Control of arterial blood pressure 1 (CVS7) Flashcards
blood pressure
-blood pressure is the outwards/hydrostatic pressure exerted by the blood on the blood vessel walls
how is blood pressure often measured clinically
by measuring the systemic arterial blood pressure
what can systemic arterial blood pressure be expressed as
- systolic blood pressure
- diastolic blood pressure
systemic arterial blood pressure =
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
systemic arterial blood pressure under resting conditions
should not normally reach or exceed 90mmHg under resting conditions
values on graph of arterial pressure against time when blood pressure
- systolic pressure (SBP) is the peak of the curve (120mmHg)
- diastolic pressure (DBP) is the dip in the curve (80mmHg)
- mean pressure= approx 93mmHg at rest (DBP + 1/3 pulse pressure)
- pulse pressure= 120-80= 40mmHg
pulse pressure
difference between systolic and diastolic blood pressure
mean arterial blood pressure (MAP)
average blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart
why is average arterial blood pressure (MAP) not obtained by averaging the systolic and diastolic pressures
because during a normal cardiac cycle, the relaxation (diastolic) portion of the cardiac cycle is about twice as long as the contraction (systolic) portion of the cardiac cycle
how is MAP estimated
-MAP= [(2xsystolic) + diastolic] divided by 3
or
-can be estimated by adding DBP + 1/3 pulse pressure (diff between SBP and DBP)
normal values of arterial blood pressure (SBP and DBP)
-
normal range of MAP
about 70-105mmHg
minimum value of MAP that is ESSENTIAL to perfuse coronary arteries, brain and kidneys
- at least 60mmHg
- if MAP drops below 60mmHg, organs wont be receiving enough oxygen and nutrients
blood supply to the heart
via coronary arteries
why does MAP need to be regulated within a narrow range
- to ensure pressure is high enough to perfuse internal organs including the brain, heart and kidneys
- to ensure pressure is not too high to damage the blood vessels or place an extra strain on the heart
relationship between MAP, CO and TPR
MAP= CO x TPR
= (SV x HR) x TPR
MAP
mean arterial blood pressure
TPR
- total peripheral resistance
- sum of resistance of all peripheral vasculature in the systemic circulation