3.1 Gastrointestinal Physiology Flashcards
what are the two basic movement of GI?
1) mixing- make a substance we can absorb
2) propulsive - move substances anally
what are the 3 mixing movements?
1) constrictor waves
2) segmentation
3) haustral contractions
define constrictor waves movement?
mixing movement
- weak peristaltic waves that mix food when it first arrives in stomach
- as time passes, it becomes more intense
define segmentation movement?
mixing movement
- strictly mixing
- RING-like contractions to compress food back and forth
- mainly in SI
define haustral contraction movement?
it is a combination of what two movements?
mixing movement AND propulsive (mainly MIXING)
- ringlike contractions anally
- mainly in LI
- moves stuff slowly so not efficient like peristalsis
- combination of segmentation and peristalsis
what are the 3 propulsive movements?
1) peristalsis
2) mass movement
3) haustral contractions
biggest difference to how segmentation and haustral looks?
haustral movement is moving stuff slowing anally, whereas segmentation moves food back and forth
what does distention mean?
relaxation due to presence of food stretching gut
define peristalsis movement?
propulsive movement
- characterized by a wave of distention (stretch) followed by a wave of contraction
- opens up sphincters via receptive relaxation
define mass movement movement?
propulsive movement
*a LARGE segment of intestine contracting simultaneously for rapid movement of contents
(in SI = explosive diarrhea)
peristalsis is usually initiated by?
by distention/stretch and coordinated by myenteric plexus
what is receptive relaxation?
an important part of peristalsis
- characterized by a leading wave of distention= relaxation ahead of the contraction
- *IMPORTANT for sphincters in order to receive what’s coming into it
What is the “Law of the Gut”?
generally, movements of the gut are analward or aboral (away from mouth)
*exception is acid reflux
define deglutition?
swallowing
what are the two phases of swalling?
1) voluntary
2) involuntary (reflex)
describe voluntary phase of deglutition?
food is pushed back into pharynx by tongue and oral muscles
describe involuntary phase of deglutition?
reflex contractino of pharynx, which moves food into esophagus (wjere peristalsis begins)
*also has two phases called pharyngeal and esophageal phase
what are the two phases of the involuntary phase of swallowing?
pharyngeal
esophageal
describe involuntary pharyngeal phase of swallowing?
- stimulation of pharyngeal mechano-receptors
- impulse transmitted to swallowing center via afferent fibers of trigeminal and glossopharyngeal nerve
- medullary swallowing center intitiates sequences of events via Efferent fibers of trigeminal, glossopharyngeal, vagus, and hypoglossal nerves
what muscles are affected during pharyngeal involuntary phase of swallowing?
pharynx, esophagus, and respiration are all affected by motor impulses from the swallowing center
pharyngeal involuntary phase sequence of events
1) soft palate elevated
2) larynx elevated to close trachea/epiglottus
3) vocal cords approximated- helps close trachea
4) respiration inhibited
5) contraction of pharynx
describe involuntary esophageal phase of swallowing?
- primary peristaltic waves of esophagus are a result of mechanical AND vagal stimulation to esophagus
- a second waves will be initiated at distension of esophagus at the location of the bolus IF food didn’t reach stomach
how long does it take for one peristaltic wave to reach the stomach?
9 seconds
what sphincter opens to allow food to enter stomach? how?
cardioesophageal sphincter opens by receptive relaxation to allow food to enter stomach
depending on the INTENSITY, peristaltic waves cause both?
mixing and emptying
parts of stomach
- cardioesophageal sphincter into stomach
- fundus (considered part of body)
- body
- antrum
- pyloric sphincter into duedenum of SI
what are gastric factors regulating emptying?
1) wave intensity -pressure at sphincter
2) presence of food -distention
3) vagal activity -gastrin
4) fluidity of chyme -liquids faster
5) enterogastric reflex -hypertonicity/irritation
6) hormones - GIP, CCK, secretin inhibit gastrin
where is vomiting center located?
medulla
what are the causes of vomiting?
1) emetics
2) motion
3) GI irritation
what are “emetics”? give an example
any chemical trigger that causes vomiting
*syrup of ipecac (used for kids)
how do emetic cause vomiting?
emetic > medullary chemoreceptors triggered> vomit center
how do motion cause vomiting?
motion> vestibular nucleus with info from semicircular canals > vomit center
how do GI irritation cause vomiting?
GI irritation (bacteria, poison)> receptors within GI tract> vomit center
responses to a triggered vomiting reflex/center?
1) deep breath
2) closure of glottis (cover trachea)
3) elevation of soft palate
4) abdominal contraction
5) relaxation of lower and upper esophageal sphincter
what are precursors to vomiting?
1) increases salivation
2) sweating
3) increase heart rate
4) pale
5) neausea
if you increase rate of stomach emptying, you increase SI?
peristalsis
what separates the SI from colon?
iliocecal valve and sphincter
valve prevents?
backflow
sphincter prevents?
forward flow (emptying)
gastroenteric reflex promotes?
emptying into colon
*increase peristalsis and decrease sphincter tone
ilieal pressure or irritation promotes?
emptying into colon
*increase peristalsis and decrease sphincter tone
what two thing promote emptying into colon?
1) gastroenteric reflex
2) ilieal pressure
what INHIBITS emptying into colon?
increase in colonic pressure, irritation, or inflammation will inhibits (decrease ilial peristalsis and increse sphincter tone) empyting into colon
typical movements of SI?
1) mixing= segmentation
2) propulsive= peristalsis
typical movements of colonand rectum?
1) mixing= haustral
2) propulsive= mass movement
factors promoting movement IN colon
1) gastrocolic reflex (food in stomach)
2) duodenocolic reflex (food in duodenum)
3) local (colonic) irritation or pressure
factors promoting defecation?
1) defecation reflex
2) valsalva maneuver
3) external anal sphincter relaxation
what are the two parts to the defecation reflex?
1) intrinsic(enteric)
- –myenteric reflex
2) extrinsic
- – spinal reflex
* *both cause mass movement and internal anal sphincter relaxation
how does the Valsalva maneuver promote pooping?
increases intra-abdominal pressure (puts pressure on colon)
how does the external anal sphincter relaxing promote pooping?
because it is striated muscle with VOLUNTARY control
define Valsalva maneuver
forced expiration against a closed glotus (aka straining)
what anal sphincter is involuntary and voluntary?
- external= striated and voluntary
* internal= smooth and involuntary
what is the ONLY structure at the end of GI tract that you have any control over?
external anal sphincter
