Parasympathetic Nervous System (Overview, Scheme) | Neuroanatomy 

Content:
Introduction 0:00
Ganglion and Nucleus 01:35
General Structure 02:06
Sympathetic VS Parasympathetic 02:55
Neurotransmitters 06:10
Craniosacral Outflow 07:35
Cranial Part 08:55
Sacral Part 17:42
Ending 19:19
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Parasympathetic nervous system is a part of the autonomic nervous system, which is under the motor division of the peripheral nervous system.
General Structures and Terms:
- Group of cell bodies in CNS - Nucleus
- Group of cell bodies outside CNS - Ganglion
- Presynaptic neuron is a cholinergic neuron (Ach binds to nicotinic receptors, allowing an influx of cations)
- Postganglionic neurons are also cholinergic neurons (Acetylcholine binds to muscarinic receptors of the target organ, activating a g-protein)
General Functional Aspects of the Sympathetic and Parasympathetic Divisions:
Antagonistic Systems:
Territory:
- Sympathetic: All areas of the body
- Parasympathetic: Not all areas, no innervation in the body wall and limbs
Activity:
- Sympathetic: More generalized and indirect. Ratio of pre- to postganglionic neurons is 1:15 or more.
- E.g., accelerated heart rate, bronchodilation, decreased peristalsis in the gut tube, closing of the sphincters, relaxation of the general bladder wall, and dilation of the pupils.
- Parasympathetic: More specific and direct, Ratio of pre- to postganglionic neurons is 1:2
- Decelerated heart rate, bronchoconstriction, increased gut peristalsis, opening of sphincters, contraction of the bladder wall, and constriction of the pupils.
Functions:
- Sympathetic: Classic ''Fight-or-Flight''. Increase levels of activity and assistance in coping with stress and physical exertion
- Parasympathetic: Classic ''Rest-and-Digest''. Homeostasis, restoration, recuperation, and relaxation
Complementary (Synergistic) Systems:
- Parasympathetic activity produces erection, and sympathetic activity results in ejaculation.
Independent function:
- Sympathetic activates sweat gland secretion, but parasympathetics play no role in sweat gland activity.
Cranial Outflow:
- Oculomotor nerve (nervus oculomotorius)
- Nucleus: Edinger-Westphal nucleus, accessory oculomotor nucleus (nucleus accessorii nervi oculomotorii)
- Synapse with Ciliary ganglion (ganglion ciliare), and innervates the ciliary body and sphincter pupillae
- Facial nerve (nervus facialis)
- Nucleus: Superior salivatory nucleus (nucleus salivatorius superior)
- Greater petrosal nerve synapse with Pterygopalatine ganglion (ganglion pterygopalatinum) to innervate the lacrimal, palatine, nasal and nasopharyngeal glands.
- Chorda tympani synapse with Submandibular ganglion (ganglion submandibulare) to innervate submandibular and sublingual glands
- Glossopharyngeal nerve (nervus glossopharyngeus)
- Nucleus: Inferior salivatory nucleus (nucleus salivatorius inferior)
- Lesser petrosal nerve synapse with otic ganglion (ganglion oticum), then innervates the parotid gland
- Vagus nerve (nervus vagus)
- Nucleus: Posterior nucleus of the vagus nerve (nucleus posterior nervi vagi)
- Innervates smooth muscle, glands, internal organs
Sacral Outflow:
- Sacral parasympathetic nuclei in the lateral horns of the spinal cord as Intermediolateral nucleus (nucleus intermediolateralis) S2, S2, and S4
- Sacral splanchnic nerves (nervi splanchnici sacrales)
- Preganglionic fibers going into the inferior hypogastric plexus (plexus hypogastricus inferior) and through organs of the lesser pelvis and synapse with purely parasympathetic ganglia.
Sources:
- Singh, I. (2017). Human Neuroanatomy (10th ed.).
- Wineski, L. E. (2019). Snell’s Clinical Anatomy by Regions (10th ed.). Pearson.
- Kozlowski, T. (2017). *Memorix Anatomy: The Complete Study Guide*. 2nd ed. Thieme Medical Publishers.
- Fryer, A. D., & Jacoby, D. B. (1998). Muscarinic Receptors and Control of Airway Smooth Muscle. *American Journal of Respiratory and Critical Care Medicine, 158*(Supplement 2), 13tac120. doi.org/10.1164/ajrccm.158.su...
- Pterygopalatine Ganglion. (n.d.). *ScienceDirect*. Retrieved 20.01.2024.
- Selective Serotonin Reuptake Inhibitors for Premature Ejaculation: Review of Erectile and Ejaculatory Side Effects - Scientific Figure on ResearchGate. Available from: www.researchgate.net/figure/F... [accessed 23 Jan, 2024]
- University lectures and notes
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