substance that promotes bowel loosening and movement
Purgative
feeling of needing to pass stool even when bowel is empty
tenesmus
Location of cells that absorb fluid:
tips of villi
Location of cells that secrete fluid:
crypts
How does sodium get in apical side for water to follow?
NHE
sodium hydrogen exchanger
How does chloride get in apical side to join sodium and water follow?
Chloride/Bicarb exchanger
Electrogenic uptake of water?
Na+ / Glucose (SGLT1-apical) (GLUT-2, basolateral)
**Cl- and H20 follow passively via tight junctions
long reflex regulator of Cl- secretion:
Ach
VIP
GI peptide in goblet and ECL cells
increases cGMP
promotes Cl- secretion via CFTR
Guanylin
Drug that activate guanylate cyclase type C to treat constipation:
Linaclotide
The bulk of fluid reabsorption is driven by?
Nutrient-coupled electrogenic sodium absorption
SGLT-1
Na/AA
How does sodium enter COLONOcytes?
ENaCs
electrogenic
mostly in distal colon
What stimulates ENaC expression in colonocytes?
Aldosterone
just like the kidney!
How does electroneutral NaCl absorption occur n the colon?
NHE’s
Na+/H+
Name some secretagogues (enhance secretion)
PNS–Ach
VIP/NO
Histamine
PG’s
gastrin
secretin
motilin
serotonin
LCFAs
bile salts
Bacterial toxins
Name some absorbagogues (enhance absorption):
SNS
somatostatin
Aldosterone
SCFAs
opiods
Diarrhea from excess secretion of CL-?
Secretory
Diarrhea from poor absorption of nutrients?
Osmotic
What regulates intestinal motility?
BER (basal electric rhythm) — cells of Cajal?
Enteric nervous system
BER cycle rate in jejunum vs ilium?
jejunum – 12/min
distal ilium – 8/min
See slide 31 and 35
for specific regulators of motility
BER at ileocecal valve vs sigmoid colon:
IC valve – 2/min
SC – 6/min
Excess production of what causes Inlammatory Bowel Disease sx?
NO
**caused by Crohn’s or ulcerative colitis
Intestine becomes more sensitive and contract more frequently?
Irritable Bowel Syndrome