Topic 52 - Motoric activity and electrophysiology of the gastrointestinal tract

Question 1

Words to include in the motoric acitivty of the GI tract, motility types

Answer 1

• Motility types
  
  • Passing movement
  • Mixing movement
  • Villi movement
• Stretch receptors
• Peristalsis
• Mingling bolus

Question 2

Words to include in the motoric acitivty of the GI tract, motor movemnts of stomach

Answer 2

• Store
• Mixes
• Chyme
• Filling
  
  • LaPlace Law
• Circular retraction
  
  • Rolling-mixing contraction
• Circular contraction
• Peristalsis
• Duodenal inhibiting effects
  
  • Neuronal reflexes
  • Hormonal (secretin, GIP, VIP)
• Gastric facilitating effects
  
  • Gastrine

Question 3

Words to include in the motoric acitivty of the GI tract, motor movemnts of ileum

Answer 3

• Mingling movemnts
  
  • Emulsification
  • Segmental movemnet
  • Villi movement
• Proceeding movements
  
  • Slow peristalsis
• Ileocecal valve
• Ileocecal sphinter
• Regulation:
  
  • BER ( Basic Electrical Rhythm)
    
    • Sow waves
  • Nervous control
    
    • N. splanchnicus
    • N. vagus
    • Sympathetic
    • Parasympathetic
  • Reflexes
    
    • Intestinal reflexes

Question 4

Words to include in the motoric acitivty of the GI tract, motor movemnts of colon

Answer 4

• Microbial digestion
• Water and electrolyte reabsorption
• Retrograde flow (Ru)
• Peristalsis
• Antiperistalsis
• Microbial synthesis (Car)

Question 5

Words to include in the motoric acitivty of the GI tract, motor movemnts of rectum

Answer 5

• Evacuation
• Defectation
• Hypothalamic and cortical control
• Reflex stretch receptors
• Afferent neurons (S1-S4)
• Efferentation
• Sphinters

Question 6

Words to include in the electrophysiology of the GI-tract

Answer 6

• Smooth muscle cells
• Slow waves
  
  • BER (Basic Electrical Rhythm)
  • Na⁺/K⁺ pump
  • Ca²⁺ channels
• Spike potentials
  
  • Action potential
  • Threshold potential (- 40 mV)
  • Overshoot of shreshold
  • Na²⁺ influx
  • Calmodulin regulatory mechanism
• Resting potential
  
  • Muscle excitabillity
• Depolarization
• Hyperpolarization
• Tonus contraction

Question 7

Topics to include in the essay

Answer 7

1. Motoric activity of the GI tract
   
   • Motility types
   • Motor movement of stomach
     
     • Motor tasks of the stomach
     • Motions of stomach
     • Regulation
   • Motor movement of ileum
     
     • Movemt types of ileum
     • Regulation
   • Motor movement of colon
   • Motor movement of rectum
2. Electrical activity of the GI-tract
   
   • Graph
   • Compartments of the graph

Question 8

Motility types of the GI tract

Answer 8

• Passing movement
  
  • Stretch receptors
  • Circular muscle layer behind the bolus is inhibited
  • Longitudinal layer is dilated
  • Dilation pushes the bolus in the aboral direction
• Mixing movement
  
  • Mingling bolus
• Villi movement
  
  • By mucosal muscle layer
  • Contact between epithelium and intestinal content

Question 9

Motor movements of stomach

Answer 9

• Motor tasks of the stomach can be classified into three groups:
  
  1. Storage
  2. Mixes food with the secretion of the stomach and form chyme
  3. Chyme is passed to the ileum to secure optimal digestion and absorption
• Filling:
  
  • No change in intragastric pressure (LaPlace law)
  • Chyme: content of the stomach after mingling
• Motions of the stomach:
  
  1. Circular retraction which is a rolling-mixing contraction
  2. Circular contraction (in corpus)
  3. Peristalsis
  4. Chyme whirls back towards the oral part of the stomach
  5. Peristaltic contraction in the pre-pyloric region of antrum helps the emptying of chyme
• Regulation:
  
  • Duodenal inhibiting effect:
    
    • Neuronal reflexes
    • Hormonal
      
      • Secretin
      • GIP
      • VIP
  • Gastric facilitating effects:
    
    • Volume of foodstuff
    • Gastrine (facilitates pyloric pump)

Question 10

Motor movements of ileum

Answer 10

• Movement types of the ileum:
  
  • Mingling movements
    
    • Increases emulsification
    • Segmental movement
    • Villi movement
  • Proceeding movements
    
    • Slow peristalsis
• Ileocecal valve prevents regurgitation of colon content
• Ileocecal sphincter is light contracted, slowing down the passing
• Regulation:
  
  • BER (Basic Electrical Rhythm)
  • Nervous control
    
    • Inhibition: N. slpanchnicus (sympathetic)
    • Excitation: N. vagus (parasympathetic)
  • Reflexes
    
    • Intestinal reflexes

Question 11

Motor movement of colon

Answer 11

• Intestinal content moves slower in colon than in the previous section of the intestines
• Retrograde flow (ruminants)
  
  • Ileum - colon -caecum -colon
  • Retention
• Peristalsis + antiperistalsis → mixing in colon
• Carnivores:
  
  • Small microbial synthesis
  • Fast movement caused by an aboral-mass peristalsis

Question 12

Motor movements of rectum

Answer 12

• Main role: evacuation (feces are stored in colon)
• Defecation is under hypothalamic and cortical control
• During feces evacuation reflex stretch receptors in the wall sends afferent neurons to S1-S4
• Efferentation: Pelvic nerves increase contraction and peristalsis, relaxes sphincters

Question 13

Give the graph of electrical activity of gastrointestinal smooth muscle cells

Define the different compartments of the graph

Answer 13

• Slow waves
  
  • Changing of GI smooth muscle cell membrane potentials by 5-15mV around RMP (-55mV)
  • BER:
    
    • The sum of electrical activity generated by slow waves
    • Caused by changing acitivity of the Na⁺/K⁺ pumps and precence of Ca²⁺ channels
• Spike potential
  
  • Action potential of GI smooth muscle cells
  • Stimulated if slow wave reaches threshold potential (-40mV)
  • Higher overshoot of threshold → more frequent contractions
• Resting potential
  
  • Influences muscle excitability
• Tonus contraction
  
  • Continous
  • Initiated by:
    
    • Hormones /factors causing permanent membrane depolarization (ø spike potential)
    • Permanent Ca²⁺ influx