1.3 Control of blood flow 32-42 Flashcards
a generic systemic tissue capillary bed is supplied by an_______ and drained by a _______, and the tissue is made up of ___________.
arteriole
venule
Metabolizing cells
How is vascular smooth muscle (tunica media) in blood vessels innervated?
sympathetic branch of the ANS
________ are the regulators of microvasculature by controlling entry into the capillaries.
arterioles
A decrease in blood flow with physiological decrease in blood vessel radius is called?
Vasoconstriction
A increase in blood flow with physiological increase in blood vessel radius is called?
Vasodilation
How is vascular smooth muscle different than striated muscle cells in contractions?
have slow, sustained, tonic contractions
vascular smooth muscle tone can be modified 3 basic ways:
mechanical stimulation
electrical stimulation
chemical stimulation
How is vascular smooth muscle stimulated mechanically to contract?
By passive stretching - rapid expansion of a vessel causes depolarization of vascular smooth muscle. This stabilizes flow and is a quick response
Increased flow/pressure in vascular smooth muscle causes _______ and thereby ________ (increasing/decreasing) flow.
Vasoconstriction: decreasing
Decreased flow/pressure in vascular smooth muscle causes _______ and thereby ________ (increasing/decreasing) flow.
Vasodilation: increasing
Increasing shear stress on healthy endothelial cells results in those cells secreting what to the underlying vascular smooth muscle? What does this cause?
- nitric oxide and prostacyclins
- vasodilation which serves to stabilize vessel diameter and
reduce such shear stresses (from turbulence)
How is vascular smooth muscle stimulated electrically to contract?
opening voltage-dependent Ca+2 channels
- action potential stimulated from a neighboring smooth muscle cell
How is vascular smooth muscle stimulated chemically to contract?
- norepinephrine, angiotensin II, vasopressin (aka ADH),
endothelin-1, serotonin (5HT) and thromboxane A2
all use standard signal transduction pathways to increase
intracellular Ca+2 and elicit contraction - Nitric oxide, PGI2 and CO2 all ultimately causing relaxation by inhibiting the contractile machinery
vascular smooth muscle cells arecomplexly covered with_______ , rendering cells sensitive to paracrine agents, hormones and
neurotransmitters from the autonomic nervous system
receptors
What are adrenergic receptors?
Receptors on vascular smooth muscle cells that bind norepinephrine and epinephrine
norepinephrine, released from the axons of sympathetic fibers cause vasoconstriction when they bind to what kind of receptors?
α1 receptors
parasympathetic fibers cause vasodilation when their axon secrete factors that bind to what kind of receptors?
Beta 2 receptors