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The sympathetic nervous system belongs to autonomic nervous system along with parasympathetic nervous system. The sympathetic nerves starts from the spinal column running towards the middle part of spinal cord in the lateral horn. It originates at the spinal cord?s first thoracic segment and extends to third lumbar segment. This nervous system is considered to have thoracolumbar outflow since the cells of these nerves originates in the lumbar and thoracic regions. The primary function of this nervous system is mobilization of the body?s nervous system due to fight or flight response.
This is done by mediating hormonal and neuronal stress response. This nervous system is continuously active to maintain stability, temperature, and pH of the body. Primarily, this nervous system counteracts parasympathetic nervous system. This system also helps in controlling the internal organs of the body such as eyes, heart, lungs, blood vessels, sweat glands, digestive system, kidney, and penis. Dilation of pupils, rate and force of contraction, dilation of bronchioles, constriction of blood vessels, activation of sweat secretion, inhibition of peristalsis, promotion of renin secretion, and promotion of ejaculation in men are all aided by this nervous system. Since the messages through this system travels in a bidirectional flow, both afferent and efferent messages help in various functions of the body such as acceleration of heart rate, widening of bronchial passages to give increased oxygen, decreased movement of large intestine, piloerection, and perspiration.
It also helps in feeling sensations like cold, heat, and pain. The stress response of this system is also known as sympathoadrenal response since the preganglionic fibers of this nervous system activates secretion of adrenaline and noradrenaline which are commonly called epinephrine and norepinephrine.
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