Muscle Contraction Mechanisms | NMDCAT 2021

About This Video!
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.
All or None Response : The contraction of each muscle ibre is based on “all or none” principle
i.e. all of its ibrils participate in contraction. The degree of contraction depends upon the number
of muscle ibers that participate in contraction.
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.
How the bridges are controlled
When the muscle is at rest, the tropomyosin is disposed in such a way that it covers the sites on the
actin chain where the head of myosin becomes attached. When the muscle is required to contract,
calcium ions bind with the troponin molecule and cause them to move slightly. This has the efect
of displacing the tropomyosin and exposing the binding sites for the myosin head. Once the myosin
head has become attached to the actin ilament, ATP is hydrolysed and the bridge goes to its cycle.
This ATP is provided by the large number of mitochondria present in each muscle cell.
From the above account it is revealed that ATP is needed to break the link between the myosin and
the actin. After death, the amount of ATP in the body falls. Under these circumstances the bridges
can not be broken and so they remain irmly bound. This results in the body becoming stif, a
condition known as rigor mortis.

[@sanaasad7553]

Aww......relaxed now ..completely relaxed after taking this lecture ...my all confusions are cleared ........mere ap k liye duain hi duain hn

[@riwayaatriwayaat1629]

every time your lectures saves my semester

[@zahrabatool9942]

Excellent lecture.... Jazak Allah sir

[@AdnanAdnan-gu4en]

This video made my concept crystal clear thanks sir

[@laibawahid5719]

MA SHA ALLAH sir g superub♡♡

[@HarmanpreetKaur-yx5it]

Brief explaintion in simple words .thank you sir

[@machalasainath2644]

Superb explanation sir.thank you sir.

[@nasimullahnasimullah8554]

Mashahallah, Sir you are so intelligent, you explain every lecture very well in a short time ❤❤❤.

[@zalankhn]

Thank u so much for this, clear all my confusion..best lecture

[@nimraiqracreation4055]

Keep continue sir our pray with u 👍👍👍👍

[@alinamalik8348]

Hats off to u sirrr bravo👏👏👏👏👏👏👏👏👏

[@aroosaishfaq8442]

V v v good lecture thnx

[@haveagoodartwork8789]

Kamal. 🔥🔥🔥🔥

[@radhamishraradhamishra3048]

Thanku so much sir love from India 😊

[@Abdullah-sy6st]

Very good way 👍

[@AbdulWahid-ce4wo]

Very good sir.you explain very essay

[@farazamin138]

Sir your lectures are really helping me out i hope u get successful in your acedimic career

[@humazafar2289]

Sir PlZz Full Lectures Upload kr den Is Chapter k...🥺Yeh Tu Sary MDcat waly hain...Proper Full Topic K Chaiyee...

[@zulqarnainmalik1395]

Excellent

[@shaistaaftab3950]

Superb👌

[@innovativeworldwithfaiza3067]

Best lecture..👏

[@user-bn4np2nb4u]

nice 👍 sir great manshallah

[@goharali0137]

اعلیٰ 👌

[@zulqarnainmalik1395]

Excellent sir g

[@AbbasKhan-dd3lc]

Wonder full lacture 👌👌👌💟💟💟

[@aijazabbasi7513]

Assalam o Alaikum Sir you are fabulous teacher mind belowing excellent lecture.

[@khalidhussian4603]

Shahzada sir 💯❣️❣️❣️

[@Pkftkhi]

Thankyuhhhh sirr

[@YasirKhan-bl5md]

Kmaaal sir g ❤️

[@balalzain9009]

Sir g very good lecture Step bi acha he But ap aik chapter ka pora lecture bna dyaa kary

[@rockgym692]

Good 👍

[@badarschool5684]

Sir ap mdcat ke ilawa bhi kr de plz FSc part 2 ke all lecture upload kre plz plz plz plz

[@Day_Dreamer_47]

Thanku sir😊

[@ikramullah2894]

Sir apki agar pore classes Ho human anatomy Plzzz I need

[@sabahameed5974]

❤✌🏻👍🏻

[@komalafaq4032]

thnkuuuuuuuu sir

[@universe.756]

Sir sarcoplasmic reticulum protein synthesis nhi krta?? Aur is mein aur endoplasmic reticulum mein calcium ions ka frq h ?

[@universe.756]

@@aleenabibi1861 Tnx

[@Scholarly_Safari]

👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍

[@Pareeshay.]

Sir 2nd year fsc kay bhi topic wise lectures post karden

[@TabeerZahra-mv1rx]

Sir g controlling actin myosin interaction by calcium ion Wala lecture upload kr de

[@xmariamk]

THANKU SM :((

[@ismaeelamir380]

Aslam alikum sir........The best lecture ever but i have one confusion please tell me about the occurence of T-tubules....the line in the book "it extends and encircles the myofibril at the level ofZ line or A or I junction"kindly explain this.Thank uh

[@sufyanirfan974]

Sir which board??

[@fizzacaptain9591]

Sir cardiac muscle and smooth muscle ka topic nhi hai

[@dalyaram9830]

sir im going through ur videos they r really gud but we cant understand in hindi bez we r from A.p so try to explain in english where everyone can understand sir

[@NZ-yk1lc]

😃👏👏👏👏

[@Islamicchannel-zt7bs]

support in plants ???

[@ALIACADEMYAR7]

Kea

[@Islamicchannel-zt7bs]

@@ALIACADEMYAR7 support in plants nahi parhaya apny???????

[@ALIACADEMYAR7]

Niii abi homeostasis chapter chl rha

[@Islamicchannel-zt7bs]

@@ALIACADEMYAR7 g thk hai sir

[@sufyanirfan974]

Sir which board??