Smooth Muscle Flashcards
What regulates smooth muscle tone?
ANS
What links smooth muscle cells together?
Dense bodies
What proteins tonicly inhibit actin-myosin interaction?
Caldesom
Calponin
What delivers action potentials through smooth muscle?
Caveolae
What regulates smooth muscle contraction?
Myosin - Ca++ involved with it
Describe single unit smooth muscle.
Visceral organs
Pacemaker activity causing a wave of contraction
Describe multiunit smooth muscle.
Not electrically coupled
Controlled by nerve signals
Important for fine control of these muscles
Describe phasic contraction of smooth muscle.
Intermittent contraction - GI tract
Describe tonic contraction of smooth muscle.
Continuously contracting - respiratory
How does the contraction cycle in smooth muscle work?
Essentially the same cross-bridge cycle with some differences
Ca++ binds to calmodulin
Thick filament regulated due to phosphorylation of myosin by MLCK
What differs non-striated and striated muscle contraction?
Smooth muscle contraction is much slower and thick filament regulated
What do calponin and caldesom do?
tonicly inhibit actin-myosin interaction
What activates MLCK?
Calmodulin
How does relaxation occur in smooth muscle?
Dephosphorylation of MLCK by myosin phosphatase
What regulates SR Ca++ in smooth muscle?
CICR
Calcium release from SR in response to neurotransmitter release and hormones causing an inositol triphosphate mediated activation of Ca++ release channel on SR
What does phospholipase C do?
Converts phosphatidylinositol biphosphate (PIP2) into IP3 which stimulates Ca++ release from SR
How is the sarcolemma Ca++ regulated in smooth muscle?
CICR
Calcium pump
Na+/Ca++ antiporter
Store operated calcium entry - moving Ca++ into SR from ECF as backup
What does latch state allow?
Energy efficient prolonged contractions consuming much less ATP
What is a way to increase force and how it this achieved?
Increasing sensitivity to calcium
Decreasing of MP and increasing activity of MLCK
