1Outermost layer of the GI tract that interfaces with the blood
Serosa
2Lumen of the gut, innermost layer
mucosa
3Where are secretary glands embedded in the GI tract?
submucosa
4What attaches the GI tract to the rest of the body?
Mesentery
5In what electrical phase does the membrane potential become less negative and move towards threshold?
Depolarization
6In what electrical phase does the membrane potential become more negative and move away from and below threshold?
Repolarization
7What is the action potential of the membrane? (threshold)
-40 mV, anything less negative than that can cause an action potential to occur
8What does the frequency of slow waves determine?
The frequency of the action potential, and therefore frequency of contractions
9What does the frequency of spikes that occur at the top of the slow waves determine?
Strength of the contraction
10What is the pattern of electrical activity created in each region of the GI tract called?
Basic electrical rythm (BER)
11branch of the enteric nervous system that controls GI movements
myenteric plexus (Auerbach's plexus)
12branch of the enteric nervous system that controls GI secretions
submucosal plexus (Meissener's plexus)
13Parasympathetic nervous stimulation will
increase most activities of the GI tract
14Sympathetic nervous stimulation will
inhibit most activities of the GI tract
15Striated muscles are controlled
voluntarily
16smooth muscles are controlled
involuntarily
17Stimulation of stomach glands is caused by
Direct stimulation by contact with food
chemical irritation
distension (stretching) of the gut
All 3 of these can activate nerve reflexes that lead to secretion, mucous cells are activated by contact with food/chyme
18What does hydrochloric acid do?
Creates the acidic environment of the stomach, denatures proteins, kills bacteria
19What does mucin do?
Protects stomach mucosa from acidic destruction
20what does gastrin do?
produced by G cells in the stomach, stimulates HCl acid secretion
21Oxyntic glands (gastric glands)
three cells types involved in the process of secretion, found in the walls of the body and fundus.
22Three types of cells in oxyntic glands
Parietal or oxyntic cells
peptic or chief cells
mucous neck cells
23what do parietal (ocyntic) cells do?
Produce HCl acid and intrinsic factor
24what do peptic (chief) cells do?
produce pepsinogen
25what do mucous neck cells do?
produce mucous
26Pyloric glands
present in the antrum of the stomach, contain G cells which produce gastrin, and mucous secreting cells
27Nervous (vagal) stimulation
increased secretion of hydrochloric acid, mucus, and pesinogen by oxyntic and mucous secreting glands, stimulates release of gastrin by pyloric glands.
28What is a secretogogue?
Something in the stomach, such as a large piece of undigested protein, that signals to the stomach that more production of secretions is nescessary to increase digestion.
29Hormonal regulation by gastrin
food causes the release of gastrin by distention of the stomach walls and by containing secretogogues, this gastrin release stimulates release of HCl
30histamine regulation
histamine causes an increase of HCl, prior to PPIs H2 receoptor antagonists were commonly used for stomach problems
31what is paracrine stimulation
when hormonal signals, such as histamine, directly impact the target receptor, such as the parietal cell, without entering the blood stream. Local hormone signaling.
32The pancrease is very similar in structure to a salivary gland. It secretes
digestive enzymes and fluid, through the pancreatic acinus
33Pancreatic dusctules are responsible for
modifying the composition of pancreatic juices via active and passive transport of electrolytes. Based on the food we eat, it modifies the pancreatic juices.
34pancreatic juices contain
large amounts of bicarbonate, which neutralizes the acidity of the chyme coming from the stomach. In addition, it produces proteolytic enzymes, such as trypsin, chemotrypsin, and carboxypeptidases. These break down proteins. In addition, it produces amylase, lipase, cholesterol esterase, phospholipase, and elastase.
35What does Cholecystokinin (CCK) do
high fat food stimulates secretion of CCK. This induces the gallbladder to contract, and the sphincter of Oddi to relax, so that bile can be excreted into the small inestine and break down lipids.