The Nervous System

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The Autonomic Nervous syetem (ANS) controls involuntary bobily functions, for example the beating heart. The autonomic nervous syetem is coposed of the numerous nerves which projects from the brain and the spinal cord to the smoothmuscles of various babily organs.There are two major parts to the autonomic syetem which often works in oppsition to each other, but not always. One is the sympathetic system. The sympathetic nervous system is often called the fight-flight response system. This system increases heart rate and bloood pressure, and distributes blood to exterior muscles.This system become activated when arousal level increases. The other part, the parasympathetic system reduces heart rate and blood pressure and diverts blood to the digestive tract. This system is active when arousal or emotional level low. It is ultimately responsible for the build up and conservation of bodily stores of energy.

When the sympathetic system become activated as a result of an increase in atousal level, severl physioloical symptoms result.

First, blood vessels in the stomach, intestines and iterior of the body tend to contract while those of the exterior muscles of the trunk and limbs tend to expand. As a result, blood is shifted from digestive functions to musclar functions in order to facilitate greater musclar activity. Second, more blood is pumped to the muscles through the circulatory system. This occurs because nervous impulses to the heart caus it to beat harder and faster, thus increasing blood pressure and pulse rate.

Sveral other autonomic changes occer during a heightended arosal start. Fear, for example is characterised by such changes as increase a pupil size, drying of the mouth, and the stopping or reversal of stomach and intestinal contractions. During an aroused start, the sympathetic system also dischages two hormones, adrenalin and noradernalin. These are secrerted by the adrenal...