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
Cholinergic (M2) receptors are sensitive to_________ and cause __________.
acetylcholine
Vasodilation
Vascular smooth muscle tone can be modified by 2 basic sources:
A. Intrinsic or “local” control
B. Extrinsic control
Intrinsic or “local” control will cause _________ of blood vessels using local paracrine agents from tissues
Vasodilation
Which modification of vascular smooth muscle is rapid and most important?
Intrinsic or “local” control
Due to increased waste production during increased tissue metabolism, what will happen?
increased blood flow
Low oxygen levels cause ________.
Hypoxia
No oxygen is called?
Anoxia
When tissues are deprived of nutrients due to oxygen deficiency?
Ischemia
Accumulation of deoxygenated blood that leads to a blue color of the tissue
Cyanosis
The primary method of setting tissue blood flow in the body is ______.
local control (which is automatic and tissue centered)
Endothelin 1 is released form where? What does it cause in the tissue?
Endothelia, vasoconstriction
Serotonin is released form where? What does it cause in the tissue?
Platelet activation, vasoconstriction
Thromboxane is released form where? What does it cause in the tissue?
Platelets, vasoconstriction
Nitric oxide is released form where? What does it cause in the tissue?
Endothelia, vasodilation
Bradykinin is released form where? What does it cause in the tissue?
Damaged blood vessels, vasodilation and increased capillary porosity
Histamine is released form where? What does it cause in the tissue?
Mast cells, vasodilation and increased capillary porosity
Prostacyclin is released form where? What does it cause in the tissue?
Endothelia, vasodilation and increased capillary porosity
What is reactive hyperemia?
Follows a brief period of ischemia where blood flow is restored in a way that matches the amount of blood that would have been delivered during ischemia. Continues until complete restoration of oxygen levels and all accumulated metabolites have been washed away. Evidence for intrinsic control
Extrinsic control will cause _________ of blood vessels using ANS and some endocrine glands
Vasoconstriction
Autonomic axons that innervate vascular smooth muscle are powerful but are completely dependent on _______.
Receptors, the sensitivity of vascular smooth muscle
What releases epinephrine and norepinephrine which attaches to the alpha 1 adrenergic receptors and causes vasoconstriction which ultimately increases blood pressure due to resisted vessels.
Adrenal medulla
Hormonal systems of extrinsic control differ from ANS extrinsic control how?
Hormonal systems are slower and have a whole body effect
Both methods are very powerful
What releases renin which causes formation of angiotensin 2?
Renal cortex of the kidneys
What is the chain reaction that occurs when renin is released from the kidneys?
It causes angiotensin 2 formation. Angiotensin 2 binds to receptors which causes endothelin 1 to be produced. Endothelin 1 binds to receptors which causes vasoconstriction
What releases vasopressin (aka ADH)]?
Posterior pituitary gland
What is the effect of vasopressin?
It effects both blood vessels and renal collecting ducts by binding to receptors that cause the production of endothelin 1 in local vascular smooth muscle which causes vasoconstriction
The diameter of blood vessels is set by effects in the tunica media of primarily arterioles. The effects are caused by what?
Local (intrinsic) and distant (extrinsic) factors that strike a balance. Mose tissue responds primarily to local factors, but neurohumeral (extrinsic) factors are very important contributors that can override local control
