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Sarcomere
-makes miyofibrils look striped. -shorten when muscle contracts
myofibrils
many small strands within a muscle cell
Muscle contraction: Step 1
Myosin head of thick filiment is attached to ATP but not to the Actin in thin filiment (muscle is relaxed)
Muscle contraction step 2
-ATP hydrolizes to ADP - the head of the myosin pivots -myosin head binds to new actin site further down the thin filiment
Muscle contraction step 3
Inorganic phosphate is released and the head pivots back pulling the actin (Power Stroke)
Muscle contraction step 4
after ADP is released, a new ATP can come and bind to the myosin and causes the myosin to release from Actin
Rigor Mortis
When your muscles run out of ATP, happens after death.
Thin Filament
Actin
Thick Filiement
Myosin
Tropomyosin
coils aroind actin blocking binding site
Troponin
calcium binding site on Tropomyosin and actin
calcium release Step 1
action potential arrives at end of motor neuron
calcium release Step 2
releases neurotransmitter (ACh) into synaptic cleft
calcium release Step 3
(ACh) binds to ACh receptors triggering depolarization of muscle cell
calcium release Step 4
Action potentials propogate down the length of the muscle cells and into the T-tubules (which intersect with the sarcoplasmic reticulum)
calcium release Step 5
Action potential reaches end of T-tubules and activate protein which opens up Caa+ channels in the Sarcoplasmic reticulum.
G-protein complex
muscle contracts whe G-protein is activated
one activated Phospholipase ?
opens many Ca++ channels
Bag of Calcium
Sarcoplasmic reticulum
SR has what channels?
-Ca++ pump into it -IP3-gated Ca++ channels
Where does IP3 come from?
IP3 = inositol triphosphate inositol = part of phospholipid molecule in membrane phospholipase = enzyme ...converts phospholipid molecule to IP3 (+ other stuff) only works when activated
if Phospholipase is activate the muscle does what?
contracts
Is the phospholipase activation an amplification?
yes because it causes many Ca++ channels to open
Signal Dampening?
cGMP + phosphodiesterase --> GMP
Signal amplification
cGMP + guanylate cyclase --> cGMP
What activates Phospholpiase?
G-Protein

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