Module 5 Section 6

Question 1

Describe the unique features of the coronary circulation.

Answer 1

The majority of blood flow doesn’t occur during ventricular systole, it actually occurs during ventricular diastole.

Systole

• When the ventricle is contracted, the vasculature within the walls of the heart are also constructed due to the force.
• The open aortic valve partially obstructs the entrance to the coronary circulation
• together, these events reduce the amount of blood that can flow during systole.

Diastole

• When the ventricular walls relax and the aortic valve closes, blood can freely flow into the coronary circulation.
• about 70% of the total blood flow to the coronary arteries occurs at this time.
• Coronary blood flow is matched to the hearts demands for 02

Question 2

Explain the oxygen demand of the heart and how it’s accommodated.

Answer 2

The heart extracts about 65% of the O2 at rear so it has a much smaller reserve.

To increase O2 delivery to the heart, coronary circulation must dilate. The signal that triggers this dilation is adenosine. When metabolic activity in the heart increase last and more ATP is consumed, adenosine is created and released. It acts like a paracrine hormone and causes the coronary circulation to dilate. This dilation allows more blood and thus more O2 to flow to the heart.

By this mechanism, cardiac O2 delivery is matched to its metabolic demand.

Question 3

Explain why you think free fatty acids are the preferred source of fuel for the heart.

Answer 3

Unlike skeletal muscle, the heart functions continuously in a regular rhythm of contraction and relaxation that’s almost exclusively aerobically. Free fatty acids are slow burning and easily stored making them the ideal fuel for the heart.

Question 4

What is the ejection fraction formula?

Answer 4

EF = SV / EDV