Gastrointestinal Lecture 3 Part 1 Regulation of Digestion Flashcards
regulation of GI processes
What stimuli trigger GI responses?
Gastrointestinal responses are triggered by four general factors reflecting the composition of the luminal contents:
- Volume of the luminal contents → distension
- Osmolarity → total solute concentration
- Acidity → pH
- Nutrient composition → monosaccharides/ fatty acids/ aa
What are the receptors and effectors of GI stimuli?
enteric nervous system
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.
What regulates GI processes via neural regulations?
enteric nervous system in wall of the intestine
- Submucosal plexus
- Myenteric plexus
Submucosal plexus
buried in the submucosa, its principal role is in sensing the environment within the lumen, regulating gastrointestinal blood flow and controlling epithelial cell function.
Myenteric plexus
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.
What are the two types of neural reflex loops in GI?
- Short reflexes
- Long reflexes
Short loop neural response
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
Long loop neural response
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
What regulates GI processes via hormonal regulations?
Responses mediated by specific enteroendocrine cells (hormones a part of the tract)
Four well-described gastrointestinal hormones
- Gastrin
- Cholecystokinin (CCK)
- Secretin
- Glucose-dependent insulinotropic peptide (GIP)
Gastrin site of production, trigger and response
- site of production → stomach
- trigger → Amino acids/peptides
- response → Stimulates acid secretion and motility (SI/LI too) to break down proteins
CCK site of production, trigger and response
- 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)
secretin site of production, trigger and response
- site of production → small intestine
- trigger → Acid
- stomach response → Inhibits acid secretion and motility,
- pancreas response → Stimulates HCO3- secretion
- liver response → Stimulates HCO3- secretion