Short Term Control of Blood Pressure Flashcards
How is blood pressure controlled short term (3)
Arterial baroreflex
Other inputs
Lon term control
When is it used (2)
Posture
Valsalva manoeuvre
Mean arterial pressure =
Cardiac output X TPR
What happens if the MAP is too low
Syncope
What happens if the MAP is too high
Hypertension
Other inputs to the medulary CV centres (4)
Cardiopulmonary baroreceptors
Central chemoreceptors
Chemoreceptors in muscle
Joint receptors
What initiates the reflex
Stretch in receptors called baroreceptors
Where are the pressure sensors primarily loctaed
Arterial walls of carotid artery sinus and aortic arch
Where does the afferent nerves take the signal once a change is sensed
Medullary Cardiovascular Centres
Features of long term regulation of blood pressure (5)
Cannot be by the arterial baroreceptors Revolves around blood volume Main sensors are cardiopulmonary baroreceptors Effects tend to be hormonal Act on blood vessels and kidneys
Hormones involved in long term blood pressure regulation (3)
- Renin-Angiotensin-Aldesterone system
- Vasopression (ADH)
- Atrial natriuretic peptide and brain natriuretic peptide
Renin-Angiotensin-Aldesterone System (2)
Angiotensin II causes arteriolar constriction and increases TPR
Which increases BP
Aldesterone increases sodium reabsorption which increases plasma volume
Vasopression (ADH)
Causes arteriolar constriction and increases TPR
Increases water permeability of collecting duct and increases plasma volume
Atrial natriuretic peptide and brain natriuretic peptide
Causes arteriolar dilation and decreases TPR
Increase in sodum excretion and decreased in blood volume
What is the effect of standing on blood flow (3)
Increased hydrostatic pressure
Reduced VR, EDV, SV, CO and MAP
Decreased baroreceptor firing rate
What is the consequence if increased hydrostatic pressure
Pooling of blood in veins/venules of feet and legs
What is the Valsalva manoeuvre
Forced expiration against a closed glottis
What effect does the Valsalva manoeuvre have on the thoracic pressure
It increases it and this is transmitted through the aorta
An increase in thoracic pressure means (5)
Decrease in venous return Decrease in EDV Decrease in SV Decrease in CO Decrease in MAP
Phase 1 VM
Increase in intrathoracic pressure becomes positive due to compression of the thoracic organs
Impeded venous return
Decreases preload
Phase 2 VM
Aortic pressure begins to fall due to reduced cardiac output as a result of reduced pre-load
Phase 3 VM
Person starts to breath normally again and aortic pressure briefly decreases and HR increases reflexively
Phase 4-5 VM
Increase in aortic pressure as the CO suddenly increases in response to a rapid increase in cardiac filling (damned blood build up)
