Smooth muscle Flashcards
What is multiunit smooth muscle?
Autoregulated smooth muscle as seen in the iris, ciliary muscle of the lens, and vas deferens. Densely innervated by the autonomic nervous system.
Unitary smooth muscle is instead spontaneously active in slow waves and is seen in the uterus, GI, ureter and bladder. With a pacemaker like activity modulated by hormones and neurotransmitters.
How does smooth muscle and skeletal muscle differ in excitation-contraction coupling?
There is no troponin.
Instead calcium regulates myosin on the thick filaments. There is NO TROPONIN on smooth muscle.
On skeletal muscle, troponin C is on the thin filament.
How do smooth muscles contract?
Depolarization of the membrane opens calcium channels. Hormones and neuro transmitters can open them as well.
Calcium entering the cell causes a release of more calcium from the SR in a caclium induced calcium release method.
Works through the IP3 DAG process.
Calcium binds calmodulin that activates myosin light chain kinase. Light chain kinase phosphorylates myosin and allows it to bind actin. Tension produced is porportional to calcium concentration.
What does myosin light chain kinase do?
Found in smooth muscle, calcium binds the myosin light chain kinase allowing it to phosphorylate myosin allowing it to interact with actin.
How can contraction force be increased in smooth muscle?
It is absolutely related to intracellular calcium concentration.
Relaxtion occurs as calcium is sequestered.
What type of muscle are perkinje fibers?
These are in the heart and act with sodium depolarization.
They are not nodal tissue.
What does calcium bind in smooth muscle that activates myosin light chain kinase?
Calcium binds to calmodulin.
