Regulation of Arterial pressure and CPR endocrinology Flashcards
what is the equation of Mean arterial pressure, and what is a normal MAP
MAP = CO x TPR = HR x SV x TPR (flow and resistance)
normal = 93.3 mm Hg
MAP = 2/3 (DBP) + 1/3 (SBP)
what are the three major systems that regulate the mean arterial pressure and what are their relative speeds of doing so?
Baroreceptor reflex (rapid)
Endocrinologically via renin-angiotensin-aldosterone system (RAAS) (slower)
Some input from ADH (vasopressin) and ANP (slower)
what is the reflex arc of the Baroreceptor
1) Detector - detect deviation from set point
2) afferent neural pathway
3) coordinator center - brain stem
4) Efferent neural pathway
5) effectors - correct deviation from set point
what are the locations of the baroreceptor in the body
Carotid sinus:
- glossopharyngeal nerve (CN IX)
- Sinus nerve of hering
Aortic sinus:
- Vagus nerve (CN X)
- Aortic nerve
what is the anatomical afferent for baroreceptors and what is the neurotransmitter used
Nucleus tractus solitarius (NTS)
-uses glutamate as neurotransmitter
what are the two type of detectors in the baroreceptor
Mechanoreceptor: respond to changes in arterial pressure to return to normal
Chemoreceptor: respond to PO2, PCO2, and pH
when does a baroreceptor fire
changes in pressure through stretch receptors on vessel walls
- increased firing rate to increased stretch
- decreased firing rate when pressure falls
can act within seconds and can last indefinitely
Most responsive to the rate of change in pressure, rather than just the magnitude of change
what are the efferents of the Baroreceptor signals
Parasympathetics: Dorsal motor nucleus of the vagus and the nucleus ambiguus
-parasympathetic activity associated with CV function
Sympathetics: Rostral ventrolateral medulla
- sympathetic activity associated with CV function
- usually has more input
what is the location in the brainstem that serves as the controller of the peripheral signals
Nucleus of tractus solitarius (NTS)
what is the total story if their is an increase in baroreceptor stretch
sends afferent to nucleus tractus solitarius with tells
this tells parasympathetics to increase: cardiac decelerator and slow down atrial node
also tells the sympathetics to slow down: (rostral ventrolaterl medulla)
- decreases vasoconstriction
- decrease contractillity
- decrease sinoatrial node firing rate
how does the Aortic and carotid respond to simulation (frequencies)
increased frequency of stimulation of receptor increases strength of action potential
-this recruitment can increase up to 200mmHG pressure of stretch
decrease frequency of stimulation: low frequency almost vanishes at 40-60mmHG
Aortic vs carotid, which one has higher threshold, and sensitivity to rate, and changes
Aortic has higher threshold for activation, but will continue to respond above saturation
aortic is less sensitive to rate of change
aortic is less effected by decreases of frequency
how does the sympathetic system respond to the baroreceptor
responds to a decrease baroreceptor firing rate
comes from preganglionic fibers below T1
Influences heart muscles, SA node directly, vessels, and adrenal gland via splanchnic
- constriction of arterioles and veins (alpha receptor)
- increased HR and contractillity (B1 receptors)
- fluid retention by kidney due to afferent arteriole constriction and renin secretion (later)
overall increased TPR and CO
how does the parasympathetic system respond to the baroreceptor
responds to a increase in baroreceptor firing
Decreases HR
-Vagus nerve signal to SA node via muscarinic receptors
Indirect vasodilation on blood vessels (stimulates the NO release)
overall decreases TPR and CO
what is an example of a baroreceptor adaptations
baroreceptors can adjust the set point to different conditions (homeostasis)
ie. hypertension moves set point to higher
for long term adjustments based on Baroreceptor information, what system do this
Vascular and body fluid dynamic changes
Renin-Angiotensin II-Aldosterone system (RAAS)
-kick in hours later but have long affects
ADH and vasopressin
ANP
what is renin and and when is it secreted
renin is an enzyme secreted by the kidney into the bloodstream in response to a drop in BP
- less renin secreted if increase in BP
- release is stimulated by B1 adrenergic receptors
- leads to decreae of NaCl at macula densa
cascade of things that renin activates
renin causes angiotensinogen to be converted to angiotensin I (inactive) in blood
Angiotensin I is converted to angiotensin II (active) in lungs and kidneys to begin the compensation mechanism to increase BP
sympathetic stimulation also increase secretion
what cell secrets renin
Juxtaglomerular cells
found in walls of renal afferent arterioles in response to low BP and sympathetic stimulation
what does angiotensi II do?
Angiotensin II causes secretion of aldosterone from the adrenal cortex
- leads to Na+ and H2O retention by kidney
- increase blood volume, preload/stroke volme, CO, and BP
also angiotensin II stimulates the secretion of antidiuretic hormone (ADH)
-reduces urine production (fluid retention)
also angiotensin II causes global vasoconstriction of arterioles by binding to specific receptors (AT1 receptors)
-increase TPR and BP
what does Vasopressin (or antidiuretic hormone) do?
acts on V1 receptors (smooth muscle)
acts on V2 receptors (collecting ducts)
to increase TPR and water retention
secreted in response to:
- angiotensin II
- atrial receptors in presence of low preload
- increased osmolality of blood
- sympathetic nervous system activation
Natriuretic Peptides, what is its function and what are the three types
Atrial (ANP)
Brain (BNP)
C-type (CNP)
increased secretion by excessive preload of atria and ventricles
causes:
- arteriolar dilation - decrease TPR
- Increase fluid loss - decrease preload
- inhibit renin - decrease both TPR and preload
protects against over stretching of cardiac chambers
what can cause a decrease in blood volume and how does it affect the cardiac output and vascular function
hemorrhage
dehydration
loss of body fluids
decrease venous return, preload, SV, CO, and MAP
Vascular function parallel shifts to the left
what is the compensatory response to hemorrhage
Carotid nerve sinus firing decreases
Heart rate, contractility, cardiac output increases
Unstressed volume will decrease to produce more venous return
TPR increases
Epinephrine, ADH, renin, angiotensin II, aldosterone all increase
decrease ANP
