Dr Gawad Physiology Course Online Exam - CVS – Course Lecture 2 – Excitability, Conductivity, Contractility

1. Within physiological limits, if the EDV is increased:

The force of cardiac contraction is increased.

The cardiac output is increased.

Starling's law is applicable.

All of the above.

2. The most rapid conduction velocity is present:

The SAN.

The AVN.

The ventricular muscle.

The Purkinje fibres.

3. About the cardiac conductivity, all the following is true except:

It is slowest in the AV node.

It is maximal in the Purkinje fibres.

It is slowest in the ventricular muscle.

It is decreased by vagal stimulation.

It occurs through modified cardiac muscle fibres.

4. In the AV conduction all the following is true except:

Conduction is the slowest.

Conduction is delayed.

Conduction is usually difficult in the ventriculo-atrial direction.

Conduction is enhanced by sympathetic stimulation.

5. The fibres of the A-V bundle & its branches :

Conduct impulses very slowly.

Are highly contractile.

Are modified muscle fibres.

Are nerve fibres

A & c

6. About cardiac contractility all the following is true except:

It depends on the interaction between actin and myosin.

It increases when the serum K+ rises above normal.

It is lost if the bathing medium is made calcium-free.

It needs ATPase activity during systole and diastole

7. The main function of the cardiac Purkinjie system is to :

Increase the speed of impulse conduction through the cardiac muscle.

Prevent premature ventricular beats.

Coordinate the valve movements with myocardial contraction.

Enable all parts of the ventricle to contract simultaneously.

Delay the systole until the ventricles fill.

8. Regarding cardiac cells excitability which is true:

ARP is too short

Tetany may occur on reptetive stimulation

Heart is applying all or none rule

None of the above