Introduction to GI Physiology Flashcards
1
Q
- Main functions of the GI Tract
- Main Properties
A
- Digestion and absorption of nutrients
- Motility and secretions
2
Q
- What are the sphincters of the GI Tract
A
- Upper esophageal sphincter (UES)
- Lower esophageal sphincter (LES)
- Pyloric Sphincter
- Sphincter of Oddi
- Ileocecal Valve
- Internal anal sphincter
- External anal sphincter
3
Q
- The ENS comprises the _ and _ plexuses
- Can exert functions without _ input
- ENS can receive signals from _,_ and _
- ENS can receive sensory information from_ and _ receptors in the mucosa
A
- Myenteric
- Submucosal
- CNS
- Parasympathetic, Sympathetic and Central Nervous Systems
- Mechanoreceptors, Chemoreceptors
4
Q
- Which parasympathetic nerves are responsible for modulating GI functions?
- Where are preganglionic cell bodies located?
- Where are postganglionic cell bodies located?
- Pre-synaptic cell releases _ on _ receptor
- Post-synaptic cell releases _ on _ receptor
A
- Vagus and pelvic splanchnic
- Preganglionic cell bodies-craniosacral regions
- Postganglionic neurons-wall of target organ
- ACh on nAChRs
- ACh on mAChRs (usually)
5
Q
Which sympathetic nerves are responsible for modulating GI functions?
Where are preganglionic cell bodies located?
Where are postganglionic cell bodies located?
Pre-synaptic cell releases _ on _ receptor
Post-synaptic cell releases _ on _ receptor
A
- Nerves running between spinal cord and prevertebral ganglia
- Preganglionic cell bodies arise within the spinal cord and end in prevertebral ganglia
- Postganglionic fibers innvervate myenteric and submucosal plexuses
- ACh on nAChR
- NE on ADRalpha or ADRbeta
6
Q
- What type of signaling/cell communication is important in GI function?
- Why?
A
- Paracrine
- Act locally over short distances
- How peptides (somatostatin) and other messenger molecules (ie: histamine) work
7
Q
- Somatostatin
A
- D cells of GI mucosa (hypothalamus and delta cells of pancreas)
- Stimulated by low luminal pH
-
Actions
- Inhibits gastric H+ secretion
- Inhibits secretions of other GI hormones
SOMATOSTATIN IS PARACRINE
8
Q
- Histamine
A
- Stored and secreted by ECL cells in gastric glands
- Targets parietal cells to stimulate acid production
HISTAMINE IS PARACRINE
9
Q
- What are the main hormones of the GI tract?
A
- Gastrin
- CCK
- Secretin
- GIP (Glucose-dependent insulinotropic peptide)
10
Q
Gastrin:
Site of secretion
Stimuli
Actions
A
- Secreted by G cells of the stomach
- Stimulated by peptides and AAs and distension of the stomach (also vagal stimulation)
- Action is to increase gastric H+ secretion and stimulate growth of gastric mucosa
11
Q
CCK
Site of Secretion
Stimuli
Action
A
- Secreted by I cells of the duodenum and jejunum
- Stimulated by small peptides and AAs, fatty acids
- Increases pancreatic enzyme secretion (increases pancreatic HCO3- secretion-not direct, potentiates effects of secretin)
- Stimulates contraction of gallbladder and relaxation of Sphincter of Oddi
- Stimulates growth of exocrine pancreas and gallbladder (trophic effect)
- Inhibits gastric emptying
- Can also act as a paracrine signal
12
Q
Secretin
Site of secretion
Stimuli
Actions
A
- Secreted by S cells of duodenum
- Stimulated by H+ and fatty acids in the duodenum
- Increases pancreatic HCO3- secretion
- Increases biliary HCO3- secretion
- Inhibits gastric secretion
- Inhibits trophic effect of gastrin on gastric mucosa
- Can also act as a paracrine signal
13
Q
-
Glucose-dependent insulinotropic peptide (GIP)
- Site of secretion
- Stimuli of secretion
- Actions
A
- Duodenum and jejunum
- Stimulated by Fatty acids, AAs, ORAL glucose
- Increases insulin secretion from beta cells of pancreas
- Decreases H+ gastric secretions
14
Q
- Incretin effect
A
States that oral glucose stimulates GIP, which stimulates insulin secretion and has DIRECT stimulatory effects of beta cells of the pancreas
15
Q
- ACh
- Source
- Actions
A
- Cholinergic neurons
- Relaxation of sphincters
- Increase salivary secretion
- Increase gastric secretion
- Increase pancreatic secretion
