Sensory neuron

Definition

A nerve cell that detects environmental or internal stimuli through specialized receptors and converts them into electrical signals (graded receptor potentials or action potentials) for transmission to the central nervous system. In arthropods, sensory neurons occur in sensilla—cuticular structures housing mechanoreceptors, chemoreceptors, thermoreceptors, or hygroreceptors—and may be bipolar, with a dendrite extending to the stimulus source and an axon projecting to ganglia or the brain.

Etymology

From Latin 'sensorius' (of sensation) + Greek 'neuron' (nerve, sinew)

Example

In the Johnston's organ of a honey bee antenna, arrays of sensory neurons detect minute deflections of the flagellum caused by air currents or sound vibrations, enabling navigation and communication.

Synonyms

• afferent neuron
• receptor neuron

Related Terms

• Sensillum
• mechanoreceptor
• Chemoreceptor
• Dendrite
• Axon
• neuroethology
• peripheral nervous system
• Johnston's organ

Usage Notes

Distinguished from motor (efferent) neurons, which carry signals from the central nervous system to effector tissues. In insects, sensory neurons are typically bipolar with cell bodies located peripherally in sensilla or nearby ganglia, unlike vertebrates where somata often cluster in dorsal root ganglia. The term is sometimes restricted to neurons that conduct action potentials, excluding those producing only graded potentials, though this usage varies.