Short term control of Blood Pressure

Question 1

what is the effect if MAP is too low/ too high?

Answer 1

too low- syncope

too high- hypertension

Question 2

how is short term control of blood pressure monitored

Answer 2

Through stretch-sensitive mehcanoreceptors called BARORECEPTORS, which are found in the walls of the aorta (aortic) and carotid artery (carotid). At normal blood pressures, they fire APs at a steady rate, however if blood pressure increases, this stretches the baroreceptor membrane and they increase their firing rate; if BP decreases, they decrease their firing rate.

Question 3

what nerve picks up signal from aortic arch baroreceptors & where does it take signal ?

Answer 3

Vagus nerve picks up signal and takes it medullary cardiovascular centre

Question 4

what nerve picks up signal from carotid baroreceptors and where does it take signal?

Answer 4

Glossopharyngeal nerve picks up signal and takes it to medullary cardiovascular centre

Question 5

what is determined in CVC ?

Answer 5

whether the response is via the sympathetic (MAP too low) or parasympathetic system (MAP too high)

Question 6

what are other inputs into the medullary CVC? (5)

Answer 6

• cardiopulmonary baroreceptors - these are found in low pressure areas in heart and lungs e.g. in walls of atria and ventricles
• central chemoreceptors - detect changes in pCO2 in blood
• muscle chemoreceptors- detect increases in metabolite concentration in muscle
• joint receptors
• higher centres - feed forward response rather than feedback like ones above

Question 7

when is short term control of blood pressure used?

Answer 7

• position

- valsalva manœuvre

Question 8

describe the effect of posture on short term control of BP

Answer 8

Standing up: when you stand up, blood flows down to the extremities and pools in the veins of the lower limbs and feet. This causes reduced EDV, preload, SV, CO & MAP. Baroreceptors detect this and decrease firing rate which causes a reflex response

Question 9

what is the valsalva manoeuvre ?

Answer 9

forced expiration against a closed glottis

Question 10

what do carotid baroreceptors control

Answer 10

blood flow to brain

Question 11

what do aortic baroreceptors control

Answer 11

blood flow to body

Question 12

in the CVC, if it is determined the response should be via the parasympathetic system, what nerve takes the signal back down?

Answer 12

vagus nerve

Question 13

in the CVC, if it is determined the response should be via the sympathetic system, what nerve takes the signal back down?

Answer 13

sympathetic nerves

Question 14

describe the effect of the valsalva manoeuvre on short term control of blood pressure

Answer 14

• intra thoracic pressure increases and this gets transmitted to the aorta.
• it results in the compression of the thoracic vena cava which reduces VR and therefore reduces EDV, preload, SV, CO & MAP
• baroreceptors detect this decrease in MAP and initiate reflex response to increase CO and TPR
• intra thoracic pressure decreases because the person starts to breathe again, and this gets transmitted to the aorta
• Venous return goes back to normal so SV increases, but reflex effects not worn off
• normal