LEC 1 (Regulatory Substances in the GIT) Flashcards
1
Q
GI hormone classification
A
- depending on structure
2. depending on function t
2
Q
GI endocrine (hormones)
A
released from endocrine cells in the GI mucosa ►portal circulation, ►general circulation ►physiologic actions on target cell
3
Q
D Cell
A
somatostatin
4
Q
G Cell
A
Gastrin
5
Q
H Cell
A
VIP
6
Q
S Cell
A
Secretin
7
Q
I Cell
A
chole-cysto-kinin(CCK)
8
Q
K Cell
A
gastric inhibitory peptide (GIP).
9
Q
G Cell location
A
in the lateral walls of gastric glands in the antral portion of the gastric mucosa
10
Q
Gastrin found in
A
stomach, pituitary gland, hypothalamus, medulla oblongata, vagus and sciatic nerve.
11
Q
Gastrin contains
A
17 amino acids (“little gastrin”)
12
Q
Gastrin form
A
- Little gastrin
2. Big gastrin
13
Q
Little Gastrin is secreted in
A
response to a meal
14
Q
Gastrin all biologic activity resides in the
A
four C-terminal amino acids.
15
Q
G17 have half-life of
A
2 to 3 minutes in the circulation,
16
Q
G34 has a half-life of
A
15 min
17
Q
Actions of gastrin
A
↑ gastric acid and pepsin secretion
↑growth of mucosa of the stomach, and small and large intestines (trophic action
↑gastric motility.
↑insulin secretion
18
Q
trophic action
A
gastrin ↑growth of mucosa of the stomach, and small and large intestines
19
Q
Patients with gastrin secreting tumors
A
hypertrophy (size of cells) and hyperplasia (number of cells) of the gastric mucosa.
20
Q
insulin secretion ؟
A
only after a protein meal, and not carbohydrate meal
21
Q
Stimuli for secretion of gastrin
A
- Luminal
- Neural
- Blood borne
22
Q
Luminal stimuli
A
- Stimuli for secretion of gastrin
- Distention of the stomach.
- Small peptides and amino acids,
23
Q
Zollinger-Ellison syndrome (gastrinoma)
A
gastrin is secreted by non-β-cell tumors of the pancreas
24
Q
Neural stimuli
A
Vagal stimulation, mediated by gastrin-releasing peptide (GRP)
.Stimuli for secretion of gastrin
25
(GRP)
is not acetylcholine (Ach).→Atropine DOSE NOT block vagally mediated gastrin secretion
26
Blood borne stimuli for secretion of gastrin
Calcium (hypercalcemia),
| Epinephrine
27
Inhibition of gastrin secretion
Luminal
| 2.Blood borne
28
Inhibition of gastrin secretion Blood borne
Secretin, somatostatin, GIP (Gastric inhibitory polypeptide also known as the glucosedependent insulin-tropic peptide), VIP (vasoactive intestinal peptide), glucagon
29
Inhibition of gastrin secretion Luminal
↑acid →direct action on G cells
→release of somatostatin.
→ no gastrin
30
acid located
in the antrum
31
pernicious anemia
acid-secreting cells of the stomach are damaged, gastrin secretion
is chronically elevated
32
CCK half-life of circulating
5 minute
33
CCK is secreted from
I cells in duodenum and jejunum
34
The biologic activity of CCK resides in the
C-terminal heptapeptide (7).
35
CCK location
In the brain, especially the cerebral cortex
36
CCK function
regulation of food intake
| the production of anxiety and analgesia
37
CCK structure
33 amino acids
38
CCK form
CCK58, CCK33, CCK22 and
CCK8
2.Big gast
small gastrin.
39
Big gastrin
The 7 C-terminal amino acids are the same
40
small gastrin
The 4 C-terminal amino acids are the same
41
the tetra-peptide (4) CCK
homologous to small gastrin
| 2.has gastrin activity as well as CCK activity
42
Actions of CCK
↑contraction of the gallbladder →relaxation of the sphincter of Oddi for secretion of bile
2. ↑ pancreatic enzyme secretion.
3. ↑ trophic effect) of the exocrine pancreas
4. كلي الباقي من سلايد 27
43
Stimuli for the release of CCK
Small peptides and amino acids
| (2) Fatty acids containing more than 10 carbon atoms and monoglycerides
44
CCK receptors
A and B)
45
CCK-A recepter found in
the periphery
46
CCK-b recepter found in
brain
47
Effect of TAG on CCK
DO NOT stimulate the release of CCK because they
| cannot cross intestinal cell membranes.
48
Secretin structure
contains 27 amino acids,(All of the amino acids are required for biologic activity)
2.homologous to glucagon; 12 of the 27 amino acids
49
The secretin synthesized by
S cells, → duodenum and the jejunum
50
The secretin half-life
5 minute.
51
Actions of secretin
1. ↑secretion of bicarbonate by the duct cells of the pancreas and biliary tract.
2. ↓H+ secretion by gastric parietal cells.
3. ↑growth of the exocrine pancreas.
4. augments the action of CCK in producing pancreatic secretion of digestive enzyme
5. has a mild effect on motility of the gastrointestinal tract
52
increase secretion of bicarbonate causes
Pancreases watery, alkaline pancreatic juice.
Pancreatic HCO3
- neutralizes H+ in the intestinal lumen.
B. Liver HCO3- and H2O secretion
increases bile production.
53
Stimuli for the release of secreti
(1) H+
(2) Protein
in the lumen of the duodenum
54
GIP
Glucose-dependent insulin-tropic peptide
| Gastro-inhibitory peptide)
55
GIP contains
42 amino acids.
56
GIP is produced by
K cells in the mucosa of the duodenum and jejunum
57
GIP is homologous to
secretin and glucagon.
58
Actions of GIP
1. Stimulates insulin release.
2. inhibits gastric secretion (large dose )
3. inhibits gastric motility ( large dose )
59
Stimuli for the release of GIP
fatty acids, amino acids, and orally administered glucose
60
only GI hormone
GIP
61
GIP named
gastric inhibitory peptide
62
Motilin is secreted by the
stomach and upper duodenum during fasting
63
Motilin function
increase gastrointestinal motility
64
↓Motilin secretion
ingestion of food
65
inter-digestive myoelectric complexes (or migrating myoelectric complexes: MMC)
Motilin stimulates waves of gastrointestinal motility that move through the stomach and small intestine every 90 minutes in a person who has fasted and MMC contraction stop when you eat مهم
66
The migrating myoelectric complex functions
to move undigested food into the colon and keep the upper parts of the GIT (small intestine and stomach) clear
67
digestive myoelectric complexes (or MMC) is divided into four phases
(1) basal (Phase I)
(2) pre-burst (Phase II)
(3) burst (Phase III)
(4) Phase IV
68
(1) basal (Phase I) is a
1. quiescent هامدperiod
2. no contractions
3. lasts from 40–60 min
69
(2) pre-burst (Phase II) consists of
1. intermittenti
2. rregular
3. low-amplitude contractions
4. lasts for 40–60 min
70
parts of the GIT can have an active migrating myoelectric complex
The mid stomach to the terminal ileum
71
(3) burst (Phase III) consists of
1. intense
2. short burst
3. regular
4. high-amplitude contractions
5. for short periods (4–6 min).
72
Phase III contractions periodically occur
every 90-120 minutes in humans.
73
Motilin administration causes
gastric phase III contractions in humans.
74
Plasma motilin level is highly associated with
the appearance of gastric phase III in humans
75
(4) Phase IV
1. short transition period back to the quiescence الهدوءof phase I
2. lasts for 0–5 min
3. with very little or no contractions
76
housekeeper wave.
all the undigested material is swept out of the stomach down to the small intestine
77
GI Paracrines are
Somatostatin
| 2.Histamine
78
GI Paracrines are released from
endocrine cells in the GI mucosa.
79
GI Paracrines diffuse
over short distances to act on target cells located in the GI tract.
80
Histamine is secreted
by mast cells of the gastric mucosa.
81
. Histamine function
increases gastric H+ secretion directly and by potentiating the effects of gastrin and vagal stimulation
82
Somatostatin is secreted in response to
H+ in the lumen.
83
Somatostatin secretion is inhibited by
vagal stimulation.
84
Somatostatin inhibits
1. the release of all GI hormones مهم
2. pancreatic exocrine secretion;
3. gastric acid secretion and motility;
4. gallbladder contraction
5. the absorption of glucose, amino acid, and triglycerides.
85
GI Neurocrines
1. Vasoactive intestinal peptide (VIP)
2. GRP (Gastrin Releasing peptide or bombesin)
3. Enkephalins (met-enkephalin and leu-enkephalin)
86
GRP (Gastrin Releasing peptide or bombesin) is released from
vagus nerves that innervate the G cells.
87
Enkephalins (met-enkephalin and leu-enkephalin) stimulate
contraction of GI smooth muscle,in
lower esophageal,
pyloric, and
ileocecal sphincters
88
GRP stimulates
gastrin release from G cells.
89
Enkephalins inhibit
intestinal secretion of fluid and electrolytes
90
opiates in the treatment of diarrhea
Enkephalins inhibit intestinal secretion of fluid and electrolytes
91
Neurocrines are synthesized in
neurons of the GI tract→ moved by axonal transport down the axon→ released by action potentials in the nerves→ then diffuse across the synaptic cleft to a target cell.
92
VIP contains
28 amino acids and is homologous to secretin
93
VIP is released from
1. neurons in the mucosa
| 2. smooth muscle of the GI tract
94
VIP has a half-life
2 minutes
95
Functions of VIP
1. relaxation of GI smooth muscle
2. ↑pancreatic HCO3- secretion and ↓ gastric H+ secretion
3. ↑intestinal secretion of electrolytes and hence of water
4. potentates the action of acetylcholine in salivary glands
96
VIP relaxation of GI smooth muscle, including the
a. relaxation lower esophageal sphincter
| b. dilation of peripheral blood vessels
97
VIP actions resembles secretin.
Stimulates pancreatic HCO3- secretion and inhibits gastric H+ secretion.
