What is meant by a reflex arc in the nervous system?

Options

A. An inherited behaviour pattern, that functions through a certain neural pathway
B. A functional unit consisting of a receptor, neural pathway, and an effector
C. Peripheral nerves, spinal cords and brain
D. A homeostatic system of sensory nerves, synapses and motor nerves

Answer

### Step-by-Step Solution:

1. **Definition of Reflex Arc**: A reflex arc is a neural pathway that mediates a reflex action. It is a fundamental component of the nervous system that allows for quick responses to stimuli without the need for conscious thought.

2. **Components of a Reflex Arc**: The reflex arc consists of several key components:
- **Receptor**: This is the sensory organ or cell that detects a stimulus (e.g., heat, pressure).
- **Sensory Neuron**: Once the receptor detects a stimulus, it sends an electrical signal through the sensory neuron to the central nervous system (CNS).
- **Interneuron**: Within the CNS, the sensory neuron synapses with an interneuron, which processes the information and relays it.
- **Motor Neuron**: The interneuron then communicates with a motor neuron, which carries the signal away from the CNS.
- **Effector**: Finally, the motor neuron transmits the signal to an effector (e.g., muscle or gland) that carries out the response (e.g., moving a hand away from a hot surface).

3. **Function of Reflex Arc**: The primary function of a reflex arc is to enable rapid responses to stimuli, which is crucial for survival. For example, if you touch something hot, the reflex arc allows your hand to pull away quickly before the brain even registers the pain.

4. **Conclusion**: In summary, a reflex arc is a functional unit of the nervous system that includes a receptor, a neural pathway (sensory neuron, interneuron, motor neuron), and an effector, allowing for quick, involuntary responses to stimuli.