blood pressure and volume Flashcards
(33 cards)
what is blood flow to tissues governed mainly by and what does it alter
intrinsic factors which alter the vascular resistance of organs.
what are the essential organs
the brain, the coronary circulation and working skeletal muscle.
what is autoregulation
intrinsic mechanisms maintain essential organ blood flow in spite of alterations in systemic arterial blood pressure.
what is arterial blood pressure maintained by
extrinsic mechanisms
examples of intrinsic mechanisms
metabolic control
paracrine control
what is active hyperaemia
increase in metabolic rate which brings about an increase in blood flow.
what does increased metabolic rate in the cells of tissues result in?
increased oxygen consumption, increased production of waste products eg co2 and lactic acid and increased K outflow from cells.
what is oxygen in relation to blood vessel diameter?
vasoconstrictor
what induces vasodilation to increase blood flow to an area
CO2, lactic acid and K+ in the interstitial fluid
what does vasodilation of the arterioles lead to
opening of more capillaries, increasing oxygen delivery to the tissue and removing the metabolic waste products.
what is ischaemia
reduced blood flow to the tissue
what can ischaemia result in
cell damage - infarction
cell death - necrosis
reduces the strength of muscular contraction
what can poorly applied bandages lead to
tissue necrosis
what can cause ischaemia
sustained contraction of skeletal muscle (weightlifting)
reflex increase in arterial blood pressure which increases perfusion pressure to the muscle (also workload on heart)
what controls blood flow to non-essential organs
extrinsic factors
what are extrinsic mechanisms governed by
central nervous system which coordinates responses via the autonomic nervous system.
what part of the brain contains the cardiovascular centre
medulla oblongata
function of the medulla oblongata
coordinates the blood flow of the non-essential organs to enable the intrinsic controls to manage the essential organs
what does the cardiovascular centre maintain
cardiac output and vascular resistance so that arterial blood pressure is kept within normal limits.
what are baroreceptors
stretch receptors that detect blood pressure situated in the aortic arch and carotid sinuses.
what do baroreceptors do
deliver action potentials to the CV centre in response to stretch.
what is the baroreflex
when the CV centre compares the information received to its reference value and makes changes as necessary
= maintains blood pressure
what is the response of the baroreflex to a decrease in blood pressure
decreased stretch detected by the baroreceptors.
decreased frequency of action potentials sent to the brain
CV centre causes increased sympathetic activity
increased contractility of the heart, increased heart rate with shortening of systole to preserve diastolic filling time and faster conduction speed
vasoconstriction of peripheral blood vessels and dilation of vessels supplying essential organs
causes decreased parasympathetic activity which causes further vasoconstriction and increased heart rate.
these changes cause increased TPR and CO which raises arterial blood pressure.
what is the response of the baroreflex to an increase in blood pressure
opposite to decrease
