Flashcards in Mammalian Cardiovascular 2 Deck (86)
what I observed in the period of the fall in pressure from systolic to diastolic?
what is the dicrotic notch a result of?
back flow of blood towards the end of systole. (Pressure in aorta begins to exceed pressure in ventricle)
what terminates the dicrotic notch
(back flow of blood) terminated by closure of aortic valve.
what is the mean blood pressure approximated by?
diastolic pressure + 1/3 (systolic - diastolic)
what is pulse pressure ?
systolic - diastolic
cause of increase in mean blood pressure
age, slightly higher in men than women.
cause of increase of pulse pressure (different to mean blood pressure due to diastolic single factor)
reduction in arterial compliance. e.g. atherosclerosis
how does an increase in pulse pressure affect mean pressure? what does this suggest
mean pressure remains constant - systolic pressure rises as diastolic falls. Suggesting that mean ABP us principle regulated variable.
equation that links ABP, CO and TPR
ABP = CO x TPR ( think Darcy's equation)
[ note: CO and TPR can be thought of as being independent of each other]
3 methods of MONITORING blood pressure
high pressure baroreceptors, low pressure baroreceptors and arterial chemoreceptors.
where are the HIGH pressure baroreceptors for monitoring blood pressure located?
carotid sinus and aortic arch.
what is required for the short term control of ABP?
high-pressure baroreceptors and chemoreceptors.
which baroreceptors are more sensitive from carotid and aortic?
carotid. (but aortic can respond to pressures above which those in carotid sinus will saturate)
how was it shown experimentally that an increase in blood pressure a carotid sinus produces a reflex reduction in blood pressure?
Cross circulation experiment with two dogs.
primary role of chemoreceptors in carotid and aortic bodies
when are the chemoreceptors in carotid and aortic bodies important for blood pressure control?
when blood pressure is very low or if PO2 is significantly reduced. High pressure baroreceptors are also relatively unresponsive under conditions of severe hypotension.
what is used for monitoring and influencing longer term control of ABP ?
low pressure baroreceptors
what are cardiopulmonary baroreceptors?
low pressure baroreceptors located in junctions of atria with their corresponding veins and in the atria themselves.
what do cardiopulmonary baroreceptors (low pressure) essentially detect?
RAP (firing rate of receptors increases with pressure)
how would RAP be detected by cardiopulmonary baroreceptors in heart failure and oedema (capillary pressures rising) ?
raised - circulation is over filled, heart can not maintain low venous pressures.
what does low RAP suggest?
cardiac output is maximal for current MSFP.
by what SYSTEMS do baroreceptors and chemoreceptors work?
what kind of experiments shows the importance of baroreceptors and chemoreceptors for regulating arterial blood pressure?
why can't some stresses on ABP such as exercise and standing up be regulated by FEEDBACK systems ?
don't cause detectable drops in ABP, can not be entirely reliant on feedback.
mechanisms are used to preserve ABP due to changes from exercise, standing up, pain and emotions?
example mechanism of feedforward control of ABP - exercise
drop in ABP prevented by inputs to medulla from cortex ("decision" to exercise) from cerebellum and from muscle and joint receptors.
where do all the feedforward mechanisms feed into ?
cardiovascular centre of medulla. (same as baroreceptors and chemoreceptors)
by what efferent pathways does the medulla control ABP?
sympathetic and parasympathetic
where do sympathetic and parasympathetic outflows work on the heart ?
sympathetic - vasculature and the heart
parasympathetic - only on heart