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Interneuron
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An interneuron is the neuron in the middle. A typical reflex arc involves the afferent neuron, usually sensory, which brings information in from the body; the efferent neuron, usually motor, which commands the movement; and one or more interneurons, which connect the two. It is the splice between the wire that brings the signal and the wire that carries it out.
In a polysynaptic reflex, meaning one in which the signal passes through interneurons, the sequence looks like this: the sensory neuron is stimulated, it activates the interneuron, and the interneuron stimulates the motor neuron, which makes the muscle move.
But not every interneuron pushes. There are inhibitory interneurons that do exactly the opposite: they switch off activity in the antagonist muscle, the one that pulls in the direction opposite to the muscle that is contracting. Some interneurons push the signal along and others put the brakes on it.
In brief
An interneuron is the nerve cell that connects the other two within a reflex arc, linking the afferent neuron, usually sensory, to the efferent neuron, usually motor.
The splice between the wire that brings the signal and the wire that carries it out.
In a polysynaptic reflex, the stimulated sensory neuron activates the interneuron, which in turn stimulates the motor neuron, producing movement.
An inhibitory interneuron does the opposite: it shuts down activity in the antagonist muscle.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingNeuroanatomy, Spinal Cord Myotatic Reflex, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingNeuroanatomy, Somatic Nervous System, StatPearlsPublished
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