Week 2 Flashcards
(38 cards)
Functions of the Gut:
1) Move food through tube from mouth to anus via muscle contraction
2) Digestion-breakdown of food into something absorbable
3) Absorb Nutrients
The tube of the Gut includes:
1) Mouth, Esophagus, Stomach, Small Intestine, Large Intestine
2) Part of the gut but not tube:
- Liver
- Gallbladder
- Pancreas
- Salivary Glands
Longitudinal muscles of Tube
- Runs length of tube
- Contraction-> length of tube shortens, lumen stays the same
Circular Muscle of the tube
- Around tube, doesn’t run along tube
- Contraction-> Lumen shrinks in diameter
Myenteric Plexus
Aka Auerbach’s plexus
- controls muscles on both sides (Circular and Longitudinal)
- can talk with each other, and communicates with Submucosal plexus
Submucosal Plexus
Aka Meissners plexus
- Controls mucosa layer of tube
- can talk w/each other and communicates with Myenteric Plexus
Types of Digestion
1) Mechanical
-force to breakdown food
-ex: mastication (chewing), Gastric Churning
2) Chemical-breaking chemical bonds via enzymes
-Saliva-amylase-> breakdown starch (Storage form of carbs/sugars for plants), humans don’t have; our form is Glycogen
-Stomach-Pepsinogen (Zymogen-inactive form)-> pepsin- breakdown proteins
-Pancreas-produces everything else
-Small intestine- Brushborder enzymes- physically apart of the cell membrane of cells
Ex: sucrase- breakdown sucrose (disaccharide)- Glucose and Fructose
Lactase- breakdown lactose-> glucose and galactose
Lactose Intolerance
1) Consume Lactose, lacking enzyme lactase to breakdown
2) Lactose-> small intestine-> Large Intestine (colon)
- LI home for lbs of bacteria and poop (2-3 lbs)
- bacteria use lactose for fuel
- colon is air tight=anaerobic-> when breakdown lactose=fermentation-> gas etc
3 ways to regulate the Gut
1) Neural
- Vagus (CN10)
- major NT produced-Ach
2) Endocrine
- Signaling molecule that hitches a ride through bloodstream
- Ex: CCK-> produced in small intestine; signaling molecule/hormone; Goes to gallbladder and tells to contract
3) Paracrine
- goes to neighboring cells (opposite of Endocrine)
- Ex: Histamine
- stomach produces locally, and uses locally in stomach
- tells stomach to produce more stomach acid
- No bloodstream
Other Functions of Gut
1) Fluid and Electrolyte Balance
- maintain normal amounts
- 8-9L/day= amount of liquid consumed; not all eaten but secretions from saliva, stomach acid, intestinal secretions
2) Immune Function
- Gut tube= barrier from outside world-> a lot of WBC
- IMMUNOLOGIC TOLERANCE-developed by the gut; exposed to bacteria etc; could be point of infection aka why we have WBC
How does wall of gut know food is present?
1) Mechanoreceptor
- respond to stretch, vibration, irritation
2) Chemoreceptors
- presence of sugar or amino acids
- These receptors send info to the Submucosal Plexus, so the submucosal plexus is aware there is food.
- Submucosal plexus sends signals to secreting cells & absorbing cells-do your job
- Submucosal plexus sends signals to myenteric plexus, stimulates churning and movement of food
Autonomic Nervous System of Gut
ANS-comes from spinal cord
1) Parasympathetic
- vagus
- always synapses on ME plexus (Parasympathetic Ganglia)
2) Sympathetic
- nerves can synapse at ME plexus, but don’t have to stop there-> Submucosal Plexus-> Mucosa Cells of lumen
- sympathetic ganglion-found just outside of spinal cord; postganglion come into gut (while preganglion comes into gut for parasympathetic)
What is most important in regulating gastroentero function?
Arch
CCK
- Source
- Target
- Effect
Cholecystokinin
1) Source=I cell of Small intestine
- responds to presence of undigested food in the small intestine
2) Target
- Gall bladder- contains bile which emulsifiers lipids/fats
- Pancreas
3) Effect
- Gallbladder-> contraction-> Bile-> Small intestine
- Pancreas- Increase production of digestive enzymes
Gastrin
- Source
- Target
- Effect
1) Source
- G cell of stomach
- released in response to the presence of food
2) Target
- Parietal Cells in stomach->stomach acid
3) Effect
- Increase acid production
GRP
- Source
- Target
- Effect
Gastrin Releasing Peptide
1) Source
- Vagus Nerve (CN10, also produces Ach and Serotonin)
2) Target
- G Cells
3) Effect
- Increase Production of Gastrin
Motilin
- Source
- Target
- Effect
1) Source
- Endocrine cells of Gut
2) Target
- ENS/SM
3) Effect
- increases motility (stomach and intestine)
Secretin
- Source
- Target
- Effect
1) Source
- S cell from small intestine
2) Target
- Pancreas
3) Effect
- Increase Production of Bicarbonate (HCO3-)
Somatostatin
- Source
- Target
- Effect
1) Source
- D-cells (stomach/intestine in tube)
- Delta Cells (pancreas)
2) Target
- GUT
3) Effect
- decrease secretions
VIP
- Source
- Target
- Effect
“Very Important Person getting out of my way”
1) Source
- endocrine of gut
2) Target
- Small intestine
- Pancreas
3) effect
- increase secretions from Small intestine and Pancrease
Disorder where your oversecreting VIP-> Diarrhea. How do you stop?
Somatostatin
Types of Motility
1) Storage
- want to store/stay in same spot
- Contract circular muscles in front and behind bolus
- relax longitudinal muscles
2) Churning
- Want to mix up bolus/not move
- contract circular muscles in front and behind bolus
- contract/relax/contract longitudinal muscles
3) Propulsion
- move through tube
- contract circular muscle behind bolus
- longitudinal muscles contract and relax to move bolus forward
- move circular muscle up to keep bolus moving
Interstitial Cells of Cajal
- Spontaneously Active (ADD students-can’t stay still)
- don’t have resting membrane potential; instead Slow-wave potential (fluctuating)
- Threshold= -40mV-> spike potentials-> goes to neighboring cells to contract=motility
- Depolarization (more positive)-influx of Ca2+
- Repolarizatoin (more negative)- K+ leaving
To get more action potentials=more motility?
- Gq coupled receptor to bring more Ca2+ in
- ex: Ach M1/M3 receptors
- results in more rapid spikes
Get less motility?
-Block Gq or Increase K+
Spincters
thick out pouching of circular muscle
- have 2 sphincters that are skeletal muscle (1 & 6)
1) Upper Esophageal Sphincter (UES) - esophagus meets pharynx
- somatic-motor; skeletal muscle (can swallow on command)
2) Lower Esophageal Sphincter (LES) - Aka cardiac sphincter, Gastroesophageal sphincter
- esophagus to stomach
- Sucks at job
- Structural/Anatomic Sphincter (not functional sphincter)-diaphragm and stomach curved-helps food not come back up
3) Pyloric Sphincter/ Gastrointestinal Sphincter - Between Stomach and 1st part of Small Intestine (Duodenum)
- Very good sphincter
4) ileocecal sphincter - between small intestine and colon (large intestine)
- good sphincter
5) Internal Anal Sphincter - smooth muscle
6) External anal sphincter - skeletal muscle
