Exercising Muscle Part 3: Muscle Contraction Flashcards
a single alpha-motor neuron, its axon, and all the muscle fibers it activates
motor unit
the functional unit of the motor system
motor unit
the motor unit represents the:
smallest increment in force that can be generated
in order for skeletal muscle cells to contract, each cell must be:
stimulated by a process of a motor neuron
during motor unit recruitment, activation of the muscle fibers occurs by:
activation of their motor neuron
motor unit recruitment is important for:
excitation-contraction coupling
a sequence of events beginning with excitation of a motor neuron, resulting in contraction of muscle fibers
excitation-contraction coupling
what is the size principle of motor unit recruitment?
the smallest alpha-motor neurons are recruited first
why are the smallest alpha-motor neurons recruited first in muscle contraction?
smaller cell volume means that the same stimulus has a greater effect on the cell’s resting membrane potential
what are the three types of motor units?
- type I: slow, smallest
- type IIa: fast, fatigue resistant, intermediate size
- type IIx: fastest, fatigue, largest
what is the recruitment pattern for motor neurons during exercise?
type I –> type IIa –> type IIx
as more force is developed, there is greater:
recruitment of motor neurons
what is the principle of orderly recruitment?
motor units are activated on the basis of a fixed order of fiber recruitment
as the intensity of the activity increases, the number of fibers recruited increases in the following order, in an additive manner:
type I –> type IIa –> type IIx
type I motor units are recruited first in graded movement as they have:
the smallest motor neurons
true or false: motor units in a muscle are always recruited in the same order
true
