neuron, its axon, the branches of the axon, the neuromuscular junctions at the distal end of each axon branch, and all of the extrafusal muscle fibers innervated by that motor neuron. The differences in shape and size of chromosomes in males and females help in concrete determination of sex. Left side of the Heart the left atrium receives oxygenated blood from the pulmonary circulation via pulmonary veins and empties blood into left ventricle through left atrioventricular valve or mitral valve. Adipokines: the chemical signals originating from adi pose tissue are recently proposed to be contributing factors for insulin resistance. Oxytocin is released from posterior pituitary that increases uterine contractions. The adrenals consist of two distinct endocrine glands, one surrounding the other: the inner adrenal medulla, surrounded by the outer adrenal cortex that consists of three layers. However, except in the inner medullary portion of the collecting duct, the rest of tubular epithelium is relatively impermeable to urea. Pulse pressure is wide due to increase in systolic and decrease in diastolic pressures. Dopamine is usually preferred in cardiogenic shock, as it maintain renal perfusion. These long portal hypophyseal vessels carry blood down the pituitary stalk to the anterior lobe of the pituitary where they end in another set of capillaries. For its profound influence on autonomic responses, Sherrington had correctly pointed out that hypothal amus is the head-ganglion of sympathetic nervous system. Renal Threshold this is the concentration of the solute in the plasma at or above which the solute first appears in urine or appears in more amount than its normal concentration. Hepatic and Gallbladder Bile There are differences between hepatic bile (bile formed in the liver) and gallbladder bile (bile stored in gallbladder) as bile is concentrated and acidified in gallbladder (Table 42. The receptors at motor end plate but not at ganglia can be blocked by bungarotoxin, whereas mecamylamine blocks receptors at the ganglia but not at the neuromuscular junction. Dense tufts or projections that are made up of filamentous proteins, which contact larger filaments in the axoplasm. The total urinary Na+ output ranges between 1 meq and 400 meq (average about 150 meq) per day, depending on the dietary salt intake of the person. As acute exercise significantly decreases blood glucose level by facilitating glucose uptake by skeletal muscles, and during exercise absorption of injected insulin is more rapid, hypoglycemia may be precipitated in diabetic patients during exercise. This manifests with severe headache, tachycardia, palpitation, extreme anxiety, perspiration, either pallor or flushing, severe rise in blood pressure and a feeling of impending death. The a subunits are present on the membrane extracellularly, whereas the b subunits traverse the membrane. Functional residual capacity: this is the volume of air remaining in lungs at the end of resting expiratory level.
Thus, cortisol in such conditions masks the actual disease and delays the diagnosis. Cells of this layer secrete glucocorticoids (mainly cortisol and corticosterone) and sex steroids. At the time of ejaculation, sperms enter into the urethra in the body of prostate through the ejaculatory duct and via urethra they come out of the genital tract. The output from the internal segment of the globus pal lidus to the thalamus is inhibitory, whereas the output from the thalamus to the cerebral cortex is excitatory. Lower Zone Alveolar pressure is lower than the pressure in all vessels (arteries, capillaries and venules), especially the venous pressure. Also, parasympathetic stimulation causes hyperpolarization (makes the membrane potential more negative) so that prepotential takes more time to reach threshold from a more negative value. Descending pathways alter motor activity mainly by altering the activity of spinal reflexes. The immunosuppressive effect of cortisol helps in prevention of transplant rejection. Otherwise, atria and ventricles would have contracted simultaneously resulting in no ventricular filling. Prolactin secretion starts increasing from end of first trimester and at term it is almost 10 times more than the pre-pregnant level. This activates renninangiotensin-aldosterone axis, therefore, edema (due to water retention) may be seen. However, the cough responses to tracheal stimulation remains intact as innervation of trachea in not interfered in such persons. The glandular cells store glycogen and secrete large quantity of carbohydrate-rich mucous and fluid. Hypothalamus also mediates the effects of cardiovas cular reflexes such as atrial stretch reflex. The presynaptic axon terminal, postsynaptic membrane and the synaptic cleft form the synapse. Within minutes of delivery of the baby, both the umbilical cord and the placenta are delivered. Features of hypometabolism similar to hypothyroidism could occur due to resistance of peripheral tissues to thyroid hormones, called as thyroid hormone resistance (Clinical Box 57. However, kidney cannot excrete the free 3 acids; instead excretes the salts of free acids while excreting H+ with other anions, the urinary buffers. Ltype is the dominant one in the heart muscle and Ttype is present in smaller amount. However, relative bradycardia at 30th beat depends also on the sympathetic reactivity. Consequently, cardiac output does not increase proportionately to that of increase in heart rate. P Wave Abnormalities: P wave may be abnormal due to atrial enlargement and intra-atrial conduction abnormalities. Thus, it indicates that loss of influences of descending pathway is the major cause in the genesis of spinal shock. Treatment Consists of identifying the renal disease, identify the precipitating factors and preventing the further renal damage. However, there is adequate overlap in innervation of heart by both sides of the sympathetic fibers. As the disease is mostly due to stress, measures to reduce the stress level are very helpful. Pyruvate and lactate are also oxidized by insulin as it stimulates pyruvate dehydrogenase activity. Low-protein diet impairs the ability of kidney to maximally concentrate urine as this decreases the urea content in the medullary interstitium. This is usually due to accumulation of Lewis factor or P factor in the ischemic muscles. Treatment of Hypothyroidism Thyroid hormone replacement is the mainstay of treat ment.
Deficiency of 21b-Hydroxylase of estrogen from adrenal gland in females becomes the important source of estrogenic activity. Basal Compartment the basal compartment is the outer compartment that mainly consists of spermatogonium. Sometimes atrial arrhythmias such as flutter or fibrillation are also seen in hyperthyroidism, especially in elderly people. Alcohol and barbiturates also act partly by increasing Cl- conductance through Cl- channels (Clinical Box 116. Thus, redness spreads out from the injury to the sur rounding skin in the form of flare. The vertebrobasilar system: Two vertebral arteries join to from the basilar artery, which finally merges into the circle of Willis. This excludes the sense of position and orientation of the body obtained by the stimulation of visual and vestibular receptors. Basket and stellate cells that are activated by mossy fiber-parallel fiber pathway finally inhibit Purkinje cell. The exact mechanism of this unique phenomenon of hypoxiainduced pulmonary vasoconstriction is not known. Upper esophageal sphincter is an example of physiological sphincter, which prevents esophageal content to regurgitate back into oral cavity. The restrictive diseases can be broadly subdivided in to parenchymal and extraparenchymal disease. Reducing Sugars in Urine the presence of sugar in urine is called glycosuria (or more accurately, glucosuria). Also, acute decrease in plasma Na+ or increase in plasma K+ stimulates the aldosterone synthesis and secretion. After 5th month of gestation, the primitive mammary bud forms about 20 secondary buds that form ductal system in the mature gland. Anterolateral system, Ascending pain pathways, Nociceptors, Visceral pain, Referred pain, Endogenous neural analgesia system, Endogenous opioid system, may come as Short Questions. It is composed of water (98%), and solids that mainly include bile salts and pigments and different ions (Table 42. Another electrode is applied to the right leg, which acts as a ground wire to prevent external disturbances during recording. Control of muscle tone and stretch reflexes: Cerebellum influences the activity of the major descending medial system pathways through its output from fastigeal nucleus, especially the vestibulospinal and reticulospinal tracts. It should be noted that there is no basal tonic discharge of sympathetic vasodilator fibers. Appreciate the basic transport mechanisms that function across the tubular epithelium. Aldosterone Aldosterone stimulates reabsorption of NaCl and water from collecting duct. Atrial ectopics are seen in physiological conditions, like anxiety, consumption of excess tea or coffee, or in heart diseases, like rheumatic heart disease, coronary artery disease, cardiomyopathies or digitalis toxicity. Structure and functions of muscle spindle, Fusimotor neuron, Spindle responses, Control of motor neuron discharge, Golgi tendon organ may come as Short Questions. This is a small and relatively straight tubule with morphological and transport charac teristics similar to that of collecting duct. Fast response action potentials are meant for immediate initiation of muscle contraction, hence seen in cardiac muscles. The patient develops clinical features of hyperaldosteronism, though the plasma aldosterone and plasma renin activity remains low. This increases entry of contents of ileum into the colon through ileocecal sphincter. Clomiphene, that binds with estrogen receptors and blocks estrogen action, induces ovulation. Histamine is synthesized from the amino acid histidine by the action of enzyme histidine decarboxylase. Structure Pacinian corpuscle consists of a body composed of concentric layers (lamellae) much like an onion. Chapter 72: Pregnancy and Parturition 645 Calcium Metabolism the demand for calcium increases in pregnancy to facilitate fetal bone formation. In her confirmed because transformed in her, Our life shall find in its fulfilled response Above, the boundless hushed beatitudes, Below, the wonder of the embrace divine.
The bundle branches enter the ventricular walls and then branch out into very small bundle of fibers in the inner walls of the ventricular muscle. In fact, it checks the overactiv ity of sympathetic system and smoothens the autonomic responses. It churns the food and breaks larger food particles (macromolecules) into smaller molecules. Therefore, the male partner should learn to stimulate the female partner appropriately and adequately even before the initiation of intercourse so that orgasms in both arrive together. Increased glucose concentration in plasma to a very high level increases its osmolality to the extent that it causes dehydration of brain cells that results in coma without affecting pH. Preganglionic fibers originate in the intermediolateral gray column of the sacral segments S2, S3, and S4 of spinal cord. Lipids are transported in micelles from the lumen to the membrane of intestinal mucosal epithelial cells where micelle dissociates and lipids are absorbed. Calcium activates myosin light chain kinase that phos phorylates myosin light chain, which in turn causes muscle contraction. It increases systolic pressure, whereas diastolic pressure does not change significantly. Spindle is stretched by the stretch of the muscle, as the spindle is present in parallel with the extrafusal fibers. Similarly, the renal corpuscles of midcortical nephrons are located in middle of the cor tex. Moreover food induced hypermotility of the colon occurring normally about one hour after the meal is reduced in many patients. This helps the muscle to draw oxygen from myoglobin, especially when blood flow ceases for a longer duration during sustained muscle contraction. Thy roid hormones induce formation of enzymes essential for neurotransmitter synthesis. The prolongation of response is due to prolonged and repeated firing of the target motor neurons. Catecholamines increase thyroid hormone secretion and promote peripheral conversion of T4 to T3 which is mediated by b2 receptors. According to the increase or decrease of plasma pH, body excretes or retains acids and bicarbonates and urine becomes acidic or alkaline respectively. Usu ally, a narrow zone of hyperesthesia occurs at the upper margin of anesthetic zone. However, O2 therapy is not beneficial in hypoxic hypoxia due to A-V shunts, as admixture occurs after oxygenation in the lungs. Enterohepatic circulation ensures preservation and reutilization of various substances. The functions of gonads slowly decrease finally resulting in complete cessation of menstrual cycle. In addition, diseases that affect corticospinal tract also affect the corticobulbar tracts that influence activities of extrapyramidal sys tems. When the diver descends into the deep sea, N2 dissolves in the body fluids, which is proportional to the depth of descent. Acid in the antrum inhibits gastric secretion by negative feedback mechanism, which is partly by direct action of acid on G cells and partly by release of somatostatin. Decreased temperature shifts the curve to the left that decreases oxygen release in the tissue, and increased temperature shifts the curve to the right that promotes oxygen release in the tissue. The gap or fenestration between the endothelial cells determines the degree of filtration and exchange. Loss of rhyth mic activity of the respiratory center leads to apnea in sleep and causes death of the infant.