Unit 6a GI Motility Control

Question 1

What are the two main types of gut motility?
a) Segmentation and peristalsis
b) Propulsion and elimination
c) Churning and filtration
d) Stretching and squeezing

Answer 1

a) Segmentation and peristalsis

Explanation: Segmentation mixes intestinal contents to enhance absorption, while peristalsis moves material forward along the GI tract.

Question 2

What are migrating motor complexes?
a) Contractions that occur during digestion
b) Tonic contractions of the esophageal sphincter
c) Waves that sweep through the GI tract between meals
d) Muscle twitches during defecation

Answer 2

c) Waves that sweep through the GI tract between meals

Explanation: Migrating motor complexes are waves of peristaltic activity that occur approximately every 90 minutes to clear debris and bacteria.

Question 3

What type of smooth muscle is found in most of the GI tract?
a) Multi-unit smooth muscle
b) Cardiac muscle
c) Skeletal muscle
d) Single-unit smooth muscle

Answer 3

d) Single-unit smooth muscle

Explanation: Most GI muscle is single-unit, connected by gap junctions and contracting together as a unit.

Question 4

What are slow wave potentials in gut smooth muscle?
a) Continuous action potentials
b) High-frequency contractions
c) Rhythmic depolarizations that may or may not reach threshold
d) Neural spikes from enteric ganglia

Answer 4

c) Rhythmic depolarizations that may or may not reach threshold

Explanation: These waves originate from interstitial cells of Cajal and help regulate the timing of contractions.

Question 5

What determines the frequency of slow wave contractions in the GI tract?
a) Parasympathetic input
b) Region-specific pacemaker cells
c) Type of food
d) Liver hormone secretion

Answer 5

b) Region-specific pacemaker cells

Explanation: Interstitial cells of Cajal between muscle layers generate slow waves at frequencies specific to each region (e.g., more frequent in duodenum than stomach).