Reflex

Definition and process:

Reflexes are involuntary and automatically occurring reactions of the body, which are coordinated by nerve cells and serve the protection of the body. In principle, we can distinguish between two types of reflexes: innate reflexes and acquired reflexes.

A reflex that everyone knows from their own experience is the knee-jerk reflex. In a light hit below the kneecap, the leg reacts with a bobbing forward motion. But how do reflexes work?

A physical or chemical stimulus hits a sensory cell, the receptor. The receptor converts the stimulus into electrical signals (transduction). These impulses pass through an afferent nerve fiber (afferent = to the central nervous system) into the spinal cord where the stimulus is processed. Finally, the signal reaches the effector via an efferent nerve fiber (usually muscle cells). The motor end plate transmits the electrical excitation from the nerve fiber to the muscle. As a result, it comes to the reaction, the contraction of the muscle.

This process is so fast and automatic that we do not realize it. Mostly the brain is not involved at all. A controlled control of the innate reflexes is therefore not possible.

Reflexes

1.) Congenital reflexes (unconditioned reflexes):

In the innate reflexes a distinction is made between intrinsic and external reflex. The most important difference is the number of synapses involved. Only one synapse is involved in a self-reflex; in a foreign reflex, several synapses are involved.

2.) Acquired reflexes (conditioned reflexes):

Besides the innate reflexes, certain reaction can also be learned (via conditioning). The best example of a conditioned reflex is the increased salivary production of Pavlov's dogs, when the bell sounds.

The early childhood reflex

The innate reflexes also include the childish reflexes. Most of these reflexes are only functional in the first months of life. As the brain progresses, some reflexes are lost again. But the automatic reactions fulfill a vital function: they protect the baby from injury and facilitate food intake.

Babinski reflex: stroking the baby centrally over the bottom of the foot, it pulls the big toe up.

Gripping reflex: on contact with the palm of the hand, the baby grabs.

Braces: also known as the Moro reflex. Sudden changes in the position of the head make babies brace.

Suction reflex: is closely connected to the swallowing reflex. The baby begins to suck as soon as something touches the palate.

Swimming reflex: often seen in baby swimming. Babies begin with paddle-like forward movements when in contact with water over a large area.

Such reflex: by touching the corner of the mouth, the baby turns his head in that direction. Helps the baby, even without visually recognizing something, to find the mother's breast.

Summary

Reflexes are involuntary and automatic reactions that are triggered under certain conditions.

Sequence of stimulus to response in a reflex: stimulus receptor afferent neuron central nervous system efferent neuron effector reaction