36 - Blood Control and Hypertension Flashcards
Short-term blood pressure regulation
Primarily neural.
The baroreflex
Part of brain that mediates baroreflex
Brainstem autonomic centres, in the medulla.
Nucleus and tractus solitarius
Baroreceptor locations
1)
2)
3)
1) Carotid sinus
2) Aortic arch
3) Pre-glomerular arteriole (near justaglomerular apparatus)
Carotid sinus
Thin-walled, highly-innervated, dilated bulb at base of internal carotid.
Baroreceptor
Neural signals from baroreceptors
More stretch leads to more neural firing.
Therefore brain responds to less firing with sympathetic activation.
Significance of thin wall of carotid sinus
Thinner wall is more compliant than a thicker one.
Therefore more sensitive (more easily-deformable) to changes in blood pressure.
How quickly can baroreceptors respond to changes in bp?
Within one cardiac cycle
How does your body normally assess adequacy of blood flow to organs?
Using blood pressure monitoring
Effect of sympathetic stimulation on cardiovascular function 1) 2) 3) 4) 5)
1) Increase heart rate
2) Decrease AV conduction time
3) Increase cardiac contractility (Ca2+ released in cardiac cells upon sympathetic stim)
4) Increase total peripheral resistance (keep blood in arteries)
5) Increase venous tone (keep blood in arteries)
Effect of parasympathetic stimulation on cardiovascular system
1)
2)
3)
1) Increase AV conduction time
2) Decrease heart rate.
3) Doesn’t really cause vasodilation (except in blood vessels of sweat glands)
Overall effect of baroreflex
Stabilises blood pressure, smooths out variations
Effect of de-innervating carotid baroreceptors
Have great swings in bloodpressure with things like speaking, standing up, eating, defecating.
How quickly can the threshold for baroreflex be changed?
Resets to new pressure levels within one to two days
When to carotid baroreceptors stop firing to medulla?
Below about 60mmHg
How is blood pressure below 60mmHg detected?
By chemoreceptors