It regulates endocrine activity via the pituitary gland it controls energy metabolism, body temperature, blood flow & blood composition and it drives behavior related to feeding, mating and emotional responses.
The hypothalamus is the major homeostatic control & circadian rhythm center of the brain. Projections from the amydala are widespread to cerebral cortex, hypothalamus, PAG, parabrachial nuclei and the NST. Memory related input comes from the hippocampus and adjacent neocortex. Autonomic input arrives from insular cortex, hypothalamus and parabrachial nuclei. It receives sensory input from thalamus and association cortex per sensory modality. The amygdala, a limbic basal nucleus of the rhinencephalon, is involved in generating visceral activity, particularly fearful emotional behavior. The medial frontal cortex (rostroventral cingulate gyrus) is a visceral motor area of neocortex. The insular cortex (deep to sylvian fissure) is a visceral sensory area of the neocortex that receives input from the thalamus (ventral posterior nuclei). The network is widely distributed in the brainstem and cerebrum, with rich connections to limbic structures involved in emotional status and behavior. (Rostrally the NST receives SVA taste from cranial nerves VII, IX,& X.)Ī network of Autonomic Control Centers process & relay visceral input and regulates visceral activity via descending projection neurons (premotor neurons) to preganglionic nuclei. It receives GVA input from glossopharyngeal and vagus nerves and sends output to parasympathetic preganglionic neurons, to premotor autonomic centers, and to the thalamus and limbic system. The nucleus of the solitary tract (NST) is the main visceral sensory nucleus in the brainstem. Conscious visceral sensations include levels of fullness and pain, the latter is typically referred pain because visceral and somatic afferent neurons generally share projection neurons. Sensory nuclei contain interneurons (for visceral reflexes) and projection neurons (for conscious and subconscious ascending pathways). Only about 10 percent of total afferent input to the CNS is visceral (GVA) compared to somatic (GSA) sense, visceral sensation is meager.Ĭentral branches of GVA primary afferent neurons synapse within sensory nuclei in the spinal cord & brainstem.
#Sensory somatic nervous system free#
Visceral receptors are generally free nerve endings (although Pacinian corpuscles are present in viscera). Spinal afferents convey noxious and temperature sensations cranial nerve afferent traffic is largely subconscious. Visceral Afferent Neurons & Sensory NucleiĬell bodies of General Visceral Afferent (GVA) primary afferent neurons reside in spinal ganglia and in the distal ganglia (petrosal & nodose) of glossopharyngeal and vagus cranial nerves.
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