Normal function of all components of the ANS is not required to maintain life, as long as
environmental conditions are a constant and optimum. Abnormal autonomic functions, however,
markedly affect the individual's ability to respond to changing conditions. This can be demonstrated
by sympathectomy, the removal of sympathetic ganglia. An animal becomes highly sensitive to heat,
cold, or other forms of stress following sympathectomy. In a hot environment the animal's ability to
lose heat by increasing blood flow to the skin and by sweating is decreased. When exposed to the
cold, the animal is less able to reduce blood flow to the skin and conserve heat. Sympathectomy also
results in low blood pressure caused by dilation of peripheral blood vessels and results in the
inability to increase blood pressure during periods of physical activity.
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