Regulation of Arterial pressure and CPR endocrinology

Question 1

what is the equation of Mean arterial pressure, and what is a normal MAP

Answer 1

MAP = CO x TPR = HR x SV x TPR (flow and resistance)

normal = 93.3 mm Hg

MAP = 2/3 (DBP) + 1/3 (SBP)

Question 2

what are the three major systems that regulate the mean arterial pressure and what are their relative speeds of doing so?

Answer 2

Baroreceptor reflex (rapid)

Endocrinologically via renin-angiotensin-aldosterone system (RAAS) (slower)

Some input from ADH (vasopressin) and ANP (slower)

Question 3

what is the reflex arc of the Baroreceptor

Answer 3

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

Question 4

what are the locations of the baroreceptor in the body

Answer 4

Carotid sinus:

• glossopharyngeal nerve (CN IX)
• Sinus nerve of hering

Aortic sinus:

• Vagus nerve (CN X)
• Aortic nerve

Question 5

what is the anatomical afferent for baroreceptors and what is the neurotransmitter used

Answer 5

Nucleus tractus solitarius (NTS)

-uses glutamate as neurotransmitter

Question 6

what are the two type of detectors in the baroreceptor

Answer 6

Mechanoreceptor: respond to changes in arterial pressure to return to normal

Chemoreceptor: respond to PO2, PCO2, and pH

Question 7

when does a baroreceptor fire

Answer 7

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

Question 8

what are the efferents of the Baroreceptor signals

Answer 8

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

Question 9

what is the location in the brainstem that serves as the controller of the peripheral signals

Answer 9

Nucleus of tractus solitarius (NTS)

Question 10

what is the total story if their is an increase in baroreceptor stretch

Answer 10

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

Question 11

how does the Aortic and carotid respond to simulation (frequencies)

Answer 11

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

Question 12

Aortic vs carotid, which one has higher threshold, and sensitivity to rate, and changes

Answer 12

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

Question 13

how does the sympathetic system respond to the baroreceptor

Answer 13

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

Question 14

how does the parasympathetic system respond to the baroreceptor

Answer 14

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

Question 15

what is an example of a baroreceptor adaptations

Answer 15

baroreceptors can adjust the set point to different conditions (homeostasis)

ie. hypertension moves set point to higher

Question 16

for long term adjustments based on Baroreceptor information, what system do this

Answer 16

Vascular and body fluid dynamic changes

Renin-Angiotensin II-Aldosterone system (RAAS)
-kick in hours later but have long affects

ADH and vasopressin

ANP

Question 17

what is renin and and when is it secreted

Answer 17

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

Question 18

cascade of things that renin activates

Answer 18

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

Question 19

what cell secrets renin

Answer 19

Juxtaglomerular cells

found in walls of renal afferent arterioles in response to low BP and sympathetic stimulation

Question 20

what does angiotensi II do?

Answer 20

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

Question 21

what does Vasopressin (or antidiuretic hormone) do?

Answer 21

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

Question 22

Natriuretic Peptides, what is its function and what are the three types

Answer 22

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

Question 23

what can cause a decrease in blood volume and how does it affect the cardiac output and vascular function

Answer 23

hemorrhage
dehydration
loss of body fluids

decrease venous return, preload, SV, CO, and MAP

Vascular function parallel shifts to the left

Question 24

what is the compensatory response to hemorrhage

Answer 24

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

Question 25

how does aerobic exercise affect the overall body, and what controls this, and how is this different

Answer 25

during most aerobic exercise forms, mose normal chemoreceptor activators and inhibitors wont change appreciably

Central command response: cerebral cortex

• increased sympathetics (B1) and decreased parasympathetics
• increased HR and contractillity
• increased venous return

Selective arteriolar vasoconstriction due to alpha 1 receptor activation (leads to overall slight increae in MAP)

• constriction of skin, splanchnic regions, kidney, and inactive muscles
• vasodilation of active musces and coronary circulation due to release of lactate, K+ and adenosine (active hyperemia)
• pulse pressure increases, SBP increase but DBP does not change much
• TPR will decrease overall

Question 26

due to the increased pressure when standing and changes in pressure how does the body compensate?

Answer 26

initially when standing up:

• MAP decreases
• no change in HR and TPR,
• decrease in SV and CO due to lack of venous return
• central venous pressure decreases (blood pools in lower extremities)

Compensatory:

• baroreceptor reflex
• increase sympathetic flow to increase TPR, HR, CO, and Blood volume
• hormonal reflex also initiate but will be to slow to have impact

-called orthostatic hypotension

Question 27

what happens when the blood accumulates in the lower limbs

Answer 27

increases venous and capillary hydrostatic pressure

leads to edema and hypotension