LECTURE 25!!!!

Question 1

What type of muscle is found in the pharynx, UES, oral third of the esophageal body, and external anal sphincter?

Answer 1

Skeletal (striated) muscle

Question 2

What type of subunits are GI sphincters made of?

Answer 2

Multi-unit

Question 3

___: single unit smooth muscle contracts and relaxes within seconds. Contraction INCREASES pressure on luminal contents while relaxation DECREASES pressure on luminal contents. Pressure gradients are required!!
A. Phasic contractions
B. Tonic contractions

Answer 3

A. Phasic contractions

Question 4

Which type of contractions are used by sphincters?

Answer 4

Tonic contractions

Question 5

If a sphincter is closed, it is ___ and the strength of tonic contraction has___

Answer 5

contracted; increased

Question 6

The enteric circuit requires which 4 enteric neurons?

Answer 6

Sensory neuron
Interneuron
Excitatory motor neuron
Inhibitory motor neuron

Question 7

___: sensory neurons of the ENS

Answer 7

Intrinsic primary afferent neurons (IPAN’s)

Question 8

True or false: There are IPAN’s that are mechanosensitive (sense distension) and those that are chemosensitive (sense nutrition)

Answer 8

True

Question 9

What NT is released by excitatory motor neurons? Inhibitory?

Answer 9

Excitatory = Ach
Inhibitory = NO

Question 10

What do the UES and the Esophageal body have in common?

Answer 10

Made of skeletal muscle
- Esophageal body (upper 1/3)

Question 11

Why is the UES usually closed?

Answer 11

High frequency of AP in vagus nerve (increased Ach)

Question 12

Why does the UES open after a swallow?

Answer 12

Decrease in AP frequency (decreased Ach)

Question 13

Which has no resting tone and is flaccid?
A. Esophageal Body
B. UES
C. LES
D. Stomach

Answer 13

A. Esophageal Body

Question 14

Why does the LES relax during swallow?

Answer 14

Inhibitory enteric motor neurons make NO

Question 15

How is the LES tone maintained?

Answer 15

Tonic input from enteric inhibitory (NO) and excitatory (Ach) neurons

Question 16

How is the swallowing reflex started?

Answer 16

Activation of sensory afferent nerves innervating the oropharynx

Question 17

The vagus n in the Nucleus Ambiguus binds to striated muscle of the ___ and ___

Answer 17

UES; upper 1/3 of esophageal body

Question 18

The vagus n in the Dorsal Motor Nucleus binds to Myenteric Plexus, which acts on smooth m in the ___, ____, and ____

Answer 18

fundus, LES, and lower 2/3 of esophageal body

Question 19

The skeletal m of the esophagus is innervated ___ by the efferent vagus n

The vagus n forms _____ on skeletal muscle

Answer 19

directly

motor endplates

Question 20

Which neurons directly innervates the myenteric neurons? Which neurons directly innervate smooth muscle?

Answer 20

Myenteric neurons = vagus n
Smooth muscle = myenteric n

Question 21

Three stages of deglutition? Which stages are voluntary? involuntary?

Answer 21

1) Oral stage - voluntary
2) Pharyngeal stage - involuntary
3) Esophageal stage - involuntary

Question 22

Extrinsic afferent nerves with sensory endings in the oropharynx are activated by pressure from bolus of food to initiated which stage of deglutition?
A. Oral
B. Esophageal
C. Pharyngeal

Answer 22

C. Pharyngeal

Question 23

Cranial sensory afferent n innervating oropharynx are activated by ____

Answer 23

food bolus

Question 24

Vagal ___ pathways include:
1) Direct vagal innervation of striated m
2) Indirect vagal innervation of smooth m

Answer 24

Excitatory

Question 25

Vagal ___ pathways immediately open LES and __ fundus

Answer 25

Inhibitory; relax

Question 26

Which type of peristalsis always follows a swallow and is mediated by long neural reflex?

Answer 26

Primary Peristalsis

Question 27

Which type of peristalsis is initiated by distension of esophageal body and occurs in absence of pharyngeal peristalsis?

Answer 27

Secondary Peristalsis

Question 28

Which cell generate and establish the frequency of the slow wave?

Answer 28

Interstitial cells of Cajal - found in the wall of the GIT and connected via gap junctions

Question 29

Smooth muscles of the ____ and ____ exhibit continuous oscillations of the resting membrane potential known as the slow wave

Answer 29

stomach; small intestines

Question 30

True or False: The esophagus, stomach, and GI sphincters have slow waves

Answer 30

False

Question 31

True or False: The slow wave is always occurring, regardless of presence or absence of smooth muscle phasic contractions

Answer 31

True

Question 32

What is requires to generates smooth muscle AP burst?

Answer 32

Membrane depolarization

Question 33

___ sets the max frequency that action potential bursts can occur in the smooth muscle

Answer 33

Slow wave

Question 34

__ is the underlying basis for all phasic contractions

Answer 34

Slow Wave

Question 35

How is the frequency of phasic contractions affected by damaged ICC’s?

Answer 35

Decreased phasic contractions

Question 36

Where in the small intestines can you generate the most contractions? least?

Answer 36

most = duodenum (12) = higher pressure
least = ileum (8) = lower pressure

Question 37

True or False: Slow waves help est. pressure gradient

Answer 37

True

Question 38

What four factors influence motility?

Answer 38

1) Slow wave
2) Enteric neurons
3) Extrinsic nerves: sympathetic and parasympathetic
4) Hormones and paracrines

Question 39

Which drugs will decrease phasic contractions?

Answer 39

Opioids

Question 40

Orad of the stomach is for ___ while the caudad is for ___

Answer 40

storage; emptying

Question 41

In the small intestines, the slow wave ___ from the duodenum to the jejunum to the ileum. This helps move chyme DOWN the small intestines

Answer 41

decreases

Question 42

In the large intestines, the slow wave ___ from the ascending to the transverse to the descending colon. This helps RETAIN fecal matter in the large intestine.

Answer 42

increases