the reflex arc details the autonomic response to a specific stimulus.
for example, pulling your hand away a fire- the external sensation of pain is the stimulus which initiates a motor response from your nervous system to pull the hand away from the fire
know how the impulse travels through the different parts of a reflex arc.
for an impulse to the spinal cord:
external stimulus -> afferent (sensory) neuron-> to the dorsal root of the spinal cord -> dorsal root ganglion (cell bodies) -> white matter -> gray matter -> [synapse on an interneuron]-> synapse on efferent (motor) neuron -> gray matter -> white matter -> out the ventral root -> to the organ for the corresponding motor response
a synapse on a interneuron may occur depending on the impulse