Vascular Smooth Muscle

Question 1

2 Differences b/w Skeletal Muscle and Smooth Muscle Contraction

Answer 1

Smooth has no troponin - process reg’d by phosphorylation activation of Myosin Regulatory Light Chain (RLC) at hinge region
No sarcomere, so extension unlimited

Question 2

2 Requirements for Phospho of RLC

Answer 2

Need Ca and ATP for Ca-Calmodulin to activate MLCK

Question 3

4 Ca Reg Sites

Answer 3

1. SR: ATP-dependent pump into SR
2. PM: ATP-dependent pump out
3. PM: Ca channel in
4. PM: Na-Ca antiporter bringing Na in via its gradient

Question 4

Adenylyl Cyclase/cAMP

Answer 4

Galphas activates and it converts ATP to cAMP. So this inhibits contraction bc it uses up ATP. Gai inhibits adenylyl cyclase this stimulating contraction. cAMP separates Reg and Catalytic subs of PKA, phospho’ing MLCK to inactivate it for more relaxation

Question 5

Guanylyl Cyclase

Answer 5

Atriopeptin stimulates it to make cGMP from GTP. This activates PKG (activates MLC phosphatase for relaxation) and GMP-dependent MLCK phosphatase for muscle relaxation

Question 6

Phosphoinositide Signaling

Answer 6

Galphaq activates PLC to split PI into IP3 and DAG. IP3 activates IP3R on SR to release Ca for contraction. DAG combines w/ PKC to activate membrane Ca channel to let even more Ca in, so double whammy

Question 7

PKA and PKG Effect on Ca Channels

Answer 7

Inhibit membrane channels thus inhibiting contraction

Question 8

K and Ca Ion Channels and Contraction

Answer 8

As K flows out, it makes the cell more negative drawing Ca in for contraction. However PKA and PKG phospho those K channels, making them super-effective! Shitload of K flows out, cell gets real negative, and for some reason this retarded professor didn’t explain this means Ca doesn’t want to come in the cell anymore