excitation contraction coupling

excitation contraction coupling

calcium from outside is required for smooth muscle to have an AP

RMP of smooth muscle

-60mv

initial depolarization of smooth muscle

LG ion channel gets stimulated and opens, allowing for graded potential (analagous to EPSP)

-40 mv

threshold:

-VG Ca++ channels open allowing calcium from the outside to enter the smooth muscle cell (rapid deparization occurs)

Ca++ in skeletal muscle 

binds to calmodulin 

Ca++ & Calmodulin complex 

dephospharylates MLCK  which activates it

-gets rid of the phosphate

active MLCK

phospralyates MLC 

phosphorylated myosin light chain

leads to cross bridge activation and contraction

inactive MLC

leads to cross bridge inactivation and relaxation

what need to happen to myosin phosphatase for MLC to be active 

myosin phosphatase needs be inactive

(phosphorylated)

how to relax a smooth muscle 

inactivate myosin phosphatase

myosin phosphatase

dephosphorylates MLC, which breaks crossbridge

active RHO Kinase

phosphorylates myosin phosphate making it inactive

when is RHO Kinase active

when its dephosphorylated

what phosphorylates rho kinase 

PKG

which enzymes in the pathways promote contraction

MLCK, MLC, RHO Kinase

which enzymes in the pathway promote relaxation

myosin phosphatase, myosin phosphatase, phosphatase, PKG

what kind of enzymes remove phosphate

phosphatase

what do kinase do

add phosphates