sliding filament model | NMDCAT 2021

About This Video!
Sliding Filament Model
When muscle ibre contracts, the thin and thick ilaments undergo shifting. The I-band reduces in
length and Z-line gets closer.
Huxley and A. F. Huxley and their colleagues suggested a hypothesis in 1954 to explain all events
in muscle contraction, this is called “Sliding ilament model” of muscle contraction. According to
this theory, the thin ilaments slide past the thick one so that actin and myosin ilaments overlap to
greater degree. Thus the Z-line is brought close together, I-band shortens, the H zone disappears.
In this process of contraction, the cross bridges of thick ilament become attached to binding sites
on the actin ilament. The cross bridges then contract to pull the actin ilament towards the center
of the sarcomere.
Infrastructure of Myoilament : Myoilament is made up of thick and thin ilaments. The
central thick ilaments extend the entire length of the A-band. The thin ilaments extend across the
I-band and partly into A band.
The thick ilament which is about 16 nm in diameter is composed of myosin. Each myosin molecule
has a tail terminating in two globular heads. Myosin tail consists of two long polypeptide chains
coiled together. The heads are sometimes called cross bridges because they link the thick and the
thin myoilaments together during contraction (Fig. 16.8).
Thin ilaments are 7 - 8 nm thick and are composed chiely of actin molecule. The actin molecules
are arranged in two chain which twist around each other like a twisted double strand of pearls.
Twisting around the actin chains are two strands of another protein, tropomyosin. The other major
protein in thin ilament is troponin. It is actually three polypeptide complex, one binds to actin,
another binds to tropomyosin while third binds calcium ions. Each myosin ilament is surrounded
by six actin ilaments on each end.
Controlling the Actin - Myosin Interaction By Ca++ ions
Muscle contraction is initiated by nerve impulse arriving at the neuromuscular junction. All the ibres
innervated by a single motor neuron are a “motor unit” and contract simultaneously in response
to the action potential ired by the motor neurons. The sarcolemma of muscle ibre penetrates
deep into the cell to form hollow elongated tube, the transverse tubule, T-tubule the lumen of
which is continuous with the extracellular luid. The thousands of T - tubules of each muscle cell are
collectively called T-system. It extends and encircles the myoibril at the level of Z-line or A and I -
junction. The T-tubule and the terminal portion of the adjacent envelope of sarcoplasmic reticulum
form triads at regular intervals along the length of the ibril. The nerve impulse is carried through
the T-tubule to the adjacent sarcoplasmic reticulum (SR). The calcium gates of the SR open releasing
calcium into the cytosol, thus binding calcium ion to troponin molecules of the thin ilament. The
binding sites are exposed and cross bridges with myosin can form, and contraction occurs.

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[@vickyjaan7644]

sir mujhe past paper ke liye hint chahiye the

[@usman-ku2xc]

Thank u sir .Aap ki video dekhte dekhte he lesson yaad ho jata he.U are a perfect biology teacher.😃🥰

[@universe.756]

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[@sabahameed5974]

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[@medicosickness9892]

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[@vickykhan6732]

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[@aliawan5030]

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[@zahrabatool9942]

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[@duarana5689]

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[@azambaloch6143]

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[@Umer159]

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[@asifmehmood4094]

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[@AbdulRehman-jg6zs]

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[@VirendraKumar-pz7sq]

Nice explanation sir

[@muhammadramzanaslam6359]

Aoa sliding filament model se next lectures show nhi ho rhy

[@PremKumar-rq7wl]

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[@aliraza1292]

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[@copyrightfreemusic9327]

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[@baltistanibiologist.6988]

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[@onlinestudy3044]

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[@ALIACADEMYAR7]

Yes my dear

[@onlinestudy3044]

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[@onlinestudy3044]

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[@onlinestudy3044]

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[@ALIACADEMYAR7]

Yes

[@mahnoorfatima7850]

sir paper ma yhi likh sakty ha jo ap samjhaty ha

[@muhammadramzanaslam6359]

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[@Byme221]

Sir Ap FSC ko Bhool gye hain...🥺 ... Saray lectures MDCAT , NMDCAT k hi miltay hain ... Chapter complete karwa dain.... Please please please 🥺

[@ALIACADEMYAR7]

Sary uploaded ha dear

[@Byme221]

@@ALIACADEMYAR7 Sir main Jo bhi topic search kar rahi hoon Repair of broken bones say agay woh MDCAT k hain .. Muscles , sliding filament , yeh nhi hain

[@Byme221]

@@ALIACADEMYAR7 How bridges are controlled bhi nhi mil raha .... I am really sorry for disturbing ... Ap k pass bhi time nhi hota ... Phir main Kahan say Karun.... MDCAT OR FSC main kiya difference hai ...??

[@ALIACADEMYAR7]

G but kuch alp k mutabik the pehly

[@Byme221]

@@ALIACADEMYAR7 Ji sir lakin yeh included thay topics ... Locomotion wala excluded hai full topic

[@faizanashfaq2253]

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[@ALIACADEMYAR7]

Yes dear