Flashcards in Control of Cardiac Function Deck (22):
What is the total oxygen consumption of the body?
250ml of oxygen a minute
What is the total oxygen consumption by the brain?
50ml of oxygen a minute
How is a constant flow of oxygen to the brain achieved?
By a constant blood pressure and a constant partial pressure of oxygen
What is the formula for ABP?
ABP = TPR x CO
What controls total peripheral resistance?
Blood vessel diameter
What is the formula for CO?
CO = HR x SV
What is the stroke volume otherwise known as?
The force of contractility
What is the normal stroke volume
70ml of blood per beat
How do you work out stroke volume?
EDV - ESV
What is the normal heart rate?
What is the total cardiac output?
70ml x 70bmp = 4900ml = about 5L/min
What is the regular blood pressure?
What is intrinsic regulation?
How the heart functions without an stimulus from the outside (neural or hormonal)
In an isolated heart what is the heart rate and where is it generated?
70bpm generated in the sino atrial node
If the sino atrial node is removed where is the heart beat generated and what is the rate?
In the atrio-ventricular node and is 60bpm
If the sino atrial node and the atroventricular node are both removed in the isolated heart where is the heart beat generated and what is the rate?
In the ventricular muscle at 30bpm
What does starlings law of the heart state about the contractility of the heart?
The more you stretch the heart the greater the force of contraction (stroke volume)
What is preload?
Venous return - the volume of blood coming back to the heart that has to be pumped out again
What happens when preload is increased?
The amount of blood returning to the heart (venous return) increases so the end diastolic volume increases so the heart is stretched more and the force of contraction is greater
What is afterload?
the pressure the left ventricle must pump against inorder to get blood into the aorta
What happens when afterload is increased?
The contractility of the heart increases due to the stretch of the left ventricle being greater by more blood coming in and so produces a greater stroke volume to pump it out again