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Cardiovascular System > Short Term Control of Blood Pressure > Flashcards

Short Term Control of Blood Pressure Flashcards

1
Q

What happens when MAP is too low?

A
  • Less venous return to the brain (syncope)

- Less venous return to the heart = lower preload = lower EDV = lower SV/CO

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2
Q

What happens when MAP is too high?

A

Hypertension, peripheral oedema

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3
Q

Where are the arterial baroflexreceptors located? (3)

A
  • carotid sinus baroreceptors = bifurcation of the internal common carotid arteries (x2)
  • aortic arch baroreceptor
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4
Q

What type of receptors are the arterial baroreceptors?

What type of pressure do they respond to?

A

Stretch receptors

indirect pressure

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5
Q

What happens when the wall of the artery is stretched?

A

The baroreceptors detect this and AP will begin to fire according to the stretch.

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6
Q

The stretch in the arteries will be due to an increase in ________.

A

MAP

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7
Q

As MAP increases, the ___________ of AP increases.

A

firing rate

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8
Q

Below what MAP do baroreceptors not fire?

A

40mmHg

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9
Q

Above what MAP does a baroreceptors firing rate stop increasing?

A

120mmHg

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10
Q

What is the centre in the brain that integrates information about BP from baroreceptors?

A

Medullary Cardiovascular centre (brain stem)

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11
Q

Which nerve transmits AP from the aortic arch baroreceptors to the medullary cardiovascular centre?

A

vagus nerve

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12
Q

Which nerve transmits AP from the carotid sinus baroreceptors to the medullary cardiovascular centre?

A

Glossopharyngeal nerve

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13
Q

Which nerve carries signals from the medullary cardiovascular centre to the heart to bring about a parasympathetic response?

A

Vagus nerve

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14
Q

What is the parasympathetic response from the medullary cardiovascular centre on the heart in response to increase MAP?

A

Causes a decrease in heart rate.

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15
Q

What is the sympathetic response from the medullary cardiovascular centre on the heart in response to decreased MAP? (2)

A

Increased heart rate and increased contractility

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16
Q

What do the sympathetic fibres from the medullary cardiovascular centre do apart from increasing heart rate and contractility to increase MAP? (2)

A
  • Cause venoconstriction and arteriolar constriction
  • cause release of adrenaline from the adrenal medulla
  • i.e. fight or flight
17
Q

Other than the arterial baroreceptors, what are the other inputs to the medullary cardiovascular centres. (5)

A
  • Cardiopulmonary baroreceptors
  • Central chemoreceptors
  • Chemoreceptors in muscle
  • Joint receptors
  • Higher centres
18
Q

Describe how cardiopulmonary baroreceptors monitor blood pressure? (3)

A
  • located in the walls of heart and lung vessels.
  • low pressure parts of the circulation.
  • stretch receptors also, which respond to an increase in MAP.
19
Q

Describe how central chemoreceptors monitor and alter blood pressure? (3)

A
  • located in the medulla oblongata
  • detect changes in CO2 in the blood
  • mainly affect respiratory drive, but can also increase HR and SV to alter BP.
20
Q

Describe how chemoreceptors in muscles work? (2)

Give an example.

A
  • respond to any increase in metabolic activity in the muscle.
  • e.g. during exercise, they fire more AP which ensures adequate blood flow to muscles to wash away waste molecules and supply adequate O2 and nutrients.
21
Q

How do joint receptors work to alter MAP?

A
  • Detect increase movement of joint.

- increase blood flow to these regions to supply hard working muscles with adequate blood..

22
Q

How do higher centres control blood pressure?

A

The hypothalamus increases blood pressure in response to a stimulus that requires an increased BP, e.g. seeing danger, fight or flight

23
Q

What are the main receptors for the long-term control of blood pressure?

A

cardio-pulmonary baroreceptors

24
Q

The regulation of blood pressure in the long term revolves around what?

A

blood volume (CO)

25
Q

Regulation mechanisms of long term blood pressure act on both the what?

A

blood vessels and kidneys

26
Q

How does standing up affect blood pressure?

A
  • increased hydrostatic pressure
  • pooling of blood in veins in legs/feet
  • reduced VR
  • reduced EDV/preload
  • reduced CO/SV
  • reduced MAP (BP)
  • less AP being sent to medullary centres
27
Q

What might happen to a person who stands up as a result of the drop in blood pressure?

A

syncope

28
Q

What would the parasympathetic reflex response to a drop in blood pressure e.g. in standing up?

A
  • reduced vagal tone
  • increased HR
  • increased CO/SV
  • increased MAP
  • arterial baroreceptors detect the MAP returning to normal.
29
Q

What would the sympathetic reflex response to a drop in blood pressure be i.e. would it up/down-regulate?

A
  • upregulate sympathetic tone
  • increased HR
  • increased SV/CO
  • increased MAP
30
Q

How would the sympathetic reflex response to drop in BP affect systemic veins?

A
  • venoconstriction
  • increased VR
  • increased EDV/preload
  • increased SV/CO
  • increased MAP
31
Q

How would the sympathetic reflex response to drop in BP affect systemic arterioles?

A
  • arteriolar constriction
  • increased TPR
  • increased MAP
32
Q

What is the Valsava manoeuvre?

What can this be thought of as?

A

Forced expiration against a closed glottis

e.g. think of a cat doing a poo.

33
Q

Explain how the valsalva manoeuvre can transmit thoracic pressure through to the aorta.

A
  • Phase 1: increased thoracic pressure = increased MAP (aorta)

Phase 2:

  • increased thoracic pressure
  • decreased VR
  • decreased EDV/preload
  • decreased SV/CO
  • decreases MAP (BP)

Phase 3:

  • MAP is detected by baroreceptors which initiate reflex
  • increased in CO (venoconstriction)
  • increased TPR (arteriolar consriction)

Phase 4:
- decrease in thoracic pressure transmitted to aorta

Phase 5:

  • VR restored
  • SV/CO increases
  • reflexes still in action

Phase 6:
- MAP restored

Cardiovascular System (37 decks)

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