Gastrointestinal System

Question 1

Enzyme that starts to digest starch

Answer 1

Alpha-Amylase, present in the saliva. Acini of the salivary gland actually secretes amylase, ductular part of the gland interacts with ions of the mouth.

Question 2

Enzyme that starts to digest triglycerides

Answer 2

Lingual lipase, secreted by the tongue.

Question 3

Positive and Negative regulators for saliva secretion

Answer 3

Positive: Conditioning, food, nausea, smell
Negative: Dehydration, fear, sleep, anticholinergic drugs

Question 4

Parietal Cells

Answer 4

Found in the stomach. Secrete HCl and intrinsic factor, which is key for vitamin B12 absorption.

Question 5

Chief Cells of Stomach

Answer 5

Secrete Pepsinogen. Low pH of stomach (1-2) enables pepsinogen to be activated to pepsin. Pepsin plays key role in protein degradation.

Question 6

Histamine

Answer 6

Secreted by the Enterochromaffin-like cells (ECL cells). Histamine will then bind to H2 receptors on parietal cells which will then allow gastric acid to be secreted. Drops in pH inhibit histamine release.

Question 7

Gastrin

Answer 7

Hormone secreted by G-cells (found in the antrum of the stomach). Since it is a hormone, gastrin is released on the basolateral side, enters the bloodstream and then works back on the stomach. Causes release of gastric acid via Histamine release from ECL cells. Stimulus is the presence of peptides in lumen of stomach.

Question 8

Secretin

Answer 8

Inhibits Gastrin (helps ensure that stomach doesn't get too, too acidic).  Also acts on ductal cells of pancreas to increase bicarb secretion into duodenum. 
Stimulus is H+

Question 9

GRP

Answer 9

Gastrin-Releasing Peptide, a neuropeptide that stimulates the release of gastrin from G-cells. Postganglionic fibers of vagus nerve cause release of GRP on G-cells.

Question 10

Somatostatin

Answer 10

Peptide hormone (remember, that means it will be secreted into bloodstream to have effects). Secreted via stomach and delta cells of pancreas. Acts on parietal cells and decreases stomach acid secretion (inhibits Gastrin, secretion and histamine).

Question 11

Amylase

Answer 11

Breaks down starch into smaller sugar units (di/tri saccharides). Secreted by the salivary glands and the pancreas.

Question 12

Seven Sphincters

Answer 12

Upper esophageal; Lower esophageal; Pylorus; Sphincter of Oddi; Ileocecal valve; Internal and External anal

Question 13

3 Mechanisms for increased surface area

Answer 13

Tissue folding<Microvilli

*most absorption in sm int

Question 14

Autonomic Innervation: two component

Answer 14

Extrinsic - afferent/efferent pathways; para/symp stimulation

Intrinsic - wholly in gut; cell bodies @myenteric, submucosal plexus; reflex circuits; also para/symp stimulation

Question 15

Parasympathetic vs. Sympathetic Innervation Characteristics

Answer 15

Para- EXCITATORY; vagus pelvic nerves; preganglionic synapse @myenteric and submucosal plexuses; then innervates smooth muscle, secretory cells, endocrine cells.
Symp- INHIBITORY; postganglionic synapse @myenteric and submucosal plexuses; directly innervate blood vessels, smooth muscle

Question 16

Enteric Innervation

Answer 16

“Little Brain” - both symp and parasymp input; also mechano, chemoreceptor input

Question 17

Major Physiologic Neurohumoral Regulators of GI function (4)

Answer 17

*Endocrine [to blood] 
(CCK; gastrin; secretin; GIP)
*Neurocrine [neuronal stim/neurotransm] 
(GRP; Ach; VIP)
*Paracrine [to neighbors]
(Histamine; prostoglandin; somatostatin)
*Immune/Juxtacrine [immune response- contact-dependent] 
(Histamine; cytokines; adenosine)

Question 18

Motility - Characteristics and Function

Answer 18

Contraction/relaxation; phasic vs. tonic contraction
Move food; mix
Smooth muscle- sheets vs. circular vs. longitudinal
Gastric stimulation: stretch; VIP
Intestinal stimulation: ENS control (myenteric; para/symp)

Question 19

Principle Digestive Enzymes of: 
-Mouth
-Stomach
-Intestine 
[+targets]

Answer 19

Mouth:
(salivary) -->amylase-->starch
(lingual)-->L.Lipase-->triglycerides
Stomach: 
pepsins-->proteins/polypeptides
G.Lipase-->triglycerides
Intestine:
the "-ases"-->proteins/polypeptides
maltase/lactase/sucrase-->M/L/S
Pancreatic and intestinal lipases --> fats

Question 20

Endocrine enzymes that affect GI Function

Answer 20

Gastrin
Cholecystokinin (CCK)
Secretin
Glucose-Dependent insulotropic peptide (GIP)
(Motilin)

Question 21

Neurocrine enzymes that affect GI Function

Answer 21

Acetylcholine
Vasoactive Intestinal Peptide
(Substance P, CCK, Somatostatin, Calcitonin-gene related peptide, 5-HT)

Question 22

Paracine hormones affecting GI Function

Answer 22

Prostaglandins
Somatostatins
(Histamine)
(5-HT, serotonin)

Question 23

Immune/Juxtacrine hormones affecting GI function

Answer 23

Histamine
(Cytokines)
(Reactive Oxygen species)
(Adenosine)

Question 24

Location of production of various digestive enzymes along GI tract.

Answer 24

Mouth (Salivary Glands, Lingual Glands)
Stomach 
Intestinal Mucosa (epithelial cells)

Question 25

Hormonal and neural factors regulating HCl secretion in stomach (+ and -).

Answer 25

1. Parasympathetic NS (Acetylcholine) +
2. Gastrin (from gastric epithelial cells, through blood) +
3. Histamine (from pancreas) +
4. Somatostatins (from GI tract) -
5. Prostaglandins (from gastric epithelial cells) -

Question 26

Intestinal sites of absorption (what and where)?

Answer 26

Duodenum - Iron, Calcium
Duodenum and Jejunum - Carbohydrates
Duodenum, Jejunum, and Proximal Ileum - Fats and Proteins
Distal Ileum - Biles salts and Vitamin B12

Question 27

Absorbable carbohydrate units

Answer 27

Monosaccharides: Glucse, Fructose, Galactose

Question 28

Absorbable protein units

Answer 28

Amino acids, dipeptides, tripeptides

Question 29

What drives absorption in the intestine?

Answer 29

Secretion! Of fluids, electrolytes, and chloride ions.