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The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. [1] [2] The autonomic nervous system is responsible for regulating the body's unconscious actions.
The reflex, controlled by the parasympathetic nervous system, involves three responses: pupil constriction, lens accommodation, and convergence. A near object (for example, a computer screen) subtends a large area in the visual field, i.e. the eyes receive light from wide angles. When moving focus from a distant to a near object, the eyes converge.
Increased parasympathetic outflow prominently affects the heart, reducing the heart rate or, in extreme cases, completely halting heart beats. This is a common cause of fainting. [3] The parasympathetic nervous system is dominant in situations of rest and relaxation, it has an activating effect on digestive organs and a relieving one on the heart.
The somatic nervous system directs all voluntary movements of the skeletal muscles, and can be sub-divided into afferent and efferent neuronal flow. The autonomic nervous system is divided primarily into the sympathetic and parasympathetic nervous systems with a third system, the enteric nervous system, receiving less recognition. [2]
Human nervous system. Human nervous system – the part of the human body that coordinates a person's voluntary and involuntary actions and transmits signals between different parts of the body. The human nervous system consists of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
The parasympathetic nervous system kicks in to quickly drop heart rate, relax the body and conserve oxygen. Learning how to turn on your parasympathetic nervous system is key to handling stress ...
The sympathetic and parasympathetic branches of the autonomic nervous system have opposing effects on blood pressure. Sympathetic activation leads to an elevation of total peripheral resistance and cardiac output via increased contractility of the heart, heart rate , and arterial vasoconstriction , which tends to increase blood pressure.
Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system. Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. The exceptions are the four paired parasympathetic ganglia of the head and neck.