Dr. Martin's notes

Tuesday September 13, 2016

The other nervous system is called the autonomic nervous system (ANS) and it controls the automatic functions of the body, such as breathing, heartbeat, digestion, kidney and other organ function, etc. The ANS nerve fibers exit from the spinal cord from T1-L3

The Autonomic Nervous System (ANS) has two subdivisions, the sympathetic and the parasympathetic divisions. Most often these two have opposing effects.

The sympathetic division causes excitation and prepares the body for heightened levels of (somatic) activity. When fully activated this produces what is known as the “fight or flight” response. This activity prepares the body for a crisis that requires sudden action or activity.
The general pattern is heightened mental alertness, increased metabolic rate, reduced digestive and urinary function, activation of emergency reserves, increased respiration, dilatation of respiratory vessels, increased heart rate, increased blood pressure and activation of sweat glands.

The sympathetic division is found in the thoracolumbar area (T1-L2). They consist of shorter preganglionic fibers and longer postganglionic fibers. All these fibers release acetylcholine (Ach) and the effects are always excitatory.

The parasympathetic division stimulates visceral response and is known for the “rest and repose” state. Your body relaxes and energy demands are minimal.

The pattern of response for the parasympathetic system is lower heart rate, lower blood pressure, increased digestion, increased urination, increased salivation, increased motility and blood flow.

This system is found in the craniosacral division (brainstem and S2-S4) and consist of longer preganglionic fibers and shorter postganglionic fibers. Most postganglionic fibers release the neurotransmitter norepiephrine (NE).

The two systems are anatomically as well as functionally distinct.