Download Properties of Cardiac muscle MCQ

Properties of Cardiac muscle (Dr.Hesham Khairy)
1. AS regarding the action potential of the cardiac muscle, phase II of
repolarization is caused mainly by:
A. Increased permeability to potassium with potassium outflox.
B. Increased permeability to sodium and rapid sodium influx.
C. Decreased permeability to potassium with increased calcium influx.
D. Closure of sodium channel and increased chloride influx.
2. The cardiac muscle is characterized by the following except:
A. Shorter and smaller than skeletal muscle.
B. Nuclei are in the periphery.
C. Rich in blood supply and mitochondria.
D. They form branching network connected by intercalated discs.
3. The excitability of the cardiac muscle is increased by the following factor except:
A. Hypokalemia.
B. Sympathetic stimulation.
C. Mild ischemia.
D. Catecholamines.
4. After complete atrioventricular block, the ventricular contractions are mostly
expected to be:
A. Above 150 beat/min.
B. 90-100 beat/min.
C. 40-60 beat/min.
D. 25 beat/min.
5. As regarding the conducting system of cardiac impulses, the part that has the
slowest conduction rate is:
A. S-A node.
B. A-V node.
C. Bundle of Hiss.
D. Purkinje system.
6. Hypercalcaemia could produce the following except:
A. Cardiac arrest during diastole.
B. Increases cardiac contractility.
C. Decreases the heart rate.
D. Decreases the conductivity of the catdiac muscle.
7. Digitalis has the following effects on the cardiac muscle except:
A. Decreases the conductivity of A-V node.
B. Increases the heart rate
C. Positive inotropic effect
D. Negative chronotropic effect.