How Does Reflex Action Work

There is one simple type of neural activity in which a stimulus results in an immediate action. This is a 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. Hall defined reflex as the automatic response of a muscle or muscles to a stimulus that excites an afferent nerve.

The term is now used to describe an action that is an inborn central nervous system activity that does not involve consciousness, in which a specific stimulus produces a stereotyped, immediate response of muscle or gland by exciting an afferent nerve.

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

The entire reflex action mechanism occurs in such a way that there is no conscious control of the brain. The peripheral nervous system is stimulated, and the response to this peripheral nerve stimulation is involuntary. The spinal cord and brain stem are responsible for reflex movements in a reflex action.

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.

Reflex Arc

The reflex arc is the neural pathway that controls the reflexes. It responds to an impulse before it reaches the brain. Some stimuli necessitate an automatic, instantaneous response without the need for conscious thought.

The receptor in this case is the sense organ that detects danger. Sensory neurons receive signals from the sensory organ and transmit them to other neurons that are interconnected. It is then received by a relay neuron in the spinal cord. The spinal cord immediately sends signals back to the muscle via the motor neuron. The sense organ’s muscles move the organ away from danger. Signals do not travel up to the brain during reflex actions.

The Action of Neuron

The pathway is dominated by two types of neurons: afferent nerves (receptors) and efferent nerves (effector or excitor).

The following is a synopsis of the events that occur:

• To begin, the receptor detects the stimulus or a sudden change in the environment, where instinct once again plays a role. A sensory organ provides the stimulus.
• The sensory neuron then transmits a signal to the relay neuron.
• Following that, the relay neuron sends the signal to the motor neuron.
• The motor neuron then sends a signal to the effector.
• The effector causes an instantaneous response, such as a hand pulling away or a knee-jerk reaction.

From the preceding explanations, it is clear that when an afferent neuron receives a signal from a sensory organ, the impulse is transmitted into the Central Nervous System via a dorsal nerve root. The signal is then carried from the CNS to the effector by the efferent neuron. As a result, the stimulus creates a reflex arc.

The signals in a reflex action do not travel to the brain; instead, they are directed into a synapse in the spinal cord, resulting in an almost instantaneous reaction.

Reflex

This type of reflex arc allows for involuntary actions. How can reflex responses benefit the organism? You jerk back your hand after touching a hot dish. Your mouth waters as you smell French fries. Your foot kicks out as the doctor taps your knee. What is going on in these situations? You’ll find out in this section. You will investigate how your body reacts to various situations.

Reflexes and Stimuli

Have you ever jumped when you heard a loud, sudden noise? When something unexpected happens, your brain protects you by triggering a startle reflex. Your muscles contract, your head moves, your heart beats faster, your eyes open wider, and your body jumps before your brain realises it. Your brain can even assist in protecting your ears from the harmful effects of loud sounds by causing tiny muscles in your ears to contract and dampen the effect of the sounds.

Your nervous system is made up of groups of neurons that work together in circuits to send and receive information. Information is sent to the brain or spinal cord via these circuits, and information about what to do is returned. Reflexes are the simplest circuits in the nervous system. A reflex is a natural response to a stimulus. A stimulus is something that causes an action to be taken. A neuron sends information about a stimulus to the brain or spinal cord and connects with a motor neuron in a simple reflex. A message is sent to a muscle by the motor neuron. The muscle contracts in response to the message.

You may recall that your behaviour is planned and controlled by the cerebral cortex. Reflexes, on the other hand, do not involve the cortex. Reflexes do not necessitate thought. Reflexes allow you to respond to a stimulus automatically. Although reflexes are the most basic way your nervous system controls your behaviour, they are not all the same.

Reflexes Work

You have a lot of reflexes. In fact, a large portion of your behaviour is made up of reflexes that protect you from danger in some way. Every day, gravity, for example, tries to make you fall over. Your body constantly makes adjustments to keep you on your bike or even in your chair without you having to think about it. Simple reflexes cause you to blink when something comes too close to your eye and to close it when dust gets into it. Vomiting is a more complex reflex that protects you from potentially harmful substances in your stomach or throat.

Messages about pain or temperature do not travel all the way to and from the brain during a reflex. Instead, they only travel as far as the spinal cord, where the spinal cord responds by sending commands to the muscles. This enables you to react to pain more quickly. When messages avoid the brain in this manner, they form a reflex arc.

Conclusion

There is one simple type of neural activity in which a stimulus results in an immediate action. This is a 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. 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). The reflex arc is the neural pathway that controls the reflexes. It responds to an impulse before it reaches the brain. The receptor in this case is the sense organ that detects danger. Sensory neurons receive signals from the sensory organ and transmit them to other neurons that are interconnected. It is then received by a relay neuron in the spinal cord. This type of reflex arc allows for involuntary actions. How can reflex responses benefit the organism? You jerk back your hand after touching a hot dish. Your nervous system is made up of groups of neurons that work together in circuits to send and receive information. Information is sent to the brain or spinal cord via these circuits, and information about what to do is returned. You have a lot of reflexes. In fact, a large portion of your behaviour is made up of reflexes that protect you from danger in some way. Every day, gravity, for example, tries to make you fall over. Your body constantly makes adjustments to keep you on your bike or even in your chair without you having to think about it.