Kinesiology Lecture on Strength and Motor Units

Flashcards covering key vocabulary terms related to motor units, action potentials, and muscle strength from the Kinesiology lecture notes.

Motor Unit

An alpha-motor neuron and all of the muscle fibers it innervates.

Innervation Ratio

The average size of a motor unit, determined by the number of fibers in a muscle divided by the number of α-motor axons in the nerve supplying it.

All or None Law

The principle that once a threshold level for activation is reached, all muscle fibers in that motor unit are activated, with no partial contractions.

Action Potential

Rapid changes in membrane potential used for long-distance communication in excitable cells, involving phases of depolarization and repolarization.

Saltatory Conduction

The propagation of action potentials along myelinated axons from one Node of Ranvier to the next, increasing conduction velocity.

Dendrites

Components of neurons that receive information.

Axon Hillock

The conical protrusion where an action potential arises before propagating along the axon.

Type I Muscle Fibers

Low-threshold motor units that are recruited first and have lower force capabilities.

Type II Muscle Fibers

Higher-threshold motor units that are recruited for high force production.

Size Principle

The concept that motor units are recruited in order of their threshold, from low-threshold (Type I) to high-threshold (Type II) muscle fibers.

Motor Unit Recruitment

The process by which the central nervous system increases the number of active motor units to produce higher force.