Select the option that correctly describes ECG phase

Options

A. P - wave - Depolarisation of the ventricles
B. P - wave - Depolarisation of the A node
C. QRS wave - Depolarisation of the ventricles
D. T - wave - Depolarisation of the atria

Answer

To solve the question regarding the correct description of ECG phases, we will analyze the components of an electrocardiogram (ECG) and determine which option correctly describes them.

### Step-by-Step Solution:

1. **Understanding ECG**:
- An electrocardiogram (ECG) is a recording of the electrical activities of the heart. It consists of different waves that represent various phases of heart activity.

2. **Identifying the Waves**:
- The main waves in an ECG are P wave, QRS complex, and T wave.
- Each of these waves corresponds to specific electrical events in the heart.

3. **P Wave**:
- The P wave represents **atrial depolarization**. This is the process where the atria (the upper chambers of the heart) contract and push blood into the ventricles.

4. **QRS Complex**:
- The QRS complex represents **ventricular depolarization**. This is when the ventricles (the lower chambers of the heart) contract to pump blood out of the heart.

5. **T Wave**:
- The T wave represents **ventricular repolarization**. This is the recovery phase of the ventricles after contraction, preparing them for the next heartbeat.

6. **Evaluating the Options**:
- Now, we need to evaluate the options provided in the question:
- **Option A**: P wave depolarization of ventricles - **Incorrect** (P wave is for atrial depolarization).
- **Option B**: P wave atrial depolarization - **Correct**.
- **Option C**: QRS wave depolarization of ventricles - **Correct**.
- **Option D**: T wave depolarization of atria - **Incorrect** (T wave is for ventricular repolarization).

7. **Conclusion**:
- The correct descriptions of the ECG phases are:
- P wave: Atrial depolarization
- QRS complex: Ventricular depolarization
- T wave: Ventricular repolarization
- Therefore, the correct option that describes the ECG phase is **Option C**: QRS wave depolarization of ventricles.