Lecture 2 - week 2A Flashcards
What would be the benefit of low theshold typ I morotr neuron tht inn slow ozifative muscle fibres?
the can lst longer durations without fatiguing and do not include SAG, so force does not decrease over time, so good for endurance activities, also lots of mitochodnira for aerobic metabolism
What would be the benefit of Large motor neurons, high threshold (Type II) motor neurons innervate fast contracting, fast fatigable or fast
These would be be beneficial for shorter term high intensity exercises as it can produce more force at a faster speed, faster twitch speed and more force
Will turn on later to help with higher power contractions
which of the following is a nearuWhich of the following is a neural strategy to grade force?
A. Firing rate
B. Action potential
C. Motor unit recruitment
D. Both A and C
D
LArge motor neuron supply ___ twitch msucle fibres while small supply____twixh fibres
large = fast twtich
small -= slow twitch
What is the input resistance for small MN and large? why?
Small MNS (type I) have a high input resistance which leads to a greater response (meaning they are easier toe xcite)
do small or large motor neurons have a high input ressitance?
small (type I) have a high input resitance as they are easier to excite
what is rheobase?
the direct measure of a current needed to put into a neuron for it to fire - the amoutn of current needed to get AP in MN
do small motor neurons have a low or high rheobase?
low - little enegrey is needed for ap
what is the defintion of conduction velocity?
how fast eth action potential goes form axon hillock to the nerve terminal
Do small MN have a slow or fast conduciton velocity
slow (type I) have a slow conduction velocity
after-hyperpolarization (AHP is ____ in large motroe neruons
shorter
what is ohms law?
current x resistance = voltage
describe resistance. rheobase, voltage and conduction veocity in terms of a water hose
resistance = diametere of hose - smalelr have greater resistacne
rheobase = flow of watter/current
conducitno velocity/voltage = pressure of water
What is the size prinple?
motor units are recruited from smallest to largest
what are the positive funcitonal consequences of the size prinple/why do we recruit in this way?
The size princple simplifies the task fo regulating force and so its not necesary for higher centres to selct combinations of MU - saves our brain processes for other tasks
it also ensures smooth force production - like dimming lights insteea dof off and an
minimizes faitgue, slow twitch rectuited, fatigue resistant first
what is one negative aspect of the size prinple recuitmemt?
cannot selctielt chose which MUs to recruit
what is the recruitment threshold?
amount of force needed to turn on motor unit
are recruitment threshold and action potential theshod the ame>
no - they are different
do firting rate of motur units match icntactile speed? what does this mean?
yes foe example sloe contractin msucle fibres have MUs with slow firing rates (eg soleus = slower) but biceps/tricps = faster
who is the boss? msucle or motor neuron? why?
Motor. neruons are the boss- the msucle msut adapt to the MN + change its properties
2 ways to modualte force control are
increase number of MU (recutiment) + rate coiding (fiing rate)
how is a person ablye to maintain a steady contraciton ifMU are only firing/duschargin at 8HZ?
each MU produed partially fused tetanus and because MU fire asynchonously the net force eis smooth
what does an EMG record?
the electrical activity of a muscle - summtion of all the msucle fibre aciton potentials happening
what is an indwelling ECG?
acts like. a miccrophone and can observe singular motor units (invasive tho)
what is it called whenhdevice is used to record. a singualr MU?
Indwelling EMG
