The parasympathetic nervous system is especially active during which physiological state?
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Contents loading... Editors loading... Categories loading... When refering to evidence in academic writing, you should always try to reference the primary (original) source. That is usually the journal article where the information was first stated. In most cases Physiopedia articles are a secondary source and so should not be used as references. Physiopedia articles are best used to find the original sources of information (see the references list at the bottom of the article). If you believe that this Physiopedia article is the primary source for the information you are refering to, you can use the button below to access a related citation statement. Introduction[edit | edit source] The parasympathetic nervous system (PNS) is one of the two functionally distinct and continuously active divisions of the autonomic nervous system (ANS). It is in opposition to the other, the sympathetic nervous system (SNS). The parasympathetic nervous system predominates in quiet “rest and digest” conditions while the sympathetic nervous system drives the “fight or flight” response in stressful situations. The main purpose of the PNS is to conserve energy to be used later and to regulate bodily functions like digestion and urination[1]. Structure[edit | edit source]Both divisions of the ANS are comprised of a complex network of pathways responsible for maintaining the physiologic integrity of organs, tissues, and cells. They are composed of pre- and postganglionic neurons that act on effector organs. The parasympathetic nervous system originates from medial medullary sites (nucleus ambiguous, nucleus tractus solitarius, and dorsal motor nucleus) and is modulated by the hypothalamus.[2]
Functions[edit | edit source]An easy acronym to remember how and where the PSNS works is SLUDD. This stands for:
Also the PNS supplied the nerves and blood vessels responsible for the male erection[3] PSNS and the Heart[edit | edit source]There are a number of special receptors for the PSNS in your heart called muscarinic receptors (M2 receptors). Parasympathetic stimulation of M2 receptors causes decreased heart rate and velocity of conduction through the AV node, inhibiting sympathetic nervous system action. This means they’re responsible for helping to maintain resting heart rate. For most people, the resting heart rate is between 60 and 100 beats per minute (on the other hand, the sympathetic nervous system increases heart rate). According to an article in the Circulation (AHA)[2] a person’s resting heart rate can be one indicator of how well a person’s PSNS, specifically the vagus nerve, is working. This is usually only the case when a person doesn’t take medications that affect heart rate, like beta-blockers, or have medical conditions affecting the heart. Eg heart failure reduces the response of the parasympathetic nervous system. The results can be an increased heart rate, which is the body’s way of trying to improve the amount of blood it pumps through the body[3]. PSNS and the Lungs[edit | edit source]In the lungs, parasympathetic stimulation of M3 receptors leads to bronchoconstriction. It also increases bronchial secretions.
Parasympathetic/Sympathetic Interactions[edit | edit source]The sympathetic and parasympathetic nervous systems are not “opposites”; rather, the interactions are complex. A dynamic interaction occurs between them; these interactions are modulated partially by secondary messengers (cAMP and cGMP). The parasympathetic nervous system can inhibit sympathetic nerve traffic presynaptically. Likewise, sympathetic activation can inhibit parasympathetic activation presynaptically. Vagal “tone” (tonic parasympathetic activation) predominates over sympathetic tone at rest.[2]
Dysfunction[edit | edit source]
References[edit | edit source]
When the parasympathetic nervous system is activated?When the parasympathetic nervous system (PSNS) is activated, it slows our heart and breathing rates, lowers blood pressure and promotes digestion. Our body enters a state of relaxation, and this relaxation breeds recovery.
Which physiologic response occurs with parasympathetic stimulation?Body functions stimulated by the parasympathetic nervous system (PSNS) include sexual arousal, salivation, lacrimation, urination, digestion, and defecation. The PSNS primarily uses acetylcholine as its neurotransmitter. Peptides (such as cholecystokinin) may also act on the PSNS as neurotransmitters.
What causes the parasympathetic nervous system to activate?Within the PSNS, acetylcholine is the chief neurotransmitter. Acetylcholine is stored within the vesicles of neurons and is released by postganglionic neurons when nerve impulses running down the neuron activate this response.
Which activity activates parasympathetic?Breathing. We discussed how the parasympathetic nervous system slows the breathing down. But if you intentionally focus on slowing your breathing, even during moments of stress or "fight-or-flight," it can trigger the parasympathetic nervous system response. Practice taking slow deep breaths from the diaphragm.
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