Gastric Motility & Neural Control Flashcards
What is the process of myosin phosphorylation?
- Calcium binds to calmoduin
- Activates myosin light chain kinase
- Phosphorylates myosin
- Phosphomyosin interacts with actin
- Contraction occurs
- Dephosphorylation occurs through myosin light chain phosphatase
What is the structure of the gut?
- lumen
- mucosa
- submusoca
- inner circular layer
- outer longitudinal muscle layer
What does the SM cell look like at rest?
- Kir channels let K+ out
- Kc channels closed
- Ca channels closed
- low Ca2+ concentration
What happens in SM cells during depolarisation?
- closes K channels
- opens voltage gated Ca2+ channel (L-type)
What are the pacemakers of gut SM?
Interstitial cells of Cajal
What are resting membrane potentials of SM cells?
-60mV
What does a slow wave look like?
Up stroke
Plateau
Down stroke
How fast do slow waves travel along the gut?
1cm/sec
Frequency of slow waves
3/min in stomach
11-12/min in duodenum
What is the slow wave mechanism in the interstitial cells of Cajal?
- Spontaneous release of Ca2+ from ER through RyR and IP3 channels
- Causes an influx of additional Ca2+ through T-type voltage gated channels
- Ca2+ influx opens chloride ANO1 channels (unusual amount of chloride inside)
- Efflux of Cl-
- Depolarisation occurs
The more ……, the more ………
Action potentials, contractions
What causes action potentials in gut SM?
- Stretch
- Acetylcholine
- Parasympathetics
What hyperpolarises SM?
- Noradrenaline
2. Sympathetics
Which nerves innervates the gut?
Vague nerve Sacral nerves (to large intestine)
Where does sympathetic gut inner action come from?
Thoracic and lumbar chord
The gut at rest is under ……. tone
Parasympathetic
Which receptors does ACh stimulate?
M3
What is eserine?
Anticholinesterase
What is atropine?
M-cholinergic antagonist
What is a slow excitatory post synapse potential (EPSP)?
Slow to onset, last a very long time - enteric nervous system
Why to prolonged EPSP and IPSPs occur?
Long duration due to GPCR not ion channels as post-synaptic receptors
What are the transmitters in the gut?
ACh: M-receptors, muscle contraction and secretion
Substance P: NK-receptors, contraction and secretion
VIP (vasoactive intestinal peptide) and NO inhibit contraction (VIP stimulates secretion)
In the gut, sympathetic tone…..
Contracts sphincters (alpha receptors) and relax other tissues (beta receptors)
What are the types of intestinal motility?
- Segmentation
- Peristalsis
- Migrating motor complex
- Retroperistalsis
