Regulation of Blood Pressure Flashcards
how does the body sense that there has been a loss/ addition of blood volume?
baroreceptors
what 3 systems regulate MAP?
barareceptor reflex (rapid); renin-angiotensin-aldosterone system (RAAS) (slower); some input from ADH (vasopression) and ANP (slower)
what are the detectors/sensors in the baroreceptor reflex?
the baroreceptors
how do baroreceptors function?
through TRP channels that sense changes in stretch of the artery walls
what is the role of the afferents in the baroreceptor reflex?
they alter their firing rate
where is the coordinator center for the baroreceptor reflex?
in the NTS-vasomotor center in the medulla
what makes up the efferent neural pathway of the baroreceptor reflex?
both parasympathetic (vagus) or sympathetics
what is the role of the effectors of the baroreceptor reflex?
change MAP by altering CO and TPR
where are the baroreceptors located?
carotid sinus and the aortic sinus
what nerves are responsible for the carotid sinus?
the glossopharyngeal nerve (CN IX) and the sinus nerve of Hering
what nerves are responsible for the aortic sinus?
the vagus nerve (CN X) and the aortic nerve
what do the afferent neurons in the nucleus tractus solitarius utilize as their neurotransmitter?
glutamate
what do chemoreceptors respond to?
PO2, PCO2, and pH
what will be the goal if there is a decrease in pressure, decrease in stretch, and decrease in firing rate of the afferent neurons located in the baroreceptor reflex?
to increase pressure
what will be the goal if there is an increase in pressure, increase in stretch, and an increase in firing rate of the afferent neurons located in the baroreceptor reflex?
to decrease pressure
increased pressure increases firing rate and frequency of stimulation; recruitment occurs up until what in carotid bodies?
200 mm Hg
decreased pressure decreases firing rate and frequency of stimulation; signal almost vanishes at what pressure?
40-60 mmHg
what is the main difference between the sensors in the aortic vs the carotid sinus?
the aortic has a higher threshold for activation- continues to respond above saturation; the aortic sinus is less sensitive to rate- it is less affected by decreases
where is the parasympathetic activity associated with CV function located?
the dorsal motor nucleus of the vagus and the nucleus ambiguus
where is the sympathetic activity associated with CV function located?
rostral ventrolateral medulla
what are the influences of the sympathetic nervous system in the baroreceptor reflex?
the sympathetics influence the heart muscles (atria and ventricle), SA node, vessels, and the adrenal gland via the splanchnic
what 3 effects does sympathetic activity have during the baroreceptor reflex?
it will constrict the arterioles and veins via alpha-receptors; it will increase HR and contractility via beta-1 receptors; and there will be fluid retention by the kidney
how do the parasympathetics decrease heart rate during the baroreceptor reflex?
the vagus nerve signals to the SA node and through muscarinic receptors
for long term adjustments to pressure what is invoked?
a hormonal response- the Renin-Angiotensin II- Aldosterone System; ADH/ vasopressin; ANP
why is the parasympathetic nervous system not always active in a patient with chronic HTN?
because the baroreceptors reset
what is angiotensinogen released by?
the liver
what converts angiotensinogen into angiotensin I?
renin (an enzyme)
what is renin released from?
the kidneys
what converts angiotensin I into angiotensin II?
ACE (an enzyme)
what is ACE released from?
kidneys and the lungs
what effect does angiotensin II have on the kidneys?
it constricts the glomerular efferent arteriole and increases Na+/H+ exchanger activity
what effect does angiotensin II have on the posterior pituitary?
it causes ADH secretion
what effect does angiotensin II have on the vascular smooth muscle?
causes hypertension
What effect does angiotensin II have on the hypothalamus?
it stimulates thirst
what effect does angiotensin II have on the adrenal cortex?
causes aldosterone secretion
Renin is released due to a response to what?
a drop in BP
what is renin release stimulated by?
B-1 adrenergic receptor activation
what specific part of the kidney secrets renin?
the juxtaglomerular cells in the walls of the renal afferent arterioles
secretion of aldosterone by the adrenal cortex leads to what?
Na+ and H2O retention by the kidney; increases blood volume, stroke volume, and cardiac output
secretion of ADH causes what?
a reduction in urine production (aka fluid retention)
vasopressin is secreted in response to what?
angiotensin II, atrial receptors in presence of low preload, increased osmolarity of blood
what is the effect of vasopressin release?
increased TPR and water retention
what are the natriuretic peptides?
ANP, BNP, and CNP
when are the natriuretic peptides secreted?
when there is excessive preload of the atria and the ventricles
what does secretion of the natriuretic peptides cause?
arteriolar dilation, increased fluid loss, and inhibition of renin
what does arteriolar dilation cause?
decrease in TPR
what does increased fluid loss cause?
it decreases preload
what does inhibition of renin cause?
a decrease in both TPR and preload
what occurs during heart failure?
there is poor ventricular function-so there is reduced cardiac output and stroke volume; there will be SNS and RAAS activation; there will be secretion of natriuretic peptides
