EXAM #2: LAB #6

Which of the following terms are NOT used interchangeably? A) motor unit - motor neuron B) muscle cell - muscle fiber C) muscle tension - muscle force D) in vivo - in the body/ the living

Which of the following is NOT a phase of a muscle twitch? A) shortening phase B) latent period C) relaxation phase D) contraction phase

Where does the acetylcholine that stimulates muscle contraction bind? A) receptors in the sarcoplasmic reticulum B) receptors in troponin C) receptors in the motor end plate D) receptors in the axon terminal

When acetylcholine binds to its receptors, it results in __________. A) a change in ion permeability B) a graded depolarization C) the end plate potential, a graded depolarization, and a change in ion permeability D) the end plate potential

Which of the following occurs during the latent period of muscle contraction? A) Acetylcholine is released at the axon terminal and an action potential is generated. B) An action potential is generated. C) Calcium is released from the sarcoplasmic reticulum. D) Acetylcholine is released at the axon terminal.

As the stimulus voltage was increased in this activity, which of the following occurred? A) The muscle force generated increased. B) The latent period increased in length. C) The latent period decreased in length. D) The muscle force generated decreased.

Which of the following describes the relaxation phase? A) The sarcomeres are increasing in length, and the force generated increases. B) The sarcomeres are increasing in length, and the force generated decreases. C) The sarcomeres are decreasing in length, and the force generated decreases. D) The sarcomeres are decreasing in length, and the force generated increases.

Which of the following can trigger a muscle twitch? A) release of acetylcholine or release of calcium from the sarcolemma B) release of acetylcholine C) release of acetylcholine or electrical stimulation D) electrical stimulation E) release of calcium from the sarcolemma

Which of the following is proportional to the amount of tension produced by a skeletal muscle? A) the length of the latent period B) the number of motor units activated C) the threshold voltage D) the length of the relaxation phase

NO force is generated during which of the following? A) the contraction phase B) the latent period C) the relaxation phase D) a muscle twitch

What is the minimum voltage needed to generate active force in the skeletal muscle? A) threshold voltage B) contraction voltage C) recruitment voltage D) stimulus voltage

A motor unit is defined as _______. A) a nerve and a muscle B) the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates C) a single neuron and a single muscle fiber D) a single muscle fiber and all its axon terminals

In the lab, a researcher finds that the threshold stimulus to induce an action potential in a muscle fiber's sarcolemma was 3.0 volts. Which of the following would result in muscle tension? A) 2.0 volts B) 3.0 volts C) 3.0 volts and 4.0 volts D) 4.0 volts E) 1.0 volt

Increasing the applied voltage in the simulation corresponds to which in vivo event? A) muscle fiber recruitment B) motor neuron recruitment C) motor unit recruitment D) muscle twitch recruitment

As the stimulus voltage increased, the resulting muscle tension _______. A) increased proportionally B) increased to a point until it reached a plateau C) decreased proportionally D) remained the same

Which of the following occurs during the contraction phase? A) Cross-bridge cycling is taking place. B) Ca2+ release from the sarcoplasmic reticulum is blocked. C) The sarcomeres are increasing in length. D) Acetylcholine binds to the sarcolemma.

Treppe is the phenomenon that results in _______. A) motor unit recruitment B) maximal force production by a skeletal muscle C) an increase in the stimulation frequency D) a progressive increase in the force generated with repetitive stimulation

When the frequency of stimulation of a muscle is great enough, _______. A) wave summation results B) full relaxation of the muscle occurs C) muscle twitches overlap D) wave summation results and muscle twitches overlap. E) full relaxation of the muscle occurs and wave summation results

When wave summation occurs, _______. A) individual muscle twitches are separated B) the muscle fiber has received a single stimulus event C) the muscle force generated decreases D) the muscle force generated increases

Why does wave summation occur? A) Muscle fibers are partially contracted when the next stimulus arrives. B) Muscle fibers have been allowed to fully relax. C) Muscle twitches are not yet overlapping. D) A large amount of time elapses between stimulations.

Which of the following produced an increase in stimulus intensity? A) clicking the mouse in rapid succession and allowing the muscle to completely relax in between contractions B) allowing the muscle to completely relax in between contractions C) clicking the mouse in rapid succession D) increasing the voltage applied

Which of the following produced an increase in stimulus frequency? A) increasing the voltage applied B) clicking the mouse in rapid succession C) clicking the mouse in rapid succession and allowing the muscle to completely relax in between contractions D) allowing the muscle to completely relax between contractions

Which of the following does NOT describe treppe? A) An incremental increase in force occurs. B) A period of relaxation can be seen on the muscle twitch tracing. C) An increase in stimulus intensity is required to see the effect. D) It is also referred to as the "staircase" effect.

Which of the following does NOT describe tetanus? A) The muscle relaxes fully between contractions. B) It can be unfused. C) The maximum force produced has reached a plateau. D) It can be fused.

Which of the following is true of the maximum stimulus frequency? A) No greater muscle force can be generated and muscle force will decrease. B) No greater muscle force can be generated. C) No greater muscle force can be generated and the muscle has reached maximal tetanic tension. D) Muscle has reached maximal tetanic tension. E) Muscle force will decrease.

Muscle twitches overlap with _______. A) unfused tetanus only B) fused tetanus only C) both fused and unfused tetanus D) threshold voltage applied

Which of the following would result in fused or unfused tetanus? A) threshold stimulus and single stimuli B) increasing the stimulus frequency C) decreasing the stimulus frequency or increasing the stimulus frequency D) decreasing the stimulus frequency

To transition from unfused tetanus to fused tetanus, _______. A) stimulus frequency increased B) wave summation was not allowed C) the muscle fibers were allowed to relax D) stimulus frequency decreased

Which of the following describes the relationship between stimulus frequency and muscle tension? A) When stimulus frequency decreases, muscle tension increases indefinitely. B) When stimulus frequency increases, muscle tension increases to a maximum value. C) When stimulus frequency increases, muscle tension increases indefinitely. D) When stimulus frequency increases, muscle tension decreases.

At what stimulus frequency was maximal tetanic tension developed? A) 130 stimuli/sec B) 146 stimuli/sec C) 50 stimuli/sec D) 140 stimuli/sec

Which of the following occurs if the load attempted is equal to or greater than the force generated by a muscle? A) Isometric muscle contraction occurs. B) The muscle shortens. C) Isotonic muscle contraction occurs. D) The muscle lengthens.

The resting length of the muscle _______. A) occurs when the muscle is relaxed B) describes the length of the muscle during contraction C) occurs when peak tension develops D) describes the muscle during stimulation

The graph of the length-tension relationship illustrates _______. A) the relationship between muscle diameter and tension and the optimal sarcomere length for muscle contraction B) the relationship between muscle diameter and tension C) the optimal sarcomere length for muscle contraction and the amount of overlap between the thick and thin filaments in the resting muscle D) the amount of overlap between the thick and thin filaments in the resting muscle E) the optimal sarcomere length for muscle contraction

Which of the following is generated when cross-bridges form between actin and myosin? A) active force B) ATP C) active force and passive force D) active force and ATP E) passive force

Which of the following describes the relationship between length and tension? A) As the muscle's resting length increases, the active force will decrease. B) As the muscle's resting length increases, the active force will increase. C) The active force can increase or decrease, depending on the starting resting length of the muscle. D) As the muscle's resting length decreases, the active force will decrease.

Why does the active force of skeletal muscle change with the muscle's resting length? A) The amount of available calcium varies. B) The amount of available ATP varies. C) The amount of resistance varies. D) The number of cross-bridges between actin and myosin varies

Which starting length of the muscle provided the maximum total force? A) the longest starting length B) an intermediate starting length C) The length of the muscle did not affect the amount of total force produced. D) the shortest starting length

At which muscle length was the passive force the greatest? A) 70 mm B) 90 mm C) 80 mm D) 100 mm

Which of the following occurs during isotonic concentric contraction? The length of the muscle decreases with contraction. The length of the muscle increases with contraction. The length of the muscle increases and decreases with contraction. The length of the muscle stays the same.

Which of the following occurs during the latent period of isotonic concentric contraction? Muscle tension is produced, and the weight will not move. Muscle tension is produced, and the weight will move. Muscle tension is not produced, and the weight will not move. Muscle tension is not produced, and the weight will move.

The speed of muscle contraction is called the _______. contraction velocity twitch velocity isometric velocity shortening velocity

For a weight to be lifted, which of the following must occur? An isometric muscle contraction with a force greater than the load. An isotonic muscle contraction with a force greater than the load. An isometric muscle contraction with a force less than the load. An isotonic muscle contraction with a force less than the load.

When the load to be lifted increases in weight, the latent period _______. decreases increases decreases and disappears remains unchanged

The shortest duration of muscle contraction occurs with _______. the lightest load the heaviest load the intermediate load The duration of muscle contraction doesn't vary with the load lifted.

The velocity of shortening _______. increased as the weight increased increased as the weight decreased decreased as the weight increased decreased as the weight increased and increased as the weight decreased

As the weight increased, the distance the weight was lifted _______. decreased until the weight was not moved at all increased did not change decreased