Sliding Filament Theory

Sliding Filament Theory

Describes the interaction between myofilaments and muscle contraction.

Sarcomere

The basic contractile unit of a myocyte, composed of actin and myosin filaments.

Myofibrils

Contractile elements of skeletal muscle, appearing striped due to the overlap of actin and myosin.

Actin

Thin filament involved in muscle contraction, has binding sites for myosin.

Myosin

Thick filament that interacts with actin during muscle contraction.

Cross Bridge

The connection formed when myosin heads attach to the binding sites on actin.

Power Stroke

The action where the myosin head pivots and pulls the actin filament toward the center of the sarcomere.

Recovery Stroke

The process where myosin heads detach from actin after the power stroke, returning to resting position.

Calcium Ions

Released from the sarcoplasmic reticulum, they bind to troponin to initiate muscle contraction.

ACh (Acetylcholine)

Neurotransmitter released at the neuromuscular junction, initiating muscle contraction.

Z line

Defines the boundaries of a sarcomere, pulled towards the H zone during contraction.

H zone

Part of a sarcomere that contains thick filaments but no thin filaments.

Thick Filaments

Composed mainly of myosin, responsible for muscle contraction.

Thin Filaments

Composed of actin, responsible for muscle contraction.

Motor Units

A motor neuron and the muscle fibers it innervates, involved in controlling muscle force.

Frequency Coding

The rate of motor unit activation that influences the force of muscle contraction.