17. Regulation of Arterial Pressure Flashcards
Mean arterial pressure (MAP) is regulated by the baroreceptor reflex and hormonally via renin-angiotensin-aldosterone system (RAAS). What are the two ways to calculate MAP?
MAP= CO x TPR = HR x SV x TPR
MAP= 2/3 DBP + 1/3 SBP
The baroreceptor reflex is located in the carotid sinus and aortic sinus which both have two afferent nerves each which lead to the nucleus tractus solitarius (NTS). What nerves does each sinus have?
Carotid Sinus has glossopharyngeal nerve CNIX (9) and sinus nerve of hering
Aortic sinus has vagus nerve CNX (10) and aortic nerve
Mechanoreceptors respond to changes in arterial pressure to return to normal while chemorecptors respond to?
PO2, PCO2, pH
Baroreceptor fibers sense stretch in vessel walls. If there is an increase in stretch, the firing rate will increase, if there is a decrease?
The firing rate will decrease
NOTE: carotid are more responsive to RATE of change in pressure not magnitude
The nucleus of tractus solitarius (NTS) receives and coordinates peripheral signals from carotid and aortic sinus. The dorsal motor nucleus of the vagus and nucleus ambiguus are related with ________ and the rostral ventrolateral medulla is related with _________.
Dorsal and ambiguus is associated with parasympathetic activty and inhibiting the heart (cardio-inhibitory)
Rostral ventrolateral is associated with sympathetic activity and activating the heart (C1/A1)
When there is an increase in stretch, this means there is an increase in BP. So the firing rate will increase to do what?
Inhibit sympathetic activation via rostral and activate parasympathetic via dorsal to decrease heart rate (phase 4)
If you have an increased frequency of stimulation, it increases the strength of the AP. If you decrease the frequency of stimulation due to low BP?
there is a decreased firing rate
The sympathetic nervous system causes a decreased baroreceptor firing rate via what 3 routes?
- constriction of arterioles and veins via A1 receptors
- Increase HR and contractility via B1 receptors
- Fluid retention by kidney d/t afferent arteriole constriction and renin secretion
The parasympathetic nervous system causes an increased baroreceptor firing rate via? (2)
Decrease HR by M2/M3 vagus N to SA node
NO release
A decreased baroceptor firing rate by decreased MAP would lead to an increase and decrease in?
Increase in sympathetic and decrease in parasympathetic activation to increase arterial pressure
An increased baroceptor firing rate by increased MAP would lead to an increase and decrease in?
Increased parasympathetic via dec HR = CO
Decreased sympathetic via dec. TPR and CO
After one hour of autonomic reflexes controlling the blood pressure, the RAAS system kicks in. What is RAAS?
Renin- Angiotensin II- Aldosterone System
Renin is stimulated to release via B1 adrenergic receptors, which is released by the kidney when BP is low. What does renin convert?
Renin converts angiotensinogen to angiotensin 1, and then in the lungs, angiotensin 1 is converted via ACE into angiotensin II
What and where is renin secreted by and why?
Secreted by juxtaglomerular (JG) cells in walls of renal afferent arterioles in response to low BP and sympathetic stimulation
Angiotensin II causes secretion of aldosterone from the adrenal cortex which leads to retention of Na and H2O by kidney and increased v=blood volume, preload, CO and BP. What else does angiotensinII stimulate/cause? (2)
- secretion of antidiuretic hormone which reduces urine production (retains fluid)
- Causes vasoconstriction of arterioles by bingds to receptors which increase TPR and BP
Vasopressin or antidiuretic hormone (ADH) is secreted in response to angiotensin II and low blood, and causes?
Increase in TPR and water retention
Natriuretic peptide (ANP/BNP/CNP) is secreted by excessive preload of atria and ventricles and causes? (3) **protects against overstretching of cardiac chambers**
- Dilation - decrease TPR
- Increase fluid loss- decrease blood volume
- Inhibits renin- decrease TPR/preload
A decrease blood volume leads to decreased venous return, preload, stroke volume, CO, and MAP. What compensatory responses would be activated?
Since there is a dec. in MAP, dec. in baroreceptor firing = increase in sympathetic activation = inc. HR, Contractility, CO, TPR (unstressed volume decreases to produce increase venous return)
Renin, AGTII, aldosterone and ADH will increase
An increased blood volume leads to increased firing rate of baroceptors, increased activation of parasympathetic, and what else?
Increase in secretion of ANP
Decrease ADH secretions
Renal vasodilation
Increased HR
During aerobic exercise, the central command response from cerebral cortex increases sympathetic output via B1 receptors and decreases parasympathetic output . What else occurs?
Increased HR/Contractility
Increase venous return
during exercise, arteriolar vasoconstriction due to A1 receptors are activated which leads to?
Constriction in skin, kidney, inactive muscle
Vasodilation via B2 at active muscle
Pulse increses,SBP increase, TPR decreases
When a person stands, intially nothing changes. After a while there is compensation, which includes?
Increase HR and TPR, Increase venous pressure, INcrease CO
