Report
Course MSCI 522 - Principles of Physiology II
Lesson EMG and Muscular Conditions
Skeletal muscle innervation
Which statements regarding motor units are true, and which are false?
True
A motor unit consists of a motor A
neuron and all the muscle bers neuron and all the muscle bers in
it innervates. it innervates.
A single muscle ber may be
innervated by two or more units of di erent sizes.
motor neurons.
Many muscles contain motor
units of di erent sizes.
Electromyography
Consider the accuracy of recording muscle electrical activity using electrodes placed on the
directly in the muscle. What are the di erences between surface and intramuscular EMG r
EMG
Can analyze the activity of a
single motor unit activity of adjacent muscles
Cannot discriminate between May be a ected by adipose
, Which statement regarding a surface EMG recording is false?
Increased amplitude of the EMG recording re ects an
increase in the strength of muscle contraction.
Surface EMG is easier to perform than intramuscular EMG,
so is more routinely used in teaching labs.
The EMG may represent the electrical activity of thousands
of individual bers.
The raw signal re ects the action potentials of nerve bers
active at that time.
Analyzing EMG
What happens to electrical activity in the muscle as the force of contraction is increased?
The electrical activity in the muscle increases as the force of the contraction is increased.
Muscle coactivation
How much activity is recorded from electrodes over the
tricep muscle when the volunteer is asked to actively
contract the bicep?
No activity.
Same activity as the bicep.
Course MSCI 522 - Principles of Physiology II
Lesson EMG and Muscular Conditions
Skeletal muscle innervation
Which statements regarding motor units are true, and which are false?
True
A motor unit consists of a motor A
neuron and all the muscle bers neuron and all the muscle bers in
it innervates. it innervates.
A single muscle ber may be
innervated by two or more units of di erent sizes.
motor neurons.
Many muscles contain motor
units of di erent sizes.
Electromyography
Consider the accuracy of recording muscle electrical activity using electrodes placed on the
directly in the muscle. What are the di erences between surface and intramuscular EMG r
EMG
Can analyze the activity of a
single motor unit activity of adjacent muscles
Cannot discriminate between May be a ected by adipose
, Which statement regarding a surface EMG recording is false?
Increased amplitude of the EMG recording re ects an
increase in the strength of muscle contraction.
Surface EMG is easier to perform than intramuscular EMG,
so is more routinely used in teaching labs.
The EMG may represent the electrical activity of thousands
of individual bers.
The raw signal re ects the action potentials of nerve bers
active at that time.
Analyzing EMG
What happens to electrical activity in the muscle as the force of contraction is increased?
The electrical activity in the muscle increases as the force of the contraction is increased.
Muscle coactivation
How much activity is recorded from electrodes over the
tricep muscle when the volunteer is asked to actively
contract the bicep?
No activity.
Same activity as the bicep.
