An Introduction to Reflex Action
A reflex is an involuntary and rapid response to the stimulus. It is a crucial component of the famed survival instinct. Depending on our previous experiences and understanding, we all have different instincts. A reflex is a response that is triggered by an instinct. Sometimes we don't know if the pan is hot or not until it's too late. To put it another way, reflex has little to do with instinct. In this article, you will understand reflex action, types of reflex action, the significance of reflex action, and some FAQs. So, let us start by understanding reflex action in the coming section.
What is Reflex Action?
An involuntary or instantaneous action by the human body parts in response to a stimulus is called reflex action. It is because of numerous neural pathways that are known as reflex arcs that act on an impulse before it reaches the brain. Reflex action doesn’t need any conscious thought or awareness about the automatic response.
What happens in Reflex Action?
When a specialized tissue receives a stimulus, it may either directly/indirectly alter the relation of other tissues or also the whole individual to the environment from where stimuli arise. Let’s understand a few examples of the mechanism of the reflex action. The pupil of the eye changes its size when light acts as a stimulus; when a pin pricks our hands or legs or we touch something very hot, we suddenly withdraw them; we cough or sneeze when foreign irritants go to our nasal passages. In these situations, our reactions are instantaneous, involuntary, and quick. It doesn’t require much of a thinking process and conscious brain control, therefore, the action is called the reflex action in scientific terms. And here, the major role is of the spinal cord and the nerve pathway which is involved in this action including a sensory nerve, a synapse in between, and a motor nerve called a reflex arc. The pathway of reflex action (reflex arc) can be clearly understood below in the diagram.
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Types of Reflex Action
To understand reflex action, we should understand all parts of the reflex arc responsible to cause a reflex action. Types of reflex action can be myotatic reflexes, tendon reflexes, or reflexes observed only in human infants such as sucking reflexes, and other reflexes such as abdominal reflexes or cough reflexes.
Reflex Arc
The reflex arc is the neural pathway controlling the reflexes and acts on an impulse even before it reaches the brain. Some stimuli require an automatic, quick response that does not involve conscious thought. The two types of reflex arcs are:
Autonomic Reflex Arc: It affects the functioning of inner organs.
Somatic Reflex Arc: It affects the functioning of muscles.
The Various Parts of the Reflex Arc are described as follows -
The reflex arc consists of a receptor, sensory neuron, interneuron, motor neuron, and effector.
Receptor
It is the part of the reflex arc responsible for detecting the stimulus. A specialized receptor cell or a particular dendrite has this receptor end in a sensory organ. It is highly sensitive to any kind of internal or external change resulting from the stimulus.
Sensory Neuron
It conveys sensory information to the brain or the spinal cord. Dendrite, cell body and axon of a sensory neuron are present to assist it in accomplishing its function. Its function is to transmit nerve impulses from the receptor into the spinal cord or brain.
Interneuron
Also known as relay neurons, it serves as a processing centre and conduct nerve impulses from the sensory neuron to a motor neuron. Interneurons are the central nodes of neural circuits, responsible for communicating between sensory or motor neurons and the central nervous system (CNS). It is the dendrite, cell body, and axon of a neuron within the brain or spinal cord.
Motor Neuron
It conducts motor output to the periphery and it is a nerve cell forming part of the pathway along which impulses travel from the brain or spinal cord to a gland or muscle. It transmits nerve impulses from the brain or spinal cord out to an effector.
Effector
Effector cells are muscles, organs, or glands that act in response to a stimulus. It responds to stimulation by the motor neuron and produces a behavioural response called a reflex.
What is the Significance of Reflex Action?
Reflex action is an involuntary response of effectors to the stimulus and it helps us in protecting us from any sudden stimulus which may harm us and thus takes care of the survival of an organism. It is the major point that explains the importance of reflex action.
The importance of reflex action is due to the fact that reflex arcs are composed of different components that are significant to create a reflex. The function of each component is explained below -
Receptor - It receives the information and assists in generating impulses.
Sensory Nerve - It carries information from the receptor to the interneurons in the spinal cord.
Interneuron - It processes the information and generates effective responses.
Motor Nerve - It carries the information from the spinal cord to the effector organ.
Effector Organ - It receives information from effector neurons and results in the appropriate response (reflex).
List Down 10 Examples of Reflex Action
Reflex Action Examples in Humans Include-
Closing of eyes when a bright light hits our eyes
Sudden withdrawing hands or legs when they touch something hot or pricking
Coughing or sneezing due to irritants in the nasal passage
Batting of eyelids frequently
Blinking eyes when insects come in contact
Rooting reflex in infants
Sucking reflex in infants
Grasp reflex in infants
The reflex of abdominal muscles to contract upon any force to the abdomen (Muscular defense)
Knee-jerk reflex is known as a patellar reflex: when the patellar tendon is stretched, the contraction of quadriceps takes place.
FAQs on Reflex Action
What does reflex action mean and explain the pathway of reflex action?
A reflex, also known as a reflex action, is an involuntary movement that occurs in response to a stimulus. The reflex arc, a neural pathway that governs reflexes, is where reflex actions take place. The sense organ that detects danger is the receptor in this case. Sensory neurons receive information from the sensory organ and send them to other interconnected neurons. The signal is subsequently received by a relay neuron in the spinal cord. The spinal cord immediately sends signals to the muscle through the motor neuron. The sense organ is moved away from danger by the muscles attached to it. The signals from reflex actions do not reach the brain.
What do you mean by monosynaptic and polysynaptic reflex action?
A monosynaptic reflex action is when a reflex arc consists of only one sensory neuron and one motor neuron where a single chemical synapse occurs. Example: Patellar reflex. Polysynaptic reflex action occurs when one or more sensory and motor signals are connected i,e, interneurons connect afferent and efferent signals.
What is a reflex arc?
A reflex arc is a nerve pathway through which different components like receptor, sensory neuron, interneuron, motor neuron, and effector function altogether to produce a reflex action. These components act in a five-step process to generate a reflex action that is initiated by a stimulus. It can be diagrammatically represented to make it more comprehensible. A reflex arc governs all the operations of reflexes. The types of reflex actions are also based on their functionalities and types. A reflex arc makes it possible for reflexes through the neural pathways that act on an impulse before reaching the brain.
Briefly describe the event that occurs in response to a stimulus in organisms?
The event that occurs in response to a stimulus in organisms are as follows:
The receptor detects a stimulus from a sensory organ as the first event. Pressure, temperature, or chemicals might be used as a stimulus.
After that, the sensory neuron transmits a signal to the relay neuron.
The signal is subsequently sent to the motor neuron by the relay neuron.
The motor neuron transmits a signal to the effector, which is an organ or cell that responds to stimuli.
Finally, the effector causes an immediate reaction, such as a knee-jerk reflex.
In a reflex action, the reflex arc is created by?
A reflex arc is created when impulses from the receptor reach the spinal cord, and the spinal cord then sends the appropriate reflex impulse to the muscles. To reduce reaction time, the impulse is not transmitted to the brain.
State the difference between afferent neurons and efferent neurons?
Here is the difference between them:
Afferent neurons carry nerve impulses from receptor organs to the spinal cord.
Different neurons carry nerve impulses from the brain or spinal cord to muscles or glands, which are known as effector organs.
What function does the brain play in reflex action?
Reflex acts are quick responses. It's an unintentional action that doesn't need any thinking. When we touch a hot object, for example, we instinctively remove our hands without thinking.
The nerves that move the muscles of the hand are related to the sensory nerves that feel the heat. A reflex arc is a link between perceiving the signal from the nerves (input) and promptly responding to it (output). Although reflex arcs occur in the spinal cord, information is still sent to the brain. There isn't much of a response in the brain to it
