short term control of blood pressure

Question 1

What happens when MAP is too low?

Answer 1

Syncope (Fainting)

Question 2

What happens when MAP is too high?

Answer 2

Hypertension

Question 3

Where are the baroreceptors located?

Answer 3

In the aortic arch and in each bifurcation of the carotid arteries

Question 4

What sort of receptors are baroreceptors?

Answer 4

Essentially they are stretch receptors, they stretch more when MAP is larger

Question 5

What happens to the baroreceptor firing rate as MAP increases?

Answer 5

It also increases

Question 6

Below what MAP do baroreceptors not fire?

Answer 6

40mmHg

Question 7

above what MAP does a baroreceptors firing rate stop increasing?

Answer 7

120mmHg

Question 8

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

Answer 8

Medullary Cardiovascular centre

Question 9

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

Answer 9

Vagus nerve

Question 10

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

Answer 10

Glossopharyngeal nerve

Question 11

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

Answer 11

The vagus nerve

Question 12

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

Answer 12

Causes a decrease in heart rate

Question 13

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

Answer 13

Increased heart rate and increased contractility

Question 14

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

Answer 14

Cause venoconstriction and arteriolar constriction, also cause release of adrenaline from the adrenal medulla

Question 15

What are the ways in which blood pressure is monitored in the short term?

Answer 15

Arterial baroreflex, cardiopulmonary baroreceptors, central chemoreceptors, chemoreceptors in muscle, joint receptors, higher centres

Question 16

How do cardiopulmonary baroreceptors monitor blood pressure?

Answer 16

They are found in areas of low pressure and monitor pressure in the same way as the arterial baroreflex (via stretch receptors)

Question 17

How do central chemoreceptors monitor and alter blood pressure?

Answer 17

They mainly affect respiratory drive but can also affect heart rate to alter BP

Question 18

How do chemoreceptors in muscles work?

Answer 18

Receptors in the vessels of muscles detect when muscles are working harder and increase blood flow to these regions to increase washing out of waste products and delivery of nutrients

Question 19

How do joint receptors work to alter MAP?

Answer 19

Detect increase movement of joint and increase blood flow to these regions to supply hard working muscles

Question 20

How do higher centres control blood pressure?

Answer 20

The hypothalamus increases blood pressure in response to an increase to a stimulus that requires an increased BP, eg seeing danger

Question 21

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

Answer 21

Cardio-pulmonary baroreceptors

Question 22

How does standing up affect blood pressure?

Answer 22

Increased hydrostatic pressure causes pooling of blood in veins and venules of the feet and legs. This causes a decreased venous return which in turn causes a decreased EDV so preload decreases and CO decreases, this causes a decrease in MAP.

Question 23

What is the reflex response to the decreases blood pressure on standing?

Answer 23

Decreased vagal tone which causes increased HR and CO. An increased sympathetic tone which causes an increased HR and CO, an increased contractility (increased SV and CO), venoconstriction and arteriolar constriction (which causes increased TPR)

Question 24

What is the Valsava manoeuvre?

Answer 24

Forced expiration against a closed glottis

Question 25

Describe the changes in MAP when performing the Valsava manoeuvre?

Answer 25

1. Increases thoracic pressure is transmitted to the aorta so MAP increases
2. The MAP then decreases as VR decreases (as increases pressure in thoracic veins causes loss of pressure gradient) which causes a decreased EDV therefore a decreased SV, CO and MAP.
3. The decrease in MAP is detected by the arterial baroreceptors which initiate a reflex to increase CO and TPR.
4. Forced expiration ceases and the decreased thoracic pressure is transmitted through to the aorta
5. VR is now restored and SV increases but the reflex effects have not worn off so BP is very high
6. Baroreceptors kick in again and MAP returns to normal