REGULATION OF BLOOD FLOW Flashcards
the heart pumps the of blood that the body needs is defined as?
cardiac output
cardiac output control by the?
autonomics
tissue control by?
local regulation
which of the tissues require the most blood?
brain and heart because of work load
what is the main cause for increase flow in local regulation?
increase metabolism or increase altitude in response to decrease local O2
what is the vasodilator theory?
increase metabolism in which the cells release chemicals to increase:
hydrogen ion concentration histamine adenosine CO2 potassium this leads to:
relax smooth muscle to decrease resistance to increase flow
what is the most potent vasodilator?
adenosine
what is the intrinsic property of smooth muscle? what type of regulatory mechanism is this?
what is the effect of increase pressure?
when stretched it contracts
non metabolic local regulatory mechanism
increases flow and increase resistance to flow is constant
so if we have multiple neighboring capillary beds vasodilating, how do upstream vessels get the message?
EDRF
endothelial derived releasing factor aka nitric oxide which is a 6 second life span
what does the heart undergo due to increased metabolic demand? population this usually occurs in?
increased vascularity due to angiogenesis which can take days to weeks
children, damaged tissue and cancers
what are the signals that stimulate angiogenesis? and this is because of ____?
vascular endothelial growth factor (VEGF)
fibroblast growth factor (FGF)
angiogenin
increased metabolic demand
what is angiogenesis?
promotes new vessels to sprout off of the existing vessels
what are the important systemic vasoconstrictor humoral agents?
NE/EPI
Angiotensin II (constricts the arterioles and increases TPR to maintain BP)
Vasopressin
endothelin (produced by damaged vessels, limits blood loss at the wound site)
what are the systemic vasodilators? how do these work?
bradykinin
histamine
increase flow and increase capillary porosity, so area becomes flushed and edematous
what are the ions below affect on vascular function?
increase ECF calcium increase ECF magnesium increase ECF potassium increase ECF hydrogen ion increase ECF PCO2
increase ECF calcium - vasoconstriction
rest, vasodilation and also in the brain when there is an increase in ECF PCO2
T/F, cardiac output is affected by autonomic regulation? if so, which ones and how
T
both sympathetic (positive ionotropism and chronotropism) and parasympathetic (negative chronotropism)
what do the sympathetics not innervate in terms of the arteries? where for the ones that do?
capillaries, precap sphincters, metarterioles
kidney
intestine
spleen
skin
not so effective in muscle and brain
what is the effect of arterial vasoconstriction?
increase resistance
increase blood pressure
decrease BF to constricted area
in terms of venous constriction, what happens when these larger veins are affected by the sympathetics?`
increase venous return
increase EDV
increase cardiac output
increase arterial pressure
what causes the sympathetics to start firing? parasympathetics?
vasoconstrictor area of vasomotor center in the medullary reticular formation controls the vasoconstrictor outflow
vasodilator center also in vasomotor center and controls parasympathetic outflow
since vessels are tonically partially contracted what is this called and mediated by?
sympathetic vasoconstrictor tone mediated by alpha one adrenergic receptors
what inputs affect the vasomotor center?
1)pons and midbrain
2)hypothalamic neurons
limbic cortex
3)baroreceptors in the carotid sinus and aortic arch
describe vasovagal syncope?
increase parasympathetic outflow leads to vasodilation and decrease venous return to decrease arterial pressure and then fainting
so when the baroreceptors in the carotid sinus work what is the effect when there is a decrease in arterial P after 10 seconds?
increase SV, HR, TPR so overall increase in blood pressure
where are key baroreceptors located? what do these sense? what is the result?
carotid sinus and aortic arch and also located in thoracic systemic arteries and these are called pressoreceptors
increase pressure causes stretch on vessel
increase vasodilator center, decrease vasoconstrictor center, increase vagal parasympathetic center
what is the sensitivity range for the baroreceptors? effect outside this range
30-180 mm Hg
less than 30, no firing
more than 30, max discharge rate
T/F, long term BP regulation is the job of baroreceptors? if not, Than what is?
nope, false but they can increase sodium and water loss (decrease plasma volume)
kidneys do long term
what is the pressure a function of?
blood volume via kidneys (long term) and vascular volume (baroreceptors regulate in the short term)
T/F, there are stretch receptors in the atria and pulmonary arteries? high or low pressure receptors? the affect on cardiac output
the atrial receptors also trigger what reflex?
T
low pressure receptors
decrease cardiac output
volume reflex
what is the volume reflex?
increase blood volume sensed, increase VR, increase atrial P leading to receptors firing which inhibit ADH released vasodilator afferent arterioles in the kidney that overall leads to urine formation decrease blood volume and the atrial reflex
the atrial reflex triggers this reflex?
bainbridge reflex which decreases the atrial P
