Events in muscle contraction

Question 1

Stage 1

Answer 1

1) Action potential arrives at motor end plates, which release the transmitter acetylcholine

Question 2

Stage 2

Answer 2

Acetylcholine binds to ligand-gated receptors on the muscle fibre membrane, causing depolarisation

Question 3

Stage 3

Answer 3

Depolarisation spreads through the transverse tubules to the sacroplasmic reticulum which releases Ca2+ ions

Question 4

What is the Sarcoplasmic reticulum responsible for

Answer 4

Ca2+

Question 5

Stage 4

Answer 5

Ca2+ bind to troponin molecules, which change shape and move tropomyosin (protein) away from actin binding sites

Question 6

What is troponin

Answer 6

Globular protein

Question 7

Stage 5

Answer 7

Actin-myosin ( contractile proteins) cross-bridges form as myosin head can now attach to the actin filament

Question 8

Stage 6

Answer 8

The myosin head bends backwards, pulling the thin filament along (the power stroke). Myosin attaching and detaching from actin causes the filament to slide relato one another. This movement reduces the sacromere length (the filaments do not change shape)

Question 9

Stage 7

Answer 9

The cross-bridge is broken using energy from the hydrolysis of ATP and myosin head is ‘re-set’ ATPase (enzymes) that does this is located in the myosin