Lecture 04 Heart Physiology 3 Flashcards
1. Understand the heart as an endocrine organ 2. Understand myocardial contractility and how cardiac output is a function of stroke volume and heart rate 3. Describe how treatment is personalised to the patient
Why are the coronary arteries important? Where do they come from?
important to perfuse the heart so that it can function
from the first branch of the aorta
What is the structure of blood supply to the heart? Why is this important?
larger vessels run over the surface with arteries going from out to in
when the heart muscle contracts the arteries are compressed, cutting off its own blood supply
in diastole the muscles relax and coronary flow can occur again
How is coronary blood flow calculated?
perfusion pressure / resistance
coronary blood flow is proportional to perfusion pressure
coronary blood flow is inversely proportional to resistance
Why is the arterial resistance important?
small changes in resistance make large charges to flow
What factors determine the resistance?
length of the tubule
viscosity of the blood
diameter of the artery
What is the myocardial oxygen consumption (ml/min/100g) of a resting heart, muscle, brain, kidney and skin?
heart 8 muscle 1 brain 3 kidney 5 skin 0.2
What is the myocardial oxygen consumption (ml/min/100g) of a heart and muscle during heavy exercise?
heart 70
muscle 50
What is the equation linking force and radius?
force is proportional to r^4
How much perfusion does the heart receive via the coronary arteries?
around 5% of all cardiac output making it one of the worst perfused tissues in terms of the metabolic activity
How does the heart compensate for its poor perfusion?
the heart extracts a lot more oxygen that other organs/tissues
more efficient in its oxygen uptake from the blood
blood returning to the heart from the coronary veins is much more deoxygenated that blood returning from other parts of the body
How is cardiac oxygen delivery (mM) calculated?
arterial oxygen concentration x coronary blood flow
What determines oxygen delivery from the coronary arteries?
coronary blood flow - how much oxygen is bound to haemoglobin
What is the normal aortic blood pressure?
contraction/systole 120mmHg
relaxation/diastole 80mmHg
Remaining aortic pressure during diastole is linked to what valve?
aortic
What is the normal ventricular blood pressure?
contraction/systole 120mmHg
relaxation/diastole ~0mmHg