Anatomy and Physiology Level 3 - Understanding muscle contractions

Anatomy and Physiology Level 3 – Understanding muscle contractions

As part of your Anatomy and Physiology Level 3 Exam, you need to have a good understand muscle contractions.

These 3 steps will simplify the confusing sliding filament theory and finally leave you understanding muscle contractions.

Watch the video below and test your knowledge using the mock question.

Anatomy and Physiology Level 3 – Understanding muscle contractions

Step 1 – The Accordion

We first need to step away from muscles in order to understand it a little better. Picture an Accordion Musical Instrument. It expands and contracts, folding onto itself. This is like a sarcomere.
A sarcomere expands and contracts as the myofilaments cross over each other.

Now imagine lots of these accordions all end on end… And they all contract and expand at the same time, like a band in unison.

One line of these accordions is like our muscle fibres, sometimes called myofibrils… which is made up of sarcomeres stacked end upon end.

When the muscle fibre is told to contract, all of the sarcomeres start to shorten in length, making a significant difference in length of the muscle. This is our muscle contracting.

Step 2 – The Sarcomere

The Sarcomere contains myofilaments, which are small contractile proteins.
Actin is the Thin myofilament and
Myosin is the Fat myofilament with the golf club heads.

These two myofilaments connect at cross bridges and pull together. This is a concentric contraction, with the muscle getting shorter.

They can also lengthen under contraction which is an eccentric contraction.

Step 3 – The big picture – the sliding filament theory

The Actin and Myosin are the smallest parts, they interact to change the length of the muscle.

The Sarcomere is made up of the actin and the myosin.

A muscle fibre, or myofibril, is made up of multiple sarcomeres end on end

A Fascicle is a bundle of muscle fibres

A Muscle belly is a bundle of fascicles.

Essentially it is a Russian dolls approach… they all stack inside of each other, which is a smart way to get as many sarcomeres as possible in each muscle. This maximizes our ability to contract and change the length of the muscles,

This pulls on the tendon which joins muscle to bone

The tendon pulls on the bone.

The bone moves, creating an angle change in the joint = joint action.



once you have watched the video do the mock question to test your knowledge:

Mock Questions - Anatomy and Physiology Level 3 - understanding muscle contractions

What is the name given to the thin myofilament?
A – Sarcomere
B – Actin
C – Myosin
D – Myofibril

Pop a comment with your answer below, and then watch the video for the answer.

If you want more mock questions for your Level 3 Anatomy and Physiology exam, then click the link to download 101 mock questions, to help you prepare.

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