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  • The portion between two successive -line is calledOption: 1

The portion between two successive Z-line is called

Option: 1

Sarcomere


Option: 2

N- band


Option: 3

M- line


Option: 4

I- band


Answers (1)

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Sarcomere -

  • The smallest unit of the skeletal muscle is called the sarcomere.
  • The sarcomere consists of the thick and thin filament. 
  • The thin filament is made up of the globular protein called actin.
  • The thick filament is made up of the protein called myosin.
  • The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin.
  • Both the proteins are arranged as rod-like structures, parallel to each other and also to the longitudinal axis of the myofibrils. 
  • In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it.
  • The thin filaments are firmly attached to the ‘Z’ line.
  • 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. 
  • The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere. The length of a sarcomere is about 2 -3 micron
  • In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments.
  • This central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.

 

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The portion of the myofibril between two successive 'Z'  lines is considered as the functional unit of contraction and is called a sarcomere. Hence, the correct option is a. Sarcomere

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Pankaj

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