13.10 Sliding filament model Flashcards
what happens to the I-band when contraction occurs?
narrows
what happens to the A-band when contraction occurs?
it stays the same
what happens to the Z-lines when contraction occurs?
move closer together
so sarcomere becomes smaller
what happens to the H-zone when contraction occurs?
narrows
relaxed vs contracted sarcomere
what is the structure of myosin?
have globular heads which can bind to ATP
what is the structure of actin?
have:
troponin
tropomyosin
actin-myosin binding site
what does troponin do?
holds tropomyosin over the binding site
releases tropomyosin when a Ca2+ ion binds to it
what happens at neuromuscular junction?
SAME AS AT SYNAPSE!!!!
acetylcholine is the neurotransmitter released
what happens when the sarcolemma is depolarised?
it causes the sarcoplasmic reticulum to open Ca2+ channels which causes Ca2+ ions to diffuse into the sarcoplasm
what do the Ca2+ ions from the sarcoplasmic reticulum do?
they bind to troponin on the actin molecules
what does the binding of Ca2+ ions to the troponin do?
causes change in troponin shape which leads to tropomyosin detaching which exposes the myosin-actin binding site
what is formed between the myosin head and the binding site?
a cross bridge
how does the myosin head pull the actin?
by flexing
how is the myosin head detached from the actin?
ADP molecule releases from the head and reacts with P to form ATP
ATP binds to the myosin head which causes the myosin head to detach by breaking the cross bridges
how does the myosin head return to normal position?
ATPase hydrolyses the ATP into ADP + P which releases energy which returns the head back to its normal position
what does the myosin head do once it returns to it’s normal position?
it binds to a binding site further along the actin filament
cycle is then repeated
how does the actin filament return to it’s resting position?
Ca2+ ions leave their binding sites and tropomyosin returns to cover the binding site
the actin filaments slide back to their relaxed positions
what ways is ATP generated for muscle contraction to occur?
aerobic respiration
anaerobic respiration
phosphocreatine
what is aerobic respiration in muscles used for?
long periods of low-intensity exercise
what causes muscle fatigue?
the build up of lactate in muscles due to anaerobic respiration
what is anaerobic respiration in muscles used for?
short periods of high-intensity exercise
what is aerobic respiration in muscles used for?
long periods of low-intensity exercise
what does phosphocreatine do?
provides a reserve supply of phosphate which can combine with ADP to produce ATP
