Physiology 7 - Control of Blood Pressure

Question 1

What is the consequence of a blood pressure that is too low?

Answer 1

Organ failure

Question 2

What is the consequence of a blood pressure that is too high?

Answer 2

Damage to vessels and organs

Question 3

How long might it take to double arterial pressure?

Answer 3

5-10 seconds

Question 4

How long might it take to halve arterial pressure?

Answer 4

10-40 seconds

Question 5

Where are the main baroreceptor locations?

Answer 5

Walls of aorta

Carotid artery

Question 6

Which nerve do afferent fibres from the walls of the aorta follow?

Answer 6

Vagus nerve (Xth cranial)

Question 7

Which nerve do afferent fibres from the carotid artery follow?

Answer 7

Glossopharyngeal nerve (IXth cranial)

Question 8

What is the result on autonomic nervous system activity if cardiopulmonary baroreceptor firing decreases?

Answer 8

Sympathetic activity increases
Parasympathetic activity decreases
Blood volume decreases

Question 9

Which nervous system are veins innervated by?

Answer 9

Sympathetic

Question 10

What is the maximum blood pressure you can maintain temporarily?

Answer 10

2.5x normal

Question 11

What is the predominant tone in nervous innervation of the heart?

Answer 11

Parasympathetic

Question 12

What type of baroreceptors are regarded as ‘low pressure’ receptors?

Answer 12

Cardiopulmonary baroreceptors

Question 13

How fast is nervous control of arterial pressure?

Answer 13

Can increase arterial pressure to 2x normal within 5-10s; can decrease arterial pressure to 50% of normal within 10-40s

Question 14

Where are the two main high pressure locations that can sense MABP in the blood vessels?

Answer 14

Aortic arch

Carotid sinus

Question 15

MABP = …

Answer 15

CO x TPR

Question 16

Which baroreceptors saturate first: carotid or aortic?

Answer 16

Carotid

Question 17

Which cranial nerve do the aortic afferent fibres follow ?

Answer 17

Xth cranial nerve –> vagus

Question 18

Upon raised BP, what type of receptors ensure increased activity to counter this change?

Answer 18

Stretch receptors

Question 19

What is the function of cardio-pulmonary baroreceptors?

Answer 19

Low pressure receptors which sense central blood volume rather than BP, lying out-with the systemic vascular system

Question 20

What is the vascular effect of decreased cardio-pulmonary baroreceptor firing?

Answer 20

Decreased venous return
–> increased sympathetic n.s. and decreased parasympathetic n.s. firing to heart and vessels
–> increased HR & SV and constriction of veins leading to increased venous return
& on arterial side, induced vessel constriction –> increased TPR

Question 21

What is the Bainbridge Reflex?

Answer 21

Detects an overload in the venous system and increases sympathetic mediated drive of the heart:
• ↑ HR and ↑ contractility
• Prevents damming of blood in veins etc.

Question 22

MABP=

Answer 22

CO x TPR

Question 23

How are vessels kept partially constricted?

Answer 23

‘Sympathetic vasoconstrictor tone’ exerts ‘vasomotor tone’ on vessels

Question 24

What is the effect of sympathetic venous innervation?

Answer 24

↓ capacitance, therefore ↑ venous return, therefore ↑ stroke volume, thus ↑ cardiac output.

Question 25

When blood flow to the medullary CVCC (cardiovascular control centre) ↓↓↓ there is:

Answer 25

↑ peripheral vasoconstriction. This almost completely occludes some peripheral vessels
↑ sympathetic stimulation of heart
↑↑ systemic arterial pressure, as high as 250 mmHg for 10 mins

Question 26

What is the concept behind myogenic theory?

Answer 26

Stretch-induced vascular depolarisation of smooth muscle (causing constriction) due to ↑ arterial pressure, thereby protecting downstream tissues and capillary beds from this increased pressure.

Question 27

What is the concept behind metabolic theory?

Answer 27

↑arterial pressure increases O2 and ‘washes out’ local factors by increasing perfusion. Washing out these factors allows the sympathetic tone to resume and smooth muscle can contract within the vessel wall, again protecting downstream tissues.