The nociceptive withdrawal reflex (NWR) is a spinal reflex intended to protect the body from damaging stimuli. The classic example is when you touch something hot and withdraw your body part from the hot object. The heat stimulates temperature and pain receptors in the skin, triggering a sensory impulse that travels to the central nervous system. The sensory neuron then synapses with interneurons that connect to motor neurons. Some of these send motor impulses to the flexors to allow withdrawal; some motor neurons send inhibitory impulses to the extensors so flexion is not inhibited - this is referred to as reciprocal innervation. While all of this occurs, other interneurons relay the sensory information up to the brain so that the person becomes aware of the pain and what happened. The NWR is also known as the flexion reflex.
- Ole K. Andersen, SMI, Aalborg University - Physiological and Pharmacological modulation of the human nociceptive withdrawal reflex