The patient then holds the wrist over the heart while the device measures blood flow and records pressure. The impact of other confounding factors affecting blood viscosity is omitted. Restoring homeostasis in these patients depends upon reversing the condition that triggered the hypervolemia. Mammalian blood with a normal hematocrit of 45% has a viscosity 2.4 times that of plasma alone. In contrast to length, the diameter of blood vessels changes throughout the body, according to the type of vessel, as we discussed earlier. Blood pressure may be measured in both the systemic and pulmonary circulation; however, the term blood pressure without any specific descriptors typically refers to systemic arterial blood pressurethat is, the pressure of blood flowing in the arteries of the systemic circulation. and more. Medications to reduce cholesterol and blood pressure may be prescribed. It is important to recognize that other regulatory mechanisms in the body are so effective at maintaining blood pressure that an individual may be asymptomatic until 1020 percent of the blood volume has been lost. An individual weighing 150 pounds has approximately 60,000 miles of vessels in the body. Venoconstriction, while less important than arterial vasoconstriction, works with the skeletal muscle pump, the respiratory pump, and their valves to promote venous return to the heart. Artery walls that are constantly stressed by blood flowing at high pressure are also more likely to be injuredwhich means that hypertension can promote arteriosclerosis, as well as result from it. The important thing to remember is this: Two of these variables, viscosity and vessel length, will change slowly in the body. Venous return to the heart is reduced, a condition that in turn reduces cardiac output and therefore oxygenation of tissues throughout the body. 1.2 Structural Organization of the Human Body, 2.1 Elements and Atoms: The Building Blocks of Matter, 2.4 Inorganic Compounds Essential to Human Functioning, 2.5 Organic Compounds Essential to Human Functioning, 3.2 The Cytoplasm and Cellular Organelles, 4.3 Connective Tissue Supports and Protects, 5.3 Functions of the Integumentary System, 5.4 Diseases, Disorders, and Injuries of the Integumentary System, 6.6 Exercise, Nutrition, Hormones, and Bone Tissue, 6.7 Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems, 7.6 Embryonic Development of the Axial Skeleton, 8.5 Development of the Appendicular Skeleton, 10.3 Muscle Fiber Excitation, Contraction, and Relaxation, 10.4 Nervous System Control of Muscle Tension, 10.8 Development and Regeneration of Muscle Tissue, 11.1 Describe the roles of agonists, antagonists and synergists, 11.2 Explain the organization of muscle fascicles and their role in generating force, 11.3 Explain the criteria used to name skeletal muscles, 11.4 Axial Muscles of the Head Neck and Back, 11.5 Axial muscles of the abdominal wall and thorax, 11.6 Muscles of the Pectoral Girdle and Upper Limbs, 11.7 Appendicular Muscles of the Pelvic Girdle and Lower Limbs, 12.1 Structure and Function of the Nervous System, 13.4 Relationship of the PNS to the Spinal Cord of the CNS, 13.6 Testing the Spinal Nerves (Sensory and Motor Exams), 14.2 Blood Flow the meninges and Cerebrospinal Fluid Production and Circulation, 16.1 Divisions of the Autonomic Nervous System, 16.4 Drugs that Affect the Autonomic System, 17.3 The Pituitary Gland and Hypothalamus, 17.10 Organs with Secondary Endocrine Functions, 17.11 Development and Aging of the Endocrine System, 19.2 Cardiac Muscle and Electrical Activity, 20.1 Structure and Function of Blood Vessels, 20.2 Blood Flow, Blood Pressure, and Resistance, 20.4 Homeostatic Regulation of the Vascular System, 20.6 Development of Blood Vessels and Fetal Circulation, 21.1 Anatomy of the Lymphatic and Immune Systems, 21.2 Barrier Defenses and the Innate Immune Response, 21.3 The Adaptive Immune Response: T lymphocytes and Their Functional Types, 21.4 The Adaptive Immune Response: B-lymphocytes and Antibodies, 21.5 The Immune Response against Pathogens, 21.6 Diseases Associated with Depressed or Overactive Immune Responses, 21.7 Transplantation and Cancer Immunology, 22.1 Organs and Structures of the Respiratory System, 22.6 Modifications in Respiratory Functions, 22.7 Embryonic Development of the Respiratory System, 23.2 Digestive System Processes and Regulation, 23.5 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder, 23.7 Chemical Digestion and Absorption: A Closer Look, 25.1 Internal and External Anatomy of the Kidney, 25.2 Microscopic Anatomy of the Kidney: Anatomy of the Nephron, 25.3 Physiology of Urine Formation: Overview, 25.4 Physiology of Urine Formation: Glomerular Filtration, 25.5 Physiology of Urine Formation: Tubular Reabsorption and Secretion, 25.6 Physiology of Urine Formation: Medullary Concentration Gradient, 25.7 Physiology of Urine Formation: Regulation of Fluid Volume and Composition, 27.3 Physiology of the Female Sexual System, 27.4 Physiology of the Male Sexual System, 28.4 Maternal Changes During Pregnancy, Labor, and Birth, 28.5 Adjustments of the Infant at Birth and Postnatal Stages. Five factors influence blood pressure: Cardiac output. The vascular tone of the vessel is the contractile state of the smooth muscle and the primary determinant of diameter, and thus of resistance and flow. The walls of veins are thin but irregular; thus, when the smooth muscle in those walls constricts, the lumen becomes more rounded. When this happens, platelets rush to the site to clot the blood. Difficulty walking. This may seem surprising, given that capillaries have a smaller size. Common sites to find a pulse include temporal and facial arteries in the head, brachial arteries in the upper arm, femoral arteries in the thigh, popliteal arteries behind the knees, posterior tibial arteries near the medial tarsal regions, and dorsalis pedis arteries in the feet. A major risk factor for both arteriosclerosis and atherosclerosis is advanced age, as the conditions tend to progress over time. 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Identify and discuss five variables affecting arterial blood flow and blood pressure, Discuss several factors affecting blood flow in the venous system. Treatment includes lifestyle changes, such as weight loss, smoking cessation, regular exercise, and an adoption of a diet low in sodium and saturated fats. As a result, compliance is reduced. A pulse pressure below this level is described as low or narrow. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. This operation is typically performed on the carotid arteries of the neck, which are a prime source of oxygenated blood for the brain. A variety of commercial electronic devices are also available to measure pulse. Normally,the mean arterial blood pressure falls within the range of 70110mmHg,so 100 is normal. Determine whether each pressure is low, normal, or high. Since pressure in the veins is normally relatively low, for blood to flow back into the heart, the pressure in the atria during atrial diastole must be even lower. Generally, a pulse pressure should be at least 25 percent of the systolic pressure, but not more than 100 mm Hg. The vascular tone of the vessel is the contractile state of the smooth muscle and the primary determinant of diameter, and thus of resistance and flow. One of the great benefits of weight reduction is the reduced stress to the heart, which does not have to overcome the resistance of as many miles of vessels. Ventricular contraction ejects blood into the major arteries, resulting in flow from regions of higher pressure to regions of lower pressure, as blood encounters smaller arteries and arterioles, then capillaries, then the venules and veins of the venous system. Pulse, the expansion and recoiling of an artery, reflects the heartbeat. Normally the viscosity of blood does not change over short periods of time. Generally, a pulse pressure should be at least 25 percent of the systolic pressure, but not more than 100 mm Hg. . Normally the viscosity of blood does not change over short periods of time. The result is more turbulence, higher pressure within the vessel, and reduced blood flow. After blood is ejected from the heart, elastic fibers in the arteries help maintain a high-pressure gradient as they expand to accommodate the blood, then recoil to keep pressure on the blood. Any factor that causes cardiac output to increase, by elevating heart rate or stroke volume or both, will elevate blood pressure and promote blood flow. Compliance is the ability of any compartment to expand to accommodate increased content. Two factors help maintain this pressure gradient between the veins and the heart. This slow flow rate allows more time for the exchange of substances between the blood and cells to occur. The clinician places the stethoscope on the patients antecubital region and, while gradually allowing air within the cuff to escape, listens for the Korotkoff sounds. The patients mean arterial pressure is 85 + 1/3 (45) = 85 + 15 = 100. The greater the compliance of an artery, the more effectively it is able to expand to accommodate surges in blood flow without increased resistance or blood pressure. Five variables influence blood flow and blood pressure: Recall that blood moves from higher pressure to lower pressure. An even more recent innovation is a small instrument that wraps around a patients wrist. If it is weak, systolic pressure has fallen, and medical intervention may be warranted. When systemic arterial blood pressure is measured, it is recorded as a ratio of two numbers (e.g., 120/80 is a normal adult blood pressure), expressed as systolic pressure over diastolic pressure. Restoring homeostasis in these patients depends upon reversing the condition that triggered the hypervolemia. As inflammation spreads into the artery wall, it weakens and scars it, leaving it stiff (sclerotic). Sometimes a plaque can rupture, causing microscopic tears in the artery wall that allow blood to leak into the tissue on the other side. Disorders of theCardiovascular System: ArteriosclerosisCompliance allows an artery to expand when blood is pumped through it from the heart, and then to recoil after the surge has passed. In many body regions, the pressure within the veins can be increased by the contraction of the surrounding skeletal muscle. Hearing problems. This is a leading cause of hypertension and coronary heart disease, as it forces the heart to work harder to generate a pressure great enough to overcome the resistance. Hypoxia involving cardiac muscle or brain tissue can lead to cell death and severe impairment of brain or heart function.