Purkinje fibers are the part of the nodal tissue of the human heart that
1. are specialized cardiac muscle cells.
2. conduct impulses much more slowly than ordinary cardiac muscle.
3. conduct action potentials through the atria.
4. connect between the SA node and the AV node.

T waves on an ECG represent
1. depolarization of the ventricles.
2. repolarization of the ventricles.
3. depolarization of the atria.
4. repolarization of the atria.

The period of the cardiac cycle where the greatest amount of ventricular filling occurs is:
1. the first one-third of diastole.
2. the middle one-third of diastole.
3. the last one-third of diastole.
4. ventricular systole.

The semilunar valves will open during a normal cardiac cycle when the pressure in the left ventricle is
1. greater than the pressure in the aorta.
2. less than the pressure in the aorta.
3. the same as the pressure in the aorat.
4. less than the pressure in the left atrium.

Stroke volume is the
1. amount of blood pumped by the left ventricle per minute.
2. difference between end-diastolic and end-systolic volume.
3. difference between systolic and diastolic blood pressure.
4. amount of blood pumped by atrial systole into the ventricles.

Cardiac output is defined as
1. blood pressure X stroke volume.
2. peripheral resistance X heart rate.
3. heart rate X stroke volume.
4. Systolic pressure – diastolic pressure.

Also sometimes called as the ‘widow maker’ the anterior interventricular artery is a branch of the
1. left circumflex artery.
2. right anterior descending artery.
3. left coronary artery.
4. right coronary artery.

What is most likely to happen if the SA node suddenly stops generating the impulse?
1. The heart will stop.
2. The ventricles will contract, but the atria will stop.
3. Another part of the heart, possibly the AV node, will become the pacemaker.
4. The atria will keep contracting, but the ventricles will stop.

Identify the correct statement regarding the cardiac muscle:
1. Cardiac muscle does not have sarcoplasmic reticulum.
2. Cardiac muscle has a plateau phase in repolarization called the plateau phase.
3. Cardiac muscle has a shorter refractory period than skeletal muscle.
4. Depolarization of cardiac muscle occurs when ${\mathrm{K}}^{+}$ and ${\mathrm{Na}}^{+}$ diffuse into the cell.

A slower heart rate or bradycardia would most likely be the result of:
1. ectopic action potentials in the atria
2. damage to the tricuspid valve
3. excessive sympathetic stimulation
4. excessive parasympathetic stimulation