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.
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.
MyotoniaCongenita • 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 • DO NOT CITE ME!!!!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.