What happens during muscle contraction in a muscle fiber?

Question

I basically want to know what happens microscopically in a muscle fiber when muscle contraction occurs?

Answer 1

This is a great question! Here's my answer:

Generally speaking, skeletal muscles are made up of two types of fibers - thick and thin filaments. In order for the muscle to contract, these filaments have to "grab onto" one another and "slide" past each other for the muscle to shorten/contract. However, the binding site on the thick filament (myosin), needs to be exposed so that the thin filament (actin) can attach. Here's how that happens microscopically:

Once an action potential reaches a skeletal muscle fiber, it travels down a series of structures known as "T-Tubules". As the action potential travels into the muscle fiber through these tubules, it will increase the release of calcium ions. These calcium ions are super important, because the calcium will bind to troponin, affecting tropomyosin (on the large myosin filament), causing the binding site for the actin (thin filament) to be exposed.

Once this binding site is exposed, a series of "power strokes" can occur where thick myosin filaments and thin actin filaments "slide" past each other and the muscle shortens/contracts. Hope this helped!

Answer 2

Good question!

What basically happens is that a muscle shortens during a contraction.

There are two types of filaments in a muscle fiber, thick filaments and thin filaments. During contraction, the thin filaments slide over the thick filaments. This is what leads to contraction force which allows us to move and push things.

I hope this helps!