Lecture 10: Intro to GI Tract Flashcards
Which plexus controls intestinal smooth muscle and participates in tonic and rhythmic contractions?
Myenteric/Auerbach’s plexus
Name the layers of the gut tract wall from outer to inner.
Serosa Longitudinal smooth muscle Myenteric plexus (auerbach) Circular smooth muscle Meissner's plexus (submucosal) Mucosa
Which plexus controls GI secretion, absorption and local blood flow?
Meissner’s/Submucosal plexus
What are the 2 layers of the mucosa layer?
Lamina propria & muscularis mucosa
T/F: propulsive movements usually are stimulated by distension and no other signals
False, usually distension, but also chemical or physical irritation or strong parasympathetic signals
Which cells periodically open and produce inward currents that may generate slow wave activity?
Cajal cells
When do spike potentials occur?
Automatically when resting membrane potential of GI smooth muscle becomes more positive than -40 mv
What are spike potentials responsible for?
Opening Ca++ channels and some Na+ channels in GI smooth muscle cells
What factors cause depolarization of the gut wall?
Stretching of muscle, stimulation by Ach, stimulation by GI hormones
What factors cause hyperpolarization of the gut wall?
Norepinephrine & epinephrine & stimulation of sympathetic nerves
Continuous repetitive spike potentials, hormones, & continuous entry of Ca++ ions results in _____.
Tonic contractions
Which reflexes go from the gut to the prevertebral sympathetic ganglia and then back to GI tract?
Gastrocolic, Enterogastric, & Colonoileal
What are 3 hormonal factors that control feedback from the duodenum?
CCK, Secretin, & GIP
What is the principal function of the colon?
Absorb water and electrolytes from chyme
What are produced by large circular constrictions plus contractions of the teniae coli?
Haustrations
