MUSCLE PHYSIOLOGY

PHYSIOLOGY

MUSCLE CONTRACTION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Only thick filaments present
A
Sarcomere
B
H zone
C
M line
D
Z disc
Explanation: 

Detailed explanation-1: -H-zone of striated muscle fiber contains only thick filaments. The H zone appears as a lighter band in the middle of the dark A band at the centre of a sarcomere.

Detailed explanation-2: -The H-zone contains only thick filaments. The A-band contains both thick and thin filaments and is the center of the sarcomere that spans the H zone. When the muscle contracts, the H-zone, I-band, the distance between Z-lines all become smaller, whereas the A band remains the same.

Detailed explanation-3: -Hint: The H zone-the central area of the A zone-contains only dense filaments (myosin) and during contraction, it is shortened.

Detailed explanation-4: -The H-zone is an area made up of only thick filaments (myosin). The I-band is thin filaments (actin) only, and the A-band is where there are thick and thin filaments. The Z-disc is dividing feature between sarcomeres and appears as dark lines in electron micrographs.

Detailed explanation-5: -Each sarcomere has a central A band made of thick myosin filaments and two half I bands made of thin actin filaments on either side of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filament is called H zone.

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