MBBS Year 1: Gastrointestinal Physiology Lectures

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Questions and Answers

What is the primary function of peristalsis in the gastrointestinal tract?

Mixing food with enzymes and acids

Waves that move a bolus through the tract (correct)

Regulating the rhythmic cycles of smooth muscle activity

Churning and fragmenting a bolus

Which of the following neurons serves as the pacemaker for smooth muscle contractions in the gastrointestinal tract?

Enteric neurons

Autonomic neurons

Sensory neurons

Interstitial cells of Cajal (correct)

What is the primary role of the enteric nervous system in regulating gastrointestinal motility?

Regulating the contraction of smooth muscle (correct)

Modulating the activity of interstitial cells of Cajal

Releasing hormones to stimulate smooth muscle contraction

Stimulating the parasympathetic nervous system

What is the primary function of segmentation in the gastrointestinal tract?

Churning and fragmenting a bolus Signup and view all the answers

Which of the following is NOT a factor that influences gastrointestinal motility?

Mechanical stretch of the tract Signup and view all the answers

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

Exciting smooth muscle contraction Signup and view all the answers

What is the primary function of sphincter tone and relaxation in the gastrointestinal tract?

Regulating the passage of food into the stomach Signup and view all the answers

What is the primary role of the autonomic nervous system in regulating gastrointestinal motility?

Stimulating smooth muscle contraction Signup and view all the answers

What is the primary function of the neural enterogastric reflex in regulating gastric emptying?

Inhibiting gastric secretion and duodenal filling Signup and view all the answers

Which hormone stimulates the secretion of HCO3- and inhibits stomach activity?

Secretin Signup and view all the answers

What is the primary function of the short reflexes operating in the enteric nervous system (ENT)?

Inhibiting gastric secretion and contractions Signup and view all the answers

What is the primary function of Motilin in regulating gastric activity?

Increasing gastric motility Signup and view all the answers

What is the primary function of the long reflexes operating via the CNS in regulating gastric activity?

Altering autonomic nerve activity Signup and view all the answers

What is the primary function of GIP (gastric inhibitory peptide) in regulating gastric activity?

Inhibiting gastric contractions Signup and view all the answers

What is the primary function of CCK (cholecystokinin) in regulating gastric activity?

Stimulating gallbladder contraction and emptying Signup and view all the answers

What is the primary function of the local reflex pathway in the gastrointestinal tract?

Regulating gastric secretion and contractions Signup and view all the answers

Study Notes

Overview of the Digestive System

MBBS Year 1 Gastrointestinal Lectures cover topics such as digestion and absorption of nutrients, salivary, gastric, and pancreatic secretions, bile and biliary system, and motility of the gut.

Motility of the Gut

Gastric smooth muscle contractions facilitate the breakdown of ingested food.
Pacemaker cells (Interstitial Cells of Cajal) serve as pacemakers for muscle contraction in the GI tract.
Neural and hormonal stimuli regulate gastric motility.

Functions of Motility

Mixing: Smooth muscle contraction mixes food with digestive enzymes.
Propulsion: Smooth muscle contraction propels food through the digestive tract.

Gastrointestinal Tract Smooth Muscle Contractile Activity

Visceral smooth muscle shows rhythmic cycles of activity.
Pacemaker cells (Interstitial Cells of Cajal) generate rhythmic activity.
Peristalsis: Waves that move a bolus through the digestive tract.
Segmentation: Churn and fragment a bolus.
Sphincter tone and relaxation: Regulate the passage of food through the digestive tract.

Factors Influencing Gastrointestinal Tract Motility

Smooth muscle functional syncytium: Electrical activity of muscle cells generates slow waves (pacemaker potentials) and spike potentials, resulting in contraction.
Neural control: Autonomic and enteric nervous systems regulate GI tract motility.
Hormonal control: Endocrine (gastrin, CCK) and local (paracrine, neurocrine) hormones regulate GI tract motility.

Gastric Contractile Activity

Most vigorous peristalsis and mixing occur near the pylorus.
Chyme is either delivered in small amounts to the duodenum or forced backward into the stomach for further mixing.

Regulation of Gastric Emptying

Gastric emptying is regulated by neural enterogastric reflex and hormonal (enterogastrone) mechanisms.
These mechanisms inhibit gastric secretion and duodenal filling.
Carbohydrate-rich chyme quickly moves through the duodenum, while fat-laden chyme is digested more slowly, causing food to remain in the stomach longer.

Regulation of Gastric Activity

Hormonal control: Secretin, CCK, GIP, and motilin regulate gastric activity.
Neuronal control: Short reflexes operating in the enteric nervous system (ENT) inhibit gastric secretion/contraction, while long reflexes operating via the CNS alter autonomic nerve activity.

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Description

Test your knowledge of the digestive system, including digestion, absorption, and gut motility, based on Physiology 5th Edition and other medical physiology resources.