Motility of GI Tract - Lopez

Question 1

Which elements of the GI Tract Wall comprise the Mucosal Layer?

Answer 1

Epithelium
Lamina Propria
Muscularis Mucosae

Question 2

Which elements of the GI Tract Wall comprise the Muscularis Propria?

Answer 2

Circular Muscle
Myenteric Plexus
Longitudinal Muscle

Note: Important for motility of GI

Question 3

What are the characteristics of Circular Muscle? Longitudinal Muscle?

Answer 3

Circular M. - Thick muscle with dense innervation; Contraction —> DECREASE diameter

Longitudinal M. - Thin muscle with fewer innervations; Contraction —> DECREASE length of segment

Question 4

What are Slow Waves? How do they differ from Action Potentials?

Answer 4

Slow Waves - depolarization/repolarization of membrane, whose frequency is set by the Interstitial Cells of Cajal found in the Myenteric and Submucosal Plexuses.

Action Potentials - Depolarization moves membrane at or above threshold.

Question 5

How are Action Potentials and strength of contraction modulated?

Answer 5

Neural Activity and Hormonal Activity

Question 6

What is a Phasic Contraction? Where do these contractions occur?

Answer 6

Periodic contraction followed by relaxation; Esophagus, Stomach (Antrum), SI, Tissue involved in mixing/propulsion.

Question 7

What is a Tonic contraction? Where do these contractions occur?

Answer 7

Maintain constant level of contraction without regular period relaxation; Stomach (orad), Lower Esoph., Ileocecal, and Internal Anal Sphincter.

Question 8

What is the relationship between Slow Waves, APs, and Contractions in smooth muscle?

Answer 8

GREATER number APs on a slow wave —> INCREASED contraction of smooth muscle segment

Question 9

What is the effect of ACh on the amplitude of Slow Waves? NE?

Answer 9

ACh —> INCREASE amplitude slow wave

NE —> DECREASE amplitude slow wave

Question 10

How does STRETCH impact the amplitude of slow waves?

Answer 10

INCREASE amplitude

Question 11

What effect do the Parasympathetic and Sympathetic have on Slow Wave amplitude?

Answer 11

Parasympathetic —> INCREASE amplitude

Sympathetic —> DECREASE amplitude
Hyperpolarize so difficult to reach threshold

Question 12

What is controlled by the Submucosal (Meissner) Plexus?

Answer 12

GI Secretions

Local Blood Flow

Question 13

What is controlled by the Myenteric (Auerbach’s) Plexus?

Answer 13

GI Movement

Question 14

Which cells are the “Pacemaker” cells for GI smooth muscle?

Answer 14

Interstitial Cells of Cajal (ICC)

Propagate slow waves —> spread via gap junctions

Question 15

Which nerve supplies most of the muscles of mastication?

Answer 15

Motor branch of 5th Cranial Nerve (Trigeminal)

Question 16

What are the 3 phases of swallowing?

Answer 16

Oral (Voluntary)
Pharyngeal (Involuntary)
Esophageal (Involuntary)

Question 17

What 2 wave types are present in the Esophageal phase of swallowing?

Answer 17

Primary peristaltic wave

Secondary peristaltic wave

Question 18

What are the characteristics of PRIMARY peristaltic wave?

Answer 18

1. CAN’T occur after Vagotomy
2. Continuation pharyngeal peristalsis
3. Controlled by Medulla

Question 19

What are the characteristics of secondary peristaltic wave?

Answer 19

1. Occurs EVEN after vagotomy
2. Controlled by Medulla and ENS
3. Occurs in absence of oral and pharyngeal swallowing phases
4. Occurs if primary wave fails to empty esophagus or if gastric contents reflux into esophagus

Question 20

What is achalasia?

Answer 20

1. Impaired peristalsis
2. Incomplete LES relaxation during swallowing
3. Elevation of LES resting pressure

Question 21

What is the mechanism for achalsia?

Answer 21

1. Lack of VIP or ENS knocked out

2. Damage to nerves in esophagus prevent it from squeezing food into stomach

Question 22

What can result from achalasia?

Answer 22

1. Backflow food in throat (Regurg)
2. Difficulty swallowing liquid/solid (Dysphagia)
3. Chest pain