Musculoskeletal System and movement - Muscles

  • Created by: megz.n
  • Created on: 16-01-19 15:18

Each muscle is called a fibre, and each fibre is made up on myofibrils. Myofibrils are made up of myofilaments - Actin and Myosin. 

The myofilaments are arranged so that each myosin is surrounded by 6 actins. The actin, being thinner, shows up as a light band under a microscope. The myosin shows as a dark band. 


Consists of 2 threads wrapped around eachother. At each twist there is a binding site for myosin. In a relaxed state a molecule called tropomyosin covers these sites. 


The head attaches to the myosin binding sites in actin where the actin and myosin filaments overlap. These attachments are called cross-bridges. The head has ATPase enzyme which releases energy from ATP to power muscle contraction. 


1) Acetylcholine is released into the synapse and attaches the receptors on the sarcolemma. 

2)The sarcolemma is depolarised, and this is spread.

3)This causes calcium to be released from the sarcoplasmic reticulum in the sarcoplasm. 

4)Calcium displaces tropomyosin, uncovering the myosin binding sites on the actin filaments. 

5) ATP attaches to the myosin heads which causes them to flex and attach to the…


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