Regulation of BP

Question 1

What short term factors affect BP

Answer 1

sleep, posture, exercise, stress

Question 2

What does baroreceptor reflex do and what is its benefits

Answer 2

Function: limits the extent to which BP varies
Benefits: keeps pressure high enough to perfuse the vital organs and maintain a constant pressure in the head, keeps pressure low enough to prevent damage to target organs, alter mean BP to cope with stress e.g. exercise

Question 3

Draw a flow chart of the determinants of mean arterial BP (include types of receptors, sympathetic vs para). How does short term and long term BP control differ

Answer 3

ref. notes.
Short term: baroreceptor reflex act via ANS (influences all factors in flow chart apart from vol)
Long term: Mainly a function of blood vol (influenced by salt consumption) which is regulated by kidneys

Question 4

Draw a flow diagram of how the baroreceptor reflex works

Answer 4

ref. notes

Question 5

Draw out how the nerves innervate the baroreceptors on the aortic arch and the carotid sinuses

Answer 5

ref. notes

Question 6

Where are baroreceptors more important and why

Answer 6

aortic arch+carotid sinuses. For CS, because of its thin walls meaning that small changes in pressures can be detected

Question 7

At which point is the baroreceptor most sensitive, how is sensitivity increased

Answer 7

most sensitive: 80-150mmHg

Sensitivity: more sensitive to rapid changes in pressure

Question 8

How do baroreceptors show adaptation

Answer 8

If new pressure is sustained, reflex becomes partially reset after a few hours

Question 9

Draw a flow chart of what happens when BP decreases

Answer 9

ref. notes

Question 10

What happens to the baroreceptor relex at orthostasis

Answer 10

blood pools at bottom->SV+CO decreases, blood flow to brain decreases, MABP upper body decreases->baroreflex activated->HR increases, vasoconstriction increases, TPR increases->change minimised or reversed

Question 11

Draw a flow chart of the effect of Na consumption on long term BP

Answer 11

increase Na consumption->increase plasma osmolarity (+increase ADH release)->increase water consumption, decrease water excretion->blood vol increase->blood pressure increase->natriuresis increases (excretion of salt)

Question 12

How does blood vol affect Na+ excretion

Answer 12

ref. notes

Question 13

How does pressure natriuresis affect Na+ excretion

Answer 13

increase renal perfusion pressure->increase blood flow in vasa recta->increase intra-renal release of NO->decrease renal Na+ reabsorption

Question 14

How does RAAS work

Answer 14

ref. notes

Question 15

Draw out Guyton model of long term BP regulation

Answer 15

ref. notes

Question 16

What does Guyton’s model indicate

Answer 16

Hypertension can only occur if Na+excretion=impaired so higher BP required to achieve same excretion. This shift could arise due to defect in PN or in extra renal mechanisms which regulate renal natriuresis e.g. RAAS or sympathetic nervous system

Question 17

what are the criticisms for Guyton’s model

Answer 17

1. Activation of SNS can increase blood pressure even when kidneys are denervated
2. Changes in BP don’t always affect Na+ excretion
3. Na+ excretion can occur without changes in BP

Question 18

How is TPR defined

Answer 18

function of resistance of all arteries and arterioles. TPR=CO/BP