Autonomic Nervous System Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the two main subdivisions of the autonomic nervous system?

Cerebral cortex and spinal cord

Sensory nervous system and motor nervous system

Central nervous system and peripheral nervous system

Sympathetic nervous system and parasympathetic nervous system (correct)

What is the enteric nervous system commonly abbreviated as?

ENS (correct)

ANS

CSN

PNS

Which part of the autonomic nervous system is primarily responsible for the fight-or-flight response?

Enteric nervous system

Parasympathetic nervous system

Somatic nervous system

Sympathetic nervous system (correct)

Which statement about the parasympathetic nervous system is accurate?

It controls involuntary functions such as digestion. Signup and view all the answers

What is a primary function of the enteric nervous system?

Managing gastrointestinal functions Signup and view all the answers

What is the primary effect of norepinephrine (NE) secretion on gastrointestinal (GIT) smooth muscle?

Inhibition of smooth muscle activity Signup and view all the answers

Which of the following is NOT a consequence of norepinephrine's action on the GIT?

Increased motility of the gut Signup and view all the answers

What type of nerve fibers innervate the gut according to the content?

Afferent sensory nerve fibers Signup and view all the answers

What components make up the enteric nervous system (ENS)?

Intrinsic and extrinsic components Signup and view all the answers

What is the role of the parasympathetic nervous system in gastrointestinal motility?

Increases motility Signup and view all the answers

In which part of the digestive system do these types of contraction primarily occur?

Esophagus Signup and view all the answers

What is a key characteristic of the voluntary stage of swallowing?

Tongue pushes food toward the pharynx Signup and view all the answers

Which of the following best describes the mechanics of the pharyngeal stage of swallowing?

The bolus is propelled into the esophagus Signup and view all the answers

What distinguishes primary peristalsis from secondary peristalsis?

Primary occurs after swallowing while secondary is reflexive Signup and view all the answers

Which of the following is NOT a function of the stomach?

Digestion of carbohydrates Signup and view all the answers

What primarily triggers an increase in peristaltic activity after a meal?

Stretching of the duodenal wall Signup and view all the answers

Which hormone is primarily associated with increasing gastrointestinal motility during fasting?

Motilin Signup and view all the answers

What is the role of the gastroileal reflex in gastrointestinal motility?

Intensifies peristalsis in the ileum Signup and view all the answers

How does motilin affect gastric and intestinal motility?

It stimulates gastric and intestinal motility Signup and view all the answers

Which of the following hormones inhibits intestinal motility?

Secretin Signup and view all the answers

What initiates the voluntary stage of swallowing?

Pressure from the tongue against the palate Signup and view all the answers

What happens to swallowing after the pharyngeal stage begins?

It is completely automatic and cannot be stopped Signup and view all the answers

Which type of contractions occur at the sphincters during digestion?

Peristaltic contractions Signup and view all the answers

What is the role of local intermittent constrictive contractions in the gastrointestinal tract?

They assist in mixing and movement of food Signup and view all the answers

Which statement best describes the voluntary stage of swallowing?

It is the only stage that can be consciously controlled Signup and view all the answers

What triggers a constrictive ring in the colon during mass movements?

Distended or irritated point in the colon Signup and view all the answers

How frequently do mass movements occur in the colon?

1 to 3 times per day Signup and view all the answers

What happens to the portion of the colon distal to the constrictive ring during mass movements?

It loses haustrations and contracts as a unit Signup and view all the answers

What reflexes facilitate mass movements in the colon?

Gastrocolic and duodenocolic reflexes Signup and view all the answers

What condition is associated with persistent mass movements in the colon?

Ulcerative colitis Signup and view all the answers

Study Notes

Gastrointestinal Tract (GIT) Motility

The GIT's motility is controlled by the Central Nervous System (CNS), Autonomic Nervous System (ANS), and the Enteric Nervous System (ENS)
Phasic and tonic contractions are two types of contractions with different functions
Phasic contractions occur rhythmically and are determined by slow waves, followed by relaxation
- Occur in the esophagus and small intestine
Tonic contractions are maintained contractions, not associated with slow waves
- Occur in sphincters
- Intensity can increase or decrease

Learning Objectives

Describe the composition of the CNS, ANS & ENS, and their relationship.
Differentiate between phasic and tonic contractions in the GIT, and where they occur.
Explain the voluntary and pharyngeal stages of swallowing.
Compare and contrast primary and secondary peristaltic movements.
Detail the functions of the stomach, including the causes of retropulsion and pyloric spasm.
Explain the motility of the small intestine, including segmentation and peristalsis, and the roles of hormones in regulating motility.
Describe the main functions of the large intestine, and how mass movements occur.
Discuss the roles of hormones in regulating gastrointestinal motility.

Neural Control of GIT Functions

The ENS, a component of the intrinsic system, consists of two plexuses:
- The myenteric plexus (Auerbach's plexus) which controls GIT movements.
- The submucosal plexus (Meissner's plexus) which controls GIT secretions and local blood flow.
The extrinsic component, the ANS, influences GIT function:
- The parasympathetic nervous system increases motility and secretions (stimulates GIT functions)
- The sympathetic nervous system inhibits motility and secretions.
The ENS functions independently.

Sensory Nerve Endings

Many sensory nerve fibers in the gut respond to stimuli like irritation, distension, and chemicals
These stimuli may cause excitation or inhibition of intestinal movements or secretions.

Swallowing (Deglutition)

Swallowing involves three stages:
- Voluntary (mouth)
- Pharyngeal
- Esophageal
The voluntary stage involves the tongue squeezing food posteriorly toward the pharynx.
The pharyngeal stage involves the stimulation of swallowing receptor areas, resulting in impulses traveling to the brain stem swallowing center.
- The palate, palatopharyngeal folds and epiglottis are involved to prevent food from entering the nasal cavities, trachea and lungs.
The esophageal stage involves primary peristalsis initiated in the pharynx, to propel the food to the stomach via the esophagus.

Esophageal Stage

Primary peristalsis is a continuation of the pharyngeal stage peristaltic wave that moves food from the pharynx to the stomach.
Secondary peristalsis occurs in response to food stuck in the esophagus
The process continues until all food that entered the esophagus is emptied into the stomach

Motor Functions of the Stomach

The stomach stores large quantities of food.
Mixes the food with gastric secretions to form chyme.
Empties chyme into the small intestine.

Retropulsion

Weak peristaltic constrictor waves (mixing waves) in the stomach
Constrictor waves in the mid-upper stomach that move towards the antrum
Propel food under higher pressure towards the pylorus

Pylorus

The pylorus opening is small and only a limited amount of antral contents is expelled per peristaltic wave.
Peristaltic wave contracts the pyloric muscle which impedes contents from emptying into the duodenum (important in the mixing process).

Motility of the Small Intestine

The small intestine utilizes mixing contractions (segmentations) and propulsive movements (peristalsis).
- Segmentation involves localized concentric contractions that mix chyme to increase its contact with digestive enzymes.
Peristalsis propels chyme through the intestines.
- The gastro-enteric and gastro-ileal reflexes enhance peristaltic activity.

Hormones and Intestinal Motility

Certain hormones increase intestinal motility, while others inhibit it.
- Gastrin, CCK, insulin, motilin, and serotonin increase intestinal motility
- Secretin, Glucagon inhibit intestinal motility.

Large Intestine

Absorption of water and electrolytes from chyme into solid feces
Storing fecal matter until expulsion.
- Mixing through haustrations, and
Propulsive movements (mass movements).

Defecation

The reflexes are transmitted by the autonomic nervous system.
Irritation can initiate intense mass movements (e.g., in ulcerative colitis).

Pyloric Spasm

Pyloric spasm is a condition where the pylorus becomes more constricted than normal.
- This leads to food staying in the stomach longer than normal, which increases stomach acidity
- This can cause vomiting and pain

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge about the autonomic nervous system with this quiz covering key concepts such as the enteric nervous system, fight-or-flight response, and gastrointestinal functions. Answer questions on the roles of sympathetic and parasympathetic divisions in the body. Perfect for students studying physiology or neuroscience!