Physiology 1 - functional anatomy Flashcards
(21 cards)
- What is the porpoise of the GI?
Provide the body with nutrients and water
- What allows the GI to perform its function?
- Movement of food in the GI tract
- exocrine secretion
- absorption
- particular blood circulation
- nervous and hormones control
- What does the enteric system consist of?
Myenteric (Auerbach) nerve plexus - deals with muscle movement
Submucosal (Messner) nerve plexus - deal with secretions
- What is the myenteric system?
Myenteric (Auerbach) nerve plexus - deals with muscle movement
- What is the Submucosal nerve plexus?
Submucosal (Messner) nerve plexus - deal with secretions
- What are the layers of the GI?
- Seriosa
- Longitudinal muscle
- Circular muscle
- 5 Myenteric nerve plexus
- Submucosa
- 5 Meissner’s nerve plexus
- Mucosa
- Epithelial lining
- Mucosal gland
- Submucosal gland
- Describe the muscles of the GI tract.
Skeletal muscles: in the mouth, upper third of the esophagus, external anal sphincter - voluntary control
Smooth muscles: the lower 2/3 of the esophagus till the colon
The muscles are connected through gap junctions to form syncytial
- Describe the electrical activity of the GI muscles?
- At rest:
1. the Vm is -60-(-50) with a slow wave pattern (probably by interstitial cells of Cajal interactions with the smooth muscle),
2. Like pacemaker
3. Voltage change made by Na pumps
4. NO AP so this is not the reason for contraction (except from the stomach) - Depolarization:
1. When Vm > -40 -> AP
But can be depo/hyperpolarized by stretch, ACh, ParasymNS
2. The result is spikes pattern (higher Vm, higher frequency)
3. Smooth muscle contraction is based on Ca entering the smooth muscle cells - Hyperploarization:
By norepinephrine and the SymNS
- What are the functions of the GI tract?
Digestion and absorption, are not regulated
Motility and secretions, are regulated (ANS)
- Describe the neural control of the GI?
We have the ENS (submucosal & myenteric plexus)
- It is mainly autonomous but it can be modulated by short reflexes from afferent neu.s from the GI or by long reflexes involving the CNS.
- Receptors in the epithelium of the GI can be stimulated by mechanical/chemical/osmolarity and send it to the ENS/CNS
- It is also modulated by the Para/SymNS
- What are the main stimuli in the GI?
- Products of digestion
- HCl
- Stretching
- Smell & sight
- Describe the reflexes?
Short reflexes:
- involving the ENS, give autonomy to the GI
- local and short
- activated by local stimuli
- affecting the 2 plexuses
Long reflexes:
- involving the CNS
- stimuli can be local or external
- para\symNS are involved (inhibit\excites)
- What are the reflexes?
- Gastrocolic reflex- stomach on the colon, cause evacuation of the colon (especially active in babies)
- Enterogastric reflex- colon on the stomach, inhibit emptying of the stomach when its full
- Colonoileal reflex- the colon inhibits the emptying of the ileal
- Pain reflex
- Defection reflex
- What are the hormones that are involved in GI regulation
Gastrin Cholecystokinin (CCK) Secretin Gastric Inhibition Peptide Motilin
- Describe the hormonal control of Gastrin
Stimulus: proteins (products of protein breakage), distention, ParasymNS
* acid inhibits release
Site of secretion: G cells, small intestine
Action: gastric acid secretion stimulation, mucosal growth
- Describe the hormonal control of Cholecystokinin (CCK)
Stimulus: protein, fat (especially), acid
Site of secretion: I cells in the duodenum, jejunum and ilium
Action: Gallbladder contraction, inhibition of gastric emptying, stimulation of bicarbonate, pancreatic enzymes production, growth of exocrine pancreas
- Describe the hormonal control of Secretin
Stimulus: low pH + Fat
Site of secretion: S cells in the duodenum, jejunum and ilium
Action: stimulation of pancreatic biliary+bicarbonate production (buffer), inhibition of acid secretion in stomach, growth of exocrine pancreas, pepsin secretion
- Describe the hormonal control of Gastric Inhibition Peptide
Stimulus: protein, fat, carbohydrates
Site of secretion: k- cells in the duodenum, jejunum and ilium
Action: inhibition of acid secretion in stomach, insulin release
- Describe the hormonal control of Motilin
Stimulus: fat, low pH, parasymNS
Site of secretion: M cells in the duodenum, jejunum
Action: inverse stomach and intestine motility
- What are G/I/S/K/M cells secrete?
G- Gastrin I- CCK S- Secretin K- Gastrin inhibition peptide M- Motilin
- Describe the blood circulation of the GI tract?
- Splanchnic circulation
- 25% of the blood outputs goes to the GI and can also increase specifically on the sites that are activated
- Blood coming from gut has nutrients and bacteria, but it goes to the liver that assign the metabolites and kill the bacteria by the portal vein
- The villus is the structure that absorb the nutrients, filled with capillaries and has a lacteral vessel where the fat goes to
