Regulation of Arterial Resistance Flashcards
what equation can be used to describe mean arterial pressure?
mean arterial pressure = cardiac output * total peripheral resistance
what would the effect be on the flow through the vascular bed if the resistance was reduced?
the flow would increase through the vascular beds
what is the effect of reducing the total peripheral resistance on the mean arterial pressure?
it would reduce the mean arterial pressure
what two things does the arteriolar radius affect?
> flow through individual vascular beds
> mean arterial pressure
what do the intrinsic mechanisms of the smooth muscle in arterioles manage?
that the needs of each individual tissue is met
what do the extrinsic mechanisms of the smooth muscle in arterioles manage?
they ensure that the total peripheral resistance of the whole body stays in the right ball park
how do the sympathetic nerves have extrinsic control?
they release norepinephrine that binds to alpha1-receptors and cause arteriole constriction, reducing the flow through that tissue and increasing total peripheral resistance
what is the hormonal extrinsic control using epinphrine of total peripheral resistance?
> epinephrine is released form the adrenal medulla and binds to alpha1-receptors causing arteriolar constriction. this decreases the flow through that tissue and increases the total peripheral pressure.
in some tissues it activates beta 2 receptors and causes dilation increasing the flow and decreasing TPR
what is the effect of angiotensin 2 on the TPR?
this is produced in response to low blood volume and causes arteriolar constriction increasing the TPR
what is the effect of vasopressin on the TPR?
It is released in response to low blood volume and causes arteriolar constriction increasing the TPR
what is the effect of atrial natriuretic peptide and brain natriuretic peptide on TPR?
it is released in response to high blood volume and causes arteriolar dilatation therefore decreasing TPR.
how is active hyperaemia used to intrinsically control TPR?
increased metabolic activity causes an increase in concentration of metabolites. this triggers the release of EDRF which causes arteriolar dilation. this increase in flow washes out the metabolites. this adaption matches the blood supply to the metabolic needs of that tissue.
how does pressure auto-regulation control TPR intrinsically?
there is a decrease in metabolites that causes a decrease in flow allowing metabolites to accumulate which triggers the release of EDRF. arterioles then dilate and flow is restored back to normal.
this ensures the tissue maintains its blood supply.
how does reactive hyperaemia intrinsically control flow to tissues?
an occlusion of the blood supply causes a subsequent increase in blood flow. this is an extreme version of pressure auto-regulation for example if you cut the blood supply to the arm.
how does response to injury intrinsically control of blood flow to tissues?
mast cells degranulate and histamine makes clefts in the capillaries open and relaxes vessels. this increases flow.
