sliding filament theory Flashcards
(13 cards)
what causes muscles to shorten when they contract?
actin slides over the myosin towards the centre of the sarcomere
what are cross bridges
-extend out from myosin
-attach to actin
-head of CB pull towards its tail
what is thin filament
*actin
-two helical chains
what are the two proteins of actin and their features
tropomyosin-thread like, covers the cross bridges binding site
tropin- bean shaped, attached directly to tropomyosin and has a calcium binding site
what is the path of a action potential signal
brain-spinal cord-motor neuron-motor unit-motor end plate
what is released at the neuromuscular junction into what when an action potential signal is sent
acetylcholine into the sarcolemma
how does the action potential signal travel from the neuromuscular junction
neuromuscular junction- sarcolemma- transverse tubules- myofilaments stimulates sarcoplasmic reticulum to release calcium
what is the role of ATP
-energizes the power stroke
-disconnects myosin cross bridges from the binding site of actin
-transports calcium into sarcoplasmic reticulum
what is happening when muscle is at rest
-actin and myosin uncoupled
-Ca in sarcoplasmic reticulum
-tropomyosin chastity belt
what is happening at excitation and coupling
-nerve impulse received
-CA released from sarcoplasmic reticulum
- Ca binds to troponin, tropomyosin uncovers actin
-ATP attached to cross bridges
-actin and myosin attach
what happens at contraction
-ATP breaks to ADP
-energy causes cross bridges to move actin over the myosin *POWERSTROKE
-length shortens by 1%
what happens during recharging
-ATP breaks down cross bridges
-actin and myosin separate
-excitation and contraction happen again
what happens during relaxation
-nerve impulses stop
-Ca is removed and brought back into the sarcoplasmic reticulum
-tropomyosin covers cross bridges
