Hypertension- regulation of arterial resistance Flashcards
State Darcys law
Flow = pressure difference/ resistance
What does poisuelles law about what factors affect resistance
Resistance is affected by, radius, viscosity and length of vessels
What has the greatest effect on totally pulmonary resistance
varying the radius of the vessels
What is the benefit of adjusting total pulmonary resistance by altering the radius
allows for re direction of blood flow
controling flow through individual vascular beds
What is the equation for Mean arterial pressure
Cardiac output X total periphery resistance
decreasing the radius of the arterioles increases the TPR, what affect does this have on the mean arterial pressure
therefore increases mean arterial pressure
How is the flow rate maintained in the capillaries beds
By maintaining mean arterial pressure within the correct range by controlling the resistance of the vessels
What is the two levels of control that maintain flow rate and Mean arterial pressure
Extrinsic control
Intrinsic control
What is extrinsic control concerned about
maintaining the total periphery resistance of the body
and maintain adequate MAP
What is intrinsic control concerned about
The needs of the individual tissue involved
What is extrinsic control due to
Sympathetic NS
Hormones
What is the affect of sympathetic NS on extrinsic control of the blood flow through vascular bed
release norepinephrine
binds to alpha1-receptors causing§ arteriolar constriction, decreasing the radius, therefore increasing the TPR, which reduces the flow rate of the blood
What are the different hormones affecting the extrinsic control of the blood flow through the vascular bed
Epinephrine from the medulla
Angiotensin
Vasopressin
Atrial natriuretic peptide & Brain natriuretic peptide
What is Epinephrine affect on extrinsic control on most muscles
binds to alpha1-receptors
causes arteriolar constriction
decreasing the radius, therefore increasing the TPR, which reduces the flow rate of the blood
What is epinephrines affect on extrinsic control of skeletal and cardiac muscle
also activates beta2-receptors
- causes arteriolar dilation
Increasing the flow rate and decreasing TPR
What do both Angiotensin and Vasopressin respond to, and what further affect does this have
Produced/released in response to low blood volume
causes arteriolar constriction therefore increasing the TPR, reducing the flow rate
What kind of hormone is vasopressin
antidiuretic hormone - controls body water balance by reducing urination
What is Atrial natriuretic peptide & Brain natriuretic peptide released in response to
released in response to high blood volume
causes arteriolar dilation decreasing TPR, increasing flow rate
What effect does Parasympathetic NS have on extrinsic control
has no effect
What is 4 examples which cause local intrinsic controls affecting the flow rate and TPR
Active metabolic hyperaemia
Pressure flow autoregulation
reactive hyperanemia
The injury response
Active (metabolic) hyperaemia process is triggered by what
An increase in metabolic activity, causing an increase in concentration of metabolites
The increase in metabolites in active hyperaemia and pressure flow regulation creates a negative feedback effect by triggering the release of what
EDFR
What affect does the release of EDFR have on the vessels in active hyperaemia and pressure flow auto regulation
Makes the smooth muscle relax and dilate causing arterial dilation, increasing flow rate
What is the purpose of active hyperaemia
To get rid of the metabolites concentration building up
and match blood supply to metabololic needs of the that tissue
Pressure flow auto regulation process is triggered by what
Decrease in mean arterial pressure causes a decreases in flow causing an increased contraption of metabolites
What is the purpose of the pressure flow auto regulation
an adaptation to ensure that a tissue maintains its blood supply despite changes in mean arterial pressure
What Intrinsic control could be possibly myogenic
Pressure flow auto regulation
What occurs in the Intrinsic control of reactive hyperanemia
Blockage of blood supply causes a subsequent increase in blood flow
What is hyperanemia an extreme version of
Pressure flow auto regulation
What occurs in the local intrinsic effect of an injury
Mast cells release histamine, this causes arterial dilation increasing blood flow
as well as increasing permeability resulting in oedema
What is the benefit of histamines indirectly increasing the blood flow
aids delivery of blood born leucocytes etc to injured area
In coronary circulation how is the blood supply interrupted
As each time the heart contracts during systole it shuts of its blood supply as aortic valves open to expel blood but the valves opening shuts of the entry to the coronary arteries
What kind of receptors do coronary circulation express a lot of
B2 receptors
How does the coronary circulation cope with the increased demand caused by exercise
its hyperaemia - release EDFR
and has an abundance of B2 receptors which both dilates the BV so doesn’t starve itself of oxygen
What local intrinsic control allows stability to be maintained in the cerebral circulation
Pressure autoregulation
How does pulmonary circulation differ to most tissues
as a decrease in oxygen causes arterial constriction
What is the purpose of the pulmonary circulations opposing effect
this ensures the blood is directed to the best ventilated part of the lungs - shunt
What is the main function of the renal circulation
Filtration
What local intrinsic control does renal circulation portray to ensure the mean arterial pressure remains stable
shows excellent pressure autoregulation
Why is it important to not vary Mean arterial pressure in the renal circulation
as would have a big effect on blood volume
What are the four special areas that allow there specific properties to correlate to their function
Coronary
Cerebral
Renal
Pulmonary
