By Q. Tizgar. Allen College.
The wall tension is proportionate to the distending pressure times the radius of the vessel effective 20 mg tadalis sx erectile dysfunction 43 years old. Neural: sympathetic nerves (Th6 L3) vasoconstrictioin purchase tadalis sx with a mastercard erectile dysfunction onset, only during orthostasis purchase generic tadalis sx online psychological erectile dysfunction young, physical effort purchase tadalis sx 20mg with amex erectile dysfunction sample pills, stress. Humoral: - catecholamines vasoconstriction - renin-angiotensin aldosterone system vasoconstriction - system kallikreins bradykinin 39 - kalidin Hageman f. Stimuli intrinsic reaction prorenin molecules are converted by tissue kallikrein renin. After exceeding of Tm the transport mechanism is saturated and the substance occurs in the urine. Glycosuria in hyperglycemia > 10 mmol/l = renal threshold for glucose TmG in men = approx. Functions of the Collecting Ducts Changes in osmolarity and volume mainly by means of the countercurrent multiplication system: Fig. Two tubes separated by semipermeable membrane with ability to transport molecules of a substance in one-way. If the tubes are fulfilled with a stationary fluid the activity of the membrane increases the concentration of the substance in tube A. When the fluid flows the mostly concentrated fluid will be accumulated at the beginning of the tube B. Application of the countercurrent system in kidneys + - Descending limb of the Henles loop is permeable for water and Na + - The ascending limb of the loop is relatively impermeable to water and permeable to Na, - Cl, urea. Interstitial hypertonicity is supported also by active resorption of Na form the duct to the interstitium. Descending vasa penetrate to the hypertonic portion there water diffuses out of the vessels and in the hypotonic portion water diffuses into the vessels. Recirculation of the water and the solutes from and into vasa recta helps to maintain hypertonicity. Concentrated and darker in early morning less water excreted at night but unchanged amounts of urinary solids. Odour: Aromatic when fresh ammoniacal on standing due to bacterial decomposition of urea to ammonia. Creatinine - from breakdown of body tissues; uninfluenced by amount of dietary protein. Ammonia - formed in kidney from glutamine brought to it by blood stream; [In the newborn, volume and specific gravity are low and composition varies. Smooth muscle coats distend as urine collects: contract periodically to expel urine to urethra. When bladder is empty and beginning to fill - inhibition of parasympathetic - activation of sympathetic Relaxation of bladder wall. In older children and adults reflex can be controlled and inhibited voluntarily. Stimulus: Distension of the receptors in smooth muscle When empty, pressure in bladder is zero. When 50 ml urine collectpressure to 10 cm H2O up to 300 or 400 ml little increase in pressure. Sensations to consciousness Micturition center: Parasympathetic S2 S4 Sympathetic efferents L1-3 - inhibits ganglia Efferent pathways: Impulses in parasympathetic nerves (pelvici)and in somatic nerves (pudendal). Differentiation of stimulus intensity: 1) by differences in action potentials firing rate 2) by differences in the number of activated receptors Intensive stimuli activation other receptors and sensory units = recruitment of sensory units. Spinothalamic tract 1) Neospinothalamic fast pain A fibres the tract passes upward to the brain in the anterolateral columns to the thalamus. Referred pain: When pain is referred it is to a structure that is developed from the same embryonic segment (dermatome) as the structure in which the pain originates = dermatomal rule. Changes in pain perception 1) Hyperalgesia 2) Hypoalgesia peripheral: stimulation of tactile and pressure receptors reduces pain perception (acupressure, acupuncture, massage) centraly: Psychogenic mechan. Physiological and pharmacological principles of the analgesia treatment of pain 49 Distracting techniques (controlled breathing, rhythmic tapping,. Afferent pathway: Sensitive fibers Centers: In spinal cord, medulla oblongata, hypothalamus. Acetylcholine - synthesis: cholin+acetylCo A (acetyltransferase) - inactivation: acetylcholinesterase: cholin+acetate Cholin the uptake for the resynthesis Ach very short effect duration Receptors for Ach - nicotinic (N) receptors - in the synapses between the pre- and postganglionic neurons, in the neuromuscular junction - muscarinic (M) receptors: postggl. Autonomic tone and excitability Tone there are discharges in autonomic nerves at rest reflex: (stimulation of baro-, chemoreceptors) central (hypothalamus) 58 sympathetic (e. Cardiovascular system the variability of cardiovascular parameters short-term, long-term Ewing battery of cardiovascular tests deep breathing orthostatic test Valsalva manoeuvre hand-grip test other cardiovascular tests oculocardiac test, diving reflex, mental and physical load. Psychosomatic relationships cerebral cortex the influence on the respiratory, cardiovascular, immune, autonomic and other systems relationships - cortex - organs organs - cortex efferent influences of the cerebral cortex: 1. Visual pathways: Collaterals of optic tract: Hypothalamus (circadian rhythm) Pretectal nuclei (accomodation, pupillary light reflex) Superior colliculus (eye movements) Field of vision: -visual area seen at given moment - monocular, binocular - blind spot (15 deg. Floaters (muscae volitantes) -slowly drifting transparent blobs of varying size and shape -particularly noticeable when lying on the ground looking up at the sky -caused by imperfections in the fluid of the eye 2. Scheerer`s phenomenon = blue field phenomenon -noticeable when viewed against a field of pure blue light - tiny bright dots moving rapidly along squiggly lines in the visual field -caused by leucocytes moving in the capillaries in front of retina 3. External ear the pinna (helps to direct sounds), the external auditory meatus, auditory Canal transmits sound waves to the tympanic membrane 2. Middle ear separated from extrenal ear by tympanic membrane (called eardrum), chain of ossicles the malleus, the incus, and the stapes. Eustachian tube connects middle ear to the pharynx and equilizes pressure differences between external and mid. Inner ear bony and membraneous labyrinth (cochlea and vestibular apparartus), receptors for two sensory functions. Cochlea spiral-shaped organ, divided by basal and Reissneri membranes to three parts scala tympani and scala vestibuli by perilymph (helicotrema), between scala media by endolymph). On basal membrane organ og Corti with receptors hair cells Adequate stimulus for auditory receptors sound - sound is produced by waves of compression and decompression transmitted in air (or other media such as water), propagation in the air 335 m/s - sound composed of many unrelated frequencies - noise - frequency (nm. The vibrations are transferred by the ossicular system through the oval window on the structures of inner ear (by the vawe movement of perilymph) - stimulation of the organ of Corti causes action potencials in nerve fibres function of mm. Axons penetrate the base of the skull through openings in the cribriform plate of the ethmoid bone as olfactory nerve filaments (fila olfactoria) to olfactory bulb. Stimulation of the olfactory cells - olfactory receptors telereceptors - they response to the odorant substance (gas) in inhaled air dissolved in the mucus 66 - chemical interaction with the membrane of the cilia + - they evoke receptor (generator) potencial by changing permeability of membrane for Na - fast adaptation - in humans ability to distinguish between 2 4000 different odors - the olfactory cells the highest degree of chemical discrimination Intensity of the stimulus depends on concentration of the odor substance (the number of stimulated receptors and the number of moleculs reaching the cell) Quality of perception depends on concentration: at low c. Function of the muscle spindle Receptors - active at rest stretching of the muscle activation of the anulospiral endings higher frequency of the impulses facilitation of the alfa motoneurons of the its own muscle. Pavlov) - originated during development = mechanisms for assurance of ability to survive and live classification: - apetitive - protective - orientation - sexual Innate mechanisms: 1. Drive: - processes which represent an immediate response to fundamental necessities of the body - they force the human to fill the needs - after filling the needs - antidrive 3. Storing of encoded information biochemical, biophysical and electrophysiological processes 3. Each receptor is highly specific for a single hormone Principal mechanisms: 1) Confirmational changes of the receptor alter the membrane permeability to ions. Properties of the hormone effects: 1) Target effect hormone acts on target cells organ (estrogen uterus, mammary gland etc. It lies in the sella turrica at the base of brain and is connected with hypothalamus by the pituitary (hypophyseal) stalk. Symptoms: Hyperglycemia (through) increased glucocorticoid activity), negative nitrogene balance, fat infiltration of the liver. Effects (three main): 1) Mammotrophic effect development of the breasts at puberty 2) Luteotrophic effect stimulation of the corpus luteum, stimulation of the progesteron secretion 3) Role in secretion of milk - producing effect. In mothers who do not nurse their baby a decrease in prolactin level to basal value in 2-3 weeks. Prolactin and estrogen synergize in producing breast growth, but estrogen antagonizes the milk-producing effect of prolactin on the breast. Effect: Lipolysis Control of anterior pituitary secretion 1) Feedback control hormone of the peripheral gland (adrenal cortex, thyroidea. Melanocytes synthesize melanins transfer to keratocytes in skin for pigmentation of hair and skin darkening in 24 hours. Transport - intraneural in the axons of neurons to their endings 85 - in the posterior lobe. Vasoconstriction in splanchnic, renal, coronary, cutaneous and uterine circulation. Single layer of cells filled with colloid Production of thyroid hormones: - thyroxine (T4), - triiodthyronine (T3) Biosynthesis: Processes: 1/Iodination, 2/ condensation of tyrosine molecules 3/ binding in peptide linkage in thyroglobulin 4/secretion 1/ Iodination Iodide trapping mechanism (iodide pump) active transport against a concentration and electrical gradient. Enzymes: 5 deiodinase (T3), 5 deiodinase (rT3), diiodothyronines In the liver T4 and T3 conjugation to sulfates, glucuronides the bile the intestine. Effects of thyroid hormones 1) Effects on growth and development: General and specific effects. Regulation increase in plasmatic Ca++ causes an immediate increase in the rate of calcitonin secretion. Feedback opposite effect increase the Ca++ concentration decreased activity of the parathyroid glands. Hypoparathyreoidism after parathyreoidectomy decrease in Ca++ plasma level signs of neuromuscular hyperexcitability: Hypocalcemic tetany: Chvosteks sign contraction of facial muscles elicited by tapping over the facial nerve. Calcium Metabolism Ca++ - in the human body about 1100 g 99 % in skeleton The plasma Ca++ - 2. D3 (cholecalciferol) is produced in the skin from 7- dehydrocholesterol by sunlight. Other Effects of Glucocorticoids 93 1) Antiinflammatory effect - stabilization of the intracellular lysosomal membranes and inhibition of lymphoid tissue. Adrenal virilism excess growth of facial hair, in women mens type of figure, muscles.
Call your medical provider if: You are vomiting order tadalis sx with a visa pump for erectile dysfunction, confused discount 20mg tadalis sx with visa drugs for treating erectile dysfunction, sleepy or short of breath or feel dehydrated generic tadalis sx 20 mg line erectile dysfunction za. Blood Sugar | Learning to Live Well with Diabetes Low Blood Sugar Hypoglycemia is the medical word for low blood sugar buy 20mg tadalis sx overnight delivery erectile dysfunction pills walgreens. When the amount of sugar in your blood If your blood sugar is low (less than 70) becomes too low, your body cannot work the way it should. Most people with diabetes dont feel eat or drink a quick-acting source well if their blood sugar drops below 70 mg/dl. Low blood sugar occurs most often in people of carbohydrate who are taking certain pills or insulin for their diabetes. If your blood sugar begins to fall too low, you may have one or more * Taking glucose is the preferred treatment of the following symptoms or feelings. A fast heart beat (palpitations) Taking medication at diferent times If your blood sugar is still too low (less than 70) eat or drink a quick-acting source of Hungry Getting more exercise than usual glucose again and recheck your blood sugar in 15 minutes. Headache Drinking alcohol After successfully treating your low blood Light-headed sugar, if your next meal is more than one hour What to do: Low blood sugar away, have one of the following: Nervous If you think your blood sugar is too low, A glass of milk Confused check your blood sugar right away! If you Cheese with some crackers dont feel well enough to check, assume Tired your blood sugar is too low. Staying healthy and preventing illness such as fu and pneumonia are especially important if you have diabetes. Getting a fu shot and a pneumonia vaccine You may not feel like eating the same foods. Your family should also get a fu shot to protect you Some medicines you might take for colds, and them. Be sure to discuss all medicines even Pneumonia those you can get without a prescription The pneumonia vaccine is given by a shot. Some people who get the shot when they are under age 65 will need to get a What to do: Sick care second shot fve years later. Cant eat or keep food down Talk to your dietitian about foods that Drink plenty of sugar-free fuid (without (if you vomit more than once). If you have type 1 diabetes, check the Have moderate or large amounts of ketones in your urine. Diabetes Medicines Most medicines should be taken Help paying for medicines at about the same time each day. You should not skip taking medicine Medicines should always be taken because of the cost. Healthy Vermonters Prescription Drug Program Talk with your medical provider, This program is for those who have no insurance for prescription medicines or those who diabetes educator, or pharmacist: do not have enough income to pay for medicines. Medicare Part D Medicare provides a prescription drug plan regardless of income, health status or About when to take your medicine. Contact your local State Health Insurance and Assistance Program regional coordinator at your Area Agency on About what you should do if you miss Aging to guide you through the plan selection process. They will determine if you are eligible for programs from the drug or dietary supplements. If your body doesnt make enough insulin, you will need to use insu- Take your medicines on time and in lin by injection (shots). Often If you want to stop taking a medi- people use two types of insulin to manage their blood sugars. If you will be doing exercise using the arm(s) or Tell your medical provider about the leg(s), it is better to give the insulin in an area not directly being exercised. Otherwise, the all the medicines you use, even over- insulin will be used too fast. For example, if you are playing tennis, dont inject the arm with the-counter products, vitamins and which you swing the racquet. It is better not to take insulin just before a warm bath or shower since the warmth will cause the insulin to be absorbed faster. If you have been taking multiple daily shots of insulin for awhile, counting your carbs and checking your blood sugar often, you might want to talk with your medical providers about an Keep the list posted in a place thats insulin pump. An insulin pump provides a steady amount of background (basal) insulin over a 24-hour period with additional (bolus) insulin given to cover meals and snacks. Many people like the fexibility Keep all your medicines in labeled that an insulin pump provides. Resources Vermont resources Diabetes Prevention and Control Program, Healthier Living Workshops Vermont Department of Health For people living with diabetes and other chronic conditions. Look for Resources for self-managing diabetes and checking risk for diabetes a regional coordinator who can tell you about workshops nearby; and prediabetes; (800) 464-4343 or (802) 863-7330 www. Eligible Vermont women can receive free screenings for heart disease or Vermont Association for the Blind and Visually Impaired breast and cervical cancer; (800) 508-2222; (800) 639-5861 x230; www. In addition to Quit Partners, available by phone or in person, 802Quits offers free nicotine replacement gum, patches or lozenges to all Vermonters. Resources 23 National resources Other things you should know American Diabetes Association Ask your medical provider or diabetes educator about: (800) 342-2383; www. National Diabetes Education Program Nerve damage (neuropathy) and how it afects many parts of the body. While visiting this site look for videos and tools available at Diabetes HealthSense; www. Magazines Resources to help you learn more Diabetes Forecast Registered dietitians can help you understand meal planning, carb counting (800) 806-7801; www. Diabetes Self-Management Diabetes educators can help you understand and manage your diabetes, includ- (800) 234-0923; www. Check with your medical provider or diabetes educator about a support group meeting near you. Resources | Learning to Live Well with Diabetes Diabetes self-management education programs Brattleboro Memorial Hospital* North Country Hospital Brattleboro (802) 251-8429 Newport (802) 334-4155 Central Vermont Medical Center* Northeastern Vermont Regional Hospital* Barre (802) 371-4378 St. Johnsbury (802) 748-7433 Berlin (802) 371-5903 Northwestern Medical Center* Montpelier (802) 223-4738 St. Randolph (802) 728-7100 Mount Ascutney Hospital and Health Care Center* Windsor (802) 674-7198 Other self-management programs are available through the Vermont Blueprint for Health. Resources 25 This guide is not meant to cover every topic about diabetes, This project was supported by Cooperative Agreement Number nor is it a substitute for the advice of trained professionals. A person with diabetes should get regularly scheduled Its contents are solely the responsibility of the authors and do check-ups from a qualifed medical provider. Haak Aliation A liation addresses are listed at the end of the article Contents & Guideline originally F o r e w o r d 522 published 05. Flowchart of antihyperglycaemic treatment of type 2 diabetes 543 Danziger Stra e10 2. The eectiveness of a multifacto- 40225 D sseldorf rial intervention in reducing macro- and micro- Tel. Medical Antihyperglycaemic Treatment of Diabetes Exp Clin Endocrinol Diabetes 2009; 117: 522557 Guidelines 523 lute risk lowered by 20% in 13. The favourable eect of an optimised antihyperglycae- treatment strategy and other factors. In the glycaemic therapy on macrovascular results in patients with light of the marked heterogeneity of type 2 diabetes, this guide- type 2 diabetes reported a relative risk reduction of 19% (Stettler line is only able to establish a framework and indicate therapeu- et al. A recent analysis The conclusions to be drawn from the results of the two studies of 42 clinical studies revealed that the eect of metformin on have been incorporated in the owchart (see section 2. Endpoint data are available for the following substances in the pharmacological antihyperglycaemic treatment of subjects with 1. This should be carried out in consultation Treatment with metformin should be initiated as described in with the treating physician taking into consideration the objec- Table 4. The eects of metformin doses between 500mg/ taken regularly by the patient if therapeutic implications for the day 2000mg/day were analysed on a total of 451 patients with short, medium and long terms are derived from the results. The most eective dosage of metformin was frequency with which the patient should monitor his/her own 2 000 mg / day, which reduced HbA1c levels by as much as 2 % blood glucose levels is dictated by the individual treatment plan, from baseline values of 9% and lowered fasting blood glucose Matthaei S et al. Medical Antihyperglycaemic Treatment of Diabetes Exp Clin Endocrinol Diabetes 2009; 117: 522557 524 Guidelines Reported eects Change with respect to starting value Table 1 E ects of metformin on components of insulin resistance. Range % e ects on diabetes control fasting blood glucose (mmol / L) 2 4 20 30 postprandial blood glucose (mmol / L) 3 6 30 40 HbA1c ( % ) 1 2 10 25 e ects on insulin concentrations fasting plasma insulin concentration (U / mL) 0 3. The fall in triglycerides revealed that the eects of metformin and sulphonylureas (19 % vs. In the combination therapies with various oral antidiabetics too, very dierent eects on the indi- 1. Medical Antihyperglycaemic Treatment of Diabetes Exp Clin Endocrinol Diabetes 2009; 117: 522557 Guidelines 525 reduced by 7% in men and by 14% in women (Haner et al. In an Italian observation study of 2002 patients with (23 % and 33 %, respectively). Mortality after 3 years was signicantly higher for the cial eect on several of the known risk factors for atherosclero- combination therapy with glibenclamide (8. Even after adjusting for many inuencing factors, the risk of mortality with the metformin-glibenclamide combina- 1. The most thorough information is available for a Particularly favourable results have been described for the com- combination therapy with metformin and sulphonylureas (Her- bination of insulin and metformin (Yki-Jrvinen et al. Evaluations of the safety of combination tite and fullness, diarrhoea is relatively rare. The most dangerous therapy with metformin and sulphonylureas have led to dier- side eect is lactic acidosis, which is extremely uncommon. The risk of the fact that the patients who were treated with a sulphonylurea death is about a third of this gure. Renal insuciency and cardiac combination therapy in a Scandinavian study (Olsson et al.
Experiments have shown that the surfactant excreted by insects reduces the surface tension of water from 73 dyn/cm to about 50 dyn/cm 20mg tadalis sx with mastercard erectile dysfunction treatment on nhs. Measurements show that during Marangoni propulsion tadalis sx 20 mg mastercard erectile dysfunction doctors, Microvelia can attain peak speeds of 17 cm/sec tadalis sx 20mg low price erectile dysfunction age group. Assume that the average density of the human body is about the same as water ( 1 g/cm3) and that the area A of the limbs w acting on the water is about 600 cm2 order discount tadalis sx line impotence under 30. If the situation is reversed, the immersed animal tends to rise to the surface, and it must expend energy to keep itself below the surface. Calculate volume of the swim bladder as a percent of the total vol- ume of the sh in order to reduce the average density of the sh from 1. The density of an animal is conveniently obtained by weighing it rst in air and then immersed in a uid. If the density of the uid is 1, the average density 2 of the animal is W1 2 1 W1 W2 Derive this relationship. If a section of coarse-grained soil is adjacent to a ner grained soil of the same material, water will seep from the coarse-grained to the ner grained soil. Calculate the perimeter of a platform required to support a 70 kg person solely by surface tension. Assume that the linear dimension of the insect is 3 101 cm and its mass is 3 102 g. Further, assume that the surface tension dierence between the clean water and surfactant altered water provides the force to accel- erate the insect. Poiseuille (17991869), was a French physician whose study of moving uids was motivated by his interest in the ow of blood through the body. In this chapter, we will review briey the principles governing the ow of uids and then examine the ow of blood in the circulatory system. Bernoullis equation states that at any point in the channel of a owing uid the following relationship holds: 1 2 P + gh + v Constant (8. The rst term in the equation is the potential energy per unit volume of the uid due to the pressure in the uid. Consider a uid owing through a pipe consisting of two segments with cross- sectional areas A1 and A2, respectively (see Fig. The volume of uid owing per second past any point in the pipe is given by the product of the uid velocity and the area of the pipe, A v. If the uid is incompressible, in a unit time as much uid must ow out of the pipe as ows into it. Therefore, the rates of ow in segments 1 and 2 are equal; that is, A1 A1v1 A2v2 or v2 v1 (8. Therefore the relationship between the parameters P,, h, and v at points 1 and 2 is 1 2 1 2 P1 + gh1 + v P2 + gh2 + v (8. Viscous friction is pro- portional to the velocity of ow and to the coecient of viscosity for the given uid. As a result of viscous friction, the velocity of a uid owing through a pipe varies across the pipe. The velocity is highest at the center and decreases toward the walls; at the walls of the pipe, the uid is stationary. The lengths of the arrows are proportional to the velocity across the pipe diameter. If viscosity is taken into account, it can be shown (see reference [8-5]) that the rate of laminar ow Q through a cylindrical tube of radius R and length L is given by Poiseuilles law, which is R4 (P P ) 1 2 3 Q cm /sec (8. In general, viscosity is a function of temperature and increases as the uid becomes colder. This fact is evident from Bernoullis equation, which shows that if the height and velocity of the uid remain constant, there is no pressure drop along the ow path. The product of the pressure drop and the area of the pipe is the force required to overcome the frictional forces that tend to retard the ow in the pipe segment. Note that for a given ow rate the pressure drop required to overcome frictional losses decreases as the fourth power of the pipe radius. Thus, even though all uids are subject to friction, if the area of the ow is large, frictional losses and the accompanying pressure drop are small and can be neglected. The ow becomes turbulent with eddies and whirls disrupting the laminar ow (see Fig. In a cylindrical pipe the critical ow velocity vc above which the ow is turbulent, is given by vc (8. The symbol is the Reynolds number, which for most uids has a value between 2000 and 3000. Therefore, as the ow turns turbulent, it becomes more dicult to force a uid through a pipe. Blood is not a simple uid; it contains cells that complicate the ow, especially when the passages become narrow. Furthermore, the veins and arteries are not rigid pipes but are elastic and alter their shape in response to the forces applied by the uid. Still, it is possible to analyze the circulatory system with reasonable accuracy using the concepts developed for simple uids owing in rigid pipes. The blood in the circulatory system brings oxygen, nutrients, and various other vital substances to the cells and removes the metabolic waste products from the cells. The blood is pumped through the circulatory system by the heart, and it leaves the heart through vessels called arteries and returns to it through veins. The mammalian heart consists of two independent pumps, each made of two chambers called the atrium and the ventricle. The entrances to and exits from these chambers are controlled by valves that are arranged to maintain the ow of blood in the proper direction. Blood from all parts of the body except the lungs enters the right atrium, which contracts and forces the blood into the right ventricle. The ventricle then contracts and drives the blood through the pulmonary artery into the lungs. In its passage through the lungs, the blood releases carbon dioxide and absorbs oxygen. The contraction of the left atrium forces the blood into the left ventricle, which on contraction drives the oxygen-rich blood through the aorta into the arteries that lead to all parts of the body except the lungs. Thus, the right side of the heart pumps the blood through the lungs, and the left side pumps it through the rest of the body. These in turn branch into still smaller arteries, the smallest of which are called arterioles. As we will explain later, the arte- rioles play an important role in regulating the blood ow to specic regions in Section 8. The arterioles branch further into narrow capillaries that are often barely wide enough to allow the passage of single blood cells. The capillaries are so profusely spread through the tissue that nearly all the cells in the body are close to a capillary. The capillaries join into tiny veins called venules, which in turn merge into larger and larger veins that lead the oxygen-depleted blood back to the right atrium of the heart. First the atria contract, forcing the blood into the ventricles; then the ventricles contract, forcing the blood out of the heart. Because of the pumping action of the heart, blood enters the arteries in spurts or pulses. The maximum pressure driving the blood at the peak of the pulse is called the systolic pressure. Ina young healthy individual the systolic pressure is about 120 torr (mm Hg) and the diastolic pressure is about 80 torr. As the blood ows through the circulatory system, its initial energy, pro- vided by the pumping action of the heart, is dissipated by two loss mecha- nisms: losses associated with the expansion and contraction of the arterial walls and viscous friction associated with the blood ow. Due to these energy losses, the initial pressure uctuations are smoothed out as the blood ows away from the heart, and the average pressure drops. By the time the blood reaches the capillaries, the ow is smooth and the blood pressure is only about 30 torr. The pressure drops still lower in the veins and is close to zero just before returning to the heart. In this nal stage of the ow, the movement of blood through the veins is aided by the contraction of muscles that squeeze the blood toward the heart. The rate of blood ow Q through the body depends on the level of physical activity. Of course, as the aorta branches, the size of the arteries decreases, result- ing in an increased resistance to ow. Although the blood ow in the nar- rower arteries is also reduced, the pressure drop is no longer negligible (see Exercise 8-2). The ow through the arterioles is accompanied by a much larger pressure drop, about 60 torr. Since the pressure drop in the main arteries is small, when the body is horizontal, the average arterial pressure is approximately constant throughout the body. The arterial blood pressure, which is on the average 100 torr, can support a column of blood 129 cm high (see Eq. This means that if a small tube were introduced into the artery, the blood in it would rise to a height of 129 cm (see Fig. If a person is standing erect, the blood pressure in the arteries is not uni- form in the various parts of the body. The weight of the blood must be taken into account in calculating the pressure at various locations.