Cardiovascular System: Regulation of Mean Arterial Pressure
baroreceptor reflexes
change peripheral resistance, heart rate, stroke volume in response to changes in blood pressure; carotid sinus, aortic arch
effects of aging
degenerative changes (arteriosclerosis, atherosclerosis, etc.) increased resistance to blood flow
CNS ischemic response: lack of oxygen causes vasomotor center to become inactive then...
extensive vasodilation follows with associated drop in BP. death in CNS ischemic response lasts longer than a few minutes
atrial natriuretic hormone (ANH) mechanism
from cardiac muscle cells when atrial BP increase --> increase urinary production --> decrease BP and blood volume
CNS ischemic response: neurons of vasomotor center strongly stimulated which...
increases blood flow to brain if vessels are intact but at the same time, decreases oxygenation of blood because blood does not go to lungs
angiotensin-converting enzyme (ACE)
inhibitors for controlling hypertension angiotensinogen --> angiotensin I --> (ACE) --> angiotensin II (active)
fluid shift mechanism
movement of fluid from interstitial space into capillaries with decreased BP to maintain blood volume and vice versa
renin-angiotensin-aldosterone mechanism
renin (kidneys) --> angiotensin I --> angiotensin II --> vasoconstriction --> increase aldosterone (increase Na+ reabsorption) requires angiotensin-converting enzyme (ACE)
long-term regulation of blood pressure
renin-angiotensin-aldosterone mechanism vasopressin (ADH) mechanism atrial natriuretic mechanism fluid shift mechanism stress-relaxation response
central nervous system ischemic response
results from high carbon dioxide or low pH levels in medulla and increases peripheral resistance elevation of BP in response to lack of blood flow to medulla oblongata vasomotor center --> vasoconstriction --> increase systemic BP only works for a few minutes and if blood vessels are intact
chemoreceptor reflexes
sensory receptors sensitive to oxygen, carbon dioxide, and pH levels of blood
adrenal medullary mechanism
stimulation of medulla by sympathetic nerve fibers releases epinephrine and norepinephrine --> increase HR and SV vasoconstriction to skin and viscera
vasopressin (ADH - antidiuretic hormone) mechanism
ADH from post. pit. gland --> vasoconstriction to increase BP and decrease urinary production
stress relaxation response
adjustment of blood vessel smooth muscle to respond to change in blood volume when blood volume suddenly declines and pressure drops, smooth muscles contract and vice versa
short-term regulation of blood pressure
baroreceptor reflexes, chemoreceptor reflexes, central nervous system ischemic response, adrenal medullary mechanism