Go through the following statements
(i) Vagus nerve decreases the rate of impulse formation from the SA node and its conduction
(ii) As the human heart is myogenic in nature, the rate of formation and conduction of cariac impulse cannot be changed by the action of nerves
(iii) The end of T-wave in ECG marks the end of systole.
(iv) If the P-wave in ECG is inverted , it indicates that SA node fails to initiate impulse and the atrial muscle depolarises by the impulse originating in A.V. node.
Whic of these are correct ?

Options

A. (i),(ii) & (iii)
B. (i),(iii) & (iv)
C. (ii),(iii) & (v)
D. All are correct

Answer

To determine which statements about the human heart and its electrical activity are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement (i)
**Statement:** Vagus nerve decreases the rate of impulse formation from the SA node and its conduction.

**Analysis:** The vagus nerve is part of the parasympathetic nervous system, which indeed decreases the heart rate by inhibiting the activity of the SA node. This statement is **correct**.

### Step 2: Analyze Statement (ii)
**Statement:** As the human heart is myogenic in nature, the rate of formation and conduction of cardiac impulse cannot be changed by the action of nerves.

**Analysis:** While the heart is myogenic (meaning it can generate its own impulses), the rate of impulse formation can still be influenced by the autonomic nervous system, including the vagus nerve and sympathetic nerves. Therefore, this statement is **incorrect**.

### Step 3: Analyze Statement (iii)
**Statement:** The end of T-wave in ECG marks the end of systole.

**Analysis:** The T-wave in an ECG represents the repolarization of the ventricles, which occurs at the end of ventricular systole (the contraction phase). Thus, this statement is **correct**.

### Step 4: Analyze Statement (iv)
**Statement:** If the P-wave in ECG is inverted, it indicates that SA node fails to initiate impulse and the atrial muscle depolarizes by the impulse originating in A.V. node.

**Analysis:** An inverted P-wave suggests that the impulse is not originating from the SA node but rather from the AV node or another ectopic focus. This statement is also **correct**.

### Conclusion
Based on the analysis:
- **Correct Statements:** (i), (iii), and (iv)
- **Incorrect Statement:** (ii)

### Final Answer
The correct statements are (i), (iii), and (iv).

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