Smooth Muscle Flashcards
What are the three ways smooth muscle can be activated
Neurotransmitters, hormones, physical activation
How can a neurotransmitter stimulate a smooth muscle
Released from varicosities and binds to receptor
Generates action potential in smooth muscle
Activates the ryanodine receptor and released Ca from SR
How does a hormone stimulate smooth muscle
It’s released from the blood and binds to receptor
Follows camp which activated Ca on SR
A release of Ca on plasma membrane causes influx of Ca from ECF
How does physical activation stimulate smooth muscle
Physical altercation of membrane protein
Open channel which generates action potential and Ca influx
Why is smooth muscle lacking troponin matter
Caldesmon binds to actin preventing myosin to attach
Calmodulin binds to Ca and this complex binds to caldesmon which dissociates from actin
What is a caldesmon regulator
Map kinase because it phosphorylates caldesmon
What causes caldesmon to dissociate from the actin filament
When Ca is released it binds to calponin and causes confirmation change
An enzyme can also phosphorylate it and cause it to release
What are the steps of muscle relaxation
Signal stops and there is a decrease in Ca levels
Ca atpase moves Ca back into SR and ECF
Myosin phosphatase dephosphorylates myosin filament and causes it to go back to original form
Rho kinase takes myosin phosphate from inactive form to active form which activates myosin phosphatase
What can the myosin light chain do
Regulate the affinity of myosin heavy chain for the actin filament
Phosphorylated MLC induces high affinity and dephosphorylated MLC induces low affinity
Between tonic and physic muscles which one contracts for long periods
Tonic
Between tonic and phasic which one contracts and relaxes frequently
Phasic
Can tonic muscles contract when the myosin light chain is dephosphorylated
Yes but we don’t know how