Reflexes are automatic and involuntary actions the body produces in response to certain stimuli. While some reflexes can involve muscles and movement, others involve internal processes within the body.

The reflex arc is a pathway taken by a nerve impulse to carry out a reflex response. Healthy reflexes are crucial in quickly reacting to potentially dangerous stimuli. Some reflexes are more complex and require multiple parts of the nervous system.

Somatic reflexes involve the somatic nervous system, which deals with the skin, muscles, and conscious activities, such as limb movement. Autonomic reflexes involve the autonomic nervous system, which deals with involuntary internal processes such as digestion.

This article will define reflexes, explain their purpose and how they work, and describe different types of reflexes.

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Reflexes are the body’s involuntary responses to different stimuli. They happen without consciously thinking about them.

Reflexes protect the body from danger or harm and help maintain homeostasis, which is a steady internal environment.

How do reflexes work?

Generally, reflexes work through a reflex arc. A reflex arc is the line of communication within the body that prompts a reflex response. The arc uses sensory nerves (to detect harmful stimuli) and motor nerves (to activate the muscle). It works to produce fast responses.

Healthcare professionals know how to assess reflexes. An overactive, weak, or absent reflex may indicate a medical condition worthy of attention.

Reflexes can occur at two different levels.

One involves the somatic nervous system. Somatic reflexes deal with muscles, skin, and movements that people are usually aware of. For example, touching a hot pan and quickly jerking away is a somatic reflex.

The other level involves the autonomic nervous system and is coordinated by certain parts of the brain. Autonomic reflexes deal with organs and internal processes such as digestion and blood flow that people are less aware of.

An example is the gastrocolic reflex, where the stomach filling up after a meal can stimulate an autonomic motility reflex within the large intestine, causing the urge to use the bathroom.

Different types of reflexes involve different pathways and processes in the body.

Several types of reflexes exist. They can include the following:

Stretch or deep tendon reflex

The stretch reflex, or deep tendon reflex, is a somatic reflex that keeps muscles at a certain length.

When a muscle starts to lengthen or stretch too much, this reflex triggers a muscle contraction to get the muscle back to its regular length. This reflex helps the body maintain posture against gravity.

There is some disagreement among experts about whether the deep tendon reflex and stretch reflex are the same thing.

According to some experts, the deep tendon reflex occurs when a medical hammer actively stretches a muscle, such as when a doctor tests a person’s knee-jerk reaction. On the other hand, the stretch reflex occurs from movement and posture.

Whether or not the stretch and deep tendon reflexes are different, they both aim to keep a muscle at a certain length.

Inverse stretch reflex

The inverse stretch reflex stops the stretch reflex from causing a muscle contraction and instead helps a muscle relax.

It prevents damage by stopping the muscle from experiencing too much tension or force. For example, the inverse stretch reflex helps muscles relax during long stretches.

Withdrawal reflex

The withdrawal reflex helps protect the body from danger in the environment. Harmful or painful stimuli trigger certain receptors in the body, activating this reflex type.

Specifically, the receptors involved in this reaction activate neurons and pathways that cause muscle movement. For example, if someone’s hand touches a hot or sharp object, the withdrawal reflex quickly causes the hand to pull away.

The stronger a harmful stimulus is, the greater the body’s reaction.

Autonomic reflexes

Autonomic reflexes involve the autonomic nervous system and the body’s internal processes. People are not conscious of autonomic reflexes.

There are many types of specific autonomic reflexes. They respond to many different functions and challenges, such as:

  • eating food
  • illness
  • blood loss
  • stress
  • temperature changes
  • debris striking the eye
  • foul-smelling odors

Several types of neurons, fibers, and pathways can trigger different autonomic reflexes.

Like other reflexes, autonomic reflexes aim to help maintain homeostasis and protect the body.

Reflexes help the body maintain a constant environment, or homeostasis, and protect the body from harm or danger. They occur without thinking through reflex arcs or neural pathways in the body.

Somatic reflexes involve the muscles, skin, and responses to external stimuli. People are usually aware of somatic reflexes. Meanwhile, autonomic reflexes have to do with internal processes that people are unaware of. Several types exist, including the stretch or tendon, withdrawal, and inverse stretch reflexes.

Many types of autonomic reflexes work in complex ways. Autonomic reflexes deal with the body’s internal environment and respond to challenges and functions such as heat, cold, food intake, stress, and more.