7. Control of blood pressure

Question 1

What is required to maintain tissue perfusion acress of the whole of the body?

Answer 1

Integration and control of the heart and blood vessels

Question 2

Why is a constant arterial pressure required?

Answer 2

• Too low = blood flow to organs would fail
• Too high = damage to vessels and organs

Question 3

How does nervous control influence arterial pressure?

Answer 3

RAPIDLY

• Increase to x2 within 5-10s
• Decrease to 50% within 10-40s

Question 4

What are the fundamental components of the reflex control system of blood pressure?

Answer 4

• Internal variable to be mainated
• Receptors sensitive to change in variable
• Afferent pathways from receptors intergrating centre for all afferent inputs
• Efferent pathways from the integrating centre
• Target effectors that alter their activites

Question 5

Mean Arterial Blood Pressure =

Answer 5

Cardiac Output x TPR

Question 6

How are baroreceptors activated? And where are they located?

Answer 6

Stretch activated

Aorta and carotid sinus (where common carotid artery bifurcates)

Question 7

What afferent nerve fibres are present at each baroreceptor?

Answer 7

• Wall of aorta; follow vagus (X) nerve
• Carotid Artery; follow glossopharyngeal (IX) nerve

Question 8

How does baroreceptor activity change with changes to blood pressure?

Answer 8

• Firing rate increases with increase BP
• Firing rate decreases with decrease BP

Question 9

What are baroreceptors sensisitve around?

Answer 9

A “set-point”

Question 10

What is the primary purpose of the carotid baroreceptor?

Answer 10

To reduce minute-to-minute variations of BP or arterial pulse

Question 11

Which baroreceptor become saturated at higher BPs?

Answer 11

Aortic = less sensitive

Question 12

What do cardiopulmonary baroreceptors sense?

Answer 12

Central blood volume changes

Question 13

Where are cardiopulmonary baroreceptors located?

Answer 13

• Atria
• Ventricles
• Veins
• Pulmonary vessels

Question 14

What occurs if the rate of firing of cardiopulmonary baroreceptors decreases (decrease in volume)?

Answer 14

SNS to heart and blood vessels increases and PSNS activity decrease

Question 15

What is the Bainbridge Reflex?

Answer 15

Sympathetic mediated reflex response to an increase of blood in the aorta

Question 16

Can the bainbridge reflex override other baroreceptors?

Answer 16

YES

Question 17

Where is the control of blood pressure integrated?

Answer 17

Medullary cardiovascular ‘vasomotor’ centre (MCVC)

Question 18

Explain the sensory area (in the brain stem) of the MCVC

Answer 18

Input from baroreceptors

Question 19

Explain the lateral portion (in the brain stem) of the MCVC

Answer 19

Efferent sympathetic nerves

Question 20

Explain the medial portion (in the brain stem) of the MCVC

Answer 20

Efferent parasympathteic (vagal) nerve

Question 21

Sympathetic effects on blood vessels

Answer 21

• Continous low-level flow affects TPR
• ‘sympathetic vasocontrictor tone’ exerts ‘vasomotor tone’ on vessels keeping them partially constricted

Question 22

What occurs when blood flow to the MCVC os decreased?

Answer 22

• Increase peripheral vasocontriction
• Increase SNS stimulation of the heart
• Increase systemic arterial pressure

Question 23

What effects can adrenaline have on the CVS?

Answer 23

• Increase venous return
• Increase TPR
• Increase SV
• Increase HR
• ALL of the above increase CO and ABP

Question 24

What influences the TPR?

Answer 24

• Neuronal, hormonal and local = arteriolar radius
• Haematocrit = blood viscosity