**Lecture 24 Flashcards
How is driving pressure maintained?
arteries are elastic, as they recoil, radius decreases so pressure increases
What affects MAP
1) blood volume –> fluid intake vs fluid loss
2) cardiac output –> HR and SV
3) resistance –> radius of arteries
4) distribution of blood between arteries/veins –> diameter of veins
What are the two responses to an increase in blood volume
Cardiovascular (fast) = vasodilation, decreased cardiac output
Renal (slow) = increased excretion of fluid into the urine
How is arteriole resistance regulated
1) Myogenic response –> reflexive constriction of blood vessel due to increased pressure (pressure increase causes arteriole stretch, opens mechanically gated channels on smooth membrane, influx of Ca, contraction increases resistance so there is less blood flow and less pressure)
2) Paracrine
a) active hyperemia = match flow to metabolic demands
release of metabolites (vasodilators) that act on smooth muscle
b) reactive hyperemia = when there is an occlusion, results in buildup of metabolites, temporary after blockage clears, vasodilation before metabolites washed out
3) SNS regulation –> tonic control due to NE on alpha 1 receptors. Activates PLC leading to production of IP3 –> contraction
E on beta 2 receptors coupled to Gs protein –> cAMP inhibits MLCK and causes relaxation/vasodilation
Describe the baroreceptor reflex
increased blood pressure sensed by baroreceptors in carotid sinus and aorta, sends signal to sensory neurons to medulla oblongata. Decreases sympathetic output, less NE released, so alpha receptor at smooth muscle dilates, beta receptor at cardiac muscle decreases force of contraction, beta receptor at SA node slows heart rate. Increases parasympathetic output to increase Ach on muscarinic receptor to decrease HR. Decreasing HR and decreases contraction force = decreased CO, smooth muscle = decreased peripheral resistance so decreased blood pressure
