GI-Part 1 Flashcards
Which layer milks and shortens the vili, making it move and interact with food?
Muscularis Mucosae
Collections of neuron cell bodies. Each of these acts like a mini brain, integrating signals coming in (afferent) and generating an efferent response. Primarily sensory.
Submucosal Plexus (Meissner’s)
Grouping of neuron cell bodies. Primary purpose is motor, stimulates the Muscularis Externa.
Myenteric Plexus (Auerbach’s)
gap junctions are also called
nexi (nexus)
Hold NTs both stimulatory and inhibitory, in visceral smooth muscle. Site of NT release
Varicosities
Visceral Smooth Muscle doesn’t have troponin it has …
Calmodulin
Assuming you do not have to defecate your external anal sphincter is …
relaxed (striated skeletal muscle)
Assuming you do not have to defecate your internal anal sphincter is …
contracted, close (visceral smooth muscle - doesn’t fatigue)
What do you need to activate MLCK?
Calmodulin and Ca Complex (Ca binds to Calmodulin)
What enzyme is always running in visceral smooth muscle?
Myosin Light Chain Phosphatase
What occurs when MLCP activity exceeds MLCK activity?
Relaxation
Where does the Vagus Nerve of the PSNS arise from and innervate?
Arises from Medulla Oblongata and innervates from the Esophagus down to the Transverse Colon
What muscle is in the upper 1/2 of the Esophagus?
Striated
Where does the Pelvic Nerves arise from and innervate in the PSNS?
Sacral Spinal Cord and from the Transverse Colon to the Anus
What kind of Reflex is the Vagus Nerve of the PSNS?
Vagovagal
In the PSNS vasovagal reflex of the Vagus Nerve is there more afferent or efferent signals?
75% of the afferents are involved in a feedback loop
The … is the post-ganglionic leg of Parasympathetic Innervation in the gut.
Enteric Nervous System
The preganglionic efferent Vagus Nerve of the PSNS innervates the …
Myenteric Plexus
Pre-Ganglionic fibers of the SNS differ from that of the PSNS, in that they are …
short
Where do the short pre-ganglionic fibers of the SNS synapse in the gut?
outside the GI tract in Prevertebral Ganglia
Post-Ganglionic fibers of SNS synapse within in the GI wall primarily on the …
Myenteric Plexi (ENS)
What is the principle NT released from the post-ganglionic fibers of the SNS in the gut?
Norepinephrine (Adrenergic)
Pre-Ganglionic Fibers of the SNS arise from the … region of the Spinal Cord.
Thoracic and Lumbar
SNS is primarily … to motility and secretions of the gut.
inhibitory
The … is the effector organ for the post-ganglionic SNS
ENS
A spontaneous wave of depolarization initiated from pacemaker cells of the smooth muscle at different points in the GI system,
Basic Electrical Rhythm (BER; slow waves)
BER may be increased by an increase in …
temperature (fever) and/or metabolic activity
The … of membrane potential of the BER is affected by Neural and Hormonal Activity (aka PSNS)
Amplitude
The BER is a spontaneous wave of depolarization initiated from pacemaker cells in what muscle?
Longitudinal Muscle of the Muscularis Externa
What is the BER of the Esophagus?
No real BER
What is the BER of the Stomach?
3/min
What is the BER of the Duodenum?
10-12/min
What is the BER of the Jejunum?
9-10/min
What is the BER of the Ileum?
8-9/min
What is the BER of the Large Intestine?
Irregular (2-13/min)
Frequency of duodenal contractions following parasympathetic activation?
Increased
Frequency of duodenal slow waves (BER) following parasympathetic activation?
No Change
Frequency of duodenal contractions following sympathetic activation?
Decreased or No Effect
Frequency of duodenal slow waves (BER) following sympathetic activation?
No effect
Frequency of duodenal contractions during fever?
Increased
Frequency of duodenal slow waves (BER) during fever?
increased
Big Gastrin is released …
between meals
Big Gastrin has a … half-life
long
Little Gastrin is produced …
during a meal
Little Gastrin has a … half life
short
Big Gastrin is cleaved into Little Gastrin, where?
in the cell, not in the lumen of the GI tract
Both forms of Gastrin are released from what cells?
G-Cells of the gastric antrum
Gastrin is released in response to luminal contact of: (5 things)
Products of protein digestion, Phenylalanine and Tryptophan, physical distention, amino acids, various secretagogues (calcium, coffee, and red wine)
Gastrin is released also by what reflexes?
Vagal and Local Cholinergic chemoreceptor-initiated Reflexes
What mediates the release of Gastrin by the the vagal and local cholinergic reflexes?
Gastrin Releasing Peptide (GRP)
Where are Gastrin receptors found in highest concentration?
Parietal Cells of the Gastric Pits of the stomach
If you have increased Gastrin in your blood what are you making?
HCl (in Parietal Cells)
Where are Parietal Cells, that produce acid, located in the stomach?
Oxyntic Gland
Gastrin stimulates the growth of …
Oxyntic Glands of the Stomach, Duodenum and Colonic Mucosa
Gastrin release is inhibited by the …
acidification of the luminal contents (pH
Where is Somatostatin released from?
Somatostatin Cell (D-Cells)
Somatostatin secreted by D-Cells, then diffuses to nearby …
G-Cells
Somatostatin blocks all stimulants of …. release
Gastrin
Somatostatin directly inhibits … secretion
Parietal Cells H+
Raising the pH of the stomach lumen doesn’t directly dis-inhibit the actions of Somatostatin and initiate Gastrin release. So what must happen to restart the secretions of Gastrin from G-Cells?
Acetylcholine released as a NT inhibits the Somatostatin D-Cell production of Somatostatin which restarts the secretions of G-Cell derived Gastrin
Pathology involving Gastrin that is mediated by a Non-Beta Cell Tumor usually found in the Pancreas or Duodenum (not stomach)
Zollinger-Ellison Syndrome
Non-Beta Cell Tumor’s produce and continually release what into the blood?
Gastrin
The continual release of Gastrin due to the Non-Beta Cell Tumor causes what to produce acid in an unregulated manner?
Parietal Cells
CCK is released from what cells of the Duodenal and Jejunal Mucosae?
I-Cells
CCK produces the contraction of the …
Gall Bladder (squeeze bile out)
CCK produces the relaxation of …
Sphincter of Oddi (bile can enter the intestine)
CCK’s main role is as a pancreatic …
enzyme secretor
CCK is a weak stimulator of pancreatic … secretion
Water and Bicarbonate
Secretin is chemically homologous to …
Glucagon
Secretin is released from …
S-Cells of the Duoenum
What is the most important stimulus of Secretin secretion?
acid
Secretin is the major … stimulator
Water and Bicarbonate
Secretin will act on Chief Cells of the Gastric Pit and stimulate their secretion of the inactive enzyme
Pepsinogen
Glucose-Dependent Insulinotropic Peptide (GIP) primary function is the prime the blood with …, before glucose ever gets absorbed into the blood.
insulin
GIP is released in response to oral glucose which stimulates … of the Duodenum and early Jejunum.
K-Cells
What does GIP inhibit?
Gastric acid secretion and gastric emptying
Motilin is secreted by what cells of the Duodenum and Jejunum?
crypt M-Cells
Motilin initiates what?
Migrating Myoelectric Complex (MMC)
What inhibits the release of Motilin?
feeding
When will you not find motilin in the body?
During feeding or within 5 hours of a meal
What is Pancreatic Polypeptide released from?
PP-Cells of the endocrine Pancreas (far away from lumen)
Pancreatic Polypeptide inhibits the release of …
both the Pancreatic Enzymes and water and bicarbonate
Where is Enteroglucagon released from?
distal small intestine,ileum, and colon
Enteroglucagon is released in response to …
glucose and fat in the chyme
Enteroglucagon stimulates …
Increased Hepatic Bile Flow
Enteroglucagon decreases …
acid secretion, and motility
What inhibits the release of all Peptide Hormones?
Somatostatin
Histamine is not a …
peptide
Histamine stimulates … cells of gastric acid secretion
Parietal Cells
What causes the release of Histamine?
Gastrin, Acetylcholine or Secretagogues
Histamine is synthesized in the … of the Oxyntic Gland of the Stomach
Enterochromaffin-Like Cells (ECLs)
Histamine amplifies … affect
Gastrin’s
May be the most potent stimulator of gastric HCl
Histamine
Vasoactive Intestinal Peptide (VIP) mediates the relaxation of …
GI and vascular smooth muscle
VIP stimulates the intestinal mucous and salivary glands to release …
pancreatic fluid, bicarb, water, electrolytes, and pepsinogen secretion by the Chief Cells
Gastrin-Releasing Peptide (GRP) mediates the Vagal Stimulated release of …
Gastrin
Nitric Oxide is produced by …
neuronal nitric oxide synthase (nNOS)
One of the most important functions of NO is the relaxation of the …
Lower Esophageal Sphincter (LES) during swallowing