Short Term Control of Blood Pressure Flashcards Preview

Cardiovascular System > Short Term Control of Blood Pressure > Flashcards

Flashcards in Short Term Control of Blood Pressure Deck (26)
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1
Q

What in MAP and why does it have to be regulated?

A

It’s the driving force pushing blood through the systemic circulation
Must be regulated as it determines the pressure gradient which pushes blood

2
Q

What are general determinants of MAP?

A

Blood flow in and out of arteries - if flow in exceeds flow out, then volume in aa. increases and so does MAP

3
Q

What are two specific determinants of MAP?

A

MAP = CO X TPR

Blood flow into aorta = CO
Blood flow out = influenced by TPR

4
Q

What can low BP cause?

A

Syncope - not enough pressure to push blood around body

5
Q

What can high BP cause?

A

Gradually damaged BV causing blindness, kidney failure etc.

6
Q

Where are baroreceptors located?

A

In walls of carotid arteries and aorta

7
Q

What type of receptors are baroreceptors?

A

Tonically active stretch receptors that fire AP continuously at normal BP

8
Q

How is firing of AP affected with increased BP?

A

Increased BP stretches baroreceptor membrane and causes increased AP firing rate

9
Q

How is firing of AP affected with decreased BP?

A

Decreased firing

10
Q

What is the action of baroreceptors?

A

If BP changes, the frequency of AP travelling from baroreceptors to the medullary CVS control centre changes

CVCC uses sensory input to initiate appropriate response - changes in CO and TPR

11
Q

What is the effect of sympathetic innervation of the heart?

A

Increases HR by innervating the SA node, shortening conduction time through the AV node (shorter depolarisation) and enhancing the force of myocardial contraction

12
Q

What is the effect of sympathetic innervation of the smooth muscle around vessels?

A

Causes arteriolar constriction which increases TPR and thus MAP and venoconstriction increases venous return to the heart (Increase EDV -> preload -> SV -> increased CO increases BP)

13
Q

What is the effect of sympathetic innervation of the adrenal medulla?

A

Stimulate secretion of adrenaline and noradrenaline

14
Q

What are 3 effects of sympathetic system which increases MAP

A

Innervation of:
Heart
Smooth muscle
Adrenal medulla

15
Q

What nerve is used to send signals from the aortic baroreceptor to the CVCC?

A

Vagus nerve

16
Q

What nerve is used to send signals from the carotid baroreceptor to the CVCC?

A

Glossopharyngeal nerve

17
Q

What is the effect of the parasympathetic on the heart?

A

Slows HR by innervating the SA node and decreasing rate of depolarisation, but has little effect on ventricular contraction

18
Q

Name 5 other input to the medullary CVCC

A
Cardiopulmonary baroreceptors 
Central chemoreceptors 
Chemoreceptors in muscle 
Joint receptors 
Higher centres
19
Q

What is the function of cardiopulmonary baroreceptors?

A

Located in low resistance areas (atria and lungs) and respond to changes in blood volume -> stimulates sympathetic NS

20
Q

What is the function of central chemoreceptors?

A

Respond to [H+] directly from CO2 to control respiratory rates

21
Q

What is the action of higher centres?

A

Feed forward effect: anticipatory effect causing BP to increase due to the hypothalamus coordinating with the sympathetic outflow signalling for body to prepare and increase HR

22
Q

What are the effects of posture on blood pressure?

A

When in supine position, gravitational forces are distributed evenly throughout your body and circulation

When you stand, gravity causing pooling of blood in the veins and venues of the feet/legs -> decreases venous return -> low EDV -> lower SV -> lower CO -> lower BP -> baroreceptor firing decrease

23
Q

What is the Valsalva manoeuvre?

A

Forced expiration against a closed glottis, so no air escapes and increases intrathoracic pressure

24
Q

What is the effect of the V manoeuvre on MAP?

A

Raising intrathoracic pressure will decrease venous return

Decrease VR -> low EDV -> low SV -> low CO -> low MAP

25
Q

What are the stages in the Valsalva manoeuvre?

A
  1. Increase thoracic pressure transmitted to aorta
  2. Increased thoracic pressure = decrease VR ->->->-> decrease MAP
  3. Decrease MAP detected by baroreceptors which initiate reflex increase in CO and TPR
  4. Stop manoeuvre and decrease in thoracic pressure
  5. VR restored so increase SV, but relax effect not worn off (period of high MAP)
  6. Back to normal
26
Q

How can the Valsalva manoeuvre treat SVT?

A

Following the release of the breath, a parasympathetic response is triggered to decrease the heart rate. This vagal influence is what may break the SVT and lowers the heart rate