Types of Reflex Action

The reflex arc is the anatomical pathway of a reflex. It is made up of an afferent (or sensory) nerve, one or more interneurons from the central nervous system, and an efferent (motor, secretory, or secreto-motor) nerve.

The reflex arc of most reflexes contains several synapses. The stretch reflex is unique in that it has only one synapse between the afferent nerve fibre and the motor neuron because there are no interneurons in the arc (see below Movement: The regulation of muscular contraction). There are at least two interneurons and three synapses in the flexor reflex, which removes a limb from a noxious stimulus.

Reflex Action

A reflex action, also known as a reflex, is a nearly instantaneous involuntary movement in response to a stimulus. When a person accidentally touches a hot object, they instinctively jerk their hand away. A reflex does not necessitate any mental effort.

A reflex arc is the path that nerve impulses take during a reflex. Most sensory neurons in the higher animals do not travel directly to the brain, but instead synapse in the spinal cord. This property enables reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of signal routing through the brain, despite the fact that the brain will receive sensory input while the reflex action occurs.

The majority of reflex arcs involve only three neurons. A stimulus, such as a needle stick, stimulates pain receptors in the skin, causing an impulse to be sent to a sensory neuron. This travels to a spinal cord, where it connects to a connecting neuron called the relay neuron via a synapse.

The relay neuron then forms a synaptic connection with one or more motor neurons, which transmits the impulse to the muscles of the limb, causing them to contract and pull away from the sharp object. Reflexes do not necessitate the involvement of the brain, though the brain can prevent reflex action in some cases.

Here are a few examples of reflex action:

When light is used as a stimulus, the pupil of the eye dilates.
When pricked by a pin, a jerky withdrawal of the hand or leg occurs.
Coughing or sneezing as a result of nasal passage irritants.
Knees jerk as a result of a blow or someone stamping on the leg.
The abrupt withdrawal of one’s hand from a sharp object.
When an insect comes very close to the eyes, there is a sudden blinking.

Some critical components are involved in the entire reflex action process. Receptor organs, sensory neurons, nerve centres, associated neurons, motor neurons, and effector neurons are all examples.

The stimuli are perceived by the receptor organs. They are located on the organs of perception. Afferent neurons, also known as sensory neurons, transport stimuli from receptors to the spinal cord. The sensory neurons are found in the spinal cord’s ganglion.

The nerve centre, where synaptic connections are formed, is the spinal cord. The neurons involved are found in the spinal cord. Motor neurons are found in the ventral horn of the spinal cord. The glands and muscles that respond to stimuli are known as effector organs.

Types of reflex action

Reflex actions can be classified into two types.

Inborn or unconditioned reflexes

Simple reflex actions are another term for inborn reflexes. Some of the reflexes are present even before birth. These are known as inborn or unconditioned reflexes. The taste of milk, for example, causes salivation even in a newborn baby who has never tasted the food before, the pupils of the eye constrict even if the eye is illuminated by light at the time of birth, and so on. Inborn reflexes are passed down through families. Inborn reflexes are triggered by specific stimuli. The reflex arcs of unconditioned reflexes are always the same.

Conditioned reflexes

Conditioned reflexes are acquired through learning or experience with stimuli that did not initially elicit a response. Conditioning reflexes involve the formation of new reflex arcs that extend into the cerebral cortex. Conditioned reflexes are transient in nature and may vanish or reappear. For example, if an animal smells food that he has not previously tasted, he does not salivate; however, if the animal sees and smells food several times before eating, saliva is produced. The animal’s nervous system has been conditioned to produce a reflex as a result of seeing and smelling food. The stimulus that causes such a reflex is known as a conditioned stimulus.

Mechanism of Reflex action

Reflex action occurs in such a short period of time that it is difficult to estimate when the stimulus was generated and when the action occurred. The stimulus of reflex action travels at a speed of 320 km per hour in humans. An example will help you understand this. When the needle is pricked in a person’s hand or leg, he immediately pulls it out. A variety of physiological activities occur in this short period of time. The pricking of a needle serves as a stimulus. This stimulus is received by the sensory organ and transmitted to the nervous system’s central nervous system via nerve fibres. The brain converts stimulus impulses into different impulses.This is communicated from the brain to the muscles of the receptor sense organ via motor nerve fibres. As a result, the organ (hand or leg) is immediately yanked from the location.

Benefits of Reflex action

Reflex actions are common occurrences in an animal’s body. The following are the advantages of reflex action:

Animals defend themselves immediately in the face of adversity.
The brain is not aware of any type of burden (while thinking) or load.
We frequently save ourselves from serious actions by acting reflexively.

Some examples of reflex action

Here are some examples of reflex actions:

When we see or smell tasty food, our salivary glands secrete saliva.
When a finger is brought close to the eye, the pupil quickly closes.
The muscles of the thorax and face begin to move as a result of yawning. The release of carbon dioxide via deep exhalation is increased as a result of such muscle movement.
Reflex actions include sneezing and coughing. Sneezing and coughing both aid in the cleaning of the nasal passage and the respiratory tract.

Physiology of reflex action

The stimulus follows the reflex arc as follows:

The receptor detects the stimulus.
These stimuli cause nerve impulses to be generated in sensory neurons, and these impulses travel through the axons of these neurons. The sensory afferent nerves leading to the spinal cord are made up of axons.
When these impulses enter the spinal cords, they initiate impulses in one or more associations or interneurons.
Then, the appropriate motor neurons receive impulses from the association neurons.
When impulses travel through motor or efferent nerves to the junction between motor neurons and muscles or glands, effectors are stimulated to perform their functions.

Conclusion

There is one simple type of neural activity in which a stimulus results in an immediate action. This is reflex action. Marshall Hall, a 19th-century English neurologist, coined the term reflex (from Latin reflexus, “reflection”) to describe how muscles reflect a stimulus in the same way that a wall reflects a ball thrown against it. A reflex action, also known as a reflex, is a nearly instantaneous involuntary movement in response to a stimulus. The majority of reflex arcs involve only three neurons. A stimulus, such as a needle stick, stimulates pain receptors in the skin, causing an impulse to be sent to a sensory neuron. Reflexes do not necessitate the involvement of the brain, though the brain can prevent reflex action in some cases. Some critical components are involved in the entire reflex action process. Receptor organs, sensory neurons, nerve centres, associated neurons, motor neurons, and effector neurons are all examples. Simple reflex actions are another term for inborn reflexes. Some of the reflexes are present even before birth. These are known as inborn or unconditioned reflexes. Conditioned reflexes are acquired through learning or experience with stimuli that did not initially elicit a response.