Short Answer Type
Long Answer TypeShort Answer TypeLong Answer TypeAnswer the following briefly :
(a) How does a muscle shorten during its contraction and lengthen during its relaxation?
(b) What biological functions are served by the skeletal system ?
(c) Why a red muscle fibre can work for a prolonged period while a white musule fibre suffers from fatigue after a shorter work ?
Short Answer TypeHow are the thick and thin filaments arranged ?
Thin or Actin filaments :
The light bands contain actin and is called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin. Actin filaments are thinner and are called thin filaments. The myosin filaments are called thick filament. The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils.
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