Lecture 6 General Principles of GI

Question 1

what is the outermost layer of the gut wall

Answer 1

Serosa (protection)

Question 2

what is just inside the serosa that shortens the bowel segment upon contraction

Answer 2

Longitudinal mucle

Question 3

what is just inside the longtudinal smooth muscle that decreases the diameter of the lumen?

Answer 3

circular muscle

Question 4

what muscle layer is deep to the circular muscle that causes changes in surface area of the epithelial surface?

Answer 4

Muscularis mucosa

mucosa with bundles of mucosal smooth muscles

Question 5

what does polarized mean?

Answer 5

something is longer than it is wide

Question 6

what nerve plexus in the gut call causes peristalsis?

Answer 6

Myenteric plexus

Question 7

Where is the myenteric plexus located?

Answer 7

Between the longitudinal layer and the circularis muscles

Question 8

What nerve plexus in the gut wall controls vasodilation and therefore secretion?

Answer 8

Meissner Plexus

Question 9

TRUE or FALSE, GI smooth muscle has significantly interconnected with bundles of cells that contract in a single direction with big gap junction for easy ion flow?

Answer 9

TRUE

Question 10

Do many or few connection exist between the major smooth muscle layers?

Answer 10

Few

Question 11

Smooth muscle DOES NOT have action potential, what happens instead?

Answer 11

It is a slow wave rhythm of MEMBRANE POTENTIAL that goes off with stretch or other stimulus (only at the top an AP becomes possible with stimulus)

Question 12

these action potentials that only occur at the top of waves are actually called?

Answer 12

spike potentials
(slow wave created by sodium leakage)
(spike potential created by Ca-Calmodulin)

Question 13

Intrinsic innervation can happen w/o extrinsic sympathetic and parasympathetic influence, true or false?

Answer 13

True

Question 14

In the extrinsic pathway, what autonomic system is inhibiting, and excitatory?

Answer 14

Parasympathetic is stimulating

Sympathetic is inhibiting

Question 15

Through what route does parasympathetic stimulation excite the Gi tract?

Answer 15

Parasympathetic stim descends down Vagus CN X, and goes to both Myenteric and Meissner plexuses, which cause contraction and vasodilation/secretion

Question 16

Besides parasympathetic stimulation increasing the membrane potential, what other two things influence it?

Answer 16

Local stretch, and acetylcholine

Question 17

What besides the sympathetic stimulus causes inhibition of the GI tract?

Answer 17

Norepinephrine or epinephrine

Question 18

Does the myenteric or submucosal/meissner plexus span the entire length of the GI tract?

Answer 18

Just the myenteric

the meissner only controls smaller portions of local mucosa

Question 19

What protein is excreted with a protein meal touches the wall of the duodenum that increases secretions ahead of time?

Answer 19

Enterokinase

Question 20

TRUE or FALSE, there are very few sensory fibers in the Myenteric plexus

Answer 20

TRUE

Question 21

What 5 things can plexus cell bodies detect in the gut and promote excitation or inhibition as a result?

Answer 21

Stretch
pH
Irritation
Hormones and signaling molecules
Chemicals (like fats proteins carbs in duodenum)

Question 22

She said just remember this….

Answer 22

Sensory cells ARE not epithelial cells

Question 23

what is the visceral-visceral loop

Answer 23

a sensory system between the nerve fibers of the gut wall and the greater myenteric & submucosal/meissner plexus. This loop bypasses the need for higher regulation

Question 24

The parasympathetic system innervates all GI structures as far as what?

Answer 24

Left colic flexure of colon

Question 25

what nervous division supplies the descending colon, sigmoid, rectum, and facilitates defecation?

Answer 25

Pelvic splanchnic nerves from s2-s4

Question 26

What symathetic plexus innervates liver, gall bladder, stomach, pancreas, large and small intestine to left colic flexure?

Answer 26

Celiac Plexus (with mostly NOREPI)

Question 27

Gastrin is released in the G-cells (parietal) cells that stimulates the production of what?

Answer 27

HCL and promotes mucosal growth (producing Na/H exchangers)

Question 28

Gastrin is located in what 3 places?

Answer 28

Stomach, duodenum, jejunum

Question 29

Gastrin is stimulated by what three local factors?

Answer 29

Presence of proteins, stomach distention, and acetylcholine

Question 30

Gastrin production is inhibited by what factor?

Answer 30

low pH (indirectly responsible for keeping esophogeal sphincter closed normally)

Question 31

Cholecystokinin does what?

Answer 31

Stimulates bicarb and enzyme secretion from the pancreas, contracts the gallbladder, promotes pancreatic growth, inhibits gastric motility

Question 32

Cholecsytokinin is located in what 3 structures?

Answer 32

I-cells of duodenum, jejunum, ileum

Question 33

Cholecsytokinin is stimulated by what 3 things?

Answer 33

proteins, fats, and H+

Question 34

Secretin does what?

Answer 34

promotes pepsin, promotes biliary and pancreatic bicarb secretion, and inhibits HCL secretion (anti gastrin hormone)

Question 35

Secretin is found where?

Answer 35

S-cells of duodenum, jejunum, ileum

Question 36

Secretin is stimulated by what 2 things?

Answer 36

Fat, and acids

Question 37

What are the 2 phases of peristalsis induced by the myenteric plexus?

Answer 37

1. Leading wave of distension

2. Peristaltic contraction

Question 38

what occurs randomly in the gut, induced by stretch or presence of food bolus?

Answer 38

mixing movments (5-30 seconds in length)