Deck 21: Electromyography: Biopac Exercise

Question 1

One of the unique characteristics of skeletal muscle is that it contracts only when stimulated by

A) motor neurons.
B) stretch of the muscle tissue.
C) certain hormones.
D) pH changes.
E) temperature changes.

Answer 1

A

Question 2

In the EMG experiment, when was tonus observed?

A) During the weakest clench
B) During the period of decreasing tension in the muscle fatigue experiment
C) During the strongest clench
D) In the periods between clenches
E) Tonus was not observed in the EMG experiment.

Answer 2

D

Question 3

Temporal summation is used in the body to

A) decrease muscle contraction in muscle fibers, to prevent damage to the cells.
B) increase the amount of force generated by skeletal muscle fibers.
C) maintain constant tension in a muscle fiber every time it contracts.
D) activate nearby skeletal muscle fibers, when a muscle fiber is under constant stimulation.
E) accomplish all of these functions.

Answer 3

B

Question 4

A twitch is the response of an entire skeletal muscle to stimulation by motor neurons.

Question 5

Which of the following is NOT true of tonus?

A) It is a state of slight muscle contraction.
B) It occurs when a muscle is fully contracted.
C) During periods of tonus, the motor units take turns contracting.
D) It keeps the motor units healthy and ready to contract at any time.
E) All of these are true of tonus.

Question 6

In the EMG experiment, the hand dynamometer was used to illustrate

A) motor unit recruitment only.
B) smooth muscle contraction.
C) muscle fatigue only.
D) cardiac muscle contraction.
E) motor unit recruitment and muscle fatigue.

Question 7

Which of the following is NOT true of muscle fatigue?

A) It involves a decrease in the force of muscle contraction, even when the muscle is still under stimulation.
B) It may be caused by conduction failure, due to accumulation of K⁺ ions in the transverse tubules of skeletal muscle fibers
C) It usually occurs when a muscle is being stimulated during very light work or exercise.
D) It may be caused by decreased responsiveness of a muscle fiber to low pH, resulting from a build-up of lactic acid
E) All of these are true of muscle fatigue.

Question 8

When a motor neuron of a particular motor unit is activated, all of the muscle fibers it innervates are stimulated to contract simultaneously.

Question 9

Muscle fatigue can be induced by sustaining maximum clench force on an object for several seconds.

Question 10

The activation of additional motor units in a skeletal muscle, in order to increase muscle tension, is called motor unit recruitment.

Question 11

In a motor unit of a skeletal muscle, each muscle fiber is innervated by several motor neurons.

Question 12

The type of muscle tissue that was used for electromyography in this lab exercise is ________ muscle.

A) mononucleated
B) cardiac
C) non-striated
D) skeletal
E) smooth

Question 13

Electromyography is a recording of voltage on the skin surface, which is derived from the contraction of skeletal muscles under the skin.

Question 14

Which of the following is NOT true of a tetanic muscle contraction?

A) A tetanic contraction only occurs if a person has been infected with the disease called tetanus.
B) It occurs when a muscle fiber is stimulated in very rapid succession.
C) During a tetanic contraction, the muscle fiber does not relax at all between stimuli.
D) A much greater amount of muscle tension can be achieved during a tetanic contraction than during a single muscle twitch.
E) All of these are true of a tetanic muscle contraction.