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Reflex Actions

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Reflex action is an involuntary and automatic response to a specific stimulus. Reflex action is a type of behavior that is not consciously controlled by the brain, but rather, it is mediated by the spinal cord and peripheral nerves. Reflex action is an essential survival mechanism that allows an organism to respond quickly to potentially harmful stimuli. Understanding reflex actions is essential for healthcare professionals, as reflex testing can provide valuable information about the function of the nervous system.

What is Reflex Action?

The word ‘reflex’ means any sudden action. Reflex action is an automatic, rapid, spontaneous protective quick response or reaction to a stimulus without being under control. Example- blinking of eyes, touching a flame, and then withdrawing hand. In general, it provides a protective pathway to prevent any injury, this action response prevents pain.

When a reflex action occurs, a sensory receptor present in the body detects a stimulus, such as heat, pain, or pressure. The receptor then sends a signal along a sensory neuron to the spinal cord. In the spinal cord, the signal is relayed to an interneuron, which in turn activates a motor neuron. The motor neuron sends a signal to the muscles, causing them to contract and produce a reflexive response. Reflex actions occur quickly, often within milliseconds of a stimulus being detected, and they are a fundamental aspect of the body’s defense mechanisms.

Reflex Action Example

A hungry mouth started watering, touching a flame, touching a needle, touching a cold object, when light acts as a stimulus, the pupil of the eye changes in size, the sudden withdrawal of leg when pricked by a pin, coughing or sneezing because of irritation in nasal passages, etc. How does our body respond to these actions? and the main question is how long will it take us to think about all this? and how our bodies solve these problems. These all questions arise the concept of  ‘reflex arc’.

Reflex Action Diagram

Reflex Action Diagram


What is Reflex Arc?

The process that controls reflex action is known as the reflex arc.

Let us understand this with the example of the sensation of heat, a nerve that detects heat connected to the nerves that move muscles more simply, the process of detecting the signal- input and response to it by output action completely quickly. Such connections are called reflex arcs. Reflex arcs are formed in the spinal cord, and the input information in form of signals goes to the brain. The reflex arc is also seen in animals because the thinking process of the brain in animals is not fast enough.

Reflex Action Pathway                                                  

Stimulus ——> Receptor (skin) —-sensory neurons—-> Spinal Cord —-motor neurons—-> Effectors (like Muscle and Glands)

The Action of Neuron 

 In a reflex action, 2 types of nerves are included those are efferent (excitatory) and afferent nerves(receptor). Both nerves work together to make any reflex action. Reflex action occurs in a series of events which are mentioned below:

  1. Any reflex action start when the afferent serve receives any signal due to any sudden change in the surrounding, here the instinct play its role. Stimulus is received bt the receptor nerves
  2. Afferent nerves are active after getting the stimulus they pass the information to the relay neves.
  3. The relay nerve passes the information to the motor neurons.
  4. Motor neurons send the signal or activate the efferent nerves.
  5. Effector’s nerves react according to the information. 

Afferent nerves active from the signals come from the sensory organ, which transfers the information via signals to the Central Nervous System. Efferent nerves give signals to the muscles to react accordingly according to the signal. Here spinal cord gives information to react or behave instead of the brain in Reflex action.

FAQs on Reflex Action

Q1: What is reflex actions?


The involuntary and sudden response to the surrounding stimuli is known as reflex action. It is the adaptive system to protect the organims from the external body harm.

Q2: What are the two main types of reflexes?


The two main type of relexes are those are:

  • Autonomic Reflex Arc
  • Somatic Reflex Arc

Q3: Why reflexes are important?


Reflexes are important as they help to protect the organisms if there are any harmful stimuli present in the surrounding. Reflexes are essential for protecting our bodies from harm. For example, the blink reflex helps protect our eyes from potentially harmful objects or substances.

Q4: What is Reflex Arc?


The reflex arc is a way which controls the reflexes. 

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Last Updated : 10 Apr, 2023
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