<P> The sympathetic system is activated during a "fight or flight" situation in which great mental stress or physical danger is encountered . Neurotransmitters such as norepinephrine, and epinephrine are released, which increases heart rate and blood flow in certain areas like muscle, while simultaneously decreasing activities of non-critical functions for survival, like digestion . The systems are independent to each other, which allows activation of certain parts of the body, while others remain rested . </P> <P> Primarily using the neurotransmitter acetylcholine (ACh) as a mediator, the parasympathetic system allows the body to function in a "rest and digest" state . Consequently, when the parasympathetic system dominates the body, there are increases in salivation and activities in digestion, while heart rate and other sympathetic response decrease . Unlike the sympathetic system, humans have some voluntary controls in the parasympathetic system . The most prominent examples of this control are urination and defecation . </P> <P> Diseases of the peripheral nervous system can be specific to one or more nerves, or affect the system as a whole . </P> <P> Any peripheral nerve or nerve root can be damaged, called a mononeuropathy . Such injuries can be because of injury or trauma, or compression . Compression of nerves can occur because of a tumour mass or injury . Alternatively, if a nerve is in an area with a fixed size it may be trapped if the other components increase in size, such as carpal tunnel syndrome and tarsal tunnel syndrome . Common symptoms of carpal tunnel syndrome include pain and numbness in the thumb, index and middle finger . In peripheral neuropathy, the function one or more nerves are damaged through a variety of means . Toxic damage may occur because of diabetes (diabetic neuropathy), alcohol, heavy metals or other toxins; some infections; autoimmune and inflammatory conditions such as amyloidosis and sarcoidosis . Peripheral neuropathy is associated with a sensory loss in a "glove and stocking" distribution that begins at the peripheral and slowly progresses upwards, and may also be associated with acute and chronic pain . Peripheral neuropathy is not just limited to the somatosensory nerves, but the autonomic nervous system too (autonomic neuropathy). </P>

Describe the sensory and motor functions of the peripheral nervous system