1. If cardiac muscle is deprived of its normal blood supply, damage would primar

Question

1.        If cardiac muscle is deprived of its normal blood supply, damage would primarily result from:

A.         a lack of blood cells to feed into metabolic pathways.

B.         a decrease in the number of available mitochondria for energy production.

C.         decreased delivery of oxygen.

D.         an inadequate supply of lactic acid.

2.        In comparing the right and left ventricular systems, the volume of blood pumped by each is

A.        similar, but the pressure generated in the adjacent arteries is much higher for the right ventricle

B.        similar, and the pressure generated in the adjacent arteries is the same

C.         similar, but the pressure generated in the adjacent arteries is much lower for the right ventricle

D.        different, with the right ventricle pumping considerably more blood for each stroke

3.        Which of the following is not a vasodilator

A.        bradykinin

B.         angiotensin II

C.        atrial natriuretic factor

D.        nitric oxide

E.        nitroglycerin

4.        Decreasing the radius of a blood vessel twofold will increase the resistance to blood flow

A.        three

B.         sixteen fold

C.        four fold

D.        eight fold

5.        Which one of the following normally does not carry highly oxygenated blood

A.        pulmonary veins

B.        aorta

C.        renal artery

D.        pulmonary artery

6.        One difference between atrial contraction and ventricular contraction is that

A.        atrial contraction is delayed and involves conducting-system fibers

B.        ventricular contraction is faster than atrial, and involves conducting-system fibers

C.         ventricular contraction is delayed and involves conducting-system fibers

D.        atrial contraction is initiated by the AV node while ventricular contraction is initiated by the SA node

7.        The initial depolarization for initiating a heart beat originates in the

A.        AV node

B.        Brain

C.        CNS

D.         SA node

8.        A person with a heart rate of 60 beats/ minute and a stroke volume of 85 ml will have a cardiac output of

A.        51.1 L/min

B.        3.06 L/min

C.        510 ml/min

D.         5.1 L/min

Explanation / Answer

1. Answer: C

Since decreased blood supply leads to decreased delivery of oxygen causing hypoxia. Also, the decreased blood supply leads to decreased supply of metabolic substrates to the cardiac muscle which depends largely on aerobic metabolic pathways to generate ATP/energy. Though cardiac muscle can use up stored glycogen via the anaerobic pathway, it is inefficient in times of hypoxia.

2. Answer: C

Both the right and left ventricles eject almost equal volumes of blood but the pressure in arteries adjacent to the right ventricle is considerably lower since a low arterial pressure has to be maintained upto the lungs for effective gaseous exchange.

3. Answer: B

Angiotensin II is a vasoconstrictor. All the others are examples of vasodilators.

4. Answer: B

The resistance of a vessel is inversely proportional to the fourth power of the radius of the vessel.

5. Answer: D

Pulmonary artery carries deoxygenated blood from the right venricle to the lungs.

6. Answer: C

Atrial contraction is initiated by the SA node and occurs prior to ventricular contraction.

7. Answer: D

Depolarization of the SA node initiates a heart beat.

8. Answer: D

Cardiac Output is calculated using the formula: Cardiac Output(L/min) = Stroke Volume x Heart rate

Hence, the answer is D

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