Go through the following statements
(i) the peripheral chemoreceptors for regulation of respiration are located in carotid veins and arch of aorta
(ii) the primary effect of pneumotaxic centre is to control the switch off point of inspiratory signal and thus limit inspiraton
(iii) the chemosensitve area for brain for respiratory control is highly sensitive to `O_(2)` concentration
(iv) In case of fetal haemoglobin the oxygen haemoglobin dissociation curve is shifted toward left
which of these are correct ?
(a) i, ii & iv
(b) ii and iv
(c) ii, iii & iv
(d) iii and iv

Options

A. (a) i, ii & iv
B. (b) ii and iv
C. (c) ii, iii & iv
D. (d) iii and iv

Explanation

To determine which statements about the regulation of respiration are correct, we will analyze each statement one by one.

### Step 1: Analyze Statement (i)
**Statement:** The peripheral chemoreceptors for regulation of respiration are located in carotid veins and arch of aorta.

**Analysis:**
- Peripheral chemoreceptors are indeed involved in the regulation of respiration, but they are located in the carotid arteries and the arch of the aorta, not in the carotid veins. Therefore, this statement is incorrect.

### Step 2: Analyze Statement (ii)
**Statement:** The primary effect of pneumotaxic centre is to control the switch off point of inspiratory signal and thus limit inspiration.

**Analysis:**
- This statement is correct. The pneumotaxic center, located in the pons, helps regulate the duration of inspiration by controlling the switch-off point of the inspiratory signal, thus limiting the length of each breath.

### Step 3: Analyze Statement (iii)
**Statement:** The chemosensitive area for brain for respiratory control is highly sensitive to O₂ concentration.

**Analysis:**
- This statement is incorrect. The chemosensitive area in the brain is primarily sensitive to carbon dioxide (CO₂) levels rather than oxygen (O₂) levels. It responds to changes in CO₂ concentration to regulate breathing.

### Step 4: Analyze Statement (iv)
**Statement:** In case of fetal hemoglobin, the oxygen hemoglobin dissociation curve is shifted toward left.

**Analysis:**
- This statement is correct. Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin, which results in a leftward shift of the oxygen-hemoglobin dissociation curve. This allows the fetus to extract oxygen from maternal blood more effectively.

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

### Final Answer
The correct option is **(b) ii and iv**.

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