muscle and motor units Flashcards
what is the first part of 4 of muscle contractions
ap stimulates release of NT across NM junction
what is the 3rd part of 4 for muscle contraction
causes release of calcium from sarcoplasmic reticulum
whats the 2nd part of muscle contraction
ap spreads across the sarcolemma/ muscle membrane and into fiber along T tubules
what is the final step in muscle contraction
calcium binds to the muscle and causes the cross-bridge cycling
what are the 3 things shows -
muscle force, temperature and length
what is a motor unit
a single neuron and muscle fibres that it innervates
where is the motor unit
ventral horn of spinal cord
what does a muscle unit do
innervates muscles
what is twitch fusion
when twitch fuse due to multiple stimulation of the muscle
one ap is what
one muscle twitch
what type of electrode is used for artificial stimulation
black anode
what is thr frequency variation in hetz
3-30
more muslce stimualtion causes what
smoother and a longer muscle twitch
twitch properties depend on what
fibre type
why does fiber type vary for muscle twitch properties
due to how fast or slow twitch, temperature and fatigue as well as firing rates of different muscles like the glutes vs. eyes
what does movement precision depend on
number of motor units
the more motor units in a muscle means
finer control and finer force modulation
lower innervation number in muscles means
more control
calf muscles have less control comapred to the
eye
lowest innovation number means
highest amount of control of the muscle
you can lose motor neurons from what
motor neuron disease slowly over time
action potentials propagate along the ..
sarcolemma
AP runs along the sarcolemma to do what
release calcium from sarcoplasmic recticulum
what will emg show
the force / activity of motor units acting together
does fast twitch has a higher or lower resting membrane potential
higher
eccentric contraction is
lengthening
concentric contraction is
shortening
which is usually has more force con or eccentric
eccentric
is torque effected by angle of muscles
yes
why is torque effected by angle of msucle
due to more or less distance to travel, bigger angles require more force
will overlapped fibres impact muscle fibres
yes - less force
why do overlapped muscles not produce as much force
due to actin an myosin overlapping ,
fibres are compensated for failing contraction in other
fibres and the force is maintained
Muscle fatigue hypothesis is ..
muscle force is reduced when stimulation was maintained at a high rate over time
fatigue is
slowing the muscle and slows the force and reduces force
what is muscle wisdom
a mechanism that will sense a fatiguing muscle and will reduce the force and fire less through the CNS
how does the nervous system know when to reduce motor neuron firing rate (3)
peripheral detection of metabolites like lactate
spinal suppression of motor neurons firing and changing in voluntary activation
why does the NS reduce the firing of neurons
reduce neuronal fatigue and help maintain fine motor control
what could happen when there is a lot of firing of the muscle
loss of control
what are the 2 types of fatigue
frequency or force
what is low frequency fatigue
caused by intense exercise, takes days to recover and caused by reduced calcium release due to mechanicals damage.
what is high frequency fatigue
caused by continuous high-frequency stimulation, recovers quickly after, caused by failure of transmission along muscle membrane
can electrical stimulation increase force
yes but not as effective as normal training by 2/3
force is modulated by
changing firing rate and or recruiting more units
muscle fatigue reduces contraction speed due to what
muscle wisdom
muscle fatigue can be partly due to
loss of neural drive - central fatigue
what is another way of measuring muscle activity
Acoustomyography or ultra sound
what is Acoustomyography (amg)
A method of measuring muscle activity which is intrinsically toed to contraction and the amplitude declines during muscle fatigue
