Reflex Action


In the human body, there are several instincts that prepare the individual for upcoming situations, which may seem to be harmful or harmless. However, depending on the pre-existing understanding and experiences the instincts are triggered within the human body. Instincts play quite a crucial role in protecting the individual. These instincts are known to be reflexes that are displayed by the human body at the time of need and most often these reflexes are gathered from responses. These responses are internalised from the accumulated knowledge or training procedures.

What is Reflex Action?

It is quite a common approach that is conducted by every organism, based on the changes in both their internal and external situations. For humans, certain functionalities are present that are carefully controlled by the CNS present within the body for survival. The reflex is a quick or rapid response that is involuntary in nature and is conducted by the body as a response to the immediate stimulus. The reflex seems to be a triggered response from the instincts that are noticed by the body.

This spontaneous action by the body is known as a reflex action. Before reaching to the brain, several neuronal pathways is present that tend to act as a response. The reason is because this kind of action is necessary for safeguarding the individual where no conscious thought process is required.

Examples of Reflex Action

Several examples are found for reflex actions that are conducted by the body that includes the following.

  • When suddenly a bright light comes into the eyes, automatically the eyes are closed.

  • If any particle enters the nasal chamber the body initiated mechanisms of sneezing or coughing in order to remove the irritant.

  • The notion of eye blinking in sudden responses, grasp reflex, sucking and rooting reflexes in infants, muscular defence in adults, patellar reflex and many more.

Defining Reflex Arc

Figure 1: Reflex Arc

The neural pathway that supports controlling all kinds of reflex actions are conducted by the body and the actions that are done in response to the impulses constitute the reflex arcs.

There are occurrences of certain stimuli that require automatic and rapid responses without the need for thoughts. Based on this, reflex arcs can be divided into two, namely, automatic reflex arc and somatic reflex arc. Automatic reflex arc creates an impact on the internal functioning of organs, whereas, somatic reflex arc impacts the muscles.

What occurs in Reflex Action?

Figure 2: Sequence of Reflex action

As there occurs the rise of any kinds of stimuli in the environment, specialized tissues are responsible for receiving such stimulus, where the alteration of tissues occurs both in direct and indirect ways. More to this, the changes may take place affecting the whole individual.

For instance, if one touches anything hot, then receptors identify stimuli that are present within the skin by the rise in temperature. Electrical impulses are sent by sensory neurons to the spinal cord through relay neurons that get connected to the motor neuron. Now motor neuron gives impulses to the effectors, resulting in the removal of the hand.

Types of Reflex Action

Varied reflex actions are noticed that include reflexes of a tendon, myotatic reflexes, abdominal reflexes, and coughing reflexes. In infants, sucking reflexes, and grasping reflexes are common.

Parts Involved in Reflex Action

Figure 3: Receptors are connected to effectors

The parts involved in reflexes include receptors, effectors, motor neurons, interneuron and lastly, sensory neurons.

  • Receptor - The receptor is responsible for identifying the stimuli. They are majorly seen in the specific dendrite that terminates in the sensory organ.

  • Sensory neuron - Then this information is conveyed to the CNS. Axon in the sensory neuron tends to assist in accomplishing the task.

This is followed by the functioning of the transmission of nerve impulses to the spinal cord from the receptors.

  • Interneuron - Now the relay neurons tend to act as the processing centre thereby conducting the nerve impulses to the motor neuron from the spinal cord.

Figure 5: Various neurons involved in Reflex Arc

  • Motor neuron - It gives the output, transmitting nerve impulses to the effectors.

  • Effectors - It effectively responds to the stimuli.


In this tutorial, the focus has been given to determining the importance of reflex actions. It is known that reflexes are essential as an instinct in the sustenance of organisms present. Reflexes works on both the external and internal changes that take place surrounding the organisms.


Q1. What are the differences noticed between afferent neurons and efferent neurons?

Ans. The major difference noticed among afferent neurons and efferent neurons is, that afferent neurons tends to carry impulses of nerves from the organs of receptors towards the spinal cord. On the other hand, when the nerve impulses are carried by varied neurons to glands as well as muscles from the brain or spinal cord, it is called as the efferent neurons.

Q2. What role is played by the human brain at the time of reflex action?

Ans. Reflex determines quick actions that are unintentional where the thinking process does not come into play. During the occurrence of reflex action, the human brain does not play any role. The reflex arc takes place in the region of the spinal cord, but still, the information is conveyed to the brain.

Q3. How reflex arcs are produced?

Ans. At the time when impulses reach the spinal cord from the receptors, the spinal cord sends impulses to the muscles without transmitting it to the brain. This arc generated at the time of reflex action is known as a reflex arc.

Updated on: 13-Apr-2023


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