Describe simple reflex arcs in terms of receptor, sensory neurone, relay neurone, motor neurone and effector (muscles and glands)

SouravNovember 3, 2024

Answer

A simple reflex arc is a neural pathway that enables a rapid response to a stimulus, involving several key components: receptor, sensory neuron, relay neuron, motor neuron, and effector. Here’s a breakdown of each component and its role in the reflex arc:

Components of a Simple Reflex Arc

1. Receptor:
   • The receptor is a sensory structure that detects a specific stimulus (e.g., heat, pressure, or pain). It converts the stimulus into an electrical signal (action potential) that initiates the reflex action. For example, skin receptors can detect touch or temperature.
2. Sensory Neuron:
   • Once the receptor has detected the stimulus, the sensory neuron transmits the electrical signal from the receptor to the central nervous system (CNS). This neuron carries information in an afferent direction, meaning it brings sensory input to the spinal cord or brain.
3. Relay Neuron (Interneuron):
   • In many reflex arcs, particularly those involving more complex responses, a relay neuron processes the information within the CNS. It connects the sensory neuron to the motor neuron. This component allows for integration and processing of the sensory input, although in simpler reflexes, this step may be bypassed.
4. Motor Neuron:
   • The motor neuron transmits signals away from the CNS to an effector. It carries information in an efferent direction, sending commands that will result in a physical response.
5. Effector:
   • The effector is typically a muscle or gland that responds to the motor neuron’s signal. When stimulated, muscles contract (producing movement), and glands secrete substances (such as hormones or enzymes). For example, in a knee-jerk reflex, the effector would be the quadriceps muscle that contracts to extend the leg.

Summary of Reflex Arc Function

The reflex arc operates as follows:

• A stimulus is detected by a receptor.
• The sensory neuron transmits this information to the spinal cord.
• If present, a relay neuron processes this information and connects it to a motor neuron.
• The motor neuron sends an impulse to an effector.
• The effector executes a response (e.g., muscle contraction or gland secretion).