GI_Lect24_motility

What is the main purpose of the HUBS192 pre-lecture material?

To help prepare for lectures and assist in note-taking, but not as a substitute for the lecture.

What are the topics covered in HUBS192 Gastrointestinal Physiology Lectures 24-27?

Lecture 24: Introduction to gastrointestinal physiology, motility and mechanical digestion; Lecture 25: Secretion in the gastrointestinal tract; Lecture 26: Chemical digestion in the gastrointestinal tract; Lecture 27: Absorption of nutrients, water and sodium.

What are the three types of regulation in the gastrointestinal tract?

Enteric nervous system, parasympathetic nervous system, and sympathetic nervous system.

What are the two reflex pathways for control of the gastrointestinal tract?

Long reflex pathways and short reflex pathways.

What is the purpose of motility in the gastrointestinal tract?

To facilitate mechanical digestion, propulsion, mixing, storage, controlled movement, and exposure to absorptive surfaces.

Which motility patterns are associated with the gastrointestinal tract?

Chewing, peristalsis, relaxation of sphincters, segmentation, and the migrating motor complex (MMC).

What is mechanical digestion?

The process of breaking food into smaller particles.

What is chemical digestion?

The process of breaking down nutrients into smaller molecules.

What are the net factors determining absorption in the gastrointestinal tract?

The net movement of substances across the epithelial lining into interstitial fluid and then into the blood or lymph.

What initiates the long reflex pathway in the gastrointestinal tract?

Stimuli such as the sight, smell, or taste of food.

How does the sympathetic nervous system affect gastrointestinal function?

It decreases the overall activity of the gastrointestinal tract.

How does the parasympathetic nervous system affect gastrointestinal function?

It increases the overall activity of the gastrointestinal tract.

What are tonic contractions in the gastrointestinal tract?

Sustained contractions that last for minutes to hours, such as in sphincters.

What defines phasic contractions in the gastrointestinal tract?

Waves of contraction and relaxation that last only for seconds.

What role do receptors in the GI tract play?

They detect changes in conditions such as stretch, pH, osmolarity, and nutrient composition.

What is retropulsion in the context of the stomach's motility?

The backward movement of chyme against the pyloric sphincter, aiding in mechanical digestion.

What is the significance of contractions of the pyloric sphincter?

They regulate gastric emptying and control the delivery of chyme to the duodenum.

What are the two types of relaxation in the stomach mentioned in the lectures?

Receptive relaxation and accommodation.

What is segmentation in the small intestine?

A motility pattern that mixes chyme with digestive secretions and exposes it to absorptive surfaces.

What is the purpose of mass movements in the large intestine?

To drive fecal material into the rectum and initiate defecation.

What are the factors affecting the rate of gastric emptying?

The size and composition of the meal, type of food, and feedback signals from the stomach and duodenum.

What is the main function of the myenteric and submucosal plexuses?

To regulate motility and secretion in the gastrointestinal tract.

What happens during the migrating motor complex (MMC) in fasting states?

It helps to remove residual secretions, undigested material, and promotes epithelial cell turnover.

What happens during the relaxation of the stomach?

It allows for storage of food while it is being digested and helps maintain pressure gradients.

What is peristalsis?

A wave of contractions that moves food and chyme along the gastrointestinal tract.

What triggers the release of major gastrointestinal hormones like gastrin and secretin?

These hormones are released from enteroendocrine cells in response to changes in the GI lumen composition.

How is the gastrointestinal tract influenced by both neural and hormonal regulation?

Neural regulation generates fast responses while hormonal regulation provides slower but longer-lasting effects.