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630: Medical Physiology > Gastrointestinal Physiology > Flashcards

Flashcards in Gastrointestinal Physiology Deck (109)
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1

What are the 2 functions of the GI tract?

digestions and absorption of nutrients

2

In order to serve these 2 functions, what are the 4 major activities of the GI tract?

(1) Motility propels ingested food from the mouth toward the rectum and mixes and reduces the size of the food
(2) Secretions from the salivary glands, pancreas, and liver add fluid, electrolytes, enzymes, and mucus to the lumen of the gastrointestinal tract
(3) Ingested foods are digested into absorbable molecules
(4) Nutrients, electrolytes, and water are absorbed from the intestinal lumen into the bloodstream

3

Describe the linear arrangement of the GI tract

Mouth --> Esophagus --> Stomach --> Small Intestine (duodenum, jejunum, ileum) --> Large intestine --> Anus

4

What are the 2 surfaces of the GI wall?

- mucosal
- serosal

5

The mucosal surface faces the _____ and the serosal surface faces the _____.

lumen

blood

6

What 3 things does the mucosal layer consist of?

- a layer of epithelial cells
- a lamina propria
- a muscularis mucosae

7

What does contraction of the muscularis mucosae do?

Changes the shape and surface area of the epithelial cell layer

8

What lies beneath the mucosal layer?

a submucosal layer

9

What is found between the submucosal layer and the serosal layer?

2 layers of smooth tissue: circular and longitudinal muscle

10

What 2 plexuses contain the nervous system of the GI tract?

- submucosal plexus
- myenteric plexus

11

The GI tract is regulated by the _____ nervous system

autonomic

12

What are the 2 components of the autonomic nervous system?

- intrinsic component
- extrinsic component

13

What is the intrinsic component called and what does it do?

Enteric system, which is wholly contained within the submucosal and myenteric plexuses. It communicates with the extrinsic component

14

The extrinsic component is the ________ and _______ innervation of the GI tract

parasympathetic

sympathetic

15

Postganglionic neurons of the parasympathetic nervous system are classified as either _____ or _______.

cholinergic

peptidergic

16

What neurotransmitter do cholinergic neurons release?

ACh

17

Parasympathetic innervation results in what 5 things?

- contraction of smooth muscle in the GI tract wall
- relaxation of the sphincters
- increased salivary secretion
- increased gastric secretion
- increased pancreatic secretion

18

Postganglionic neurons of the sympathetic nervous system are classified as _____.

adrenergic

19

What neurotransmitter do adrenergic neurons release?

norepinephrine

20

Sympathetic innervation results in what 5 things?

- relaxation of smooth muscle in the GI tract wall
- contraction of the sphincters
- increased salivary secretion

21

GI peptides are classified as what 3 things?

- hormones
- neurocrines
- paracrines

22

What are hormones?

Peptides released from endocrine cells of the GI tract

23

Describe the path hormones take to reach their target cell

They are excreted into portal circulation, pass through the liver, and enter the systemic circulation.
The systemic circulation then delivers the hormone to target cells with receptors for that hormone.

24

What are paracrines?

Peptides released from endocrine cells of the GI tract

25

How do paracrines differ from hormones?

They act locally within the same tissue that secretes them.

26

Paracrines reach their target cells by way of _____.

diffusion

27

What are neurocrines?

Peptides that are synthesized in neurons of the GI tract and released following an action potential

28

After neurocrines are released following an AP they ______ across the synapse to act on its target cell.

diffuse

29

What does motility refer to?

contraction and relaxation of the walls and sphincters of the gastrointestinal tract

30

What 4 things does motility do to ingested food to prepare it for digestion and absorption?

- grinds
- mixes
- fragments
- propels