Parasympathetic Nervous System Overview
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Questions and Answers

What role does the oculomotor nerve have in the eye?

  • It provides sensory input for vision.
  • It regulates the production of tears.
  • It stimulates the dilator pupillae muscles.
  • It controls the constrictor pupillae muscles. (correct)

How does the parasympathetic system affect gastrointestinal function?

  • It inhibits peristalsis.
  • It constricts blood flow to the intestines.
  • It increases secretion of digestive enzymes. (correct)
  • It decreases gastrointestinal motility.

What is the role of the facial nerve in secretion?

  • It controls the secretion of tears from the lacrimal glands. (correct)
  • It enhances insulin secretion from the pancreas.
  • It stimulates the secretion of gastric juices in the stomach.
  • It regulates saliva production in the submandibular gland.

Which function is associated with the glossopharyngeal nerve?

<p>Controlling secretion of saliva in the parotid gland. (B)</p> Signup and view all the answers

What is the effect of the vagus nerve on the heart?

<p>It decreases heart rate and reduces inherited rhythm of the SA node. (C)</p> Signup and view all the answers

What is the primary effect of the vagus nerve on the heart?

<p>Decrease conductivity and rhythmicity (A), Promote vasoconstriction of coronary blood vessels (C)</p> Signup and view all the answers

Which of the following accurately describes the role of the parasympathetic nervous system in the gastrointestinal tract?

<p>Produces vasodilatation of blood vessels (B)</p> Signup and view all the answers

What is the primary function of the facial nerve in relation to salivary secretions?

<p>Production of true salivary secretion (B)</p> Signup and view all the answers

Which function is associated with the glossopharyngeal nerve?

<p>Stimulation of salivary secretion from the parotid gland (B)</p> Signup and view all the answers

Which of the following statements about sympathetic and parasympathetic interaction in salivary secretion is true?

<p>Sympathetic response inhibits salivary secretion. (D)</p> Signup and view all the answers

What effect does the vagus nerve have on the bronchi and bronchioles?

<p>Broncho-constriction and increased mucous secretion (B)</p> Signup and view all the answers

Which of the following is NOT a function of the parasympathetic nervous system in the pelvic region?

<p>Inhibition of bowel movement (A)</p> Signup and view all the answers

Which of these areas receives sympathetic innervation only?

<p>Heart ventricles (C)</p> Signup and view all the answers

What is a primary function of the oculomotor nerve in the parasympathetic nervous system?

<p>Narrowing of the pupil (B)</p> Signup and view all the answers

Which nerve is primarily involved in the secretion of saliva from the submandibular and sublingual glands?

<p>Facial nerve (A)</p> Signup and view all the answers

What is one of the key functions of the glossopharyngeal nerve in the parasympathetic system?

<p>Triggers true secretion in the parotid gland (B)</p> Signup and view all the answers

The vagus nerve primarily influences which of the following in the parasympathetic nervous system?

<p>Decreasing heart rate (D)</p> Signup and view all the answers

What physiological action is controlled by the facial nerve in the context of mucosal management?

<p>Secretion of mucus in the nasal cavity (B)</p> Signup and view all the answers

What effect does the vagus nerve have on the gastrointestinal tract?

<p>Stimulates digestive enzyme secretion (A)</p> Signup and view all the answers

What function does the constrictor pupillae muscle perform when activated by the oculomotor nerve?

<p>Narrows the pupil (B)</p> Signup and view all the answers

Which cranial nerve is responsible for triggering vasodilation of blood vessels in the face?

<p>Facial nerve (C)</p> Signup and view all the answers

Flashcards

Parasympathetic Structure

Structures controlled only by the parasympathetic nervous system include the constrictor pupillae muscles and the glands of the stomach and pancreas.

Autonomic Tone

The baseline activity level of the sympathetic and parasympathetic nervous systems.

Sympathetic Tone Effect

Sympathetic tone keeps blood vessels constricted, maintained by continuous sympathetic fiber discharge and basal adrenaline/noradrenaline release.

Parasympathetic Tone Function

Parasympathetic tone influences the heart (vagal tone) to slow down heart rate and the gastrointestinal tract to maintain normal function.

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Autonomic Reflexes

Most autonomic functions are carried out through reflexes that control functions like digestion, heart activity, breathing, and urination.

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Spinal Cord Reflexes

Reflexes like urination and defecation are controlled by the primitive centers in the spinal cord, independent of higher brain control.

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Brain Stem Autonomic Centers

The brain stem houses centers for things like heart function, breathing, digestion, and vomiting.

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Hypothalamus Autonomic Control

The hypothalamus controls most brain stem autonomic centers, influencing both parasympathetic and sympathetic functions.

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Cerebral Cortex Influence

The cerebral cortex (higher brain) affects emotional and conscious control over autonomic functions (like heart rate, digestion) and complex reflexes (urination, defecation).

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Parasympathetic Nervous System Origin

The parasympathetic nervous system originates from cranial nerves 3, 7, 9, and 10, and from the sacral segments (S2-S4).

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Cranial Nerves

Cranial nerves are nerves that originate from the brain and brainstem, carrying signals to and from different parts of the head, face, and body.

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Oculomotor Nerve (III)

Controls the muscles that move the eye ball and adjust pupil size and the lens for near vision.

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Facial Nerve (VII)

Facial expression, taste, and some glands in the head are controlled by this nerve that relays at the spheno-palatine ganglion.

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Glossopharyngeal Nerve (IX)

This cranial nerve plays a role in controlling swallowing, taste and salivation, relaying at the otic ganglion.

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Vagus Nerve (X)

The vagus nerve is the longest cranial nerve, affecting many functions including the heart, lungs, and digestive tract.

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Sacral outflow

The parasympathetic nerves arise from the lumbar and sacral spinal cord and supply the pelvic organs.

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Parasympathetic tone

Continuous input from the parasympathetic nervous system to regulate different body activities.

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Sympathetic and Parasympathetic Tone

The balance between sympathetic and parasympathetic nervous systems regulates bodily functions, and in most instances, a synergistic relationship is observed.

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Parasympathetic Function (Head & Neck)

Consists mainly in regulating glandular secretions in the head and neck and adjusting blood vessels.

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Pupil size (miosis)

Narrowing of the pupil due to parasympathetic stimulation.

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Accommodation

Adjustments in the shape of the eye lens to focus on near objects, controlled by the parasympathetic nervous system.

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Lacrimal Glands

Glands that produce tears, stimulated by the parasympathetic nervous system.

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Salivary Glands (Submandibular & Sublingual)

Glands making watery saliva, primarily controlled by the parasympathetic system.

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Salivary Glands (Parotid)

Glands making a thicker saliva, stimulated by a parasympathetic nerve.

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True Salivary Secretion

The type of saliva produced by the parasympathetic nervous system, rich in enzymes for digestion.

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Trophic Salivary Secretion

Saliva produced by the sympathetic nervous system, not directly involved in digestion but aiding in structure maintenance.

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X (Vagus) Nerve

A cranial nerve that carries 75% of the parasympathetic output, influencing various organs in the thorax and abdomen.

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Parasympathetic Thorax & Abdomen

Parasympathetic control over organs in the thorax & abdomen, affecting heart rate, bronchi, and digestive processes.

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Parasympathetic Functions (Heart)

Slowing heart rate, decreasing cardiac contraction and excitability, and constricting coronary blood vessels.

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Parasympathetic Functions (Lungs)

Contracting bronchi and bronchioles, increasing mucus secretion, and widening pulmonary blood vessels.

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Parasympathetic Functions (GI Tract)

Contracting GI muscles, relaxing sphincters, and enhancing secretions like HCL and mucous.

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Parasympathetic Functions (Liver and Gall Bladder)

Stimulating bile secretion and gall bladder contraction, leading to bile release.

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Parasympathetic Functions (Pancreas)

Stimulating pancreatic enzyme secretion and insulin production.

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Parasympathetic to Pelvis

Part of the parasympathetic system controlling urination, defecation, and sexual function in the lower body.

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Sympathetic-Parasympathetic Antagonism

Often opposing actions between sympathetic and parasympathetic systems, like in heart and lungs.

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Sympathetic-Parasympathetic Synergism

Sometimes, sympathetic and parasympathetic work together, as in the case of salivary secretions.

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Sympathetic Functions (Only)

Controlling functions like pupil dilation, heart ventricles, most blood vessels, and others.

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Study Notes

Parasympathetic Nervous System

  • The parasympathetic nervous system (PNS) regulates a wide range of bodily functions, typically promoting "rest-and-digest" responses.

  • Objectives: The lecture aims to cover the origin and components of the parasympathetic nervous system (PNS). It also touches on the parasympathetic tone, the functions of the PNS in various areas of the body, its relation to the sympathetic nervous system, and its roles in functions like micturition.

Cranial Outflow

  • Cranial nerves 3, 7, 9, and 10 are part of the parasympathetic system
  • III - Oculomotor nerve
  • VII - Facial nerve
  • IX - Glossopharyngeal nerve
  • X - Vagus nerve

Sacral Outflow

  • The sacral outflow originates from the lumbar spinal cord segments 2, 3, and 4
  • The preganglionic fibers form the pelvic nerve

Parasympathetic Supply to Head and Neck

  • III - Oculomotor nerve: The PNS, via this nerve, causes pupil constriction (miosis) and facilitates focusing the eye for near vision (accommodation). This process occurs at the ciliary ganglion.

  • VII - Facial nerve (Chord tympanic branch): PNS stimulation via this nerve increases salivary secretion (true saliva) in submandibular & sublingual salivary glands, and causes vasodilation in the blood vessels of the face and anterior 2/3 of the tongue. This action takes place within the submandibular ganglion.

  • IX - Glossopharyngeal nerve: PNS stimulation by this nerve triggers true salivary secretion in the parotid salivary gland and vasodilation in the blood vessels of the parotid gland and posterior 1/3 of the tongue, happening at the otic ganglion.

Parasympathetic to Thorax and Abdomen

  • X - Vagus nerve: The vagus nerve represents a significant portion (75%) of the parasympathetic supply to the thorax and abdomen.

  • Relay occurs in terminal ganglia within the thoracic and abdominal viscera.

  • Thorax (heart and lungs): Parasympathetic functions in the thorax include reducing heart rate, decreasing conductivity, contractility, excitability, & rhythmicity, constricting the coronary blood vessels, reducing blood flow to the cardiac muscle. The vagus nerve also causes bronchoconstriction in the lungs, increasing mucous secretion and vasodilation.

  • Abdomen (GI tract, liver, pancreas): The parasympathetic system stimulates motility in the gastrointestinal tract, increases secretions (HCl and mucus) in the gastric glands, causes vasodilation in the blood vessels, stimulates bile secretion in the liver, and stimulates pancreatic juice secretion and insulin secretion in the pancreas.

Parasympathetic to the Pelvis

  • Origin: Sacral segments 2, 3, and 4.

  • Relay: Terminal ganglia

  • Urinary bladder: The PNS contracts the bladder wall and relaxes the internal urethral sphincter, facilitating urination.

  • Rectum and anal canal: The PNS contracts the rectum and relaxes the internal anal sphincter, promoting defecation.

  • Sex organs: Parasympathetic activity supports vasodilation in the blood vessels of the sex organs.

  • Autonomic Nervous System Control: Autonomic functions are controlled by reflexes. Reflexes are routed through the spinal cord, brain stem (medulla oblongata, pons, midbrain), and the hypothalamus (temperature, water balance, eating, & behavior).

  • The cerebral cortex has higher controls over micturition and defecation, and the hypothalamus controls the activity of autonomic centers in the brain stem.

Sympathetic and Parasympathetic Tone

  • The tone is the basal rate of activity of both the sympathetic and parasympathetic systems.
  • Sympathetic tone is responsible for maintaining the constriction of blood vessels. The sympathetic tone is continuously stimulated through sympathetic fibers and by the level of adrenaline and noradrenaline secretion from the adrenal medulla.
  • Parasympathetic tone is critical for heart rate control and GI function (decreasing SA node's high rhythm, and maintaining normal functioning of the GI tract).

Structures Supplied Primarily by Each System

  • Sympathetic Systems: Supplies dilator pupillae muscle, ventricles of the heart, most blood vessels, spleen, adrenal medulla, and skin

  • Parasympathetic Systems: Supplies sphincter pupillae muscles, stomach glands, pancreas.

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Description

This quiz explores the origin and components of the parasympathetic nervous system, focusing on its functions and relation to the sympathetic nervous system. Key areas discussed include cranial and sacral outflows, as well as the specific roles of cranial nerves in regulating bodily functions. Test your understanding of the PNS and its significance in maintaining homeostasis.

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