Question

1. The T wave in an ECG signifies atrial depolarization.

True

False

2. All cardiac cells are self-excitable.

True

False

3. The brain causes the heart to beat.

True

False

4. An ECG can predict whether you're going to have a heart attack up to 30 minutes after having an ECG.

True

False

Answer 1

1) FALSE

Electrocardiogram is a picture of the electrical conduction of the heart. In a physiologically normal person there are 6 waves on the ECG, i.e. P,Q,R,S & T wave.

The P wave indicates atrial depolarization. The QRS complex consists of a Q wave, R wave and S wave and represents ventricular depolarization. The T wave indicates VENTRICULAR REPOLARIZATION.

2) FALSE

The human heart consists of two types of muscle cells:

• Myocardial contractile cells: It constitute the bulk of the cells in the atria and ventricles. These cells contract on receiving impulse and helps in pumping blood from the hear to either pulmonary or systemic circulation.
• Myocardial conducting cells: Cells are self-excitatory and form the conduction system of the heart. These initiate and propagate the electrical impulse that travels throughout the heart and trigger the contractile cells.

So all cardiac cells are not self excitatory.

3) FALSE

The human heart is autorythmic in nature. It has self excitatory cells that causes the heart beat. The brain doesn't cause the heart to beat. Rather it may regulate the heartbeats by the sympathetic or parasympathetic nervous system, thus increasing or decreasing the heart rate.

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