38 Regulation of GI function Flashcards
Mechanism(s) that control the motility and secretion via GI reflexes are governed by
A. Nutritional state of the body
B. Volume of luminal content
C. Composition of luminal content
B and C
State the receptors for each of the parameters respectively:
Distention: volume of luminal contents stretching GI wall
Acidity: pH of chyme
Osmolarity
Digestion products (FA, peptides, amino acids and glucose)
Distention: volume of luminal contents stretching GI wall - mechanoreceptors
Acidity: pH of chyme - chemoreceptors
Osmolarity: osmoreceptors
Digestion products (FA, peptides, amino acids and glucose) - chemoreceptors
What kind of neurons can act as all of the receptors above?
Sensory neurons of the ENS
Endocrine cells on the GI tract act on which kind(s) of receptors?
A. mechanoreceptors
B. Osmoreceptors
C. Chemoreceptors
C
In neurohormonal regulation,
A. CNS acts on ANS
B. ANS acts on CNS
A
For extrinsic ANS, parasympathetic ______ GI function while sympathetic innervation __________ GI function.
A. Increases; decreases
B. Decreases; increases
A
Cholinergic fibers in GI occurs in _________ fibers while adrenergic fibers in GI occurs in ___________ fibers.
A. Postganglionic; preganglionic
B. Preganglionic; postganglionic
B
What are the 2 components of the intrinsic ENS
- Submucosal plexus
2. Myenteric plexus (in muscularis externus)
What do Submucosal plexus
and Myenteric plexus control resepctively?
Submucosal plexus: GI secretion and local blood flow (remember that they are with the major vessels!)
Myenteric plexus: GI movements (they are with the longitudinal and circular muscles!)
Which of the following is correct:
A. ENS cannot function on its own
B. ANS functions via interaction with ENS
C. ENS contains as much neurons as the spinal cord
D. CNS can affect gut activity
All except A.
A: ENS can be independent
ENS contains adrenergic and cholinergic + NANC neurons
(non-adrenergic-non-cholinergic) e.g. peptides (VIP) and non-peptides
Reflexes in the ENS within the nerve plexuses are called short reflexes
sent to smooth muscle or gland for response (secretion and motility)
All GI hormones are peptides but not all peptides are GI hormones
Which 3 types of GI peptides are classified?
- Endocrine: peptides
- Paracrine: peptides or non-peptides (via diffusion)
- Neurocrine: peptides or non-peptides (via synaptic cleft)
A true hormone must be:
A. a physiological stimulus
B. The response is able to be elicited after denervation between 2 parts of the tract
C. An extract of mucosa taken from the site, where the stimulus was applied, reproduces the response when injected into the blood
D. The substance must be isolated, purified and synthesized chemically.
All of the above
Otherwise, it is called a candidate hormone
Gastrin is secreted by antral G cells and duodenal G cells. It is released upon stimuli of peptide and AA. List the 3 actions of gastrin.
- increase gastric motility
- stimulates growth of gastric gland mucosa
- Stimulates gastric acid secretion
CCK is secreted by I cells in jejunum and duodenum upon stimulation of what substances?
Fatty acids and amino acids
List the 3 actions of CCK.
- Stimulates gall bladder contraction
- stimulates pancreatic enzyme secretion
- Inhibits gastric emptying
Remember:
CCK: see see o5ok, I~ 我要減肥啦!
What kind of hormone is secreted by S cells in the duodenum when stimulated by acid (<3.5) ?
Secretin
List the 4 actions of the hormone secretin.
- Inhibits gastric acid secretion (SHH keep it secret don’t let acid come out!)
- Stimulates pancreatic HCO3- secretion
- Stimulates biliary HCO3- secretion
- Stimulates growth of exocrine pancreas
*for neutralization!
GIP (gastric inhibitory peptide) / GLP-1 is released by what cells upon stimulation of glucose?
K cells and L cells in duodenum and jejunum?
Party with KL!! > eat food
Upon stimuli like fat/acid/nerve, the hormones motilin is secreted in the jejunum. What is its function?
Stimulates gastric and intestinal motility, regulate migrator motor complex (MMC)
Gastrin, CCK, Secretin, GIP and Motilin are all
A. Endocrine peptides
B. Neurocrine peptides/non-peptides
C. Paracrine peptides/non-peptides
A
Somatostatin and Histamine are both hormones in _____ fashion.
A. Neurocrine
B. Endocrine
C. Paracrine
C
they are synthesized and released from endocrine cells
Somatostatin is a/an _____ while histamine is a/an__________.
A. non-peptide; peptide
B. peptide/non-peptide
B
Somatostatin is secreted by D cells in the stomach and delta cells in pancreas.
List the 2 functions of somatostatin.
- inhibits gut hormones and intestinal secretions
2. inhibits gastrin release from antral G cells, mediate gastric acid secretion.
Histamine is a hormone derived from histidine (aa). It is synthesized in what cells?
Enterochromaffin-like cells (ECL) cells throughout the GI mucosa
What are the 2 functions of histamine?
- Stimulate gastric acid secretion (hishis聲叫acid出黎）
2. Potentiate acid secretion by parietal cells by interacting with gastrin and Ach
Vasoactive intestinal peptide (VIP) works in _______ fashion.
A. Endocrine
B. Paracrine
C. Neurocrine
C (peptide)
List 3 functions of VIP.
- Relax sphincters (or else may lead to achalasia) or gut circular muscle
- Stimulate pancreatic/ intestinal secretion (or else there will be pancreatic cholera)
- Regulate blood flow
Which neurocrine peptide mediate vagally stimulated gastrin release in gastric mucosa?
GRP Gastrin releasing peptide/ Bombesin
What is the only non-peptide that works in neurocrine fashion in the GI? (Hint: Peptides are VIP and GRP)
Acetylcholine. It is released from nerve endings, and it regulates acid secretion.
