MSK/CT Flashcards
what is the voltage sensing mechanism in the T-tubule?
dihydropyridine receptor - coupled to RyR in SR –> Ca release from sarcoplasmic reticulum
what does Ca do to troponin C?
binds it, causes tropomyosin to move out of myosin-binding groove on actin
what is the power stroke?
myosin released bound ADP and P –> displacement of myosin on actin filament
which parts of sarcomere shorten with mm contraction? which stay the same?
HIZ shrinkage
A is Always the same
what is type 1 muscle?
slow twitch red fibers with oodles of mitochondria and myoglobin
sustained contraction
what is type 2 muscle?
fast twitch white fibers without much mitochondria or myoglobin
hypertrophy with weight training
how does an action potential trigger smooth muscle contraction?
causes Ca influx through L-type Ca channel
Ca binds calmodulin
Ca-calmodulin activates myosin-light-chain kinase
myosin is phosphorylated –> crossbridging and contraction
how does NO trigger smooth muscle relaxation?
causes increase in guanylate cyclase activity
GTP –> cGMP
cGMP activates myosin-light-chain phosphorylase
phosphorylated myosin gets dephosphorylated –> relaxation
what kind of ossification happens in axial/appendicular skeleton, skull base?
endochondral
1) cartilaginous model by chondrocytes
2) OCs and OBs replace with woven bone
3) OCs and OBs remodel to lamellar bone
what kind of ossification happens in calvarium, facial bones?
membranous
1) OCs and OBs make woven bone without cartilaginous model
2) remodel to lamellar bone
how do OBs work?
secrete collagen and catalyze mineralization
differentiate from mesenchymal stem cells
how do OCs work?
secrete acid and collagenases
multinucleated
differentiate from monocytes, macrophages
what effects does estrogen have on OBs and OCs?
inhibits OB apoptosis
promotes OC apoptosis
