And sarcoplasmic reticulum respectively. Hach Column-I with...

and sarcoplasmic reticulum respectively. Hach Column-I with Column-II and select the correct woin from the codes given below. Column-I Column-II A Structural and functional (i) $\mathrm{H}$-zone unit of a myofibril Q Protein of thin filament (ii) Myosin C Protein of thick filament (iii) Sarcomere Q The central part of thick (iv) Actin filament not overlapped by thin filament

and sarcoplasmic reticulum respectively. Hach Column-I with Column-II and select the correct woin from the codes given below. Column-I Column-II
A Structural and functional
(i) $\mathrm{H}$-zone unit of a myofibril
Q Protein of thin filament
(ii) Myosin
C Protein of thick filament
(iii) Sarcomere
Q The central part of thick
(iv) Actin filament not overlapped
by thin filament

Key Concepts

Sarcomere

The sarcomere is the fundamental contractile unit of striated muscle tissue, defined as the segment between two Z-discs. It contains the organized arrangement of thick and thin filaments whose interactions produce muscle contraction, thus playing a crucial role in converting chemical energy to mechanical force.

Thick Filament

Thick filaments are composed primarily of the protein myosin. They interact with thin filaments during the muscle contraction process and are critical for generating the force necessary for muscle shortening through the sliding filament mechanism.

Thin Filament

Thin filaments are mainly made up of the protein actin, along with regulatory proteins such as troponin and tropomyosin. These filaments form the tracks on which myosin heads attach to create cross-bridges, essential for muscle contraction.

H-zone

The H-zone is the central region within the sarcomere where only thick filaments, primarily myosin, are present without overlap from thin filaments. Changes in its width during contraction reflect the degree of filament overlap and are indicative of muscle contraction dynamics.

Myofibril

Myofibrils are long, cylindrical structures within muscle cells composed of repeating sarcomeres aligned end-to-end. They are the primary sites where muscle contraction occurs, giving the muscle its striated appearance and coordinated contractile properties.

Sarcoplasmic Reticulum

The sarcoplasmic reticulum is a specialized endoplasmic reticulum in muscle cells that functions to store and release calcium ions. Calcium release from this organelle is essential for initiating the contraction cycle by enabling the interaction between myosin and actin.

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