ABSTRACT
The simplest operation the nervous system can execute is the reflex, which couples sensory input to motor output. A reflex is a stereotyped response to a particular stimulus. When it involves the autonomic nervous system it is an autonomic reflex and the effector is typically cardiac or smooth muscle or a gland. When it occurs in the somatic nervous system it is a motor reflex and the effector is skeletal muscle. They are mediated by specified neural circuits sometimes called reflex arcs (Figure 1), which consist of a sensory neuron, a motor neuron and usually interneurons interposed between the two, which may be excitatory or inhibitory.
