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Regulation of blood pressure (short-term (neural) (Baroreceptor (pressure)…
Regulation of blood pressure
short-term
(neural)
heart rate (HR)
diameter of arteries/arterioles
contractility of ventricles
Baroreceptor (pressure) reflex
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stretch (physical, mechanically gated) receptors are located in the walls of the carotid sinuses and aortic sinuses
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upon stretch the transmembrane Na channels of the receptor open, causing depolarization, which sends signals via afferent fibers
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when BP rises, this causes stretch, glossopharyngeal (CN IX) and in afferent fibers in the vagus (CN X) increase firing rate, they synapse in the medulla (CV center)
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the medulla decreases CO (decrease HR, decrease contractility), causes peripheral vaso-constriction = return to homeostasis
Where do you find baroreceptors to monitor blood volume?
right atrium
vasomotor center
cluster of neurons in the medulla
steadily impulses are transmitted along sympathetic efferent (T1-L2) to innervate SMC of arterioles
vasomotor activities are modified by input
Chemoreceptor Reflex
peripheral chemoreceptors in carotid bodies and aortic bodies primarily are sensitive to PO2, but also responsive to PCO2 and blood pH
central chemoreceptors in the medulla are most sensitive to PCO2, as the brain is intolerant to decrease in blood flow
higher brain centers:
ANS response mediated by the hypothalamus has profound effects on BP
long-term
(hormonal)
regulate blood pressure by changing blood volume (BV)
volume regulation via kidneys
renin-angiotensin-aldosterone system
hormones
ADH
origin:
hypothalamus
target:
collecting tubules of kidneys
trigger:
increased osmolarity
effect:
lower BV
aldosterone
trigger:
low Na+, low BV
target:
distal convoluted tubules in kidneys
origin:
adrenal medulla
effect:
increased BV
atrial natriuretic peptide
origin:
right atrium
trigger:
increased BV
target:
glomerulus in kidney
effect:
decreased BV