An automatic and innate response to a particular stimulus. A reflex response is extremely rapid. This is because it is mediated by a simple nervous circuit called a reflex arc, which at its simplest involves only a receptor linked to a sensory neuron, which synapses with a motor neuron (supplying the effector) in the spinal cord, without the sensory and motor signals having to travel to and from the brain. Such reflexes are known as monosynaptic spinal reflexes; an example is the stretch reflex. Other spinal reflexes involve more than one synapse (see polysynaptic reflex); an example is the withdrawal reflex of the hand from a painful stimulus (such as fire). Cranial reflexes are mediated by pathways in the cranial nerves and brain; examples are the blinking and swallowing reflexes. See also conditioning.