Which is the correct sequence of the compounds of a reflex arc

Options

A. Receptors`to`Muscles `to`Sensory neuron `to`Motor neuron`to` Spinal cord
B. Receptors`to` Motor neuron `to`Spinal cord`to` Sensory neuron`to`Muscle
C. Receptors`to` Spinal cord`to`Sensory neuron`to` Motor neuron`to` Muscle
D. Receptors`to`Sensory neuron `to`Spinal cord`to` Motor neuron `to`Muscle

Explanation

To answer the question about the correct sequence of the compounds of a reflex arc, we can break down the process step by step:

### Step-by-Step Solution:

1. **Stimulus Detection**: The reflex arc begins when a stimulus is detected by sensory receptors. For example, when you touch a hot plate, thermoreceptors in your skin detect the heat.

2. **Signal Transmission via Sensory Neurons**: Once the receptors detect the stimulus, they generate a nerve impulse. This impulse is transmitted through sensory neurons to the spinal cord.

3. **Integration in the Spinal Cord**: The sensory neurons connect to interneurons in the spinal cord. Here, the information is processed, and a decision is made to respond to the stimulus.

4. **Response Transmission via Motor Neurons**: The spinal cord sends a signal through motor neurons to the muscles involved in the reflex action. In our example, the motor neurons send a signal to the muscles of the hand.

5. **Muscle Response**: Finally, the muscles receive the signal and contract, pulling the hand away from the hot plate. This is the reflex action.

### Correct Sequence of Components of a Reflex Arc:
- Receptor (thermoreceptors)
- Sensory Neuron
- Spinal Cord (interneurons)
- Motor Neuron
- Effector (muscle)

Thus, the correct sequence of the compounds of a reflex arc is: **Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector (Muscle)**.