Q.Redraw, complete and label the diagram given below, which relates to reflex arc (see figure).

The completed reflex arc has five labelled components in sequence: receptor (skin, detects the pin prick) → afferent/sensory neuron (carries the impulse to the spinal cord via the dorsal root) → spinal cord (grey matt...

A reflex arc diagram must show the receptor, sensory neuron, spinal cord (with a relay neuron), motor neuron and effector muscle, connected in that order.

To redraw and complete the given partial diagram: sketch the transverse section of the spinal cord showing the outer white matter and the inner butterfly-shaped grey matter, with a dorsal (posterior) root and a ventral (anterior) root on one side. Label the 'pin prick' stimulus acting on a receptor in the skin, connected by a sensory (afferent) neuron running through the dorsal root ganglion and dorsal root into the dorsal grey horn of the spinal cord. Inside the grey matter, show a small interneuron (relay neuron) connecting the sensory neuron to a motor (efferent) neuron in the ventral g …