Viscerosensation refers to senses of the viscera. The term viscera may be used several ways; in this context it refers to structures rich in smooth muscle, cardiac muscle, or gland cells, such as internal organs, blood vessels, and some glands. These are the same tissues that receive input from autonomic neurons, and many autonomic reflexes have an afferent part involving viscerosensory neurons linked to an efferent part involving autonomic neurons. Some people use the term autonomic sensation instead of the term viscerosensation, in which case they discuss the autonomic nervous system as having a sensory (afferent) part and a “motor” (efferent) part; these people use the term motor for any type of efferent neuron, instead of just efferent neurons that control skeletal muscle cells. Similar types of stimuli, receptors, and peripheral neurons are involved in viscerosensation as for somatosensation, but this information travels in different pathways in the central nervous system.
Viscerosensory information travels into the spinal cord via spinal nerves, or into the brainstem, primarily in the glossopharyngeal and vagus nerves. The trigeminal and facial nerves carry this information for some parts of the head, while the glossopharyngeal and vagus nerves carry this information from many tissues of the body. This information then travels to a nucleus called the solitary nucleus in the lower brainstem, as well as several other brainstem areas. Most, if not all, of these areas probably project bilaterally via the solitariothalamic tracts to both thalami, which then probably project mostly to the insula and neighboring cortex, which is probably where viscerosensation is perceived.
Viscerosensory information is only occasionally consciously perceived, such as the awareness of a full urinary bladder. Instead, most of this information contributes to unconscious autonomic and endocrine (hormonal) functions.