Gastrointestinal Lecture 3 Part 1 Regulation of Digestion

Question 1

regulation of GI processes

Answer 1

Question 2

What stimuli trigger GI responses?

Answer 2

Gastrointestinal responses are triggered by four general factors reflecting the composition of the luminal contents:

1. Volume of the luminal contents → distension
2. Osmolarity → total solute concentration
3. Acidity → pH
4. Nutrient composition → monosaccharides/ fatty acids/ aa

Question 3

What are the receptors and effectors of GI stimuli?

Answer 3

Question 4

enteric nervous system

Answer 4

The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract.

Question 5

What regulates GI processes via neural regulations?

Answer 5

enteric nervous system in wall of the intestine

• Submucosal plexus
• Myenteric plexus

Question 6

Submucosal plexus

Answer 6

buried in the submucosa, its principal role is in sensing the environment within the lumen, regulating gastrointestinal blood flow and controlling epithelial cell function.

Question 7

Myenteric plexus

Answer 7

The myenteric plexus is principally responsible for the peristaltic movement of the bowels. While it can act independently from the central nervous system, it receives innervation from the autonomic nervous system, connecting the central and enteric nervous systems.

Question 8

What are the two types of neural reflex loops in GI?

Answer 8

1. Short reflexes
2. Long reflexes

Question 9

Short loop neural response

Answer 9

Sensory neuron detects something on the surface and signal is sent back to generate a response

stimulus → chemoreceptors, osmoreceptors, mechanoreceptors → nerve plexus → smooth muscle or gland → response

Question 10

Long loop neural response

Answer 10

Received in the wall and processed in CNS and response is sent back to initiate a response

stimulus → chemoreceptors, osmoreceptors, mechanoreceptors → afferent neurons → CNS (hunger) → efferent neurons → nerve plexus → smooth muscle or gland → response

Question 11

What regulates GI processes via hormonal regulations?

Answer 11

Responses mediated by specific enteroendocrine cells (hormones a part of the tract)

Question 12

Four well-described gastrointestinal hormones

Answer 12

• Gastrin
• Cholecystokinin (CCK)
• Secretin
• Glucose-dependent insulinotropic peptide (GIP)

Question 13

Gastrin site of production, trigger and response

Answer 13

• site of production → stomach
• trigger → Amino acids/peptides
• response → Stimulates acid secretion and motility (SI/LI too) to break down proteins

Question 14

CCK site of production, trigger and response

Answer 14

• site of production → small intestine
• trigger → Amino acids, fats
• stomach response → Inhibits acid secretion and motility, slows down intake
• pancreas response → Stimulates enzyme secretion (Lipolytic and protelytic)
• gallbladder response → Stimulates contraction (Release of bile to help solubility fat)

Question 15

secretin site of production, trigger and response

Answer 15

• site of production → small intestine
• trigger → Acid
• stomach response → Inhibits acid secretion and motility,
• pancreas response → Stimulates HCO₃^- secretion
• liver response → Stimulates HCO₃^- secretion

Question 16

GIP site of production, trigger and response

Answer 16

• site of production → small intestine
• trigger → glucose. fat
• pancreas response → Stimulates insulin secretion

Question 17

CCK

Answer 17

Cholecystokinin

Question 18

GIP

Answer 18

Glucose-dependent insulinotropic peptide

Question 19

phases of GI regulation

Answer 19

reflecting the site of stimulation

• Cephalic phase → Sight, smell, taste,…
• Gastric phase → Distension, acidity, amino acids/peptides,…
• Intestinal phase → Distension, acidity, osmolarity, digestive products,