Smooth Muscle - Questions - High Yield Flashcards
Why is smooth muscle not striated?
The thick and thin filaments
Where does cytosolic Ca2+ enter smooth muscle?
from the ECF and sparse intracellular stores
What does cytosolic Ca2+ do when it enters the smooth muscle?
activates cross-bridge cycling via biochemical reactions that result in the phosphorylation of myosin
Define: Multiunit Smooth Muscle
neurogenic
requiring stimulation by autonomic nerves
Define: Singleunit smooth muscle
myogenic
able to initiate its own contraction w/o any external influence due to automatic shifts in ion fluxes
How does an action potential spread in single unit smooth muscle?
once AP is generated, the electrical activity is spread by gap junctions so the entire sheet contracts as a unit
How does the autonomic nervous system, hormones, and local metabolites affect single unit smooth muscle?
they can modify the rate and strength of the contractions
How do agonists work with single unit smooth muscle cells?
they trigger the production of IP3 in the cytosol -> results in Ca2+ release from the SR
What effect does stretch or increase in wall pressure have on smooth muscle?
it can directly activate it
the bladder
Smooth muscles and skeletal muscles generate about the same force per cross sectional area, but shortening velocity is much ___ in smooth muscles
slower
Smooth muscle tone is also known as
tonic contraction
Why does smooth muscle tone require little ATP consumption to be maintained?
because of the slow cross bridge cycling rate
Force can be maintained w/o continually detaching and reattaching the cross-bridges and utilizing ATP
Why is detachment of myosin slowed in smooth muscle?
The myosin becomes dephosphorylated while the cross-bridge is still attached
In skeletal muscle, myosin is always….
“on”
ATP hydrolysis energizes the head at rest
In smooth muscle, myosin is…
“off” until enzymatic changes activate it
