cardiovascular: BP regulation

Question 1

where is BP normally measured? how does BP below and above the heart vary wrp to one another? why is there a difference?

Answer 1

brachial artery
below heart-> higher
above heart-> lower
due to the effect of gravity

Question 2

short term factors affecting BP

Answer 2

sleep
posture
stress
exercise

Question 3

survival benefits of baroreceptor reflex

Answer 3

keeps pressure high enough -> adequate perfusion of vital organs
keeps pressure low enough-> no damage to target organs
mean BP can be altered-> body can cope with stress

Question 4

BP and CO equation

Answer 4

BP=CO X TPR

CO= HR X stroke volume

Question 5

how does arterial tone affect BP

Answer 5

+ arterial tone -> + TPR-> +BP

also +afterload -> - stroke volume

Question 6

how does venous tone affect BP

Answer 6

+venous tone-> -venous capacitance -> increased CVP preload -> increased stroke volume-> increased CO-> increased BP

Question 7

how does blood volume affect BP

Answer 7

+ blood volume-> +preload-> increased stroke volume-> increased CO-> increased BP

Question 8

how does cardiac contractility affect BP

Answer 8

+ contractility-> + stroke volume-> increased CO-> increased BP

Question 9

route of impulses from baroreceptors-> afferents -> comparator

Answer 9

carotid sinus-> carotid sinus nerve-> CNIX (glossopharyngeal) -> nucleus tractus solitarius
aortic arch-> aortic nerve-> CNX -> nucleus tractus solitarius

Question 10

how does reduced pressure affect baroreceptor firing

Answer 10

baroreceptor firing is reduced

Question 11

range of pressures where BP regulation is most sensitive

Answer 11

80-150 mmHg

Question 12

how PNS and SNS affect BP

Answer 12

SNS: arterial tone(a1)/ cardiac contractility(b1)/venous tone(a1)/ HR(b1)/ stroke volume(b1)
PNS: HR(M)

Question 13

how baroreceptor reflex responds for orthostasis (standing up)

Answer 13

stand up-> blood pools in lower extremities-> -stroke volume/ -CO -> -blood flow to brain, - MABP in upper body-> baroreflex activated-> +HR/ +Vasoconstriction/ +TPR

Question 14

effect of salt consumption on blood pressure

Answer 14

+na consumption-> +plasma osmolality -> +ADH/ +water consumption/ -water excretion-> +blood volume-> +preload/CVP -> +CO-> +BP

Question 15

how is blood pressure/osmolality restored following consumption of Na, in the long term

Answer 15

increased water consumption/decreased water excretion restores OSMOLALITY
increased natriuresis restores BP

Question 16

how does increased blood volume lead to increased natriuresis

Answer 16

+ blood vol-> +CVP-> +atrial stretch -> +ANP release-> +natriuresis
+ blood vol-> +CVP-> +atrial stretch -> +cardiopulmonary receptors-> -SNS to kidneys-> -RAAS -> +natriuresis
+blood vol-> -RAAS-> +natriuresis
+blood vol-> +BP-> -RAAS/+pressure natriuresis-> +natriuresis

Question 17

mechanism of pressure natriuresis

Answer 17

+renal perfusion pressure-> +blood flow in vasa recta(capillaries around LOH)-> +intra-renal NO release-> - renal Na reabsorption

Question 18

RAAS system

Answer 18

-blood vol/bp -> SNS activation-> +renin release;
angiotensinogen-> angiotensin I BY RENIN;
angiotensin I-> angiotensin II BY ACE;
angiotensin II-> vasoconstriction/+ADH/+aldosterone;
(aldoesterone-> +Na reabsorption

Question 19

Guyton’s model

Answer 19

+na intake-> +extracellular fluid volume-> +blood vol-> +CVP/preload-> +CO-> +BP-> +pressure natriuresis-> +Na excretion

Question 20

guyton’s model implications

Answer 20

renal function controls LT BP
slight + BP-> HUGE na excretion (infinite gain)
hypertension only happens if Na excretion is impaired (eg pressure natriuresis/RAAS/SNS)

Question 21

neurogenic model of BP regulation

Answer 21

SNS can mediate/control BP
SNS can +BP when kidneys are denervated
Na excretion occurs w/o changes in BP
changes in BP dont always affect Na excretion

Question 22

guyton’s model in normotension vs hypertension

Answer 22

normotension: vertical line
hypertension: +vely linear