Which of the following statements are incorrect?

Options

A. (1) among all the four chambers of heart left ventricle has the thickest walls
B. (2) contraction of the ventricle in the heart begins by the command from SA node
C. (3) QRS complex in ECG is related with ventricular contraction and atrial relaxation
D. (4) human heart is myogenic

Answer

To determine which statements are incorrect, let's analyze each statement one by one:

1. **Statement 1**: "Among all the four chambers of the heart, the left ventricle has the thickest wall."
- The left ventricle indeed has the thickest wall compared to the other chambers because it needs to pump blood to the entire body, which requires more force.
- **Conclusion**: This statement is **correct**.

2. **Statement 2**: "Contraction of the ventricle in the heart begins by the commands from a node."
- The contraction of the ventricles is initiated by electrical signals from the sinoatrial (SA) node, which is often referred to as the pacemaker of the heart.
- **Conclusion**: This statement is **correct**.

3. **Statement 3**: "The QRS complex in ECG is related to ventricular contraction and RTL relaxation."
- The QRS complex represents the depolarization of the ventricles, which occurs just before ventricular contraction. However, it does not represent RTL relaxation; rather, it is associated with the contraction of the ventricles.
- **Conclusion**: This statement is **incorrect**.

4. **Statement 4**: "The human heart is myogenic."
- The human heart is indeed myogenic, meaning that its contractions are initiated by the heart muscle itself rather than by external stimuli.
- **Conclusion**: This statement is **correct**.

### Summary of Incorrect Statements:
- The only incorrect statement is **Statement 3**.