Regulation of Arterial Pressure - Ballam Flashcards
2 Methods of control of arterial pressure
- rapid baroreceptor reflex
2. slower hormonal mediated
Baroreceptor reflex
Negative feedback
Responds to a change in arterial pressure by invoking processes to return to original level
Acts within seconds and last indefinitely
Both short and long term compared to long term hormone control
When metabolic demand is high
More blood is released through capillary beds by reducing resistance of arterioles
Baroreceptor location
Carotid sinus
Aortic arch
Baroreceptors and firing rate
Increase firing rate in response to increasing vascular wall stretch
Decrease firing rate when pressure falls
Baroreceptors send input to the control center in the medulla called the
Vasomotor center
Vasomotor Center
Clusters of cells responsible for acting via outputs traveling either in the parasympathetic (vagus) nerve or the symp nerves
Main parasympathetic nerve
Vagus
Increased firing of baroreceptors and symp/para outflow
Decreases sympathetic outflow
Increases parasympathetic outflow
Decreased firing of baroreceptors and symp/para outflow
Increases symp outflow
Decreases parasymp outflow
Equation
BP =
CO x TPR
Equation
CO =
SV x HR
Stroke volume dependent on
Sympathetic stimulation of heart
Preload
HR dependent on
Symp and parasymp stimulation
TPR dependent on
Sympathetic stimulation of arterioles
Sympathetic causes
Constriction of arterioles and veins - alpha
Increases contractility - beta1
Fluid retention by kidneys
Increases secretion
Parasympathetic causes
A decrease of heart rate (muscarinic receptors)
Sympathetic and kidneys
Sympathetic system causes fluid retention by kidney due to afferent arteriolar constriction and increased renin secretion
Renin
Enzyme secreted by kidney into bloodstream in response to a drop in BP
Causes angiotensinogen to be converted to angiotensin I in blood
If BP higher than normal, how much renin is secreted?
Less
Angiotensin I
Converted to angiotensin II in lungs by ACE to begin the compensation mechanism
Afferent in kidneys means
Towards glomerulus
Juxtaglomerular cells
In walls of renal afferent arterioles
Renin production in response to low BP and in response to sympathetic stimulation
Angiotensin II
Causes secretion of aldosterone from adrenal cortex
Acts directly on kidney to increase sodium and water
Increases thirst
Stimulates secretion of antidiuretic hormone (ADH)
Causes global vasoconstriction of arterioles via specific receptors
