SCT III - Gastrointestinal Tract: Regulation Flashcards
(28 cards)
What is the enteric nervous system?
Myenteric Plexus (Auerbach’s)
- More neurons
- Controls muscle motility
Submucosal Plexus (Meissner’s)
- Less neurons
- Controls secretion & absorption
Stimulation and inhibition of distributor neurons & effect neurons
What is a vago-vagal reflex?
What is the impact of PNS on the GI tract?
PNS = Rest & digest
What is the impact of SNS on the GI tract?
SNS = Fight-or-flight (antagonistic)
How does the GI tract receive PNS stimuli?
PNS - Preganglionic
- Vagus N. (CN X)
- Pelvic Splanchnic N. (S2-S4)
PNS - Postganglionic
- nAChR
- Effector is postganglionic neuron
How does the GI tract receive SNS stimuli?
SNS - Postganglionic (Sympathetic Trunk)
- Greater Splanchnic N. (T5-T9)
- Lesser Splanchnic N. (T10-T11)
- Least Splanchnic N. (T12)
- Lumbar Splanchnic N. (L1-L2)
How can the SNS impact the local arc response of the GI tract (draw)?
How does the SNS effect interneurons?
α-2 Receptors
- G-protein (i) - Inhibitory
- Neuron inhibition
How does the SNS effect effector neurons?
α-2 Receptors
- G-protein (i) - Inhibitory
- Neuron inhibition
How does the SNS effect local arc response?
β-2 Receptors
- G-protein (s) → [cAMP]i ↑
- Smooth M. relaxation
α-1 Receptors
- G-protein (q) → [Ca2+] ↑
- Sphincter contraction (closure)
What is meant by monospecific and pleiotropic complexity?
Monospecific
One hormone one function
Pleiotropic
One hormone multiple functions
What are the possible products of proglucagon in the pancreas?
- GRPP = Glicentin-Related Pancreatic Polypeptide
- Glucagon
- Heavy Proglucagon Fragment
What are the possible products of proglucagon in the small intestine?
- Glicentin
- GLP-1 & GLP-2 (Glucagon-like-peptide)
- GRPP & Oxyntomodulin
What is the function of D-cells?
D-Cells [PARACRINE]
- Paracrine inhibition of neighboring secretory cells
- Vasoconstriction
Stimulus: Low stomach pH
Peptide: Somatostatin
Location: Stomach
What is the function of L/A-Cells?
L/A-Cells
- Carbohydrate metabolism
- Insulin ↑
- Intestinal mucosa cells ↑
Stimulus: N/A
Peptide: Glucagon, Glicentin, GLP-1, GLP-2, Oxyntomodulin
Location: Pancreas (A) & small intestine (L)
What is the function of G-cells?
G-Cells
- HCl ↑
- Growth factor
Stimulus: Distension AA, GRP, stress
Peptide: Gastrin
Location: Stomach & small intestine
What is the function of I-cells (CCK)?
I-Cells (CCK)
- Pancreatic juice ↑
- Gallbladder contraction
- Slowing of stomach emptying
- Intestinal motility ↑
- Food intake ↓
Stimulus: AA & FA
Peptide: Cholecystokinin (CCK)
Location: Duodenum & jejunum
What is the function of F-cells (PP, D1)?
F-Cells (PP, D1)
- Absorption ↓
- Pancreatic enzyme ↓
- Bicarbonate secretion ↓
Stimulus: ACh, low blood-sugar
Peptide: Pancreatic peptide
Location: Small intestine, pancreas
What is the function of S-cells?
S-Cells
- Pancreatic juice ↑
- Bile ↑
Stimulus: FA & H+
Peptide: Secretin
Location: Duodenum
What is the function of M-cells?
M-Cells
- Motility of stomach and GIT ↑
Stimulus: Fasting
Peptide: Motilin
Location: Small intestine
What is the function of GIP-cells (K)?
GIP-Cells (K)
- HCl ↓
- Insulin ↑
Stimulus: FA & glucose
Peptide: GIP
Location: Intestinal mucosa
What is the function of ECL-cells?
ECL-Cells [PARACRINE]
- HCl
Stimulus: Gastrin & Pacap
Peptide: Histamine
Location: Stomach
What is the function of enterochromaffin cells?
Enterochromaffin cells [PARACRINE]
- Carcinoid tumors, carcinoid syndrome
Stimulus: N/A
Peptide: Serotonin
Location: Gastric/intestinal mucosa
