Blood Clotting, Skeletal Muscle contraction, Smooth Muscle Contraction

What's stage 1

Vascular spasm (reduce blood flow to wound)

What's stage 2

Platelet Plug formation

What's stage 3

Intrinsic and extrinsic pathways

What's stage 4

Clot formation (make plug permanent)

What happens in stage 1

Blood vessel narrows

What's happens in stage 2

Collagen fibers exposed, von willebrand factor bind to collagen, Platelets stick to vWF and are activated. they then release ADP and A2 to get more platelets, more platelets come forming a patelet plug

What happens in stage 3 INTRINSIC

Factor XII to XI to IX, activated factor IX and VIII, X

What happens in stage 3 EXTRINSIC

Factor III + VII, X

What's factor X?

thrombokinase

What happens in stage 4

X activates V, together they convert prothombin to thrombin, thrombin makes fibrinogen to fibrin, XIII cross-links fibrin over platelet plug, clot contracts.

Skeletal Muscle Contraction

Ca²⁺ → troponin → tropomyosin moves → myosin binds actin → power stroke → contraction

Smooth Muscle Contraction

Ca²⁺ → calmodulin → MLCK → myosin phosphorylation → actin–myosin interaction → contraction

Key Diff

Skeletal: Calcium binds to troponin, moving tropomyosin to expose binding sites on actin. Smooth: Calcium binds to calmodulin, activating MLCK, which phosphorylates myosin.