Ans Nervous System Essay

1297 WordsMar 30, 20056 Pages
The Structure & function of the Autonomic Nervous System Introduction: The organs of our body are controlled by many systems in order to function correctly and efficiently in order to survive within the environment we live in. These include the heart, stomach and intestines and other vital organs and body systems. All of the systems in our body are regulated by a part of the nervous system called the autonomic nervous system (ANS). The ANS is part of the peripheral nervous system and it controls many organs and muscles within the body. Rather bizarrely we are unable to determine or feel its presence in our bodies as it is working involuntary, as a reflexive manner. A common example of this involuntary action is best understood when…show more content…
The preganglionic fibre from the medulla or spinal cord projects to ganglia very close to the target organ and makes a synapse. This synapse uses the neurotransmitter called acetylcholine. From this ganglion, the postganglionic neuron projects to the target organ and uses acetylcholine again at its terminal. Figure. 1: Autonomic nervous system Para-sympathetic and sympathetic differences: The sympathetic and parasympathetic nervous system generally have opposing effects on organs they supply, and this enables the body to make rapid and precise adjustments of involuntary activities in order to maintain a steady state. An example is an increase in heart rate due to the release of noradrenalin by sympathetic neurones, this is then compensated for by, the release of acetylcholine by parasympathetic neurones. This prevents heart rate from increasing beyond its working capabilities and allows it to reduce and settle back to its resting state. The effects of sympathetic and parasympathetic stimulation are tabulated below in figure. 2. Notice that the effects are generally in opposition to each other, in relation to each organ affected by a particular reflex. Feature Sympathetic Parasympathetic Origin of Neurones Emerge from cranial, thoracic and lumbar regions of CNS Emerge from cranial and sacral regions of CNS Position of Ganglion Close to spinal cord Close to effector Length of Fibres Short

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