Week 1 part 2 Flashcards
What is the mean arterial blood pressure?
The average arterial blood pressure during a single cardiac cycle
How is MAP calculated?
(2xdiastolic) +systolic /3
CO x TPR
HR x SV x TPR
A MAP of at least what is needed to perfuse the coronary arteries, brain and the kidneys?
60mmHg
What is the short-term regulation of the MAP?
Baroreceptor reflex
Where are the baroreceptors?
Aortic arch
Carotid sinus
What control mechanism prevents postural hypotension?
Baroreceptor reflex
If high blood pressure is sustained, what happens to baroreceptor firing?
It decreases (they re-set)
What is the long term control of MAP controlled by?
Blood volume
What are the hormones which regulate extracellular fluid volume?
Renin-Angiotensin-Aldosterone System
Atrial Natriuretic Peptide
Antidiuretic Hormone
Where is renin released from?
Kidneys
What does angiotensin II do?
Stimulates the release of aldosterone from the adrenal cortex
Causes systemic vasoconstriction (increases TPR)
Stimulates thirst
What does aldosterone do?
Increases sodium and water retention
What is the rate limiting step for RAAS? (renin-angiotensin-aldosterone pathway)
RENIN SECRETION
When is the atiral natriuretic peptide hormone released?
In response to atrial distension
What does atrial natriuretic peptide do?
Causes excretion of salt and walter in the kidneys
Reduces blood volume and blood pressure
What is the counter mechanism for the RAAS?
ANP
What do the angtiotensin II and antidiuretic hormones do to the vascular system?
Cause constriction of the blood vessels
What does adenosine do to arterioles?
Vasodilates them
What do histamine, bradykinin and nitric oxide do to the arteriolar smooth muscle?
Relax it causing VASODILATION
What do leukotrienes, thromboxane A2, endothelin and serotonin do to arterioles?
Vasoconstrict
What does an increase in vasomotor tone do?
Increases TPR and MAP
What does an increase in venomotor tone do?
Increases venous return, SV and MAP
How does sympathetic stimulation increase heart rate?
Iincreases the rate of firing of the SA node and decreases AV nodal delay
Increases force of contraction
