Human Body Function 102: Parasympathetic Nervous System

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Questions and Answers

Which cranial nerve is responsible for increasing mucous secretion in the nose, mouth, pharynx, and palate?

Facial nerve (correct)

Glossopharyngeal nerve

Vagus nerve

Optic nerve

Which of the following correctly describes the origin of the sacral part of the parasympathetic nervous system?

Nuclei of the 10th cranial nerve

Nuclei of the 3rd cranial nerve

Lateral gray horn of S2-S4 segments (correct)

Nuclei of the 9th cranial nerve

Which cranial nerve relays in the otic ganglion to innervate the parotid gland?

Vagus nerve

Trigeminal nerve

Glossopharyngeal nerve (correct)

Facial nerve

What is the primary function of the facial nerve's chorda tympani branch?

Vasodilation of salivary gland blood vessels (A) Signup and view all the answers

Which of the following is NOT a function of the facial nerve related to parasympathetic action?

Heart rate modulation (A) Signup and view all the answers

Which of the following structures does NOT receive innervation from the parasympathetic nervous system?

Skeletal muscles of the limbs (B) Signup and view all the answers

The term 'cranio-sacral outflow' refers to which components of the parasympathetic nervous system?

Cranial and sacral parts (D) Signup and view all the answers

What is the major function of the vagus nerve in the context of the parasympathetic nervous system?

Influencing heart rate and gastrointestinal motility (C) Signup and view all the answers

How do postganglionic fibers of the facial nerve contribute to the function of saliva production?

They stimulate the secretion of watery saliva (B) Signup and view all the answers

What is the main role of the vagus nerve in the thorax?

It inhibits cardiac properties. (C) Signup and view all the answers

Which statement about the parasympathetic nervous system's effect on the gastrointestinal tract is correct?

It promotes contraction of the esophagus for swallowing. (A) Signup and view all the answers

What is a function of the vagus nerve regarding the blood vessels?

It causes vasodilation in the thoracic region. (B) Signup and view all the answers

How does parasympathetic stimulation affect the bronchioles?

It increases mucous secretion and causes broncho-constriction. (C) Signup and view all the answers

What do the preganglionic fibers of the sacral division primarily innervate?

Organs of the pelvis and lower abdomen. (A) Signup and view all the answers

Which statement describes the overall effect of vagus nerve stimulation on the heart?

It decreases rhythmicity. (C) Signup and view all the answers

What is primarily stimulated in the liver by the parasympathetic nervous system?

Bile secretion. (A) Signup and view all the answers

Which action is NOT typically a function of the vagus nerve?

Increase in heart rate. (B) Signup and view all the answers

Which of the following structures does NOT receive parasympathetic innervation from the vagus nerve?

Kidneys. (B) Signup and view all the answers

How does the vagus nerve affect the smooth muscles of the gastrointestinal tract?

It relaxes the sphincters. (D) Signup and view all the answers

What is the primary role of the pelvic nerve in micturition?

Contraction of the bladder wall and relaxation of the internal urethral sphincter (B) Signup and view all the answers

Which statement best distinguishes between the internal and external sphincters?

The internal sphincter is more fatigue-resistant than the external sphincter. (A) Signup and view all the answers

What happens during the process of defecation?

Contraction of the rectum wall and relaxation of the internal anal sphincter (C) Signup and view all the answers

In terms of the sympathetic and parasympathetic systems, what is true about their relationship?

Synergistic actions are evident in salivary secretion. (C) Signup and view all the answers

During sexual intercourse, what role does the parasympathetic system primarily play?

It promotes erection in both males and females. (D) Signup and view all the answers

Which component is NOT associated with the 'rest and digest' responses of the parasympathetic system?

Increased metabolic rate (A) Signup and view all the answers

Which statement about the vagus nerve is incorrect?

It has a direct effect on increasing heart contractility. (D) Signup and view all the answers

What is a key function of the prostate and seminal vesicles in male reproductive physiology?

They stimulate secretion to aid in sperm transport. (A) Signup and view all the answers

Which physiological response is NOT functionally associated with the sympathetic system?

Stimulation of urination (B) Signup and view all the answers

What differentiates the roles of the pudendal nerve in relation to the sphincters?

It facilitates voluntary control over the external sphincter. (D) Signup and view all the answers

Study Notes

Faculty of Medicine Details

Academic Year: 2024-2025
Year: 1
Module: Human Body Function (HBF) 102

Parasympathetic Nervous System II

Presented by: Dr. Mohamed abo El Hassan and Dr. Ramadan Saad
Department: Clinical Physiology

Objectives

Describe the functions of the parasympathetic cranial nerves (VII Facial, IX Glossopharyngeal, and X Vagus).
Describe the functions of the sacral part of the parasympathetic nervous system.
Illustrate the relationship between the sympathetic and parasympathetic nervous systems.
Compare the functions of sympathetic and parasympathetic systems.

Origin of Parasympathetic Nervous System

Cranial outflow: Nuclei of the 3rd, 7th, 9th, and 10th cranial nerves in the brainstem.
Sacral outflow: Lateral gray horn of S2-S4 segments of the spinal cord.

Cranial Outflow

Preganglionic fibers from cranial outflow are carried by the 3rd, 7th, 9th, and 10th cranial nerves.
These fibers terminate in ciliary, pterygopalatine, submandibular, otic, and peripheral ganglia.
Postganglionic fibers innervate organs of the head, neck, thorax, and abdomen.

VII - Facial Nerve

Origin & Relay: Superior salivary nucleus in pons, relays in the sphenopalatine ganglion via the superficial petrosal nerve.
Functions:
- Secretion of tears to lacrimal glands
- Increase mucous secretion to mucous glands in nose, mouth, and pharynx
- Vasodilation (VD) of blood vessels.

Chorda Tympani Nerve (Branch of Facial Nerve)

Relay: Submandibular ganglion
Postganglionic fiber functions:
- Stimulation of submandibular and sublingual salivary glands, resulting in watery saliva with lower organic substance content.
- Vasodilation of blood vessels in the anterior 2/3 of the tongue.

IX - Glossopharyngeal Nerve

Origin & Relay: Inferior salivary nucleus in medulla oblongata, relays in the otic ganglion.
Functions:
- Stimulate secretion in the parotid salivary gland.
- Vasodilation (VD) of blood vessels in the posterior 1/3 of the tongue

X - Vagus Nerve

Origin & Relay: Dorsal nucleus in medulla oblongata, relays in terminal ganglia in thoracic and abdominal viscera.
Functions:
- Represents 75% of the parasympathetic supply.

Parasympathetic to thorax & abdomen

In the Heart: Inhibits cardiac activity (decreases conductivity, contractility, excitability, and rhythmicity), constricts coronary blood vessels (decreasing blood flow).
In the Lungs: Causes bronchoconstriction (contraction of bronchi and bronchioles), increases mucous secretion, and dilates pulmonary blood vessels.
In the Gastrointestinal Tract: Contracts smooth muscles of the esophagus, stomach, small intestine, and proximal large intestine, relaxes sphincters, promotes swallowing and evacuation of food from the GIT, increases HCL and mucous secretion from gastric glands, and dilates blood vessels.
In the Liver: Stimulates bile secretion, and contracts gall bladder wall and relaxes the sphincter of Oddi for bile evacuation.
In the Pancreas: Stimulates pancreatic juice secretion rich in enzymes and insulin secretion by B-cells.

Why It's Called Vagus?

Afferent and efferent functions
Stimulatory and inhibitory effects
Widespread distribution

Sacral Outflow

Preganglionic fibers arise from the L2,3,4 sacral segments.
Carried by pelvic splanchnic nerves to terminal ganglia in the pelvis where they synapse.
Postganglionic fibers innervate organs of the pelvis and lower abdomen.

Sacral Division of Parasympathetic

Origin: Sacral nerve roots S2, S3, and S4
Relay ganglia: Hypogastric ganglia

Parasympathetic to the Pelvis (Pelvic nerve)

Urinary bladder: Wall contraction and internal urethral sphincter relaxation, enabling micturition.
Rectum & anal canal: Wall contraction and internal anal sphincter relaxation, enabling defecation.
Sex Organs: Vasodilation of blood vessels in the genitals, contributing to erection in males and clitoris in females.

Micturition

Pelvic nerve contracts the urinary bladder wall and relaxes the internal urethral sphincter to allow urine passage.

Defecation

Pelvic nerve contracts the rectum wall and relaxes the internal anal sphincter to facilitate stool passage. Important Note: External urethral/anal sphincters are under somatic control (pudendal nerve), not autonomic.

Summary of Parasympathetic Activity

"Rest and digest" responses including:
- Decreased metabolic rate
- Decreased heart rate and blood pressure
- Increased secretion from salivary and digestive glands
- Increased digestive tract motility and blood flow
- Stimulation of urination and defecation.
Also known as the anabolic system, which increases nutrients in the blood for growth and development and storing as lipids or glycogen for energy.

Relation between Sympathetic and Parasympathetic

Commonly antagonistic (opposed) action in the heart, lungs, and pelvis
Sometimes synergistic (collaborative) in, for example, salivary secretion; when one system provides trophic/nutritious support, the other provides the active secretion.
Complementary actions in sexual intercourse, where parasympathetic nerves regulate erection and sympathetic nerves regulate ejaculation in males and orgasm in females.
Generally, these actions are balanced to maintain homeostasis.

Contrast between Sympathetic and Parasympathetic

Sympathetic (GAS PEDAL): Fight or flight, protection and survival, stress response, adrenal activation.
Parasympathetic (BRAKE PEDAL): Rest, digest, relax, growth, development.

Interactive Questions

General vagus nerve, except for absence of direct effect on ventricular contraction
Pelvic nerve stimulation, with regards to specific actions or regions of the body.
Sympathetic tone initiation, factors affecting control, and effects of blocking drugs.
Effects of vagal tone on the heart.

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Description

This quiz covers the crucial aspects of the parasympathetic nervous system as taught in Human Body Function (HBF) 102. Explore the functions of important cranial nerves and compare the sympathetic and parasympathetic systems. Deepen your understanding of cranial and sacral outflows and their physiological relevance.