motility of intestine and water absorption Flashcards
what are the 3 motility patterns?
1) peristalsis
2) tonic contraction
3) segmentation
what is peristalsis?
wave-like distention of gut wall
what is tonic contraction?
sustained contractions in sphincters
what is segmentation?
rhythmic contraction of circular muscle (breakdown)
what is the activity of smooth muscles like?
occurs as slow waves in rhythmic pattern
what is the activity of smooth muscle modulated by?
intrinsic (enteric) and extrinsic (autonomic) nervous system and hormones
what are iccs cells?
interstitial cells of cajal act as pacemaker to generate slow waves
where are ICCs located?
between longitudinal and circular muscle layers in submucosa
what is basic electrical rhythm?
spontaneous depolarization/repolarization of ICCs - determined by the slow waves
what is water absorption driven by in small intestine?
absorption of Na+
- local osmotic force
- transcellular or paracellular routes
in what mechanisms is Cl- also reabsorbed?
Na+/glucose co-transport
Na+/amino acid co-transport
epithelial Na+ channels - ENaC
what cells secrete Cl- ?
crypt cells
through which processes does Cl- secretion occur?
Na+/K+ ATPase
Na+/K+/2Cl- co transporter (NKCC1)
K+ channels
what drives inward movement in NKCC1?
low intracellular Na+
