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. Option1 Four
B. Option2 Three
C. Option3 Two
D. Option4 One

Answer

To determine how many statements about the human heart are correct, we will analyze each statement 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 that it generates its own electrical impulses to initiate contraction. This is primarily due to the sinoatrial (SA) node.
- However, the statement claims that the body cannot alter stroke volume. This is incorrect. The body can alter stroke volume, especially during physical activity or exercise, to meet the increased demand for blood. Therefore, this statement is **incorrect**.

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

- The P-wave in an electrocardiogram (ECG) represents the depolarization of the atria, which is followed by atrial contraction (systole). Therefore, this statement is **correct**.

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

- Adrenal medullary hormones, primarily adrenaline (epinephrine) and noradrenaline (norepinephrine), are released during stress and they do act on the SA node to increase heart rate. Thus, this statement is also **correct**.

### Conclusion
- From the analysis:
- Statement (i) is **incorrect**.
- Statement (ii) is **correct**.
- Statement (iii) is **correct**.

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

### Final Answer
The number of correct statements is **2**.

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