muscles and motor units Flashcards
what is EMG?
electromyography
during muscle contraction what is released over a neuromuscular junction?
neurotransmitter
what’s released from the sarcoplasmic reticulum during muscle contraction
?
calcium
what is a motor unit
one alpha neuron that activates muscle fibres
what does one action potential generate ?
singular twitch
what does multiple APs generate ?
continuous force
can lead to tetanic force
how do muscles generate extra force ?
recruits more motor units
increased firing frequency
what affects twitch properties ?
fatigue
temperature
how does the innervation number effect motor control
lower innervation leads to higher control
how does electromyography work ?
needle/electrode instead into the muscle or on surface of skin
records electric signals
what’s the relationship between muscle activity and force?
amplitude of EMG signal is proportional to force produced by the muscle
why do fast twitch fibres generate larger electrical responses ?
higher resting membrane potentials
higher sodium density
faster APs
do muscles produce more force eccentrically or concentrically ?
eccentrically
why do muscles produce less EMG during eccentric contraction ?
prevent damage
how does the NS know when to reduce firing rate ?
detection of metabolites and pain e.g. lactate
spinal suppression of motor neuron firing rates
changes in voluntary action
