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Muscle Contractions: Micro Level

Muscle Contractions: Micro Level

Author: Aaron Mullally

This lesson will go into more detail describing how a muscle contracts.

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Terms to Know

The primary energy molecule that cells use for energy; composed of adenosine and three phosphate groups; when the bonds that hold the phosphates together are broken energy is released for work.


Referred to as the thin filament of a sarcomere, creates the lighter color within a sarcomere and interacts with myosin to create movement.

Action potential

The technical term for a nervous impulse; when a wave of depolarized electrical energy travels down the length of a cell/tissue.


A mineral/ion that has many physiologic uses to humans; calcium is stored in the sarcoplasmic reticulum (SR) of skeletal muscles and when released it prepares actin and myosin for interaction.


A muscle fiber generates tension, causing the muscle to shorten.

Motor unit

The term used to describe one motor neuron and all of the muscle fibers it innervates at once.


Referred to as the thick filament of a sarcomere, creates the darker colors within a sarcomere and contains various heads that pull on actin filaments to create movements.


The functional and contractile units of skeletal and cardiac muscles; created by a specific arrangement of myofilaments called actin and myosin; each sarcomere is bordered by a z-line.

Sarcoplasmic reticulum (SR)

A specialized form of smooth endoplasmic reticulum (SER) found within skeletal muscles used for calcium storage.

Sliding filament mechanism

A theory used to describe how the microfilaments within the sarcomere interact with one another; actin and myosin cling together and slide past one another.


A term used to described a prolonged muscle contraction; often used to describe a person who has been exposed to Clostridium tetani toxin.


The way a skeletal muscle contracts, sarcomeres quickly pull inward and create a quick, jerky twitch.