Unlabeled Reflex Arc Diagram – Blank Sheet With a Key

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

One spinal reflex, drawn with nothing written on it. A pin touches the skin at the top left, a muscle lies at the bottom left, and the spinal cord is cut across at the right, its back at the top.

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Word bank for labeling the blank reflex arc

Receptor, sensory neuron, integration center, motor neuron, effector: the five parts, in the order the signal meets them. Eight more lie along the way: dorsal root ganglion, dorsal root, synapse, interneuron, ventral root, spinal nerve, gray matter, white matter. A class may write afferent for sensory and efferent for motor.

Lines that are easy to swap

The nerve trunk forks into two roots. The upper one, toward the back of the cord, is the dorsal root, and the oval swelling on it is its ganglion; the lower one is the ventral root. Arrowheads point toward the cord on the sensory neuron and away from it on the motor neuron.

The pin is the stimulus. It is an event, not a part of the body, so no line ends on it.
Afferent fibers arrive at the cord and efferent fibers exit it: the first letters match.

Questions and answers

Where do the labels go on a reflex arc unlabelled diagram?

At the free end of each line, twelve in all. The thirteenth name, effector, has no line: write it on the muscle.

What is the difference between the dorsal root and the ventral root?

The dorsal root holds sensory fibers, and the cell bodies of its neurons sit in the dorsal root ganglion. The ventral root holds motor fibers. The two join to form the spinal nerve, which is why every spinal nerve is a mixed nerve.

Is the reflex arc on the diagram monosynaptic or polysynaptic?

Polysynaptic. An interneuron links the sensory neuron to the motor neuron, so the signal crosses two synapses. In a monosynaptic arc the sensory neuron ends directly on the motor neuron, with a single synapse between them.

Is a reflex arc somatic or autonomic?

It can be either. In a somatic reflex the effector is a skeletal muscle, as on this diagram. In an autonomic reflex the effector is smooth muscle, heart muscle or a gland.