Reflex Arc Diagram Labeled – Receptor to Effector

All 13 parts on the diagram

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The five parts of a reflex arc 5

Receptor It detects the stimulus and starts the signal.
Sensory neuron (afferent neuron) It takes the signal into the spinal cord.
Integration center Where the signal is processed and passed to the motor neuron.
Motor neuron (efferent neuron) It carries the command out to the effector.
Effector The muscle or gland that carries out the response.

Along the way 8

Dorsal root ganglion It holds the cell bodies of the sensory neurons.
Dorsal root The sensory root: it carries signals into the cord.
Synapse The junction where one neuron passes the signal to the next.
Interneuron It links the sensory neuron to the motor neuron.
Ventral root The motor root: it carries signals out of the cord.
Spinal nerve A mixed nerve: it holds both sensory and motor fibers.
Gray matter Made of nerve cell bodies and fibers without myelin.
White matter Made of nerve fibers wrapped in myelin.

How this list was compiled: Every name and detail line was checked on 2026-09-30 against Kenhub, Reflex arc, https://www.kenhub.com/en/library/anatomy/reflex-arc; the US National Cancer Institute SEER Training Modules, The Peripheral Nervous System, https://training.seer.cancer.gov/anatomy/nervous/organization/pns.html, and Nerve Tissue, https://training.seer.cancer.gov/anatomy/nervous/tissue.html; Wikipedia, Reflex arc, text only; and Henry Gray, Anatomy of the Human Body, 1918 (public domain), https://archive.org/details/anatomyofhumanbo00grayrich. Hints and detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work

How it works

This reflex arc diagram labeled part by part shows a spinal reflex: a pin touches the skin, the signal runs into the spinal cord, and a command runs back out to a muscle.

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The path of the signal

A receptor in the skin detects the pin. The sensory neuron carries the signal along the spinal nerve and the dorsal root into the gray matter; its cell body sits in the dorsal root ganglion. An interneuron passes it on. The motor neuron carries the command out by the ventral root to the effector, here a muscle.

Inside the spinal cord

The cord is cut across, its back at the top. The butterfly is gray matter and the rest white matter. The dashed box is the integration center, where the neurons meet at synapses.

The arrowheads show which way the signal travels.
The brain is not on this path: the spinal cord sends the command before the brain registers the touch.

Questions and answers

What are the 5 parts of a reflex arc?

Receptor, sensory neuron, integration center, motor neuron and effector, in that order. The receptor detects the stimulus, the integration center in the spinal cord or brainstem processes it, and the effector, a muscle or gland, responds.

What does the interneuron do in a reflex arc?

It sits inside the gray matter and links the sensory neuron to the motor neuron. The simplest reflexes, such as the knee jerk, have no interneuron: the sensory neuron ends directly on the motor neuron.

Why is a reflex so fast?

The signal does not have to travel to the brain and back. The spinal cord sends the command to the muscle itself, and the brain registers what happened only afterward.

Is this the key to “accurately label the components of a reflex arc”?

That sentence is a publisher’s labeling activity. This page shows the same components on a drawing of our own, so the layout differs, but the names are the standard ones.