Neuromuscular communication Flashcards
What is the order of how muscle contracts
electrical, chemical, mechanical
what is the electrical signal called
action potential
what generally causes an action potential
shift in membrane ion concentration
how is an action potential measured
voltage change
what are the 4 phases of an AP
resting, depolarization, repolarization/hyperpolarization, refractory period
what is typically the threshold mV
-70mV
why do APs have to convert to chemical signals
they can’t cross the synapse
how do AP cross the synapse
use neurotransmitters
what is the most common neurotransmitters that APs use to cross synapse
acetylcholine
what does ACh do to the synapse
attaches to ligand gated channels to open it
what do APs travel down
motor neuron axon
where do APs release ACh
neuromuscular junction
what is the result of ACh traveling down the neuromuscular junction
AP moves along muscle fibers
what is the one key determinant of muscle force
number of cross-bridges
what is a motor unit
alpha motor neuron +axon + all the muscle fibers it innervates
what is the result of an AP in an alpha motor neuron
muscle contraction
can the number of motor units vary
yes
how are muscle fibers distributed
throughout, not in clusters
what is innervation ratio
number of muscle fibers innervated by 1 alpha motor neuron
what is the result on more innervation ratio
more force
3 types of motor units
S, FR, FF
what is the S type of motor unit
slow, non-fatiguable
what is the FR type of motor unit
fast, fatigue resistant
what is the FF type of motor unit
fast, fatiguable
what are the two characteristics that are responsible for force in a motor unit
innervation ratio and cross-sectional area
what is the characteristic that is responsible for fatiguability in a motor unit
fiber type
3 ways to measure signals in a neuron
EMG, tissue sample, force output
what is the purpose of an EMG
detects activity but doesn’t stimulate the neuron
when measuring force, why doesn’t the it start at zero
electromechanical delay
how is recruitment measured
number of active motor units
what happens when there is more recruitment of motor units
more force
is small or large motor units recruited first
small
how is rate coding measured
number of cross bridges
what does an increasing of firing APs result in
increase in force
what size motor unit fiber does an activity that requires less force recruit
S and maybe FR
