Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ANAT2012 > Muscle L4: Using electromyography to understand the control of movement > Flashcards

Muscle L4: Using electromyography to understand the control of movement Flashcards

1
Q

Why is EMG (electromyography) used?

A

Advance our understanding of movement control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Some physiotherapists use EMG in the clinic for _______.

A

Biofeedback

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does a motor unit consist of?

A

motoneuron, motor axon and all of the muscle fibres it innervates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Motor units range in size allows _____, _____ and ____ force.

A

graded, sustained and controlled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Motor units get input from _______, ______ & ______.

A

descending pathways, spinal interneurons; afferent fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Measuring electrical activity generated by the __________ provides information about the neural drive to muscles.

A

muscle action potentials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is depolarisation?

A

Many Na+ gates open, influx of ++

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is repolarisation?

A

K+ move out Na gates closed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is hyperpolarisation?

A

Na+ out, K+ in via Na+/K+ pumps – influences maximal discharge rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the neuromuscular junction?

A

The connection between the nervous system and the muscle is the neuromuscular junction (motor point, motor end plate, synaptic cleft)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Surface ECM: Where is the signal coming from? What affects an EMG signal?

A

Every discharge of an action potential in the motoneuron = action potential in the muscle fibres that belong to that motor unit

  • Myoelectric action potentials (red arrows) are initiated by the Ach released by the motor neuron.
  • The action potential sweeps across the muscle fibre and into the transverse (T) tubules.
  • This initiates the release of calcium that regulate muscle activity.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Steps of muscle contraction

A
  1. Axon of motor neuron and synaptic terminal (release ACh)
  2. Changes in membrane potential of muscle
  3. Once muscle cell reaches threshold, generation of AP (run in both direction), along muscle fibre from neuromuscular junction (these AP are recorded in EMG)
  4. Down T-tubules to help release of Ca2+ from sarcoplasmic reticulum to allow process of actin and myosin to start to bind
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

A myoelectric action potential propagates at ~2-6 m/s along all muscle fibres from _____ same/different motor unit

A

same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

It propagates in both directions from the ____ to the _______.

A

motor point; end of the muscle fibre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are 2 ways to record action potentials?

A
  1. Surface electrode on skin (overlye activated muscle)
  2. Insert wires into muscle (record from much smaller area of muscle)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Electromyography records a complex summation of ________.

A

overlapping asynchronous action potentials

17
Q

What are 4 biological determinants of EMG signal?

A
  1. Motor unit discharge
  2. Fibre angle, fibre type
  3. Change in muscle position
  4. Cross talking, other muscles
18
Q

Biological determinants of EMG signal: How does motor unit discharge affect EMG?

A
  • EMG is altered by number & discharge rate of motor units
  • Motor unit discharge Also by the number of muscle fibres in the motor unit
  • More drive, more action potentials, greater EMG amplitude -many biological and technical factors influence the EMG signal
19
Q

EMG is altered by the ________ and _______ of motor units

A

number; discharge rate

20
Q

Biological determinants of EMG signal: How does fibre angle, fibre type affect EMG?

A
  • EMG is influenced by muscle fibre direction relative to electrode position and fibre type
    • Aligned with muscle fibre
    • Not perpendicular = signal cancellation remove good signals from recording
    • Do this by looking @ this on ultrasound fibres & pennation angle
  • More muscle fibres in a larger unit – more myoelectric action potentials.
  • Slow twitch (Type 1, postural) have a slower myoelectric action potential conduction velocity
    • Slow AP in slow twitch (fibre type dependent)
    • If muscle fibre direction changes during a dynamic task- can change amount of area being recorded
21
Q

EMG is influenced by muscle ________relative to electrode position and fibre type

A

fibre direction

  • Must be align with muscle fibre.
  • Make sure that its not perpendicular = signal cancellation remove good signals from recording
22
Q

Slow twitch (Type 1, postural) have a ______ (slower/faster) myoelectric action potential conduction velocity. How does that affect EMG?

A

Slower

  • Slow AP in slow twitch (fibre type dependent)
  • If muscle fibre direction changes during a dynamic task- can change amount of area being recorded
23
Q

Biological determinants of EMG signal: How does a change in muscle position affect EMG?

A
  • An electrodes recording zone is the region or muscle from which the myoelectric signal can be recorded.
    • Affects where skin lies over muscle
    • If muscle/skin relationship changes can have inaccurate recording
  • Consider if the electrodes will be above the muscle belly throughout motor task
  • Cross talk - The recording zone of an electrode may be bigger than the muscle being measured
24
Q

An __________ is the region or muscle from which the myoelectric signal can be recorded.

A

electrodes recording zone

25
Q

Biological determinants of EMG signal: How does cross talk affect EMG?

A

The recording zone of an electrode may be bigger than the muscle being measured

26
Q

How does cross talk relate to surface EMG and fine wire EMG? (based on SCM and scalenes)

A

Surface

Inspiration: EMG recorded conclusion- both SCM & scalenes produce a bit of force

  • During surface electrodes, both SCM & scalenes are producing force
  • During fine wire electrodes, only scalenes are producing force, not SCM
27
Q

What are 3 technical determinants of EMG signal?

A
  1. Skin preparation
  2. Other electrical noise
  3. Electrode placement
28
Q

Technical determinants of EMG signal: How does skin preparation affect EMG?

A
  • Use sand paper, exfoliating cream- clean skin
  • Shave skin
29
Q

Technical determinants of EMG signal: How does other electrical noise affect EMG?

A

Normally around us (in environment) = 50Hz

30
Q

Technical determinants of EMG signal: How does electrode placement affect EMG?

A
31
Q

Does EMG differ between contraction types?

A
  • During concentric contraction
    • Single motor units are discharging at a higher rate than when eccentric
  • Long muscle = same length = same torque = same but driving single motor units harder in concentric compared to eccentric
32
Q

What are mechanism for higher muscle force for same neural drive?

A
  • Active force is generated through the actin and myosin cross-bridge.
  • In eccentric movements actin and myosin ‘hold on’, more stretch of the elastic components (eg titin) > more force for same energy (# action potentials)
  • Decreased rate of cross-bridge detachments >> greater force production on the eccentric bout.
  • EMG provides a good indication of neural activation of a muscle.
    • No elastic info about how long myosin and actin stay together
  • EMG cannot provide any information about passive forces.
  • EMG does not = force Consider how muscle length and contraction type may change during the motor task.
33
Q

____ force is generated through the actin and myosin cross-bridge.

A

Active

34
Q

In ______ movements actin and myosin ‘hold on’, more stretch of the elastic components (eg titin) > more force for same energy (# action potentials)

A

eccentric

35
Q

Decreased rate of cross-bridge detachments >> greater force production on the ______ bout.

A

eccentric

36
Q

EMG provides a good indication of _____of a muscle. However, there is no ___info about how long ____and _____ stay together, ____ forces and ___________.

A

neural activation; elastic; myosin; actin; passive forces; how muscle length and contraction type may change during the motor task.

37
Q

What is electromechanical delay? How it can be measured? How may it affect the way that we can assess movement?

EXAM QUESTION

A
  • is the time lag between onsets of muscle activation and muscle force production and reflects both electro-chemical processes and mechanical processes
  • Measuring onset of EMG does not tell you when the muscle force is produced.

ANAT2012 (31 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions