Any damage or injury to a particular area causes nociceptors to release some chemicals, which carry the signal to the higher centres in the nervous system for the processing and a subsequent action. However, there is a difference in the way in which the stimulus is received which is related to the acuity of the detection. Fingertips are more sensitive as compared to the forearm. Following reasons for the observed phenomenon were suggested.
i. The receptive fields in the fingertip are smaller.
ii. The number of nociceptors per receptive field in the forearm is lesser.
iii. The amount of prostaglandins released by the nociceptors per receptive field is more in fingertips.
The most probable reason(s) for this may be:

Options

A. i
B. i,iii
C. ii,iii
D. i,ii,iii

Explanation

To solve the question regarding the sensitivity of fingertips compared to the forearm, we need to analyze the given statements and determine which ones are correct based on the physiological characteristics of nociceptors and receptive fields.

### Step-by-Step Solution:

1. **Understanding Nociceptors**:
- Nociceptors are sensory receptors that respond to potentially damaging stimuli by sending signals to the spinal cord and brain. They play a crucial role in the sensation of pain.

2. **Sensitivity of Fingertips vs. Forearm**:
- The question states that fingertips are more sensitive than the forearm. This sensitivity can be attributed to several factors related to the structure and function of nociceptors.

3. **Analyzing the Statements**:
- **Statement i**: "The receptive fields in the fingertip are smaller."
- This statement is true. Smaller receptive fields allow for more precise localization of stimuli, which contributes to increased sensitivity.

- **Statement ii**: "The number of nociceptors per receptive field in the forearm is lesser."
- This statement is also true. The density of nociceptors is higher in the fingertips compared to the forearm, which enhances sensitivity in the fingertips.

- **Statement iii**: "The amount of prostaglandins released by the nociceptors per receptive field is more in fingertips."
- This statement is misleading. While nociceptors can release prostaglandins, the amount released is not necessarily greater in the fingertips than in the forearm. The sensitivity is more related to the density of nociceptors rather than the quantity of prostaglandins.

4. **Conclusion**:
- Based on the analysis, the correct reasons for the increased sensitivity of the fingertips compared to the forearm are statements i and ii. Therefore, the most probable reasons for the observed phenomenon are:
- **i** and **ii** are correct.

### Final Answer:
The most probable reason(s) for the observed phenomenon is:
- i. The receptive fields in the fingertip are smaller.
- ii. The number of nociceptors per receptive field in the forearm is lesser.