Download - Electromyography. EMG Measures a muscle’s electric potential – Surface EMG – Intramuscular EMG
Electromyography
EMG• Measures a muscle’s electric
potential
– Surface EMG
– Intramuscular EMG
Muscles!!!
• Motor Unit:
– A motor neuron and all the muscle fibers
it innervates.
Muscles!!!
• Contraction
– State of mechanical activity.
– Either isotonic or isometric.
– Triggered when a nerve impulse at
neuromuscular junction causes acetylcholine to
spread over the muscle surface/sarcolemma as
an electrical depolarization.
Neuromuscular Junctions (my favorite!... Seriously.)
Video
• http://highered.mcgraw-hill.com/olc/
dl/120107/bio_c.swf
Muscle Types• Cardiac
– Striated
– Involuntary
• Skeletal
– Striated
– Voluntary
• Smooth
– Non-striated
– Involuntary
Fatigue
• 2 Types:
–Muscle Fatigue:
• Exercising muscle can no longer respond to
stimulation with the same degree of
contractile activity.
– Central or Psychological Fatigue:
• CNS no longer adequately activates the
motor neurons supplying the working
muscles.
EMG• Shape Indicates:
– Composition of motor units, number of
muscle fibers innervated by a motor
unit, muscle type, health, etc.
• Used to diagnose neuropathies and
myopathies
EMG• Neuropathy:
– An AP amplitude 2x normal due to increase # of
fibers/motor unit because of re-innervation of de-
innervated fibers.
– Increase in duration of AP.
– Decrease # of motor units in muscle.
• Myopathy:
– Decrease duration of AP.
– Reduction in area to amplitude ratio of AP.
– Decrease # of motor units in muscle.
Myotonia Congenita• Fainting goats
• Abnormality of Cl-
channels. They can’t act
as buffers against APs;
muscles relax slowly.
• Cold makes condition
worse.
• Cl- channels don’t open
fast enough after AP to get
membrane potential back
to negative.
Methods
• Should be in PAST tense!
• Should be DETAILED. How many trials did you
run? How long was each? How did you measure
the cues? What are the data you collected?
• DATA IS A PLURAL WORD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
– These data were recorded using the labscribe
program.
A GREAT answer!
• Reflexes to auditory stimuli occur faster than reflexes
to visual stimuli. This is due to the neural pathways
for visual and auditory systems being different.
Auditory receptors are ionotropic in that the stimulus
is translated into an electrical signal, while the visual
receptors are metabotropic, which translates the
stimulus into a chemical signal (Hill 2008).
– DO NOT CITE ME!!!!
HOMEWORK!!!!
• Answer all questions.
• Write a methods and results section.
• Make sure to check my rubric (Will be
posted on the website!). I will use it to
grade assignments from this point forward.
• Be thorough. My grading gets harder, not
easier as the semester progresses.