Flashcards in CPR BP regulation and CPR endo Deck (19)
What is the MAP formula?
MAP = CO x TPR = HR x SV x TPR
MAP = 2/3(DBP) + 1/3(SBP) b/c heart spends more time in diastole than systole
What are the three main systems that regulate MAP?
Baroreceptor reflex (rapid)
Renin-angiotensin-aldosterone system (RAAS) (slower)
ADH (vasopressin) and ANP (slower)
What are the two main baroreceptor locations?
Carotid sinus - CN IX
Aortic sinus - CN X
Both lead to nucleus tractus solitarius (NTS)
What are baroreceptors most sensitive to in terms of pressure change?
The rate of change more than the magnitude of the change
Where is the NTS located?
What does the NTS communicate with to alter BP?
Parasympathetic - dorsal motor nucleus of vagus and nucleus ambiguus
Sympathetic - rostral ventrolateral medulla
How do the baroreceptors work?
Increased frequency of stimulation due to increased stretch for high BP (vice versa for low BP)
Is aortic or carotid baroreceptor more sensitive to rate?
Carotid more sensitive to rate
Aortic has higher threshold for activation
What does the sympathetic NS do in response to decreased baroreceptor firing rate?
Constricts arterioles and veins via alpha receptors
Increases HR and contractility via beta 1 receptors
Fluid retention by kidney due to afferent arteriole constriction and renin secretion (later)
What does the parasympathetic NS do in response to increased baroreceptor firing rate?
Decreases HR, vagus nerve signals SA node via Ach muscarinic receptors
Indirect vasodilation via stimulation of NO release
What do baroreceptors do in someone w/ HTN?
Reset to be able to regulate pressure at higher set point
What hormone systems are in place for longer-term BP adjustments?
What is the RAAS? How does it work?
Regulates blood volume and TPR, overlaps w/ sympathetic system. Renin released by kidney (juxtaglomerular cells) via B1-adrenergic receptor activation. Renin converts angiotensinogen to angiotensin I which is converted to angiotensin II in the lungs/kidneys
What does angiotensin II do?
Causes secretion of aldosterone from adrenal cortex which causes Na+/H20 retention by kidneys
Stimulates secretion of ADH (reduces urine production, increases H20 retention)
Causes global vasoconstriction of arterioles via AT1 receptors (this increases TPR)
What are natriuretic peptides?
Induce excretion of Na+ by kidneys which induces excretion of H20
ANP (atrial), BNP (brain), and CNP (c-type)
How do natriuretic peptides work?
Cause arterioles to dilate to decrease TPR
Increase fluid loss which decreases preload
Inhibits renin which decreases both TPR and preload
Released when excessive preload of atria/ventricles is detected. Protects against overdilation or overstretching of cardiac chambers
What happens to the vascular function curve with decreased blood volume?
What does alpha 1 receptor activation do during aerobic exercise?
Constricts vessels to skin, splanchnic regions, kidney, inactive muscle
Dilates vessels at active muscle and coronary circulation
TPR decreases overall