GI - Pt 1 Intro/Gastrin Flashcards
What are the 4 major functions of the GI tract?
Neuro & Endocrine Regulation
Motility
Secretion
Digestion & Absorption
The vagus nerve innervates “everything” in the GI tract, from the top –> [] colon.
transverse
Crypts of [] are found in the gastic [] layer.
Crypts of Lieberkuhn are found in the gastic mucosa layer.
List the layers of the Gastric tissue from lumen to serosa
Gut Lumen
Mucosa (Epithelium/lamina propria)
Muscularis Mucosae
Submucosa
Muscularis Externa
Serosa
T/F
The muscularis mucosae has 2 layers of smooth muscle.
True
What 2 layers of muscle residein the muscularis mucosae?
Inner layer of circular SM
Outer layer of longitudinal SM
The submucosa contains, large [], [], [] vessels and the [] Plexus (or [] plexus)
The submucosa contains, large arteries, veins, lymphatic vessels and the submucosal Plexus (or Meissner’s plexus)
The muscularis externa contains an inner layer of [] SM and an outer layer of [] SM as well as the [] plexus (or [] Plexus)
The muscularis externa contants an inner layer of circular SM and an outer layer of longitudinal SM as well as the Myenteric plexus (or Auerbach’s Plexus)
The myenteric plexus mostly cause smooth muscle [] - responsible for the [] of food through the GI.
contraction, movement
If food doesn’t contact the wall of the intestine, it will [] [] absorbed.
If food doesn’t contact the wall of the intestine, it will not be absorbed.
Smooth muscle are connected by []. These receive signals from nerves release of NT via [] located near smooth muscle.
Smooth muscle are connected by nexi. These receive signals from release of NT via varicosities located near smooth muscle.
T/F
Myosin light chain kinase is always on and its action must be overcome by the action of myosin lightchain phosphatase to produce muscle relaxtion.
FALSE
- Flip it. Myosin light chain phosphatase is always on. MLCK must overcome MLCP to elicit a contraction.
The 2 main nerves forming the parasympathetic innervation of the GI tract are the [] nerve and the [] nerve.
The 2 main nerves forming the parasympathetic innervation of the GI tract are the Vagus nerve and the Pelvic nerve.
The Vagus Nerve:
- arises from the [] []
- Innervates –>
- esophagus to the [] colon
- [] [] in the upper 1/3 of the esophagus
- Uses [] NT and receptors for preganglionic/postganglionic innervation.
- arises from the medulla oblongata
- Innervates –>
- esophagus to the transverse colon
- Striated muscle in the upper 1/3 of the esophagus
- Uses cholinergic NT and receptors for preganglionic/postganglionic innervation.
Pelvic Nerve
- Arise from the [] spinal cord
- Innervates –>
- [] colon
- [] colon
- []
- Anal canal - specifically the [] [] sphincter
- Uses [] “NT/Receptors”
- Arise from the sacral spinal cord
- Innervates –>
- Descending colon
- sigmoid colon
- Rectum
- Anal canal - specifically the internal anal sphincter
- Uses cholinergic“NT/Receptors”
- The submucosal plexus and the myenteric plexus make up the [] [] system.
- This system is considered to be []-[] PNS fibers.
- The submucosal plexus and the myenteric plexus make up the enteric nervous system.
- This system is considered to be post-ganglionic PNS fibers.
The enteric nervous system [] [] on its own without para/symp innervation.
The enteric nervous system can operate on its own without para/symp innervation.
Describe the flow of innervation from Cranial Nerve X –> GI mucosa.
- Cranianl Nerve X –> Vagus Nerve
- Vagus Nerve –> Myenteric Plexus
- Myenteric Plexus –> Submucosal plexus
- Submucosal plexus to GI epithelium/glands/secreting cells.
What are the 4 prevertebral, synaptic ganglion in the sympathetic nervous sytem?
Celiac Ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Hypogastric ganglion
- In the sympathetic nervous system, postganglionic fibers arise from [] ganglia and synapse with the [] [] system of the GI tract.
- In the parasympathetic nervous sytem, the postganglionic fibers are synonymous with the [] [] system.
- In the sympathetic nervous system, postganglionic fibers arise from prevertebral ganglia and synapse with the enteric nervous system of the GI tract.
- In the parasympathetic nervous sytem, the postganglionic fibers are synonymous with the enteric nervous system.
A [] [] is a spontaneous wave of depolarization initiated from pacemaker cells of the smooth muscl (primarily [] muscle cells) at different points int the GI tract.
A slow wave is a spontaneous wave of depolarization initiated from pacemaker cells of the smooth muscle (primarily longitudinal muscle cells) at different points int the GI tract.
Basic Electrical Rhythms:
- Occur independent of [] innervation and at a fixed [] for a particular segment of the gut
- not a muscle contraciton but an incresased number of [] [] the wave may generate a muscle contraction.
- [] is unaffected by neural and hormonal activity
- May be influenced by [] and [] activity
- Occur independent of extrinsic innervation and at a fixed rate for a particular segment of the gut
- not a muscle contraciton but an incresased number of action potentials the wave may generate a muscle contraction.
- Rate is unaffected by neural and hormonal activity
- May be influenced by temperature and metabolic activity
An increase in temperature and metabolic activity, like in fever, would [] the BER and contraction of smooth muscle.
increase
Parasympathetic stimulation of BER [] [] change the rate of BER, but changes the []. Leading to a [] of the membrane (but not necessarily an action potential)
Parasympathetic stimulation of BER does not change the rate of BER, but changes the amplitude. Leading to a depolarization of the membrane
- Sympathetic stimulation of BER causes a [] of the membrane.
- What does this do to contractions?
- hyperpolarization
- Most likely the frequency of contractions would decrease.
What is the BER for the following segments of the GI?
- Stomach
- Duodenum
- Jejunum
- Ileum
- Large Intestine
- Stomach - 3 min
- Duodenum - 12 min
- Jejunum - 10 min
- Ileum - 8 min
- Large Intestine - 3-5 min
Paracrine Signaling:
- Released from [] cells within the mucosa
- Dont have to travel through the [], but still require a [] at the target
- Usually released near their []
- Released from endocrine cells within the mucosa
- Dont have to travel through the blood, but still require a receptor at the target
- Usually released near their receptor
Neurocrines:
- syntheszied in cell bodies of []
- released form an axon [] and [] to the target
- Does not transmit an [] []
- syntheszied in cell bodies of neurons
- released form an axon varicosity and diffuse to the target
- Does not transmit an electrical potential
2 types of Gastrin:
- [] Gastrin
- released between meals
- 1/2 life of [] minutes
- Little Gastrin
- Released in [] to a meal
- 1/2 life of [] minutes
-
Big Gastrin
- released between meals
- 1/2 life of 38 minutes
- Little Gastrin
- Released in response to a meal
- 1/2 life of 7 minutes
Gastrin:
- Produced by [] cells, which are located primarily in the [] of the stomach and also the [] mucosa
- Gastrin is released in response to luminal contact by:
- products of [] digestion
- small peptides: [] & []
- Amino acids
- Physical []
- Secretogens: [], [], and []
- Produced by G cells, which are located primarily in the Antrum of the stomach and also the duodenal mucosa
- Gastrin is released in response to luminal contact by:
- products of protein digestion
- small peptides: Phenylalanine & Tryptophan
- Amino acids
- Physical distention
- Secretogens: Calcium, coffee, wine
Gastrin:
- released by [] and local [] reflexes
- which are mediated by [] [] [] (GRP, or [])
- Gastrin stimulates:
- gastric acid ([] secretion by [] cells of the [] pits of the sotmach
- Growth of…
- The [] Glands
- [] and [] mucosa
- released by vagal and local cholinergic reflexes
- which are mediated by Gastrin releasing Peptide (GRP, or Bombesin)
- Gastrin stimulates:
- gastric acid (HCL) secretion by Parietal cells of the gastric pits of the sotmach
- Growth of…
- The Oxyntic Glands
- Duodenal and colonic mucosa
- Gastrin release is inhibited by []of the lumiinal contents, below pH of []
- this inhibition is primarily done by [].
- Gastrin release is inhibited by acidification of the lumiinal contents, below pH of 3
- this inhibition is primarily done by somatostatin.
Gastrin Inhibition:
- pH below 3 –> Stimulation of [] Cells (D-Cells) via [] input from enteric nervous system
- Somatostatin, D-Cells produce []
- Somatostatin acts as a [] hormone and blocks all stimulants of [] release and inhibits [] cells and their HCL secretion
- pH below 3 –> Stimulation of Somatostatin Cells (D-Cells) via chemoreceptor input from enteric nervous system
- Somatostatin, D-Cells produce somatostatin
- Somatostatin acts as a paracrine hormone and blocks all stimulants of Gastrin release and inhibits Parietal cells and their HCL secretion
- Raising the [] does not stimulate the release of Gastrin.
- [] released as a NT [] the somatostatin D-cell production which restarts secretion of [].
- Raising the pH does not stimulate the release of Gastrin.
- Ach released as a NT inhibits the somatostatin D-cell production which restarts secretion of G-cells.
Somatostatin blocks all stimulants of Gastrin release except for []
Acetylcholine
