parasympathetic nervous system

(redirected from Parasympathetic nervous systems)
Also found in: Dictionary, Thesaurus, Medical.
Related to Parasympathetic nervous systems: Parasympathetic division

parasympathetic nervous system:

see nervous systemnervous system,
network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
..... Click the link for more information.

Parasympathetic nervous system

A portion of the autonomic system. It consists of two neuron chains, but differs from the sympathetic nervous system in that the first neuron has a long axon and synapses with the second neuron near or in the organ innervated. In general, its action is in opposition to that of the sympathetic nervous system, which is the other part of the autonomic system. It cannot be said that one system, the sympathetic, always has a excitatory role and the other, the parasympathetic, an inhibitory role; the situation depends on the organ in question. However, it may be said that the sympathetic system, by altering the level at which various organs function, enables the body to rise to emergency demands encountered in flight, combat, pursuit, and pain. The parasympathetic system appears to be in control during such pleasant periods as digestion and rest. The alkaloid pilocarpine excites parasympathetic activity while atropine inhibits it. See Autonomic nervous system, Sympathetic nervous system

Parasympathetic Nervous System


the part of the autonomic nervous system whose ganglia are located very close to or in the innervated organs. The centers of the parasympathetic nervous system are found in the mesencephalon and medulla oblongata and in the sacral part of the spinal cord. The fibers of the parasympathetic nervous system proceed to the viscera as part of the third (oculomotor), seventh (facial), ninth (glossopharyngeal), and especially the tenth (vagus) cranial nerves and as part of the pelvic nerve.

In many cases, the parasympathetic and sympathetic nervous systems are directly opposed to one another in their effect on organs. Whereas sympathetic stimulation will act to accelerate and intensify heart contractions, raise the blood pressure, and dilate the pupils, parasympathetic stimulation will act to slow and weaken the heartbeat, lower arterial pressure, and contract the pupils. Efferent neurons of the parasympathetic nervous system are typically situated in the innervated organ proper and not in the separate trunk, as is the case in the sympathetic nervous system. The mediator substance formed in the nerve endings of the parasympathetic nervous system is acetylcholine; the predominant mediator substance in the sympathetic nervous system is norepinephrine.


parasympathetic nervous system

[¦par·ə‚sim·pə′thed·ik ′nər·vəs ‚sis·təm]
The craniosacral portion of the autonomic nervous system, consisting of preganglionic nerve fibers in certain sacral and cranial nerves, outlying ganglia, and postganglionic fibers.
References in periodicals archive ?
In the absence of heart failure pathology, the sympathetic and parasympathetic nervous systems work together to tightly regulate appropriate cardiovascular function in response to stresses encountered during normal activities of daily living.
The sympathetic and parasympathetic nervous systems evolved over millennia to protect us in potentially life-threatening situations.
Tai said the study supported the hypothesis that anxiety plays a role in PE and that clomipramine's antianxiety effects may be responsible for its efficacy in retarding ejaculation, and it suggested that men with PE might have an imbalance in their sympathetic and parasympathetic nervous systems, with early or dominant sympathetic activity.
Some benefits of breathwork are: managing pain and physical healing; balancing the left and right hemispheres of the brain; retraining your nervous system to tolerate higher charges of energy; balancing the sympathetic and parasympathetic nervous systems of the body; getting past resistance; accessing deeply unconscious psychical material, including prenatal, birth, and death; resolving early trauma; and enhancing the experience of deep spiritual connection.
Osvaldo Font, an MD in Puerto Rico who was recently nominated for the Nobel Prize in Medicine for his development of Electroneuromedular Therapy, has identified an electrical resistance or blockage in the spinal cord that causes a short circuit in the sympathetic and parasympathetic nervous systems.

Full browser ?