Gut Motility

Question 1

What does the noradrenaline sympathetic NS affect gut motility?
(7)

Answer 1

1-Relaxes the gut
2-Down regulates smooth muscle contraction 
3-binds to Beta receptors
4-Activates Adenyl Cyclase
5-Increases Cellular cAMP
6-Activates PKA 
7-Decreases cytosolic ca2+

Question 2

a) How does ACH, the parasympathetic system affect the gut?
(6)

b) How does Acetylcholine influence contractions in the gut?

Answer 2

1-Contracts the gut 
2-Up regulates smooth muscle contraction 
3-Binds to Muscarinic receptors 
4-Activates phospolipase C
5-Cleaves PIP2 into DAG and IP3
6-increases Cytosolic ca2+

B) By increasing the rate of ICC depolarisation and causing direct stimulation of contractile pathways in smooth muscle

Question 3

What cell is responsible for the spontaneous release of Ca2+?
How is the electrical signal passed onto neighbouring smooth muscle?

Answer 3

Interstitial cells of Cajal

-Via Direct electrical coupling proteins

Question 4

What does the depolarization of the smooth muscle by the ICC do within the smooth muscle cell to elicit contraction?

ICC = interstiital cells of cajal

Answer 4

Opens L-type Ca2+ channels causing Ca2+ entry and Ca2+-induced Ca2+ release