Skeletal and Smooth Muscle info Flashcards
small to large skeletal muscle naming
myofilaments to myofibrils to fibers
what is the smallest contractile unit of skeletal muscle?
sarcomere
motor unit definition
all muscle fibers innervated by one somatic motor neuron
motor end plate definition
post synaptic region of the skeletal muscle cell at NMJ
are the nicotinic/ionotropic receptors at the NMJ permeable to K or NA?
both but let more Na in to make depolarization and EPP
what is the calcium channel in T tubules in skeletal muscle?
L-type or DHP receptor
what is the calcium channel in the sarcolemma in the skeletal muscle
ryanodine receptor
how are the L type/DHP receptor of T tubule and the ryanodine receptor of the sarcolemma linked in skeletal muscle and why is this important?
DHP receptor is voltage gated calcium channel and when it opens it pulls the ryanodine channel open too…this leads to release of hella amounts of calcium
how does calcium lead to activation of skeletal muscle?
calcium binds troponin that is sitting on top of tropomyosin…the troponin then changes and releases the tropomyosin from blocking myosin binding sites on actin and you can have cross bridge cycling now
what gets Ca back into the sarcoplasmic reticulum?
SERCA or sarcoplasmic reticulum Ca ATPase
does smooth muscle have sarcomeres? does it have actin and myosin? how are fibers arranged?
no sarcomeres but does have actin and myosin
arrangement is diagonally
what molecule regulates smooth muscle contraction?
calcium
where do you mainly find smooth muscle?
surrounding lumens
what controls smooth muscle contraction?
it is involuntary muscle that is controlled by hormones, nts, and local stimuli
multiunit smooth muscle cell info
not much communication between smooth muscle cells…leads to finer control…can have some contracting and some relaxing…all or none too
single unit smooth muscle cells info
electrical coupling between cells via gap junctions leads to coordination
line many visceral organs
are blood vessel smooth muscle cells multi unit or single unit?
actually somewhere in between
steps of smooth muscle activation
Ca released from SR or from extracellular
Ca binds to calmodulin
CA-calmodulin complex activates the Myosin Light Chain Kinase
MLCK then phosphorylates the MLC and leads to contraction
what enzyme lessens smooth muscle cell contraction?
MLC phosphatase…this is always active
what is unique about smooth muscle cell and calcium control?
higher calcium concentration leads to harder contraction..more tension
what AA does NO come from and what is the enzyme that makes it?
L arginine
NO synthase
Where is NO made?
endothelial cells
NO steps and role in smooth muscle
ROLE-relax smooth muscle
STEPS:
from endothelial cell goes into smooth muscle
stimulates production cGMP
cGMP leads to Ca reuptake
Ca levels fall and MLCK activity decreases
relaxation
