Short Term Control of BP Flashcards

1
Q

What is the arterial baroreflex?

A
  • 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
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2
Q

Where are the baroreceptors located that control BP?

A

Carotid and aortic sinus

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3
Q

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

A
  • Vagus
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4
Q

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

A
  • Glossopharyngeal nerve
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5
Q

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

A
  • Vagus (parasympathetic)
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6
Q

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

A
  • Sympathetic nerves
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7
Q

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

A

Adrenal gland

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8
Q

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

A

Increase contractility of the ventricle

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9
Q

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

A

B1

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10
Q

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

A

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

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11
Q

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

A
  • TPR increases - Due to arteriolar constriction
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12
Q

Where are cardiopulmonary baroreceptors found?

A
  • Atria - Other low pressure areas of the system
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13
Q

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

A
  • Increase resp drive if CO2 levels high - Also affect the medullary cardiovascular centres to increase cardiac output
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14
Q

What will cause muscle chemoreceptors to be activated?

A

An increase in metabolites

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15
Q

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

A

Increase it

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16
Q

What are higher centres of the heart?

A
  • Cause a feedforward reaction - When you are asked to do exercise your heart will start beating faster before hand to get the body ready
17
Q

What does standing up cause to increase?

A

Hydrostatic pressure in veins/venules of the feet

18
Q

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

A

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

19
Q

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

A

Decreases it

20
Q

What will the reflex response cause to happen?

A
  • 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
21
Q

What is the valsalva manoeuvre?

A

Forced expiration against a closed glottis

22
Q

What happens at stage 1?

A
  • Increased thoracic pressure transmitted to aorta
23
Q

What happens at stage 2-3?

A
  • Thoracic pressure still high
  • Venous return reduced
  • Low EDV
  • Decreased SV, CO and MAP
24
Q

What happens at stage 3-4?

A
  • Decreased MAP detected by baroreceptors
  • Reflex initiated
  • CO and TPR increase
25
Q

What happens at stage 4?

A
  • Decrease in thoracic pressure transmitted through aorta
26
Q

What happens at stage 5?

A
  • VR restored so SV goes back up
  • Reflex effects not worn off so remains higher
27
Q
A
28
Q
A