Short Term Control of BP

Question 1

What is the arterial baroreflex?

Answer 1

• Strain of blood vessels measured by baroreceptors - Baroreceptors stretch enough to fire an action potential to the medullary cardiovascular centres - Medullary centres innervate return pressure to normal

Question 2

Where are the baroreceptors located that control BP?

Answer 2

Carotid and aortic sinus

Question 3

What nerves is the stretch signal sent through from the aortic sinus?

Answer 3

• Vagus

Question 4

What nerve is the stretch signal sent through from the carotid sinus?

Answer 4

• Glossopharyngeal nerve

Question 5

What nerve will reduce heart rate by acting on the SA node if BP is too high?

Answer 5

• Vagus (parasympathetic)

Question 6

What nerve will increase HR by acting on the SA node if BP is too low?

Answer 6

• Sympathetic nerves

Question 7

What other structure is innervated by the same sympathetic nerve to increase HR?

Answer 7

Adrenal gland

Question 8

What other effect on the heart does the sympathetic innervation have to increase BP?

Answer 8

Increase contractility of the ventricle

Question 9

What receptors does the sympathetic system work on in the heart to increase HR and increase ventricle contractility?

Answer 9

B1

Question 10

What other effect around the body will the sympathetic system have to increase BP?

Answer 10

Can act on A1 receptors on veins and arteries to make them contract

Question 11

What will happen to TPR when the sympathetic system is active?

Answer 11

• TPR increases - Due to arteriolar constriction

Question 12

Where are cardiopulmonary baroreceptors found?

Answer 12

• Atria - Other low pressure areas of the system

Question 13

What part do central chemoreceptors play in the regulation of BP?

Answer 13

• Increase resp drive if CO2 levels high - Also affect the medullary cardiovascular centres to increase cardiac output

Question 14

What will cause muscle chemoreceptors to be activated?

Answer 14

An increase in metabolites

Question 15

What effect will the activation of muscle chemoreceptors have on cardiac output?

Answer 15

Increase it

Question 16

What are higher centres of the heart?

Answer 16

• Cause a feedforward reaction - When you are asked to do exercise your heart will start beating faster before hand to get the body ready

Question 17

What does standing up cause to increase?

Answer 17

Hydrostatic pressure in veins/venules of the feet

Question 18

What effect will standing up (and increase in hydrostatic pressure have on venous return, EDV, preload, SV, CO and MAP?

Answer 18

ALL decrease - VR - EDV - Preload - SV - CO - MAP

Question 19

What effect does an increase hydrostatic pressure in the legs have on baroreceptors?

Answer 19

Decreases it

Question 20

What will the reflex response cause to happen?

Answer 20

• Decreases vagal tone therefore HR and CO up - Increases sympathetic tone therefore HR and CO up - Increased contractility - Increased SV - Increased venoconstriction therefore VR, EDV, SV and CO increase - Increased arteriolar constriction therefore TPR increases

Question 21

What is the valsalva manoeuvre?

Answer 21

Forced expiration against a closed glottis

Question 22

What happens at stage 1?

Answer 22

• Increased thoracic pressure transmitted to aorta

Question 23

What happens at stage 2-3?

Answer 23

• Thoracic pressure still high
• Venous return reduced
• Low EDV
• Decreased SV, CO and MAP

Question 24

What happens at stage 3-4?

Answer 24

• Decreased MAP detected by baroreceptors
• Reflex initiated
• CO and TPR increase

Question 25

What happens at stage 4?

Answer 25

• Decrease in thoracic pressure transmitted through aorta

Question 26

What happens at stage 5?

Answer 26

• VR restored so SV goes back up
• Reflex effects not worn off so remains higher