Describe a simple reflex arc in terms of: receptor, sensory neurone, relay neurone, motor neurone and effector

SouravNovember 14, 2024

Answer

A simple reflex arc is a neural pathway that mediates a reflex action, allowing for rapid responses to stimuli without the need for conscious thought. It consists of several key components: the receptor, sensory neuron, relay neuron, motor neuron, and effector. Here’s a detailed description of each component:

1. Receptor

• Function: The receptor is the first component of the reflex arc and is responsible for detecting a specific stimulus (e.g., heat, pressure, or pain).
• Location: Receptors are located in sensory organs or tissues (such as skin, muscles, or internal organs).
• Example: In a withdrawal reflex, pain receptors in the skin detect a sharp object.

2. Sensory Neuron

• Function: The sensory neuron transmits the electrical impulse generated by the receptor to the central nervous system (CNS).
• Structure: Sensory neurons typically have a long dendrite that carries signals from the receptor to the cell body and a short axon that extends into the spinal cord.
• Example: In response to the detected stimulus, the sensory neuron carries the impulse towards the spinal cord.

3. Relay Neuron (Interneuron)

• Function: The relay neuron processes the incoming signal from the sensory neuron and connects it to the appropriate motor neuron.
• Location: Relay neurons are located within the CNS (specifically in the spinal cord or brain).
• Example: In a reflex arc, an interneuron may receive input from multiple sensory neurons and transmit it to one or more motor neurons.

4. Motor Neuron

• Function: The motor neuron carries impulses away from the CNS to effectors (muscles or glands) that will execute a response.
• Structure: Motor neurons typically have a long axon that extends from the spinal cord to the target muscle or gland.
• Example: In response to signals from relay neurons, motor neurons activate muscles to contract.

5. Effector

• Function: The effector is any muscle or gland that responds to the motor neuron’s signal, resulting in a physical action or change in function.
• Example: In a withdrawal reflex, muscles in the arm contract to pull away from a painful stimulus.

Summary of Reflex Arc Pathway

1. Stimulus (e.g., touching something hot) activates a receptor.
2. The sensory neuron transmits an impulse to the spinal cord.
3. The impulse is relayed through a relay neuron in the spinal cord.
4. The motor neuron transmits signals from the spinal cord to an effector.
5. The effector (e.g., muscle) responds by contracting or performing an action (e.g., pulling away from heat).