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Flashcards in Gastrointestinal Physiology - Theoretical Questions Deck (127)
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1

What are the components of the Gastrointestinal Nervous system:

Intrinsic - Enteric Nervous system (Aka "Peripheral Brain")
Extrinsic - Sympathetic and Parasympathetic (ANS)

2

What are the Gastrointestinal plexuses? Where are they located?

1) Myenteric Plexus (Auerbach's) - Between Inner-Circular and Outer Longitudinal parts of Muscularis Externa
2) Meissner Plexus - in the Submucosa layer

3

How is the Autonomic nervous system acts on GI system - Generally?

Sympathetic - Inhibits Digestion
Parasympathetic - Activates Digestion

4

What are the Short Reflexes coming through the Meissner Plexus:

Meissner Plexus:
1) Stimulation of Glands and Enteroendocrine Cells
2) Dilation of Blood Vessels

5

What are the Short Reflexes coming through the Myenteric Plexus:

Myenteric Plexus:
-Motility reflexes for stomach and Peristaltic contractions of Intestinal tract

6

Long Reflexes Parasympathetic:
Passage of Stimulus, Border between paths

Long Reflexes Parasympathetic: (Vagovagal)
From Vagal or Pelvic Nerves to the Enteric Plexuses.
Cannon-Bohm point is the edge of Vagal stimulation and the Beginning of Pelvic nerve.

7

Long Reflexes Parasympathetic:
Neurotransmitter used (Postganglionic)

Substance P, VIP and Ach

8

Long Reflexes - Sympathetic:
Passage of Stimulus

Long Reflexes - Sympathetic:
Celiac, SM, IM and Hypogastric ganglions are carrying the fibers to Greater, Lesser and Lumbar splanchnic Nerves. These could stimulate directly the muscles of the GI tract with/Without Synapsing with Enteric Plexuses.

9

Long Reflexes - Sympathetic:
Neurotransmitter used (Postganglionic)

Norepinephrine

10

Long Reflexes - Sympathetic:
Direct Innervation

Alpha-2 : NE - SMC relaxation

11

Long Reflexes - Sympathetic:
Indirect Innervation

Alpha-1 : NE - SMC contraction (Sphincters) and Vasoconstriction.
Beta-2 : NE - SMC relaxation

12

What are the Local Stimuli that start the Long and Short Reflexes?

GI Chemoreceptors (Epithelium) - pH, Food Content
GI Mechanoreceptors (Epithelium) - Sterch

13

What makes GI hormone unique?
What are the four ones fall to this specific category?

Released by GI Mucosa Endocrine cells travel into the portal circulation, enter the general circulation, and have physiologic actions on target cells.
Gastrin, Cholecystokinin (CCK), Secretin, Glucose Dependent Insulinotropic Peptide (GIP)

14

Gastrin:
Family type, Site of Secretion

Gastrin:
Gastrin-CCK Family
G-Cells of Stomach

15

Gastrin:
Stimuli, Actions

Stimuli of Gastrin:
Peptides and Amino acids, Stretch signal (GRP), Inhibited by H+ and SST.
Actions (Gq): Parietal Cells H+ Release, Histamine secretion from ECL cells.

16

CCK:
Family and Secretion sites

CCK:
Gastrin-CCK family
Secreted from I cells of Duodenum and Jejunum

17

CCK:
Stimulus

CCK Stimulus:
Peptides, Amino and Fatty acids.

18

CCK: Actions

CCK:
1)Contraction of gallbladder and Relaxation of sphincter of Oddi
2)Pancreatic Enzymes and Bicarbonate secretion↑
3)Growth of Exocrine Pancreas and Gallbladder ↑
4)Inhibits gastric emptying

19

Secretin:
Family and Secretion sites

Secretin-Glucagon Family
S cells of Duodenum

20

Secretin:
Stimulus and Actions

Stimulus - H+ and FA in Duodenum
Actions - Pancreatic bicarbonate secretion↑, Biliary bicarbonate secretion↑, Gastric H+ secretion↓

21

GIP:
Family and Secretion sites

GIP:
Secretin-Glucagon Family
Duodenum and Jejunum

22

GIP:
Stimulus and Actions

GIP:
Stimulus -FA and Amino acids, and Oral Glucose (an Incretin Function) .
Actions - ↑ Insulin secretion,
↓ Gastric H+ secretion

23

What are the Paracrine Hormones: Enterochromaffin (EC)

SST - D cells; Inhibition of H secretion and SMC contraction.
HIstamine - ECL cells; Acid Production
Serotonin - SMC Contraction

24

What are the "Candidate" Hormones?

Motilin - SMC ↑
GLP - Epithelial Proliferation↑
Leptin (from Adipose) and Ghrelin (from Stomach)

25

What are the types of contraction of the gastrointestinal tract smooth muscle layers?

Tonic (Basal) contractions and Phasic Contractions

26

What is the neurogenic basis for the Tonic contractions?

The Tonic contractions are the result of general fluctuations of the potential levels of the SMCs. They originate from the Interstitial Cajal cells that are linked by Gap junctions to the SMCs. This keeps a Basal level of "Slow waves" of Repol. and Depol. thae allow for these weak contractions.

27

What type of SMCs are the ones that are found in the GI tract?

Single unit, they are connected via gap junctions meaning that they excite each other and contraction practically simultaneously.

28

What is the molecular basis for Slow wave production in the interstitial cajal cells?

Special Slow Na+ Channels are responsible for the Depolarization and Repolarization is caused simply by general K channels.

29

What is the molecular basis for the SMC contractions once depolarized by the Slow waves?

Ca2+ VDC

30

What are the rhythm of the contractions in the Stomach (Lowest) and in the Duodenum (Highest)?

Stomach - 3 per Min
Duodenum - 12 per Min