The sympathetic and parasympathetic nervous systems are two divisions of the autonomic nervous system, which is responsible for involuntary bodily functions. They have complementary roles and often act in opposition to maintain homeostasis. Here are five key differences between the sympathetic and parasympathetic nervous systems:
Function:
Sympathetic Nervous System: The sympathetic nervous system is often referred to as the “fight or flight” system. Its primary function is to prepare the body for stressful situations by increasing alertness, heart rate, and metabolic rate. It redirects blood flow to the muscles and releases energy reserves.
Parasympathetic Nervous System: The parasympathetic nervous system is known as the “rest and digest” system. Its primary function is to promote relaxation and recovery. It slows heart rate, stimulates digestion, and conserves energy.
Neurotransmitters:
Sympathetic Nervous System: The primary neurotransmitter of the sympathetic system is norepinephrine (noradrenaline). It is released at various target organs to activate the “fight or flight” response.
Parasympathetic Nervous System: The primary neurotransmitter of the parasympathetic system is acetylcholine. It is released at various target organs to promote the “rest and digest” response.
Location of Ganglia:
Sympathetic Nervous System: Sympathetic ganglia are located closer to the spinal cord. This arrangement allows for rapid and widespread activation of the sympathetic response.
Parasympathetic Nervous System: Parasympathetic ganglia are located closer to or within the target organs. This arrangement allows for more localized and specific control of the parasympathetic response.
Pupil Dilation/Constriction:
Sympathetic Nervous System: The sympathetic system causes pupil dilation (mydriasis) to improve vision in preparation for a potential threat.
Parasympathetic Nervous System: The parasympathetic system causes pupil constriction (miosis) to reduce the amount of light entering the eye and promote near vision.
Effect on Digestive System:
Sympathetic Nervous System: Sympathetic activation inhibits digestive processes. Blood flow is diverted away from the digestive organs, and digestive activities are temporarily suppressed during the “fight or flight” response.
Parasympathetic Nervous System: Parasympathetic activation stimulates digestive processes. It increases blood flow to the digestive organs, enhances secretion of digestive enzymes, and promotes nutrient absorption.
In summary, the sympathetic and parasympathetic nervous systems have opposing effects on various physiological functions. The sympathetic system prepares the body for action in response to stress, while the parasympathetic system promotes relaxation and recovery during restful periods. These systems work together to maintain a balance in the body’s autonomic functions.