GI Motility, Secretions, Swallowing (lec 2)

Question 1

GI tract made of what type of mm?

Answer 1

unitary smooth mm

EXCEPT pharynx, up 1/3 esoph (including up esoph sphincter), and external anal sphincter (striated mm)

Question 2

Contraction of circular smooth mm happens where in relation to bolus?

results in?

contraction caused by what substances?

relax caused by what substances?

Answer 2

contracts behind bolus

↓ diameter of tract (pushes bolus forward, keeps bolus from moving back up the tract)

ACh, Substance P

VIP, NO

Question 3

Contraction of longitudinal smooth mm happens where in relation to bolus?

results in?

Answer 3

in front of bolus

shortens length of GI tract

Question 4

Phasic contractions are?

happens where?

purpose?

Answer 4

periodic contract followed by relax

esoph, antrum, small intest

mix and propulsion

Question 5

Tonic contractions are?

happens where?

purpose?

Answer 5

constant contraction (tone) w/o regular relaxation

low esoph sphincter, up stomach, ileocecal and internal anal sphincters

block passage, keeps separation of compartments

Question 6

Phasic mixing movements are?

promote/facilitate?

Answer 6

back-forth w/o forward movement

digestion and absorption

Question 7

Phasic propulsive movements?

controlled by?

Answer 7

contractile waves (peristalsis)

intrinsic myogenic activity

Question 8

Orthograde wave is?

Answer 8

relax/contract of long and circular smooth mm to move bolus forward

Question 9

Slow Waves of GI smooth mm are?

purpose?

Answer 9

cyclic depol/repol of resting memb potential of VSMC (vasc smooth mm cell)

set frequency of action potentials by bringing memb potential to threshold

Question 10

If Slow Wave hit threshold, what happens?

Answer 10

results in “spike potential” causing strong smooth mm contraction

**slow wave does not cause the contraction, is NOT an action potential

Question 11

Muscle tension developed by VSMC Slow Wave is increased by what?

decreased by what?

Answer 11

increased by ACh

decreased by NE

**NEITHER affects wave frequency

Question 12

Frequency of smooth mm contractions dictated by?

Answer 12

frequency of Slow Waves

Question 13

Rate of Slow Waves is slowest where?

fastest where?

Answer 13

stomach

duodenum

Question 14

Cephalic phase of digestion is?

Answer 14

auto and endo reflexes triggered by anticipation of and 1st sensory contact with food

prepares GI tract

Question 15

Cephalic phase results from activation of what?

causes what?

Answer 15

PNS efferents

↑ saliva, gastric acid, gastrin, pancreatic enz

Question 16

Saliva is basically what?

Answer 16

alkaline solution that moistens food

Question 17

Components of saliva? (3)

Answer 17

1) Mucus (lubricant)
2) ⍺-amylase (starch digestion)
3) Lingual Lipase (fat digestion)

Question 18

Acinus is?

Made of?

Does?

Answer 18

structure in salivary glands

made of acinar, myoepithelial and ductal cells

makes saliva

Question 19

Initial Saliva made by what cells in Acinus?

with electrolyte composition similar to?

Answer 19

acinar cells

plasma (same [Na+, K+, Cl-, HCO3-])
\\ it’s isotonic

Question 20

Ductal cells modify Initial Saliva how?

Answer 20

lumen side (takes from blood and secretes into saliva):
HCO3-
K+

basal side (absorbs from saliva and dumps into blood): Amount of solute into blood is&raquo_space; amount of solute still in saliva.
Na+
Cl-

net result is:
\\ saliva becomes hypotonic to plasma

Question 21

At slowest saliva flow rate, osmolarity of saliva is?

Answer 21

low:
[Na+, Cl-, HCO3-] lowest
[K+] highest

ductal cell has more time to modify saliva

Question 22

At highest saliva flow rate, osmolarity of saliva is?

Answer 22

isotonic to plasma and acinar cells

saliva pH ↑ from ↑ HCO3- secretion

ductal cells have less time to modify saliva

Question 23

Unique property of salivary secretion regulation?

Answer 23

increased by BOTH PNS and SNS

**PNS is more important

Question 24

Symp stim of salivary glands originates where?

goes where/release what?

target what?

Answer 24

Originate: T1-T3

Post-gang neurons in superior cervical ganglion
release NE

adrenergic receptors in acinar and ductal cells

Question 25

Parasymp stim of salivary glands originate where?

go where/release what?

target what?

Answer 25

CN VII and IX

post-gang neuron in submandibular/sublingual glands (CN VII)
and otic (CN IX) ganglia in parotid gland,
release ACh

muscarinic receptors in acinar and ductal cells

Question 26

Salivary Center located where?

Stimulated by?

Releases what?

Answer 26

medulla

taste, tactile, smell

ACh and VIP from parasymp post-gang nerves

Question 27

Esophagus extends b/w?

Answer 27

pharynx and stomach

Question 28

Esophagus made of what type of mm?

Answer 28

up 1/3 = striated
mid 1/3 = striated and smooth
low 1/3 = smooth

Question 29

Upper Esophageal Sphincter (UES) purpose?

Answer 29

closes to keep air from stomach during breathing

Question 30

Lower Esophageal Sphincter (LES) purpose?

Answer 30

prevents reflux

Question 31

Swallowing coordinated by what part of the brain?

Answer 31

medulla

Question 32

What happens during Oral Phase of Swallowing?

Answer 32

voluntary initiation

tongue pushes bolus to pharynx ->
stimulates somatosensory ->
starts swallowing reflex,
respiration and glottal closure inhibited

Question 33

What happens during Pharyngeal Phase of Swallowing?

Answer 33

soft palate pulled up (stop nasophary reflux),
epiglottis seals trachea,
UES relaxes,
peristalsis pushes bolus into esophagus

Question 34

What happens during Esophageal Phase of Swallowing?

Answer 34

bolus pushed to LES,
UES closes,
LES relaxes for bolus to pass,
LES contracts pushing bolus into stomach