HES 202 MIDTERM EXAM QUESTIONS AND
ANSWERS LATEST UPDATE
what a motor unit
- motor neuron
- all muscle fibers it innervates
Whats the functional Unit of all movements
Motor Unit
How is force controlled by the MU
1. Rate coding (firing rate)
2. Frequency of firing
3. Motor unit recruitment
If you increase force you _____ MU
Add more Motor Units
Motor Unit Diagram
Axon Hillocks
allows us to generate an Action Potential
- because exicitatory post-synaptic potentials summate there to generate an AP
How is Force Controlled?
- altering # of active MUs (recruiting more or derecruiting them)
- Changing frequency of activatioin
Action Potential
AP moves down the Axon by saltatory conduction and Myelination
Benfitis of Saltatory conduction and myleniation
- Increase conduction velocity w/o changing azon diameter
- Reduce metabolic cost bc only certain spots on the axon need the Na / K pump to
restore resting mem
neuromuscular junction
tells muscle to contract by releasing neurotransmitters (acetylcholine Ach)
Curare (d-tubocurarine)
Prevents Ach binding to the Ach receptor so then the muscle cant contract and is
paralized (8-30hrs)
Botox (botulinum toxin)
prevents to release of Ach (inhibits excitation along sarcolemma)
- lasta 6-8 weeks
Motor unit types
type 1 - Slow Oxidative (small/slow)
type 2a - Fast Oxidative Glycolytic (fatigue resistant)
type 2x - Fast Glycolytic (fast/big/fatiguable)
Twitch
physiological response of a MU to stimulation (force response)
Twitch is modulated by?
- # of recruited MU
- Rate coding (discharged rate of AP)
, types of twitches
Input Resistance
small Motor Neurons (Type 1) have high input resistance which leads to a greater
response (easier to excite)
Rheobase
amount of current needed to bring neuron to threshold (current being put into neuron to
get it to fire)
Rheobase / Imput resistance hose theory
- input resistance is the diametere of the hose
- rheobase is the flow of water
Size Principle
- motor units are recruited from smallest to largest
- modulates force so you arent using Type 2x for a task that requires little energy
- minimizes fatigue
NEGATIVE - you cant selvively choose what MU to recruite
Recruitment threshold
amount of force needed to "turn on" a motor unit
Rate coding / force-freq curve
firing rate match contractile speed
MU force control
- increase # of Motor Units recruited
- Increase rate of of individual motor units
How are we able to maintain a steady contraction if our MUs are firing at low Hz
Each MU produces a partially fused tetanus and MU fire asynchronously with eachother
creating a smooth contraction
Surface Electromyography (EMG)
- Record the electrical activity of a muscle from the surface
- Muffeled
- Not exact pin point of 1 MU gets all in the recording
- Non invasive
Indwelling EMG
- Inserting needle into muscle (intramuscular)
- More exact reading of 1 specific MU
- Invasive
Why is there a difference in recruitment range between muscle groups?
- muscles are composed of different types of muscle fibers
- larger muscles have greater recruitment range bc they have more MU and MF
- training adaptations
- biomechanical function (hand muscls are used for fine motor control)
Divergence
a single neuron synapses on multiple neurons
One > Alot
Convergence
Multiple Neurons converge onto fewer neurons
Alot > One
Afferent / Efferent
ANSWERS LATEST UPDATE
what a motor unit
- motor neuron
- all muscle fibers it innervates
Whats the functional Unit of all movements
Motor Unit
How is force controlled by the MU
1. Rate coding (firing rate)
2. Frequency of firing
3. Motor unit recruitment
If you increase force you _____ MU
Add more Motor Units
Motor Unit Diagram
Axon Hillocks
allows us to generate an Action Potential
- because exicitatory post-synaptic potentials summate there to generate an AP
How is Force Controlled?
- altering # of active MUs (recruiting more or derecruiting them)
- Changing frequency of activatioin
Action Potential
AP moves down the Axon by saltatory conduction and Myelination
Benfitis of Saltatory conduction and myleniation
- Increase conduction velocity w/o changing azon diameter
- Reduce metabolic cost bc only certain spots on the axon need the Na / K pump to
restore resting mem
neuromuscular junction
tells muscle to contract by releasing neurotransmitters (acetylcholine Ach)
Curare (d-tubocurarine)
Prevents Ach binding to the Ach receptor so then the muscle cant contract and is
paralized (8-30hrs)
Botox (botulinum toxin)
prevents to release of Ach (inhibits excitation along sarcolemma)
- lasta 6-8 weeks
Motor unit types
type 1 - Slow Oxidative (small/slow)
type 2a - Fast Oxidative Glycolytic (fatigue resistant)
type 2x - Fast Glycolytic (fast/big/fatiguable)
Twitch
physiological response of a MU to stimulation (force response)
Twitch is modulated by?
- # of recruited MU
- Rate coding (discharged rate of AP)
, types of twitches
Input Resistance
small Motor Neurons (Type 1) have high input resistance which leads to a greater
response (easier to excite)
Rheobase
amount of current needed to bring neuron to threshold (current being put into neuron to
get it to fire)
Rheobase / Imput resistance hose theory
- input resistance is the diametere of the hose
- rheobase is the flow of water
Size Principle
- motor units are recruited from smallest to largest
- modulates force so you arent using Type 2x for a task that requires little energy
- minimizes fatigue
NEGATIVE - you cant selvively choose what MU to recruite
Recruitment threshold
amount of force needed to "turn on" a motor unit
Rate coding / force-freq curve
firing rate match contractile speed
MU force control
- increase # of Motor Units recruited
- Increase rate of of individual motor units
How are we able to maintain a steady contraction if our MUs are firing at low Hz
Each MU produces a partially fused tetanus and MU fire asynchronously with eachother
creating a smooth contraction
Surface Electromyography (EMG)
- Record the electrical activity of a muscle from the surface
- Muffeled
- Not exact pin point of 1 MU gets all in the recording
- Non invasive
Indwelling EMG
- Inserting needle into muscle (intramuscular)
- More exact reading of 1 specific MU
- Invasive
Why is there a difference in recruitment range between muscle groups?
- muscles are composed of different types of muscle fibers
- larger muscles have greater recruitment range bc they have more MU and MF
- training adaptations
- biomechanical function (hand muscls are used for fine motor control)
Divergence
a single neuron synapses on multiple neurons
One > Alot
Convergence
Multiple Neurons converge onto fewer neurons
Alot > One
Afferent / Efferent
