Read the following statements (i - iv) about human heart :
(i) Human heart is myogenic and our body has the ability to alter the heart rate , cardiac output but not stroke volume.
(ii) P - wave in ECG marks the atrial systole .
(iii) Adrenal medullary hormones acts on SA node and increases heart rate.
How many statement is/are correct form the above ?

Options

A. Four
B. Three
C. Two
D. One

Answer

To solve the question, let's analyze each statement about the human heart one by one:

### Step 1: Analyze Statement (i)
**Statement (i):** "Human heart is myogenic and our body has the ability to alter the heart rate, cardiac output but not stroke volume."

- The human heart is indeed myogenic, meaning it generates its own electrical impulses for contraction.
- The body can alter heart rate and cardiac output through various mechanisms (like hormonal regulation and neural control).
- However, the statement claims that stroke volume cannot be altered, which is incorrect. Stroke volume can also be influenced by factors such as venous return and contractility.

**Conclusion for Statement (i):** Incorrect.

### Step 2: Analyze Statement (ii)
**Statement (ii):** "P-wave in ECG marks the atrial systole."

- The P-wave on an electrocardiogram (ECG) represents the depolarization of the atria, which leads to atrial contraction (systole).
- Therefore, this statement is correct.

**Conclusion for Statement (ii):** Correct.

### Step 3: Analyze Statement (iii)
**Statement (iii):** "Adrenal medullary hormones act on SA node and increases heart rate."

- Adrenal medullary hormones, primarily adrenaline (epinephrine) and norepinephrine, do indeed act on the SA node (sinoatrial node), which is the natural pacemaker of the heart.
- These hormones increase the heart rate by enhancing the rate of depolarization at the SA node.

**Conclusion for Statement (iii):** Correct.

### Final Conclusion:
- Statement (i) is incorrect.
- Statement (ii) is correct.
- Statement (iii) is correct.

Thus, **2 statements are correct** (statements ii and iii).

### Answer:
**2 statements are correct.**

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