Anatomy & Physiology I and II

Anatomy & Physiology Study Guide • At the capillaries, blood pressure transports water and solutes out of the plasma and across capillary walls. Water moves out of the capillaries, through the peripheral tissues, and returning to the bloodstream by way of the lymphatic system. Water movement across capillary walls is determined by the interplay between osmotic pressures and hydrostatic pressures. • Osmotic pressure (OP) is a measure of the pressure that must be applied to prevent osmotic movement across a membrane. Osmotic water movement continues until solute concentrations are equalized, or the movement is prevented by an opposing hydrostatic pressure. • The rates of filtration and reabsorption gradually change as blood passes along the length of a capillary, as determined by the net filtration pressure (the difference between the net hydrostatic pressure and the net osmotic pressure). Cardiovascular regulatory mechanisms involve autoregulation, neural mechanisms, and endocrine responses: • Homeostatic mechanisms guarantee that tissue perfusion (blood flow) conveys adequate oxygen and nutrients. • Autoregulation, neural mechanisms, and endocrine mechanisms affect the coordinated regulation of cardiovascular function. Autoregulation includes local factors altering the 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-termadjustments (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: ©2018 Achieve Test Prep Page 275 of 367