Dr. Sullivant - Objectives only

What is the resting membrane potential of GI smooth muscle?

-50 to 60 mV

What affects GI smooth muscle contractility?

neurotransmitters, hormones, stretch, and irritating substances

What are slow waves?

slow, rhythmic increases in the resting membrane potential

What are spike waves?

true action potentials

What effect does the parasympathetic nervous system have on GI motility and blood flow?

excitatory

What effect does the sympathetic nervous system have on GI motility and blood flow?

inhibitory

What are the two types of enteric plexuses?

myenteric and submucosal

What is the major parasympathetic nervous system neurotransmitter in the gut?

acetylcholine

What is the major sympathetic nervous system neurotransmitter in the gut?

noreepinephrine

What organs does the vagus nerve supply?

esophagus, stomach, pancreas, small intestine, and half of the large intestine

What NS is the vagus nerve apart of?

parasympathetic

What houses the parasympathetic fibers to distal large intestine?

s2s3s4

What triggers gastrin?

gastric distention, proteins, and gastrin releasing peptide

What does gastrin do?

secretes gastric acid and mucosal growth

Where does motilin come from?

stomach and duodenum

What does motilin do?

activates interdigestive myoelectric complex

What is propulsive motility?

peristalsis

What are mixing movements?

constructive churning

What are intestinal villi susceptible to injury?

less oxygen on tip

What cranial nerves is involve in swallowing?

5, 9, 10, 12

What are the three phases of swallowing?

oral, pharyngeal, and esophageal `

What does the lower esophageal sphincter prevent?

reflux of stomach contents into esophagus

What does the pylorus control?

opening of the distal part of the stomach

What duodenal stressors cause the stomach to empty slower?

distention, mucosal irritation, acidic contents, hyper/hypo osmolaity of chyme, proteins/fat in lumen

What does gastrin do to stomach motility?

increases it

What does secretin do to stomach motility?

inhibits it

What does CCK do to stomach motility?

inhibits it

What is the purpose of peristalsis?

propel chyme along gut

What is the purpose of mixing movements?

chopping action on chime

What hormones increase small intestinal motility?

Gastrin, serotonin, CCK, motilin, insulim

What hormones decrease small intestinal motility?

secretin, glucagon

What does MMC do?

clears intestine during the unfed state

What hormone regulates MMC?

motilin

What are the three motor functions of the colon?

sluggish mixing, absorption of water and electrolytes, storage of fecal matter

What part of the nervous system strengthens the defecation reflex?

parasympathetic defecation reflex

What are the 4 steps of hormonal influence on gland secretion?

hormone releases, hormone enters bloodstream, hormone binds to target, secretions occur

What are the two types of neuroendocrine cells?

enterochromaffin-like cells and somatostatin cells

What do ECL cells secrete?

histamine

What are the types of cells in oxyntic glands?

Mucous neck cells, peptic cells, parietal cells, enterchromaffin-like ceslls

What do mucus neck cells secrete?

mucus

What do parietal cells secrete?

HCL and intrinsic factor

What do peptic (chief) cells secrete?

pepsinogen

What do oxyntic glands secrete?

mucus, HCl, pepsinogen, intrinsic factor, and histamine

What is gastrin?

a hormone

What cells make gastrin?

g cells

How does gastrin trigger gastric acid secretion?

by stimulating ECL cells ti secrete histamine to start gastic acid release

What does the acid pump do?

H or Cl goes into lumen for exchange for K

Where is the acid pump?

cytoplasm of parietal cells

What three hormones stimulate gastric acid production?

Histamine, Ach, and gastrin

What is gastric acid?

HCl acid

What is the purpose of gastric acid?

protein digestion

What are the protective mechanisms against acid injury in the stomach?

gastric mucosal barrier, bicarbonate layer, mucus, PGE2

What hormones decrease gastric secretion?

somatostatin, secretin, gastrin inhibitory peptide, and vasoactive intestinal polypeptide

What do chief cells secrete?

pepsinogen

What cells are in the pyloric glands?

mucous cells and G cells

What do the cells of the pyloric glands secrete?

mucous and gastrin

What are the properties of saliva?

mucus and serous portions

Where are K and HCO3 secreted into?

salivary duct lumen

What are acinar cells?

exocrine portion of pancreas

What do acinar cells do?

make and secrete digestive enzymes

What triggers pancreatic secretons?

chyme in the small intestine (especially fats and proteins)

How is trypsin actiavted?

once it reaches the duodenal lumen

How is chymotrypsin activated?

once it reaches the duodenal lumen

How is carboxypolypeptidase activated?

once it reaches the duodenal lumen

What is the inactive form of trypsin?

trypsinogen

What is the inactive form of chymotrypsin?

chymotrypsinogen

What is the inactive form of carboxypolypeptidase?

procarboxypolypeptidase

What does trypsin do?

spilts proteins into peptides

What does chymotrypsin do?

spilts proteins in peptides

What does carboxypolypeptidase do?

splits peptides into amino acids

How is the pancreas protected from autodigestion?

zymogens stored away from lysosomes, sphincter of pancreatic duct, a2 macroglobulin inactivates some proteases

What does enterokinase do?

actives trypsinogen into trypsin

Where does enterokinase come from?

the brush border of the duodenum and upper jejunum

What are the two major functions of bile?

fat digestion. and excretion of wastes (cholesterol and bilirubin)

What is CCK?

hormone

What triggers CCK release?

presence of fatty acids/proteins in the duodenum

Where does CCK come from?

I cells

What does CCK do?

stimulates gallbladder contraction

How is bile secreted?

as bile salts

What hormone stimulates water and NaHCO3 to be secreted into the bile ducts?

Secretin

What happens in the crypts of the intestine?

cell growth

What is the normal epithelial cell turnover rate?

2-5 days

What enzymes are in the brush border?

peptidases, surface, lipases

What do the enzymes of the brush border do?

breakdown food

Where are Brunner’s gland?

wall of the first few cm of the duodenum

What do Brunner’s glands secrete?

alkaline mucus

What is hydrolysis?

the basic process that starts digestion

What are the end products of CHO, lipid, and protein digestion?

glucose (lipase, amino acids, monosaccharides)

What is the brush border?

enzymes of the enterocytes

What do lipases digest?

fats

What do peptidases digest?

proteins

What do maltases digest?

carbohydrates

What does sucrose digest?

carbohydrates

What does lactase digest?

carbohydrates

Organization of lacteals and blood supply in villi?

lacteal in center

How are CHO absorbed?

Na co-transport

How are proteins absorbed?

Na co-transport

How are fats absorbed?

as micelles

How is water absorbed?

diffusion in small and larger intestine

How is Na absorned?

Na/K ATPase pump