Sunday, 22 December 2013

Physiology

Physiology Updates:
Heart receives <5% (4.7%) of cardiac output at rest
• Coronary blood flow is 250mL/min at rest- this can increase by 200-300% (500- 750mL/min)
• In terms of per 100g/ min, coronary blood flow- 84mL/100g/min (blood flow in resting skeletal muscle is 3- 4mL/100g/min; increases to 50 to 80mL/100g/min during exercise)
• Heart is a hard working organ (”thank God”), needs a lot of oxygen!
• Basal oxygen consumption (ref Ganong pg 550
24th edi)- 2mL/100g/min (much more than the oxygen consumption by resting skeletal muscle,
which is 0.2mL/100g/min)
• Oxygen consumption by a beating heart-
9mL/100g/min
• At rest heart extracts 70-80% of the oxygen
from each unit of blood delivered to it (“heart is the organ with maximum oxygen extraction at rest”).
So whenever there is an increase in oxygen
demand coronary blood flow will also show an increase.

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