Anatomy & Physiology

Anatomy & Physiology Study Guide pattern of blood flow inside capillary beds as a response to chemical changes in interstitial fluids. Neural mechanisms respond to adjustments in arterial pressure or blood gas levels. Hormones can help with short-term adjustments (changes in cardiac output and peripheral resistance) and long-term adjustments (changes in blood volume that influence cardiac output and gas transport). • Peripheral resistance is adjusted in the tissues by local factors that result in the dilation or constriction of precapillary sphincters. • Cardiovascular (CV) centers of the medulla oblongata modify cardiac output and peripheral resistance to maintain adequate blood flow. The vasomotor center contains one group of neurons responsible for controlling vasoconstriction, and another group responsible for controlling vasodilation. • Baroreceptor reflexes monitor the degree of stretch within expandable organs. Baroreceptors are located in the carotid sinuses, the aortic sinuses, and the right atrium. • The endocrine system provides short-term regulation of cardiac output and peripheral resistance with epinephrine and norepinephrine from the suprarenal medullae. • Hormones included in the long-term regulation of blood pressure and volume are antidiuretic hormone (ADH), angiotensin II, erythropoietin (EPO), and natriuretic peptides (ANP and BNP). • Chemoreceptor reflexes respond to changes in the oxygen or CO2 levels in the blood. They are triggered by sensory neurons located in the carotid bodies and the aortic bodies. The cardiovascular system adjusts to physiological stress and sustains a vascular supply to the heart, brain, and lungs: • During exercise, blood flow to skeletal muscles rises at the expense of blood flow to non- essential organs, and cardiac output rises. Cardiovascular performance improves with training. Athletes have larger stroke volumes, slower resting heart rates, and larger cardiac reserves than do non-athletes. • Blood loss decreases blood volume, venous return, and cardiac output. Compensatory mechanisms can include an increase in cardiac output, a mobilization of venous reserves, peripheral vasoconstriction, and the release of hormones that further the retention of fluids and the creation of erythrocytes. • The blood–brain barrier, the coronary circulation, and the circulation to alveolar capillaries in the lungs are instances of special circulations, in which cardiovascular dynamics and regulatory mechanisms are different from those in other tissues. The pulmonary and systemic circuits in the cardiovascular system display three general functional patterns: • The peripheral distributions of arteries and veins are identical on both sides of the body, except near the heart. In the pulmonary circuit, deoxygenated blood enters the lungs in arteries, and oxygenated blood leaves the lungs via veins: • The pulmonary circuit consists of the pulmonary trunk, the left and right pulmonary arteries, and the pulmonary veins, which evacuate into the left atrium. Achieve Page 277 of 368 ©2018