Electromyography

Question 1

Distribution of muscle fibres of a motor unit

types of muscle fibre

Answer 1

S motoneurons innervate Slow Oxidative Muscle fibres forming S motor units

FR motoneurons innervate FOG Muscle fibres forming FR motor units

FF motoneurons innervate FG Muscle fibres forming FF motor units

Question 2

Twitch Contraction

Answer 2

Single twitch FF produce most force
Repeated twitches for an hou
FF fatigue the fastes
FR take longer to fatigue
S almost never fatigue

Question 3

Differences in sizes of motor units
Leakiness
excitablity
Conductivty

Answer 3

FF have larger motor neurons to produce more power and innervate more muscles

FF need more excitement to reach the threshold than S and have more SA so Na+ can leak out more

FF also conduct faster

Question 4

Orderly motor unit recruitment

Answer 4

Smaller motor units fire first, like the S type

the more force needed, the larger the diameter of MU are recruited

S first, then FR, then FF

they are de-recruited (RELAX) in the opposite order

Question 5

What are recruited from when Im standing to walking to running the sprinting

Answer 5

S MU recruited to stand

during walking, FR are recruited as muscle demand becomes greater

When sprinting FF are recruited for largest muscle demand

Question 6

What did Elwood Henneman measure about MU fibre diameter and numberof muscle fibres it innervated

Answer 6

The diameter of fibres determined how many fibres it innervates

Question 7

Surface Electromyography

where does it go

how is it placed

how do we prepare

Answer 7

Measure of muscle action potential
and how action potential travels down Sarcolemma and muscle

and measure electrical signals from muscle contraction

Place an ENG over the BELLY, or thickest part of the muscle

with the PENNATION ANGLE or direction muscle goes

Skin must be cleaned and abraded to remove dead skin cells to improve signal quality