Gastrointestinal Tract Physiology Quiz

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Questions and Answers

What is the primary effect of hyperpolarization on muscle fibers?

Makes muscle fibers overexcitable

Decreases muscle excitability (correct)

Increases muscle excitability

Has no effect on muscle fibers

Which of the following factors can lead to tonic contraction in smooth muscle?

Continual action potentials

Continuous repetitive spike potentials (correct)

Inhibition of calcium ion entry

Continuous entry of sodium ions

Which statement about the enteric nervous system is correct?

It solely relies on the central nervous system for operation

It is referred to as the 'little brain' (correct)

It is only found in the brain and not in the GI tract

It contains fewer neurons than the spinal cord

The myenteric plexus is located in which part of the gastrointestinal tract?

Between the longitudinal and circular muscle layers (A) Signup and view all the answers

Which type of nervous supply does the intrinsic nerve supply refer to in the gastrointestinal tract?

Enteric nervous system (B) Signup and view all the answers

What is a characteristic of tonic contractions in smooth muscle?

They can last several minutes or hours (C) Signup and view all the answers

Which ions are primarily involved in the mechanisms leading to tonic contraction?

Calcium ions (A) Signup and view all the answers

Extrinsic nerve supply to the gastrointestinal tract includes which of the following?

Peripheral nerve fibers connecting to the CNS (C) Signup and view all the answers

What is the main role of interstitial cells of Cajal in the gastrointestinal tract?

To act as electrical pacemakers for smooth muscle cells (D) Signup and view all the answers

Which type of channels primarily contribute to the action potentials in GIT smooth muscle?

Calcium-sodium channels (C) Signup and view all the answers

What typically excites muscle contraction in the gastrointestinal tract?

Spike potentials (B) Signup and view all the answers

How do spike potentials in GIT smooth muscle differ from those in large nerve fibers?

They last significantly longer (B) Signup and view all the answers

What is the primary function of Auerbach plexus?

Regulating movements of the gastrointestinal tract (A) Signup and view all the answers

Which factor is NOT mentioned as contributing to depolarization of the GIT membrane?

Innervation by sympathetic nerves (A) Signup and view all the answers

Which neurotransmitter is primarily associated with stimulating gastrointestinal activity?

Acetylcholine (D) Signup and view all the answers

What type of currents do interstitial cells of Cajal generate that may lead to slow wave activity?

Inward (pacemaker) currents (B) Signup and view all the answers

Where is the Meissner plexus located?

Between the muscular layer and the submucosal layer (C) Signup and view all the answers

Why do calcium-sodium channels contribute to the long duration of action potentials in GIT smooth muscle?

They slowly open and close (A) Signup and view all the answers

Which type of nerve supply primarily increases the activity of intestinal smooth muscle?

Parasympathetic nerve supply (A) Signup and view all the answers

Which of the following statements is true about the interaction between slow waves and spike potentials?

Spike potentials result from slow wave activity (C) Signup and view all the answers

Which of the following is an inhibitory neurotransmitter involved in regulating GIT motility?

Vasoactive intestinal polypeptide (VIP) (D) Signup and view all the answers

What role does norepinephrine play in gastrointestinal activity?

Inhibits gastrointestinal activity (D) Signup and view all the answers

Which sphincter is influenced by inhibitory signals from the Auerbach plexus?

Pyloric sphincter (D) Signup and view all the answers

What is the role of the Meissner plexus in the gastrointestinal tract?

Regulates secretory functions (B) Signup and view all the answers

What is the primary role of sympathetic nerve fibers in the GI tract?

Inhibit movements and decrease secretions (D) Signup and view all the answers

Which neurotransmitter is released by parasympathetic nerve fibers in the GI tract?

Acetylcholine (A) Signup and view all the answers

From which segments of the spinal cord do the preganglionic sympathetic nerve fibers arise?

T5 to L2 (A) Signup and view all the answers

Where do the preganglionic parasympathetic nerve fibers for the stomach synapse?

Myenteric plexus (A) Signup and view all the answers

Which cranial nerve is responsible for conveying parasympathetic signals to the esophagus and stomach?

Vagus nerve (B) Signup and view all the answers

What causes stimulation of afferent sensory nerve fibers in the gut?

Gut irritation and distention (D) Signup and view all the answers

What percentage of the nerve fibers in the vagus nerve are afferent?

80% (D) Signup and view all the answers

What is primarily affected when sympathetic fibers cause constriction of sphincters?

Gut motility (C) Signup and view all the answers

What is one of the primary actions of gastrin?

Stimulation of growth of the gastric mucosa (D) Signup and view all the answers

Which hormone is primarily secreted by 'I' cells in the ileum in response to fatty substances?

Cholecystokinin (CCK) (D) Signup and view all the answers

What effect does cholecystokinin have on the stomach?

Inhibits gastric contraction (A) Signup and view all the answers

What is the role of secretin in the gastrointestinal system?

Promotes pancreatic secretion of bicarbonate (A) Signup and view all the answers

Gastric inhibitory peptide has a mild effect on which of the following?

Decreasing motor activity of the stomach (A) Signup and view all the answers

Motilin is primarily released during which state?

Fasting state (A) Signup and view all the answers

What is the primary function of motilin?

Increases gastrointestinal motility (D) Signup and view all the answers

Which hormone helps neutralize acidic gastric juice in the small intestine?

Secretin (D) Signup and view all the answers

What is the primary function of propulsive movements in the gastrointestinal tract?

To move food forward along the tract (C) Signup and view all the answers

What initiates peristalsis in the gastrointestinal tract?

Distention of the gut wall (B) Signup and view all the answers

Which component is essential for effective peristalsis to occur in the gastrointestinal tract?

Myenteric plexus (B) Signup and view all the answers

Which of the following factors can stimulate peristalsis?

Chemical irritation of the gut lining (C) Signup and view all the answers

In what part of the gastrointestinal system is the movement termed 'mixing movements' primarily responsible for keeping contents mixed?

Stomach (D) Signup and view all the answers

What happens to peristalsis when atropine is administered to a person?

Peristalsis is completely blocked (B) Signup and view all the answers

How do mixing movements differ from propulsive movements in the gastrointestinal tract?

Mixing movements do not involve coordinated muscle contractions like propulsive movements (D) Signup and view all the answers

Which nerve signals can elicit strong peristalsis in the gastrointestinal tract?

Parasympathetic nervous signals (D) Signup and view all the answers

Study Notes

Gastrointestinal Tract (GIT) Physiology

The GIT is a continuous tube from mouth to anus, serving as a nutrient and water absorption portal.
It involves:
- Movement of food through the tract
- Secretion of digestive juices and food digestion
- Absorption of water, electrolytes, and digestive products
- Blood circulation through digestive organs to carry absorbed substances
- Control of these functions by nervous and hormonal systems.

Anatomy of the GIT

The diagram shows the organs (mouth, esophagus, stomach, small intestine, large intestine (colon), liver, gallbladder, pancreas) and their general functions, some for passage, others for storage or digestion/absorption. -The small intestine is adapted for digestion and absorption. -The stomach for storage. -The esophagus for passage.

GIT Motility

The intestinal wall consists of layers (serosa, longitudinal muscle, circular muscle, submucosa, mucosa).
The GIT smooth muscle is continuously electrically active.
- Slow waves of electrical activity cause rhythmic contractions.
- Spike potentials, are the true action potentials, which lead to muscle contractions (in some areas). -Factors that increase excitability; stretching, acetylcholine, specific gastrointestinal hormones. -Factors that reduce excitability; norepinephrine, epinephrine.

Nerve Supply to the GIT

Intrinsic nerve supply: The enteric nervous system, controls GI secretions and movements.
- Contains myenteric plexus and submucosal plexus, nerve cell bodies, receptors.
Extrinsic nerve supply: From the autonomic nervous system (sympathetic and parasympathetic).
- Sympathetic fibers generally decrease GI activity and constrict sphincters.
- Parasympathetic fibers (vagus and sacral nerves) generally increase GI activity.

Gastrointestinal Reflexes

Reflexes can occur entirely within the gut wall or connect to the brain/spinal cord.
They control secretions, peristalsis (movement), and mixing contractions.

Hormonal Control of GIT

Gastrointestinal hormones are released into the portal circulation, acting on target cells via receptors.
Examples of hormones and their roles: Gastrin: Stimulates gastric acid secretion and growth. Cholecystokinin (CCK): Contracts gallbladder, inhibits stomach motility. Secretin: Stimulates pancreatic secretions and inhibits stomach acid. Gastric inhibitory peptide: Inhibits gastric emptying and motility. Motilin: Increases gastrointestinal motility.

Movement Types

Propulsive movements (like peristalsis) move food forward.
Mixing movements blend and churn food content and are important for optimal absorption and digestion.

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Description

Test your knowledge on the anatomy and physiology of the gastrointestinal tract (GIT). This quiz covers the movement of food, digestive processes, and the organs involved in digestion and absorption. Understand how motility and control mechanisms operate within the GIT.