The spinal cord is a particularly important part of the nervous system. It connects the central nervous system with the peripheral nervous system. The peripheral nervous system itself consists of sensory and alpha motor neurons. These mediate our ability to sense and engage in voluntary behavior. The spinal cord integrates and mediates feedback between pathways involved in sensory and motor abilities. This is how we are able to engage in limb movements and locomation.
Different spinal segments control different parts of the body. The segments near the top deal with the neck’s sensory and muscle information. Those are the bottom deal with the toes. There are 3 coccygeal, 5 sacral, 5 lumbar, 12 thoracic and 8 cervical cord segments, numbered from top to bottom. The functioned of the aforementioned alpha motor neurons is to innervate muscle cells. These cells then cause limbs to move.
In addition to the central nervous system is the autonomic nervous system. This controls organs with smooth muscles as well as the heart, glands and intestines. The autonomic nervous system is divided between the sympathetic and parasympathetic nervous systems. The first prepares the body for action. It does so partially by decreasing intestinal activity so that the body prepares to either fight or flee something. Norepinephrine is the sympathetic nervous system’s primary neurotransmitter and acetylcholine is the parasympathetic nervous systems primary neurotransmitter. The first speeds things up and the second slows things down.
Norepinephrine prepares the body for action. The adrenal medulla is the means by which much o this happens. Digestive functions dexcrease, bladder contractions and blood flow to the genitals are inhibited and the pupil becomes dilated.
Amthor, Frank (2011-11-09). Neuroscience For Dummies (Kindle Locations 979-980). Wiley. Kindle Edition.