Skeletal Muscle Structure

Functions of skeletal muscles

1. Volitional movement

2. Maintaining posture + balance

3. Joint stabilization

Structure (layers) of skeletal muscle

Muscle fibers → Endomysium → Fascicle → Entire muscle → Epimysium

Epimysium

A dense layer of connective tissue that surrounds the entire muscle

Fascicles

Bundles of muscle fibers within the muscle, each are surrounded by the perimysium

Muscle fibers

Long, cylindrical cells inside each fascicle that are individually wrapped in endomysium

Neuromuscular junction/motor end plate

Synapse between muscle and nerve

Type I

Slow oxidative fibers

• Endurance fibers

• Produce low power contractions over a LONG period of time

EX. Running a half marathon

Type II a

Fast oxidative glycolytic

• Intermediate fibers

• Produce moderate contractions that fatigue more quickly than Type I fibers

EX. Running a 5K

Type II x

Fast twitch fibers

• Produce large contractions that fatigue rapidly

EX. 100 meter sprint

Electromyography (EMG)

The detection, amplification, and recording of changes in skin voltage due to muscle contraction

Dynamometry

Measurement of power (the amount of work done per unit of time)