Control of Circulation Flashcards
What mechanisms regulate Ca entry?
Pharmacomechanical coupling, electrochemical coupling, Ca-calmodulin complex
How does pharmacomechanical coupling work?
G-protein activates PLC which activates IP3 which increases Ca release
How does electromechanical coupling regulate Ca entry?
Ca is released via voltage gated channels in the sarcolemmaq
How does the Ca-Calmodulin complex work?
Ca binds to calmodulin to change its comformation, it phosphorylates inactive myosin through ATP hydrolysis, ATP binds to myosin causing it to flex
What are the intrinsic mechanisms for the control of peripheral blood flow?
autoregulation, metabolic regulation, and endothelial regulation
What is the MOST important intrinsic mechanism to control peripheral blood flow?
Metabolic regulation
What is the end result of metabolic regulation?
the washout of CO2, lactic acid, and metabolites
What does metabolic regulation depend on?
basal tone
What is active hyperemia?
increase in organ blood flow that is associated with increased metabolic activity of an organ or tissue
What is reactive hyperemia?
the transient increase in organ blood flow that occurs following a brief period of ischemia
What is ischemia?
an inadequate blood supply to an organ or part of the body
What is autoregulation?
the constant flow of blood to tissue despite blood pressure fluctuations
What does increased transmural pressure cause?
vasoconstriction
In what range does autoregulation maintain flow?
60-190 mmHg
Below the autoregulatory range, what happens to flow?
it decreases as perfusion pressure decreases
What is critical closing pressure?
when blood pressure is below critical value
What happens when BP is below critical closing pressure?
arterioles close and flow stops
What regulates endothelial regulation?
paracrines
What does nitric oxide cause?
vasodilation
What does prostacyclin cause?
vasodilation
What does endothelin I cause?
vasoconstriction
What are extrinsic mechanisms of peripheral blood flow
Nervous system and humoral regulation, sympathetic, and parasympathetic
Is extrinsic control necessary for peripheral blood flow?
no
When does nervous system and humoral regulation come into play?
during exercise, hemorrhage, and the like
What is the adrenergic response?
sympathetic control
How does the adrenergic response work?
it releases norepinephrine to activate the cardiovascular system
What is the adrenergic response also known as?
the pressor response
What is the cholinergic response?
parasympathetic control
How does the cholinergic response work?
acetyl choline release to inhibit the heart
What are baroreceptors?
stretch receptors
Where type of baroreceptors are there?
atrial and carotid sinus baroreceptors and cardiopulmonary
What is the end goal of extrinsic peripheral blood flow?
arterial pressure regulation
What is the most important mechanism for acute blood pressure control?
the arterial baroreceptor reflex
In the arterial baroreceptor reflex, what does an increase in blood pressure cause?
increase stretch, increase in afferent traffic, decrease in sympathetic output, and therefore vasodilation
In the arterial baroreceptor reflex, what does an decrease in blood pressure cause?
decrease stretch, decreased afferent traffic, decreased sympathetic output, and therefore vasoconstriction
What does chronic stimulation of the arterial baroreceptor reflex cause?
a decrease in receptor sensitivity
What is the blood pressure range for maximum firing of the arterial baroreceptor reflex?
180-200 mmHg
What is the blood pressure range for no stimulation of the arterial baroreceptor reflex?
50-60 mmHg
What are the hormonal vasoconstrictor agents involved in controlling blood pressure?
epinephrine, norepinephrine, angiotensin II, vasopresin
What are hormonal vasodilator agents involved in controlling blood pressure?
natriuretic peptides and ‘various agents’
How does epinephrine work in skeletal and cardiac muscle?
it is a mild vasodilator
When are hormonal vasodilator agents released?
in response to stretch
How does the renin-angiotensin-aldosterone system regulate blood pressure?
by regulating blood volume because it is a potent vasoconstrictor
What does angiotensin II cause in regards to the renal system (why is this important, I have no idea)?
it causes salt and water retention due to the aldosterone release from the adrenal glands
How does the renal-body fluid mechanism work in response to high blood pressure?
there is a direct increase in renal output of Na and water which decreases extracellular fluid retention and blood volume to lower blood pressure
How does the renal-body fluid mechanism work in response to low blood pressure?
it decreases renal output of Na and water which causes fluid retention and increased blood pressure
What are short term mechanisms that regulate arterial blood pressure in response to an acute change in pressure?
baroreceptors, chemoreceptors, CNS ischemic response, Renin-Angiotensin vasoconstriction
What is the long term mechanism that regulates arterial blood pressure in response to an acute change in blood pressure?
Renin-blood volume pressure control
Where are atrial and coronary baroreceptors located
located in carotid sinus
What is the function of atrial and coronary baroreceptors?
respond to vessel stretch and deformation caused by increase in blood pressure; inhibits sympathetic output which leads to lower blood pressure
What type of baroreceptors are cardiopulmonary baroreceptors?
low pressure receptors
What do cardiopulmonary baroreceptors respond to?
a decrease in volume
