GI Physiology Flashcards
RMP of GI smooth muscle cells during slow waves
-56mV
Pacemaker of GI Tract
Interstitial cells of cajal
Excitatory/Inhibitory:
Parasympathetic system
Excitatory
Excitatory/Inhibitory:
Sympathetic system
Inhibitory
Origin of of parasympathetic nervous system
Craniosacral:
Cranial: vagus nerve
Sacral: S2-S4
Origin of sympathetic nervous system
Thoracolumbar
T5-L2
Myenteric plexus
Auerbach plexus
Submucosal plexus
Meissners plexus
Control tonic contractions of GIT
Myenteric plexus
Control GI secretions
Meissners plexus
Swallowing center
Medulla and lower pons
Cranial nerves involved in swallowing reflex
CN V,IX,X,XII
Phases of swallowing reflex
Oral phase-voluntary
Pharyngeal phase- involuntary
Esophageal phase- involuntary
Stimulatory hormones in GI
Ach
Gastrin
Inhibitory hormones in GI
Norepinephrine
What increases gastric emptying?
Gastrin
Vomiting center
Medulla
Chemical trigger zone
Area postrema
Location of chemical trigger zone
Roof of 4th ventricle
Circumventricular organ
Area postrema
Lack tight junction- no BBB
Type of motility characterized by mixing and churning, non propulsive
Segmental
Type of motility that results in elimination of GI contents
Propulsive
Range of RMP in GI smooth muscle
-40 to -80 mV
Inhibitory/excitatory
VIP and NO
Main site for digestion and absorption
Small interstine
Biggest part of small intestine
Ileum-55%
Jejunum-40%
Duodenum-5%
Predominant movement of SI:
Segmentation
Basic mechanism of glucose transport in Intestine
Via Na cotransport
Produces entirely serous ptyalin rich saliva
Parotid gland
States that intestine contracts behind a bolus and relax infront
Law of intestine
Overdistention of one segment of intestine will cause distention of another part of intestine
Intestinointestinal reflex
If there is increased gastric secretion and motor activity, there is also increased movement through ileocecal valve
Gastroileal reflex
Parietal cells
Intrinsic factor
Hcl
G cells
Gastrin
D cells
Somatostatin
Enterochromaffin cells
Serotonin
Mucous neck cells
HCO3
Chief cells
Pepsinogen
Most abundant GI secretory cell
Chief cells
ECL cells
Histamine
I cells
CCK
S cells
Secretin
At what ph is pepsin most active
2.0
At what ph is pepsis inactivated
6.5
Autoimmune attack on parietal cells
Pernicious anemia
3 physiologic agonists for acid secretion
Ach
Gastrin
Histamine
Antagonist for acid secretion
Somatostatin
PGE PGI
EGF
Amount of gastric juice secreted per day
2 liters
Most important pancreatic enzymes to digest protein
Trypsin
Chymotrypsin
Carboxypeptidase
Action of CCK in GB and Sphincter of Oddi
Contract GB and relax sphincter of oddi
Amount of bile secreted per day
500ml
Stimulate HCO3 secretion
Secretin
Phase of pancreatic secretion with greatest release of pancreatic fluid
Intestinal phase
Most abundant substance secreted in bile
Bile salts
Max volume of GB
30-60ml
2 most important action of bile salts
Emulsification/detergent function
Micelle formation
Cleaves alpha 1,4 glycosidic bond
Alpha amylase
Bursts of intense electrical and contractile activity in fasting state
Migrating myoelectric complex
Most common site of perforation
Cecum
Most common site of obstruction
Sigmoid
Primary site of water and electrolyte absorption
Proximal colon
Action is to counteract hcl
Secretin
Enzyme that convert trypsinogen to trypsin
Enterokinase
2 examples of primary bile acid
Cholic acid
Chenodeoxycholic acid
Digests protein
Pepsin
Inhibit gastrin secretion when ph is <3
Somatostatin
K cells in duodenum
GIP
Increase insulin and decrease H secretion
GIP
Control of salivary secretion
Parasympathetic
