Reflex Action

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In the body of an animal two types of activities take place: voluntary and involuntary. Voluntary action happens according to the will of the individual while there is not any control of will over involuntary action. Involuntary action may again be divided into two categories. The action of first category is related to internal body organs. It is controlled by medulla oblongata. The second type of action is performed by outer body organs. It is under the control of spinal cord. In broader sense, all the involuntary actions are reflex action. But the term reflex action is applied only to those actions which are performed by external body organs without any control of ones will.

is an immediate involuntary response to a stimulus. In an involuntary response, a sensory impulse on reaching central nervous system is itself returned to a specific effector as a motor impulse without neuronal analysis and integration. Reflex responses occur below the level of consciousness. s are sudden and autonomic. For instance, if ones foot is trickled the leg is drawn at once and this will happen even when one is busy in other activities upon which all the attention is concentrated and perhaps without even being conscious of the irritation. Therefore, we can say that reflex actions are those actions which result from the conversion of sensory impulses into motor impulse by a nerve center, like spinal cord, without the intervention of brain. Some common examples of reflex actions are:

The knee jerk reflex, when tendon of the knee cap is tapped, it stimulates the stretch receptors in the tendon and leg is involuntarily and momentarily straightened.
The quick closing of the eyelids or blinking reflex, when an object approaches the eye.
Sneezing reflex in response to irritation of lining of nose.

Types of reflexes

s may be divided into the following two types:

Inborn or unconditioned reflexes : Inborn reflexes are also celled as simple reflex actions. Some of the reflexes are present even at the time of birth. These reflexes are called inborn or unconditioned reflexes. For example, taste of milk causes salivation even in a new born baby, even though the infant has not tasted the food earlier, the pupil of the eye constricts even if the eye is illuminated by Light at the time of birth and so on. Inborn reflexes are transmitted through heredity. Inborn reflexes are elicited in response to definite stimuli. The reflex arcs of unconditioned reflexes are constant.

Conditioned reflexes : Conditioned reflexes are acquired through Learning or experience to stimuli which originally failed to elicit a reaction. The conditioned reflexes involve the establishment to new reflex arcs and that close into the cerebral cortex. Conditioned reflexes are temporary in nature and may disappear or reappear again. For example, if an animal smells food which he has not tasted earlier it does not salivate, but if the animal sees and smells food many times before eating, saliva is produced. Seeing and smelling of food has conditioned the nervous system of the animal to produce a reflex. The stimulus which produces such a reflex is termed as conditioned stimulus.

Reflex Arc

The structural and functional unit in the simple reflex is termed as reflex arc. In its basic form reflex arc is regarded as simple nervous pathway connecting a receptor and an effector. Reflex arc has the following parts:

Receptor : Receptor represented by single sensory cell or a group of cells which receives stimuli.

Sensory or afferent neuron : Sensory connects the receptor to the spinal cord. The cell body of sensory is stimulated in the dorsal root ganglion of the spinal nerve. Sensory conveys impulses from the receptor to the spinal cord.

Interneuron or association neuron : Interneuron is present in the spinal cord. Interneuron connects afferent and efferent neurons and passes impulses from afferent to efferent neuron. Generally, there is only one association neuron in the reflex but sometimes two or more are involved in one reflex arc.

Motor neuron or efferent neuron : Motor neuron is located in the ventral root of spinal cord. Motor neuron transmits impulses to the effecteo organ.

Effector organ : It responds to the impulses received. E.g., a muscle or a gland.

Mechanism of

happens in so less time that it can hardly be estimated that when was the stimulus generated and when the action took place. In man the stimulus of reflex action travels with a speed of 320 km per hour. This can be understood with an example. If a needle is pricked in the hand or leg of a person, it is instantly pulled out by him. In this short span of time, a number of physiological activities take place. Pricking of needle functions as stimulus. The sensory organ receives this stimulus which is transmitted to the center of nervous system through nerve fibers. The impulse of stimulus is converted into efferent impulse by the brain. This is transmitted from brain to muscles of the receptor sense organ through motor nerve fibers. AS a result the organ (hand or leg) is instantly pulled out from the place.

A reflex action is an involuntary action that occurs in response to a stimulus. It is mediated by the spinal cord and does not involve the brain. Reflexes are essential for survival, as they allow us to respond quickly to changes in our Environment.

There are two main types of reflexes: somatic reflexes and autonomic reflexes. Somatic reflexes are mediated by the somatic nervous system, which controls voluntary movement. Autonomic reflexes are mediated by the autonomic nervous system, which controls involuntary functions such as heart rate, breathing, and digestion.

Reflexes are initiated when a sensory receptor detects a stimulus. The sensory receptor sends an impulse along a sensory nerve to the spinal cord. The spinal cord then sends an impulse along an motor nerve to an effector, which is the muscle or gland that produces the reflex response.

There are many different types of reflexes, each with its own pathway. Some common reflexes include the knee jerk reflex, the stretch reflex, and the pupillary reflex.

The knee jerk reflex is a classic example of a somatic reflex. It is elicited by tapping on the patellar tendon below the kneecap. This causes the quadriceps femoris muscle to contract, which straightens the leg.

The stretch reflex is a type of proprioceptive reflex that helps to maintain muscle tone. It is initiated when a muscle is stretched. The sensory receptors in the muscle send an impulse to the spinal cord, which then sends an impulse back to the muscle, causing it to contract. This contraction helps to keep the muscle from becoming too stretched.

The pupillary reflex is an example of an autonomic reflex. It is controlled by the autonomic nervous system, which is responsible for involuntary functions such as heart rate, breathing, and digestion. The pupillary reflex is responsible for controlling the size of the pupils. When light enters the eye, it stimulates the sensory receptors in the retina. These receptors send an impulse to the brain, which then sends an impulse to the muscles that control the size of the pupils. The muscles contract, which causes the pupils to constrict. This helps to protect the retina from damage from bright light.

Reflexes are essential for survival. They allow us to respond quickly to changes in our environment. Without reflexes, we would be unable to walk, talk, or even breathe. Reflexes are also important for maintaining homeostasis, which is the body’s ability to maintain a stable internal environment.

Reflexes can be affected by a number of factors, including age, disease, and injury. In older adults, reflexes may become slower and less responsive. This is due to a decline in the function of the nervous system. Diseases such as Parkinson’s disease and multiple sclerosis can also affect reflexes. These diseases damage the nerves, which can slow down or prevent reflexes from occurring. Injury to the spinal cord can also affect reflexes. This is because the spinal cord is responsible for relaying information between the brain and the body. If the spinal cord is damaged, it can disrupt the pathway of reflexes, which can prevent them from occurring.

Reflexes are an important part of our nervous system. They allow us to respond quickly to changes in our environment and maintain homeostasis. Reflexes can be affected by a number of factors, including age, disease, and injury.

What is a reflex?

A reflex is an involuntary action that occurs in response to a stimulus.

What are the different types of reflexes?

There are two main types of reflexes: somatic reflexes and autonomic reflexes. Somatic reflexes are controlled by the somatic nervous system, which is responsible for voluntary movement. Autonomic reflexes are controlled by the autonomic nervous system, which is responsible for involuntary functions such as heart rate, breathing, and digestion.

What are some examples of reflexes?

Some examples of reflexes include the knee jerk reflex, the pupillary reflex, and the gag reflex.

How do reflexes work?

Reflexes work through a pathway called a reflex arc. The reflex arc consists of a sensory neuron, an interneuron, and a motor neuron. The sensory neuron detects the stimulus and sends a signal to the interneuron. The interneuron then sends a signal to the motor neuron, which causes the muscle to contract.

What are some disorders that can affect reflexes?

What is the role of reflexes in the body?

Reflexes play an important role in the body by helping to protect us from harm and by helping us to maintain homeostasis.

What are some interesting facts about reflexes?

Some interesting facts about reflexes include the fact that the fastest reflex in the body is the blink reflex, which occurs in about 0.02 seconds. The slowest reflex in the body is the Achilles tendon reflex, which occurs in about 0.3 seconds.

What are some common misconceptions about reflexes?

Some common misconceptions about reflexes include the belief that reflexes are always involuntary and the belief that reflexes are always fast. In fact, some reflexes can be voluntary and some reflexes can be slow.

What are some future research directions in the study of reflexes?

Some future research directions in the study of reflexes include the study of how reflexes are controlled by the brain and the study of how reflexes can be used to improve human performance.

Sure, here are some MCQs without mentioning the topic Reflex Action:

Which of the following is not a type of reflex?
(A) Stretch reflex
(B) Withdrawal reflex
(C) Babinski reflex
(D) Accommodation reflex
The stretch reflex is also known as the:
(A) Tendon reflex
(B) Muscle stretch reflex
(C) Myotatic reflex
(D) All of the above
The withdrawal reflex is also known as the:
(A) Flexor reflex
(B) Extensor reflex
(C) Babinski reflex
(D) None of the above
The Babinski reflex is a reflex that is present in infants but disappears after a few months. It is elicited by stroking the sole of the foot from the heel to the toes. The normal response is for the toes to fan out. If the toes curl up, it is a sign of neurological problems.
The accommodation reflex is the reflex that allows the eye to focus on objects at different distances. It is controlled by the ciliary muscles, which change the shape of the lens.
The pupillary reflex is the reflex that causes the pupils to constrict in bright light and dilate in dim light. It is controlled by the autonomic nervous system.
The corneal reflex is the reflex that causes the eyelids to close when the cornea is touched. It is controlled by the trigeminal nerve.
The gag reflex is the reflex that causes the back of the throat to close when something touches it. It is controlled by the vagus nerve.
The sneezing reflex is the reflex that causes the body to expel air from the nose and mouth when something irritates the nasal passages. It is controlled by the trigeminal nerve.
The coughing reflex is the reflex that causes the body to expel air from the lungs when something irritates the airways. It is controlled by the vagus nerve.
The swallowing reflex is the reflex that causes the body to swallow food and drink. It is controlled by the vagus nerve.
The vomiting reflex is the reflex that causes the body to expel food and stomach contents from the stomach. It is controlled by the vagus nerve.
The micturition reflex is the reflex that causes the body to urinate. It is controlled by the spinal cord.
The defecation reflex is the reflex that causes the body to defecate. It is controlled by the spinal cord.
The sexual reflexes are the reflexes that control sexual arousal and orgasm. They are controlled by the spinal cord and the brain.

I hope these MCQs are helpful!