PSC1002/L10 Control of Blood Pressure

Question 1

Give the 2 major control mechanisms in control of mean arterial blood pressure.

Answer 1

Short term
Long term - involves kidneys

Question 2

Describe the baroreceptor reflex response in short term control of MABP. (3)

Answer 2

Baroreceptors detect change in BP
Signal cardiovascular control centre (brainstem)
ANS changes HR, SV, VR

Question 3

Where are baroreceptors located? (2)

Answer 3

Aortic arch
Carotid sinuses

Question 4

Where are nerve endings of baroreceptors located?

Answer 4

Adventitia layer of arteries

Question 5

Where are the afferents of the aortic arch and carotid sinus found?

Answer 5

AA - carotid depressor
CS - Hering’s/IX glossopharyngeal

Question 6

What is the role of afferents?

Answer 6

Sending information about MABP to cardiovascular control centre in brainstem (medulla)

Question 7

What are baroreceptors?

Answer 7

Sensors of changes in stretch of the artery due to changes in BP - mechanoreceptors

Question 8

What do baroreceptors respond best to?

Answer 8

Pulsatile changes in pressure
Adapt to maintained changes

Question 9

Which mechanism of MABP regulation are baroreceptors important in?

Answer 9

Short-term

Question 10

Describe the pathway from increased BP to baroreceptor response. (3)

Answer 10

Increased BP increases stretch of artery
Receptors fire more action potentials to CCC
Response

Question 11

What is venous pooling? (2)

Answer 11

Approximately 500ml of blood from intrathoracic vessels into veins of lower limbs when standing up from lying
Takes about 15 seconds

Question 12

What occurs as a result of venous pooling? (4)

Answer 12

VR decreases
SV decreases
CO falls (Starling mechanism)
ABP falls

Question 13

Reflex action of baroreceptors due to venous pooling results in what? (4)

Answer 13

Reflex tachycardia
Positive inotropic effect
Vasoconstriction in skeletal, GI and renal beds
Restoration of MABP

Question 14

Define postural hypotension.

Answer 14

Decrease in systolic BP of 20mmHg or more after 1 min of standing, compared to supine values
Can lead to syncope

Question 15

What is involved in long-term regulation of BP?

Answer 15

Atrial pressure receptors
Renal receptors which control fluid excretion/reabsorption
Control of fluid intake

Question 16

What is the role of ANP (atrial natriuretic peptide)?

Answer 16

Increases Na+ and water excretion from kidney

Question 17

What is the role of renin-angiotension-aldosterone system (RAAS)?

Answer 17

Promotes Na+ and water reabsorption into body

Question 18

What is the role of ADH (vasopressin)?

Answer 18

Promotes water uptake into body

Question 19

Give 3 examples where there is a decrease in blood volume.

Answer 19

Haemorrhage (hypovolaemic hypotension)
Vomiting and diarrhoea
Severe burns
Diabetes
Excessive use of diuretics

Question 20

Give 3 examples where there is an increase in blood volume.

Answer 20

Diet - excessive salt intake
Too much aldosterone
Genetic diseases e.g., Liddle syndrome

Question 21

Explain why stress can lead to fainting - vasovagal syncope. (5)

Answer 21

Decrease in sympathetic supply to skeletal muscle
Relaxes SM in arterioles
Decreases TPR
Increase in parasympathetic output to heart
Decrease in HR
Combined effect of rapid decrease in BP and reduced flow to brain

Question 22

Describe feeding behaviour. (4)

Answer 22

Increased BP
Increased intestinal motility
Increased intestinal blood supply
Decreased blood supply to muscles

Question 23

Describe defense behaviour. (4)

Answer 23

Increased BP
Decreased intestinal motility
Decreased intestinal blood supply
Increased blood supply to muscles