Control of Blood Pressure

Question 1

MAP = ? x ?

Answer 1

MAP = CO x TPR

Question 2

what do the arterial baroreceptors measure?

Answer 2

stretch –> blood pressure

Question 3

where can the arterial baroreceptors be found?

Answer 3

in the aortic arch and at the bifurcation of the common carotid arteries

Question 4

in cases of low blood pressure will the baroreceptors fire more or less?

Answer 4

less

Question 5

when do arteries stretch more - with high or low blood pressure?

Answer 5

high

Question 6

below which mean arterial pressure are the arterial baroreceptors ‘silent’?

Answer 6

< 40 mmHg

Question 7

above which mean arterial pressure are the arterial baroreceptors saturated?

Answer 7

> 120 mmHg

Question 8

which nerve do the arterial baroreceptors in the aortic arch use to travel to the brain?

Answer 8

vagus

Question 9

which nerve do the arterial baroreceptors in the carotid sinus use to travel to the brain?

Answer 9

glossopharyngeal

Question 10

where does info from both sets of arterial baroreceptors travel to in the brain?

Answer 10

medullary cardiovascular centres

Question 11

if blood pressure is too high, what do the medullary cardiovascular centres do?

Answer 11

increase parasympathetic action on sinoatrial node (via vagus) –> increase heart rate

Question 12

if blood pressure is too high, what do the medullary cardiovascular centres do?

Answer 12

increase sympathetic action on sinoatrial node –> increase heart rate
on ventricles –> increase contractility
on blood vessels –> venoconstriction and arteriolar constriction

Question 13

what other inputs do the medullary cardiovascular centres have?

Answer 13

cardiopulmonary centres
central chemoreceptors
chemoreceptors in muscle
joint receptors
higher centres

Question 14

does gravity reduce venous return?

Answer 14

not necessarily

Question 15

what is the first event in the valsalva manoeuvre?

Answer 15

increase in thoracic pressure is transmitted through to aorta

Question 16

what is the second event in the valsalva manoeuvre?

Answer 16

increase in thoracic pressure leads to decreased venous return, decreased end diastolic volume, decreased stroke volume, decreased cardiac output and decreased mean arterial pressure

Question 17

what is the third event in the valsalva manoeuvre?

Answer 17

decreased mean arterial pressure is detected by baroreceptors which initiate a reflex increase in cardiac output and increase in total peripheral resistance

Question 18

what is the fourth event in the valsalva manoeuvre?

Answer 18

decrease in thoracic pressure is transmitted through to aorta

Question 19

what is the fifth event in the valsalva manoeuvre?

Answer 19

venous return is restored so stroke volume increases, but reflex effects are still wearing off

Question 20

what is the sixth event in the valsalva manoeuvre?

Answer 20

everything returns to normal

Question 21

is long term control of blood pressure mediated by the arterial baroreceptors?

Answer 21

nope

Question 22

which three hormone systems are involved in long term control of blood pressure?

Answer 22

renin - angiotensin - aldosterone system
antidiuretic hormone (ADH / vasopressin)
atrial natriuretic peptide and brain natriuretic peptide

Question 23

where is renin produced?

Answer 23

juxtaglomerular apparatus of the kidney

Question 24

what triggers renin production?

Answer 24

decreased mean arterial pressure detected by the cardiopulmonary centres –> sympathetic action on juxtaglomerular apparatus
decreased distension of afferent arterioles
decreased delivery of Na+/Cl+ through the tubule

Question 25

what does renin do?

Answer 25

converts angiotensinogen to angiotensin I

Question 26

what does angiotensin I do?

Answer 26

not a lot really, just gets converted to angiotensin II

Question 27

what converts angiotensin I to angiotensin II?

Answer 27

angiotensin converting enzyme (ACE)

Question 28

what does angiotensin II do?

Answer 28

stimulates release of aldosterone
increases release of ADH
vasoconstriction –> increased total peripheral resistance

Question 29

where is aldosterone produced?

Answer 29

adrenal cortex

Question 30

what does aldosterone do?

Answer 30

increases Na+ reabsorption in loop of Henle –> reduces diuresis, increases plasma volume

Question 31

what does antidiuretic hormone do?

Answer 31

increases water permeability of the collecting duct –> reduces diuresis, increases plasma volume
increases thirst
vasoconstriction

Question 32

where is ADH synthesised?

Answer 32

hypothalamus

Question 33

where is ADH released?

Answer 33

posterior pituitary

Question 34

what triggers ADH release?

Answer 34

decrease in blood volume (from cardiopulmonary centres)
increase in osmolarity of interstitial fluid (osmoreceptors in hypothalamus)
angiotensin II

Question 35

where are ANP and BNP produced?

Answer 35

myocardial cells in the atria (ANP) and ventricles (BNP)

Question 36

what triggers ANP and BNP release?

Answer 36

increased distension of atria and ventricles

Question 37

what do ANP and BNP do?

Answer 37

increase excretion of Na+ (natriuresis)
inhibit release of renin
acts on medullary cardiovascular centres to reduce mean arterial pressure

Question 38

what percentage of hypertension patients have secondary hypertension?

Answer 38

5-10%