Skeletal Muscle Fibers and Levers Practice Flashcards

A set of vocabulary flashcards covering skeletal muscle fiber types, muscle attachments, fiber arrangements, and the mechanics of first, second, and third-class levers.

Slow oxidative (SO) fibers

Small, dark red fibers that are endurance-focused, powered by aerobic respiration, and resist fatigue due to high myoglobin content.

Fast oxidative (FO) fibers

Intermediate size, lighter red fibers designed for moderate duration that rely on aerobic respiration but have less oxygen supply than SO fibers.

Fast glycolytic (FG) fibers

The largest, white fibers used for short bursts; they depend on glycolysis, making them powerful but fatigue-prone.

Fast-twitch Fibers

Fibers that contract quickly and strongly starting at $0.01\,ms$ and lasting $7.5\,ms$, exhibiting faster myosin ATPase activity.

Slow-twitch fibers

Fibers that excel in endurance with slower electrical signaling and calcium cycling, starting at $0.00\,ms$ and lasting $100\,ms$.

Lever

A rigid bone that moves on a fixed point (joint) when a force (muscle contraction) is applied to it.

First-class lever

An arrangement where the fulcrum is in the middle between the effort and resistance, such as the atlanto-occipital joint.

Second-class lever

An arrangement where the resistance is between the fulcrum and effort; standing on tiptoe is a typical example where the joint is the fulcrum.

Third-class lever

An arrangement that places the effort between the fulcrum and resistance, allowing for faster movements such as the elbow lifting the forearm.

Origin

The less movable attachment point of a muscle.

Insertion

The more movable attachment point of a muscle.

Superior attachment

A less movable muscle attachment point.

Inferior attachment

A more movable muscle attachment point.

Circular muscles

Muscles arranged in a circle around an opening, such as sphincters or the orbicularis oris.

Parallel muscles

Muscles with fibers running straight along their length; they have a middle belly that widens when tightening and are good for repeated movements but are not very strong.

Belly

The middle part of a parallel muscle that gets wider when the muscle tightens.

Advantages of First-class levers

Can move any resistance quickly over a large range and provides fine control of movement.

Advantages of Second-class levers

Generates large force with small muscle contractions and can lift or move heavy loads efficiently.

Advantages of Third-class levers

The greatest arrangement for speed and range of motion, enabling fine rapid movements.

Disadvantages of First-class levers

This arrangement requires more force to move a resistance.

Disadvantages of Second-class levers

The range of motion is limited and it requires precise positioning.

Disadvantages of Third-class levers

Requires more muscle and is less efficient for generating large forces.