bio 2301 lab exam 1 comprehensive review lab 4 CSCC

What does the electromyography (EMG) measure

Voltage changes between two electrodes posted on the skin.

What do you expect to happen to the amplitude of the EMG spikes as muscle contracts with more force?

increase

Name 2 ways in which the nervous system adjusts force production by a muscle.

increase intensity, increase frequency of contraction

Name one clinical application of an EMG.

Distinguish between myopathy and neuropathy

TRUE or FALSE: In a myopathy, there is a loss of some of the peripheral neurons

false, peripheral neuropathy

TRUE or FALSE: Spectral analysis of EMG data provides an indication of the various frequencies at which motor units are being stimulated within the muscle

True

Which of the following EMG changes is expected as a muscle increases force production?

increased spike amplitude

An increase in the number of motor units involved in a contraction would result in which of the following?

an increase in the force of contraction

Weakness due to a loss of muscle cells would be associated with which of the following?

low amplitude on the EMG

Weakness due to a loss of neurons would be associated with which of the following?

neuropathy

Where does the electrical activity measured by the EMG originate?

sarcolemma (muscle cell membrane)

How does the electrical activity measured by the EMG relate to muscle function?

increase in electrical activity means increase in action potentials means increased contractile activity

Does the pattern of electrical activity of a muscle change when it is developing different forces?

Yes. More electrical activity, more force being exerted.

Which of the electrical parameters seems to have the strongest correlation with force production? What on the graphs told you this?

The graphs that have a slope: p-p and mean of integrated EMG

For a given amount of force, are both arms generating that force in the same way? Use the data to support your answer.

No, non-dominant requires greater electrical activity to generate same force => more activation in weaker muscles

Individuals with cerebral palsy often display a great deal of muscle spasticity especially in the lower limbs. Drugs and therapies that reduce spasticity in the periphery have been shown to improve function. How could the EMG be employed to evaluate the usefulness of a proposed new drug or therapy? What electrical parameter(s) would be valuable to monitor?

Run EMG before and after treatment to see if there was a decrease in muscle activity.

p-p and mean integrated EMG

Name the technique that allows analysis of changes in the frequency of electrical activity within a muscle.

spectral analysis

Describe the changes in frequency and amplitude that would be expected when a muscle is contracted to greater force

Increase in wave frequency and amplitude

What form of neuromuscular pathology is associated with a low amplitude, high frequency EMG tracing?

myopathy

What form of neuromuscular pathology is associated with a high amplitude, low frequency EMG tracing

neuropathy

Romberg test unable to be performed as patient is unable to balance reliably with feet together even with eyes open. Where is problem

cerebellum issue

A patient with normal strength but resting tremor in left arm, goes away when arm is in motion.

extrapyramidal motor system damage (?)

Patient is unusually clumsy and can't determine if toe is up or down

proprioceptors issue

Patient has normal vitals signs and displays a positive Romberg test. Senses digits in space fine, but feels dizzy.

vestibular apparatus

Blind patient has ear infection and can't balance.

inflammation in the ear is inhibiting some function of vestibular apparatus and patient is already blind. MUST have 2 of 3 functioning parts for balance. Only has 1.