GI3 Flashcards
action potentials can occur when threshold potential is more ___ than (depolarized relative to) ~40mV.
positive`
what is the input for action potentials in the GI tract?
PS NS
what provides a low-resistance pathway for ions to move between smooth muscle cells?
gap junctions
in the absence of PS input:
- slow waves only
- no AP
- no contraction
- no change in muscle tension
PS input enables what:
- slow waves
- APs
- contraction
- increase in muscle tension
what do excitatory neurohormonal substances do?
- depolarize RMP, Vm
- increase likihood of contraction
- increase contraction/motility
what does sympathetic input do to the resting potential?
- hyperpolarizes it
- decreases contraction/motility
what cranial nerves are involved in prehension? sensory/motor
sensory: 1,2,5
motor: 5,7,9
mastication incorporates what into food?
salivary amylase
what are the two phases of swallowing?
- voluntary
- involuntary
what are the steps of swallowing?
- closure of pharynx
- glottis pulls under epiglottis
- closure of larynx
what kind of muscle is in the esophagus?
striated and smooth muscle
striated muscle of esophagus is under what kind of control?
somatic motor control by vagus
smooth muscle is under what kind of control?
ENS/ANS control
what plexus is present throughout the length of the esophagus?
myenteris plexus
both sphinters of the esophagus are normally (open/closed)
closed
what is the proximal part of the fundus?
fundus (storage region)
how does the fundus accomodate ingesta?
adaptive (receptive) relaxation
what is the distal part of the stomach?
antrum
what is the role of the antrum?
grind ingesta and present it to the SI
muscular activity of the antrum is increased by what?
PS (ACh) input
what hormones stimulate gastric motility?
- gastrin
- motilin
what hormones inhibit gastric motility?
- CCK
- secretin
- CIP
stomach emptying matches ___ and ___
-digestion and absorption
what are the 2 kinds of motility during the digestive phase of the SI?
-propulsive and non-proulsive
what are charactertics of propulsive motility in the SI
- aboral
- peristaltic
- slow waves
- travel slow distances
what are characteristics of non-propulsive motility in the SI?
- segmentation: results from localized contractions
- 3-4 cm long
- mixing action
is there digestion in the inter-digestive phase in the GI tract?
yes
what does MMC stand for/do?
- migrating motility/myoelectric complex
- pushes undigested material out of SI
when is MMC most present?
between meals
___ _____ ultimately produces intense peristalsis and propulsive motility
-excitation-contraction coupling
what are the general functions of the colon?
- water and electrolyte absorption
- fermentation
- storage of feces
colonic motility facilitates ___ and thereby optimizes colonic functions.
mixing
what are two structural specializations of the colon?
- haustra (saccules)
- segmentation
what is colon mixing optimized by?
-haustra and segmentation
what is a strong mixing property of the colon?
retropulsion
what processes are influence by colonis motility?
- absorption
- fermentation
carnivores have a colonic pacemaker located near the juncture between ____ and ___ colon segements
transverse and descending
the horse has a colonic pacemaker located near the _____
pelvic flexure (ascending colon)
the internal smooth muscle anal sphincter is relaxed by what NS?
PS
the internal smooth muscle anal sphincter is relaxed by what NS?
sympathetic
the external striated muscle anal sphincter is (voluntary/involuntary)? and intervated by what?
- voluntary
- GSA pudendal nerve
what is the glandular stomach of the avian?
proventriculus
what is the muscular “gizzard” of the avian?
ventriculus
what happens in the crop?
mucous secretion/storage of fod
what happens in the paired ceca?
- urinary excretions
- reabsorption of water and electrolytes
