2.01 Swallowing and Motility

Question 1

saliva helps to form a bolus with what key components?

Answer 1

water, electrolytes, enzymes (amylase), mucins

Question 2

what do the lingual lipase and alpha amylase enzymes in saliva digest respectively?

Answer 2

initial triglycerides and starch

Question 3

what kind of reflex is swallowing?

Answer 3

parasympathetic

Question 4

what are the three main phases of swallowing?

Answer 4

oral, pharyngeal, and esophageal

Question 5

what phases of swallowing are involuntary and controlled by the brainstem?

Answer 5

pharyngeal and esophageal

Question 6

How is the upper 1/3 of esophagus innervated and muscle makeup?

Answer 6

striated (somatic), via CN IX and CNX

Question 7

How is the lower 2/3 of esophagus innervated and muscle makeup?

Answer 7

smooth muscle (ENS & ANS) CNX

Question 8

during esophageal peristalsis how is the process alternating and generating pressure to move bolus?

Answer 8

contract above generating positive pressure to push bolus into relaxed portion below with negative pressure

Question 9

What is the LES doing under normal conditions?

Answer 9

contracted to maintain high pressure barrier (sympathetic innervation)

Question 10

how is the peristalsis contraction wave triggered?

Answer 10

presence of bolus in UES decreasing the pressure + neuronal response leading to the LES relaxing a bit

Question 11

What is the baseline pressure of the UES, esophageal body, and LES?

Answer 11

UES and LES = high to maintain contraction (closed sphincter)

esophageal body is relatively low

Question 12

What happens once you swallow to the LES baseline pressure?

Answer 12

it falls (muscle relaxes) to pass bolus and steadily increases to high resting pressure

Question 13

Why does the UES in particular have such a quick spike up in baseline pressure faster swallowing?

Answer 13

to prevent backflow of bolus/content to the pharynx

Question 14

swallowing initiates what response from brainstem?

Answer 14

vagal CNX

Question 15

Key NT needed to relax LES?

Answer 15

NO and VIP

Question 16

what state does the sphincter muscle have to be in to allow LES relaxation?

Answer 16

hyperpolarization

Question 17

What is the neuronal pathways to relax the LES? (PARA)
extrinsic vagal response

Answer 17

(pregang vag) myenteric plexus synapse
Ach to N2 receptors on inhibit motor neurons (post gang) that release NO and VIP that bind to sGC and VAPC1 to hyperpolarize the PDGFR a+ cell to cause smooth muscles hyperpolarization (or directly)

Question 18

What are the neuronal pathways to relax the LES? (PARA)
ENS/INTRINSIC response

Answer 18

descending IPAN
Ach - N2
descending interneuron* (+/-)
Ach - N2 receptor
inhibit motor neuron
PDGFRa+ - NO and VIP release to sGC and VAPC
smooth muscle cell relax

Question 19

What is the neuronal tone pathway for normal tone of the LES?

Answer 19

thoracolumbar pre gang (T5-L2)
prevertebral celiac ganglia Ach to N2
post ganglionic NE to B2 (esophageal body relax) or a1 (LES contract) at myenteric plexus varicosities

Question 20

Failure for the LES to relax leading to dysphagia is called?

Answer 20

Achalasia

Question 21

What is a common cause/dysfunction found in achalasia?

Answer 21

dysfunction of post ganglionic inhibitory motor nuerons

Question 22

GERD is associated with what problem to the LES?

Answer 22

spontaneous relaxation of LES that leads to very low (<5) resting pressure and retrograde flow of gastric contents

Question 23

What common drug is known to relax smooth muscle and potentially lead to GERD symptoms? What condition?

Answer 23

CCB for HTN
blocks calcium needed in smooth muscle cells to relax

Question 24

What can cause a hypotensive LES?

Answer 24

inadequate barrier function, reflux trigger sensitivity, mucosal damage

Question 25

GI symptoms of chagas targets what part of LES that can lead to a megaesophagus?

Answer 25

destruction of neurons in the submucosal and myenteric plexus - LES cant relax and accumulates pressure

Question 26

Do ICCs create action potentials?

Answer 26

NO, they make slow wave potentials that move rhymical via ion channels that precede an AP and typically cannot trigger itself (smooth muscle contraction)

Question 27

Distention of the gut with a food bolus leads activates what via stretch?

Answer 27

IPAN (excitatory) nerves

Question 28

What is being release alongside ICC to raise the threshold to activate an AP to trigger smooth muscle contraction?

Answer 28

Ach and SubP

Question 29

What are the unique characteristics of slow wave membrane potentials when at rest, stimulated, or inhibited at the GI tract?

Answer 29

Rest = slow waves and some spikes = some muscle tone stimulated = more slow waves, more spikes = more muscle tone inhibited = less slow waves, no spikes = no muscle tone

Question 30

what are the frequency GI contractions of the stomach?

Answer 30

3-5 contract/min

Question 31

what are the frequency GI contractions of the small intestine?

Answer 31

12-20 contract/min

Question 32

what are the frequency GI contractions of the large intestine?

Answer 32

6-8 contract/min

Question 33

what generally can help depolarize membrane for GI contraction?

Answer 33

stretched muscle parasympathetic stim Ach

Question 34

what generally can help REpolarize membrane for GI contraction?

Answer 34

NE sympathetic stim