Simple Reflex Arc

There is no cognitive regulation of the brain during the entire reflex action mechanism. The stimulation of peripheral nervous system leads to spontaneous response. The spinal cord and brain stem collectively control the reflex actions.

Several essential components comprise the entire reflex action process. They are sensory neurons, motor neurons, effector neurons, associated neurons, receptor organs, and nerve centres.

Table of Contents

Definition

The neural network that manages a reflex is known as a reflex or simple reflex arc. In vertebrates, most sensory neurons synapse in the spinal cord rather than entering the brain directly. By activating the spinal motor neurons, faster reflex actions can be induced without waiting for signals to travel to the brain. The processing of the signal occurs after the reflex action, while the input to the brain occurs as the reflex has been carried out.

There are two reflex arcs — somatic reflex arc, which affects the internal organs of the body, and autonomic reflex arc, affecting the muscles. Some somatic reflexes are more brain-mediated, while certain autonomic reflexes often involve spinal cord mediation.

Reflex Arc Components

Sensory neurons (receptors) are the primary elements of the reflex arc. After being stimulated, these neurons connect to other neurons, activating muscle cells, also known as effectors, which carry out the reflex action.

In a reflex arc, sensory, relay, and motor neurons are the three basic types of neurons.

  • Sensory neurons deliver signals from sensory organs to the CNS (brain or spinal cord).
  • Relay neurons are located within the CNS, connecting sensory and motor neurons.
  • Motor neurons transmit signals from the CNS to the effectors (glands or muscles).

This reflex arc involves three different types of neurons, but it can alternatively be a two-neuron arc in which the receptor establishes direct contact with the motor neuron. Simple reflexes are rapid, brief, automatic, and involve only a small portion of the body in a two-neuron arc.

Simple reflexes include the contraction of a muscle in reaction to stretching, salivation at the view of food, and blinking of eyes when the cornea is touched. These types of reflexes often help maintain homeostasis.

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Frequently Asked Questions – FAQs

Q1

What is a reflex action?

A reflex action or reflex is an involuntary movement that occurs almost instantly in reaction to stimuli. Reflex actions are carried out via the reflex arc, a neural pathway that regulates reflexes. The sensory neurons receive signals from the sense organ and transmit them via other connected neurons. The sense organ that detects threats is the receptor.
Q2

How is the reflex arc formed?

A reflex arc is formed when impulses from the receptor travel to the spinal cord and are then translated into the proper reflex impulse and transmitted to the muscles. The impulse is not sent to the brain to speed up response time.
Q3

Why is swallowing not considered a simple reflex action?

Essentially an involuntary reflex, swallowing only occurs when there is saliva or another item to swallow. Initially, food is transported to the back of the oral cavity; however, once it has reached the back of the mouth, the reflex action to swallow takes control and prevents retraction.