chapter 30 Flashcards
what is the cardiovascular systems vital role in maintaining homeostasis depends on
continuous, controlled movement of blood through capillaries
hemodynamics
A collection of mechanisms that influence the dynamic (active and changing) circulation of blood
Circulation control mechanisms must accomplish what functions
Maintain circulation
Vary the volume and distribution of the blood circulated
perfusion pressure
pressure gradient needed to maintain blood flow through a local tissue
what is P1-P2
symbol used to represent a pressure gradient, with P1 representing the higher pressure and P2 the lower pressure
Blood circulates from the left ventricle to the right atrium of the heart
because a blood pressure gradient exists between these two structures
Aortic reflex
sensory fibers extend from baroreceptors located in the wall of the arch of the aorta through the aortic nerve and through the vagus nerve to terminate in the cardiac control center
Peripheral resistance
resistance to blood flow imposed by the force of friction between blood and the walls of its vessels
Factors that influence peripheral resistance
blood viscosity
high plasma protein
high hematocrit
Vasomotor mechanism:
muscles in walls of arteriole may constrict (vasoconstriction) or dilate (vasodilation), thus changing diameter of arteriole
Vasomotor control mechanism:
controls changes in the diameter of arterioles; plays role in maintenance of the general blood pressure and distribution of blood to areas of special need
Vasomotor chemoreflexes:
located in aortic and carotid bodies are sensitive to hypercapnia(too much carbon dioxide), hypoxia(too little of oxygen), and decreased arterial blood pH
Medullary ischemic reflex:
acts during emergency situation when blood flow to the medulla is decreased; causes marked arteriole and venous constriction
Vasomotor control by higher brain centers:
impulses from centers in cerebral cortex and hypothalamus transmitted to vasomotor centers in medulla to help control vasoconstriction and dilation
Local control of arterioles: several mechanisms produce localized vasodilation;
relative hyperemia
Venous return:
amount of blood returned to the heart by the veins
Stress-relaxation effect:
occurs when a change in blood pressure causes a change in vessel diameter (because of elasticity) and thus adapts to the new pressure to keep blood flowing (works only within certain limits
Venous pumps
blood-pumping action of respirations and skeletal muscle contractions facilitate venous return by increasing pressure gradient between peripheral veins and venae cavae
Total blood volume
changes in total blood volume change the amount of blood returned to the heart
Antidiuretic hormone mechanism
decreases the amount of water lost by the body by increasing the amount of water that kidneys reabsorb from urine before it is excreted from the body; triggered by input from baroreceptors and osmoreceptors
Renin
released when blood pressure in kidney is low; leads to increased secretion of aldosterone, which stimulates retention of sodium, causing increased retention of water and an increase in blood volume
Angiotensin II
intermediate compound that causes vasoconstriction, which complements the volume-increasing effects of renin and promotes an increase in overall blood flow
Atrial natriuretic peptide mechanism
adjusts venous return from an abnormally high level by promoting the loss of water from plasma, causing a decrease in blood volume; increases urine sodium loss
Arterial bleeding(more critical)
blood escapes from artery in spurts because of alternating increase and decrease of arterial blood pressure
