The neuronal pathway that allows for
somatic sensation involves the somatosensory system. Somatic sensations from
the skin, muscles, and tendons in joints are received by specific receptors.
There are three broad types of somatic sensations namely epicritic,
protopathic, and deep sensations. Sensory pathways are either part of the
somatosensory system or part of the viscerosensory system. Each sensory pathway
is formed by two or three neurons namely first, second, and third-order
neurons.
Somatic motor
control is achieved through neural control via feedback signals between the
central and peripheral nervous system as well as the skeletal muscles. The
sympathetic system increases somatic motor activity while the parasympathetic
system decreases it. Both sympathetic and parasympathetic systems release
neurotransmitter substances at the neuromuscular junction. Acetylcholine or
nitric oxide is the neurotransmitter for parasympathetic control whereas norepinephrine
is the neurotransmitter for sympathetic control.
The autonomic
nervous system in healthy individuals is regulated at the level of the sympathetic
and parasympathetic divisions. Activation and inhibition systems act on the
sympathetic division whereas the vagal regulation system acts on the
parasympathetic division.
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