muscles Flashcards
structure of muscles (biggest to smallest structure)
muscle- muscle fibre- myofibril- myofilament (actin and myosin
Sarcolemma
plasma membrane of muscle cells
sarcoplasmic reticulum
where calcium ions are stored and released
multinucleate definition
multiple nucleus
myofibrils
long cylindrical organelles that consist of actin and myosin
thick myofibril and its appearance under a microscope
myosin, dark
thin myofibril and its appearance under a microscope
actin, light
a band
only myosin
h zone
middle part where there is no actin
I band
part where there is no myosin
sarcomere
region between 2 z lines
what happens to the bands/ zones when sarcomeres contract
h zone gets smaller, i band gets smaller, a band stays the same length
Sliding Filament theory- Stimulation
action potential arrives, depolarises sarcolemma and SER this causes calcium ions to be released, they bind to troponin, this causes a shape change, the tropomyosin that’s blocking the actin myosin binding site moves
Sliding Filament theory- Attachment
myosin head binds to the actin myosin binding site forming a cross bridge, this causes a power stroke- the actin filament slides over the myosin, ADP is removed from the myosin head
Sliding Filament theory- Detachment
Fresh ATP binds to the myosin head removing it from the binding site. ATPase then breaks down the ATP into ADP+ Pi and this returns the myosin head to its original place.