GI Motility DSA

Question 1

What GI layer faces the lumen?

Answer 1

mucosal layer with the epithelial cells that have absorptive and secretion functions. also villi to increase surface area

Question 2

What muscle layer is more densely innervated and its contraction shortens the diameter of the segment?

Answer 2

Circular smooth muscle layer

Question 3

What muscle layer is thin with few nerve fibers and its contraction causes propulsion of food?

Answer 3

longitudinal smooth muscle layer (outer)

Question 4

What is the importance of gap junctions in smooth muscle?

Answer 4

Cells electrically coupled via low resistance pathways

Permit rapid cell-to-cell spread of actions potential

Question 5

Sympathetic stimulation by NE causes GI sm m to do what?

Answer 5

hyperpolarization - inhibiting

Question 6

Parasympathetic stimulation by ACh causes GI sm m to do what?

Answer 6

increase amplitude of slow wave
cause depolarization
stimulating

Question 7

Describe phasic contraction vs tonic contraction

Answer 7

Phasic: periodic contractions followed by relaxation
Tonic: constant level of contraction or tone without regular period of relaxation

Question 8

What do subthreshold action potentials produce?

Answer 8

Small contraction/basal contractions

Question 9

How many slow waves per minute occurs in the GI tract?

Answer 9

3 to 12
stomach 3 w/m
duodenum 12 w/m

Question 10

Where do slow waves originate?

Answer 10

intestinal cells of Cajal