7. Control of blood pressure Flashcards
What is required to maintain tissue perfusion acress of the whole of the body?
Integration and control of the heart and blood vessels
Why is a constant arterial pressure required?
- Too low = blood flow to organs would fail
- Too high = damage to vessels and organs
How does nervous control influence arterial pressure?
RAPIDLY
- Increase to x2 within 5-10s
- Decrease to 50% within 10-40s
What are the fundamental components of the reflex control system of blood pressure?
- 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
Mean Arterial Blood Pressure =
Cardiac Output x TPR
How are baroreceptors activated? And where are they located?
Stretch activated
Aorta and carotid sinus (where common carotid artery bifurcates)
What afferent nerve fibres are present at each baroreceptor?
- Wall of aorta; follow vagus (X) nerve
- Carotid Artery; follow glossopharyngeal (IX) nerve
How does baroreceptor activity change with changes to blood pressure?
- Firing rate increases with increase BP
- Firing rate decreases with decrease BP
What are baroreceptors sensisitve around?
A “set-point”
What is the primary purpose of the carotid baroreceptor?
To reduce minute-to-minute variations of BP or arterial pulse
Which baroreceptor become saturated at higher BPs?
Aortic = less sensitive
What do cardiopulmonary baroreceptors sense?
Central blood volume changes
Where are cardiopulmonary baroreceptors located?
- Atria
- Ventricles
- Veins
- Pulmonary vessels
What occurs if the rate of firing of cardiopulmonary baroreceptors decreases (decrease in volume)?
SNS to heart and blood vessels increases and PSNS activity decrease
What is the Bainbridge Reflex?
Sympathetic mediated reflex response to an increase of blood in the aorta
