Short Term Control of Blood Pressure

Question 1

What would happen when the mean arterial pressure is too low or too high?

Answer 1

• too low - syncope

- too high - hypertension

Question 2

Describe the mechanism of the arterial baroreflex.

Answer 2

• arteriole constricts
• this increases resistance and therefore increases total peripheral resistance
• as TPR x CO = MAP - mean arterial pressure increases
• this triggers baroreceptors to fire and cause the baroreflex
• the baroreflex decreases the cardiac output and so MAP is restored

Question 3

Where are baroreceptors found?

Answer 3

• aortic arch

- carotid sinus

Question 4

Which nerves travel to the medullary cardiovascular centres?

Answer 4

• vagus nerve
• glossopharyneal nerve
• sympathetic nerves

Question 5

What is the effect on standing of short term control of blood pressure?

Answer 5

• increases hydrostatic pressure causes pooling of blood in the veins/venules of the feet/legs
• leads to a decrease in venous return, end diastolic volume, preload, stroke volume, cardiac output and mean arterial pressure
• this leads to a reduction in baroreceptor firing rate

Question 6

Define the Valsalva manoeuvre.

Answer 6

• forced expiration against a closed glottis

Question 7

Describe the Valsalva manoeuvre.

Answer 7

• increase in thoracic pressure is transmitted through to the aorta
• leads to a decrease in venous return, end diastolic volume, stroke volume, cardiac output and mean arterial pressure
• the decrease in MAP is detected by baroreceptors which initiate baroreflex
• leads to an increase in cardiac output and total peripheral resistance
• decrease in thoracic pressure is transmitted through to the aorta
• venous return is restored so stroke volume increases