L24 Coronary blood flow

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During exercise, why does the coronary blood flow increase 3 to 4 times?

To compensate for the decreased coronary blood flow during systole
To meet the increased energy demands of the heart (correct)
To allow for more efficient oxygen extraction by the coronary vessels
To reduce the risk of myocardial ischemia

What happens to coronary blood flow during systole in the left ventricle muscle?

It remains constant to ensure steady oxygen delivery
It fluctuates according to diastolic changes
It increases to provide more oxygen to the heart muscle
It falls to a low value due to compression of blood vessels by muscle contraction (correct)

Why is the subendocardial portion of the left ventricle the most common site of myocardial ischemia and infarction?

It has higher O2 consumption at rest
It receives the least amount of coronary blood flow
It has fewer anastomoses between large arteries (correct)
It has a high rate of O2 extraction ratio

Why does a narrowed coronary vessel with atherosclerosis lead to severe angina pain during exertion?

Decreased blood supply due to narrowed vessel with exertion (A) Signup and view all the answers

What percentage of the total cardiac output is directed towards coronary blood flow during resting conditions?

5% (D) Signup and view all the answers

In coronary arteries, what is the function of anastomosis?

To provide alternative routes for blood flow in case of blockages (D) Signup and view all the answers

What characterizes coronary arteries as functionally END arteries?

Lack of sufficient anastomosis between large arteries (C) Signup and view all the answers

During which phase of the cardiac cycle does blood flow rapidly through the coronary arteries?

Diastole (A) Signup and view all the answers

What is the primary control mechanism for coronary blood flow?

Metabolic factors (B) Signup and view all the answers

Which of the following metabolites is NOT involved in the regulation of coronary blood flow?

Lactic acid (C) Signup and view all the answers

What is the mechanism behind autoregulation of coronary blood flow?

Myogenic activity (D) Signup and view all the answers

Within what range of mean arterial pressure does autoregulation maintain consistent coronary blood flow at rest?

60-160 mm Hg (D) Signup and view all the answers

Which of the following statements about coronary blood flow is TRUE?

Blood flow to the right ventricle decreases during diastole due to the low force of contraction. (A) Signup and view all the answers

Which of the following is NOT a factor affecting coronary blood flow?

Respiratory factors (C) Signup and view all the answers

Which of the following statements accurately describes the origin of the coronary arteries?

The right and left coronary arteries arise from the aorta just above the aortic valve. (A) Signup and view all the answers

Which of the following statements accurately describes the distribution of the right coronary artery?

The right coronary artery supplies the right atrium, right ventricle, posterior interventricular septum, and posterior part of the left ventricle. (D) Signup and view all the answers

Which of the following statements accurately describes the distribution of the left coronary artery?

The left coronary artery supplies the left atrium, left ventricle (anterior and lateral walls), and anterior interventricular septum. (D) Signup and view all the answers

Which of the following statements accurately describes the venous drainage of the heart?

The major venous drainage of the heart is through the coronary sinus, which opens into the right atrium. (D) Signup and view all the answers

Which of the following statements accurately describes the capillary density in the heart?

The capillary density in the heart is extremely high, exceeding 3000/mm^2, compared to 400/mm^2 in skeletal muscle. (A) Signup and view all the answers

Which of the following statements accurately describes the effect of systole on the blood flow in the subendocardial plexus?

The blood flow in the subendocardial plexus is reduced during systole because the intramuscular coronary vessels are compressed by ventricular muscle contraction. (C) Signup and view all the answers

Which of the following statements accurately describes a characteristic of the coronary vessels?

The orifices of coronary vessels are always open due to the current of blood flow. (B) Signup and view all the answers

Which of the following statements accurately describes the relationship between arterial blood pressure (ABP) and coronary blood flow?

Decreased ABP leads to decreased coronary flow, causing coronary artery dilation to increase flow back to normal. (D) Signup and view all the answers

During which phase of the cardiac cycle is the coronary blood flow to the left ventricle maximal?

Ventricular diastole (C) Signup and view all the answers

Which of the following statements accurately describes the direct effect of sympathetic stimulation on coronary vessels?

Sympathetic stimulation causes vasoconstriction of the coronary vessels through stimulation of α-adrenergic receptors. (C) Signup and view all the answers

Which of the following hormones causes direct coronary vasoconstriction?

Both B and C (C) Signup and view all the answers

Which of the following statements accurately describes the effect of parasympathetic stimulation on coronary vessels?

Parasympathetic stimulation causes indirect vasodilation of coronary vessels by decreasing metabolites. (C) Signup and view all the answers

During which phase of the cardiac cycle is the coronary blood flow to the right ventricle maximal?

Rapid ejection (systole) (C) Signup and view all the answers

What percentage of oxygen is typically extracted from the coronary arteries by the heart at rest?

50% (A) Signup and view all the answers

Which of the following statements accurately describes the effect of catecholamines on coronary blood flow?

Catecholamines increase cardiac activity, leading to increased metabolites and coronary vasodilation. (C) Signup and view all the answers

Which of the following statements accurately describes the characteristics of the coronary blood vessels?

Coronary blood vessels have a thick muscular wall and are highly innervated. (A) Signup and view all the answers