Which of the following is not a component of the reflex arc?

Options

A. Receptor
B. Effector
C. Motor neuron
D. Plexus

Explanation

To determine which of the following is not a component of the reflex arc, we need to understand what a reflex arc consists of. A reflex arc is a neural pathway that controls a reflex action and typically includes the following components:

1. **Receptor**: This is the part that detects the stimulus (e.g., pain, heat).
2. **Sensory Neuron**: This transmits the signal from the receptor to the central nervous system (CNS).
3. **Integration Center**: This is usually located in the spinal cord or brain where the sensory neuron synapses with a motor neuron.
4. **Motor Neuron**: This carries the response signal from the CNS to the effector.
5. **Effector**: This is the muscle or gland that performs the response (e.g., moving a hand away from a hot surface).

Now, let's analyze the options provided:

- **Option A: Receptor** - This is a component of the reflex arc.
- **Option B: Effector** - This is also a component of the reflex arc.
- **Option C: Motor Neuron** - This is a necessary component of the reflex arc.
- **Option D: Plexus** - This term refers to a network of nerves or vessels in the body, and it is not a component of the reflex arc.

Based on this analysis, the correct answer is:

**The component that is not part of the reflex arc is: Plexus.**