Physio Lab Homework

Question 1

Skeletal muscles are connected to bones by

Answer 1

Tendons

Question 2

Skeletal muscles are composed of hundreds to thousands of individual cells called?

Answer 2

Fibers

Question 3

The term motor unit refers to

Answer 3

One motor neuron and all of the skeletal muscle fibers it innervates

Question 4

The motor neuron and muscle fiber intersect at what is called

Answer 4

the neuromuscular junction

Question 5

A twitch is

Answer 5

One contractile response to a single action potential

Question 6

What is the period of time that elapses between the generation of an action potential and the start of muscle tension development in the muscle fiber?

Answer 6

The latent period

Question 7

What occurs during the latent period of these isometric contractions?

Answer 7

All of the steps of excitation-contraction coupling occur

Question 8

An action potential in the motor neuron triggers the release of which neurotransmitter?

Answer 8

Acetylcholine

Question 9

The term skeletal muscle fiber refers to

Answer 9

an individual skeletal muscle cell

Question 10

The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called?

Answer 10

an EPP (end-plate potential)

Question 11

Which of the following is not a phase of skeletal muscle twitch?

Answer 11

hyperpolarization phase

Question 12

Which of the following correctly matches the twitch phase with its definition?

Answer 12

The contraction phase: the time between the end of the latent period and peak muscle tension

Question 13

Skeletal muscle fibers are innervated (stimulated) by

Answer 13

Motor neuron

Question 14

A single action potential propagating down a motor axon results in

Answer 14

A single action potential and single contractile event in the muscle fibers it innervates

Question 15

In resting skeletal muscle, calcium is stored in

Answer 15

The sarcoplasmic reticulum

Question 16

During the latent period for an isometric contraction

Answer 16

the cellular events involved in the excitation-contraction coupling occur

Question 17

What is the lowest stimulus voltage that induces active force in the skeletal muscle?

Answer 17

Threshold voltage

Question 18

Motor unit recruitment refers to

Answer 18

an increase in the number of active muscle fibers to increase the force developed in the muscle.

Question 19

Active tension (or force) in a skeletal muscle fiber results from

Answer 19

Activation of cross bridge cycling via increased intracellular calcium levels.

Question 20

The (blank) is the minimal stimulus needed to cause depolarization of the muscle plasma membrane (sarcolemma)

Answer 20

Threshold voltage

Question 21

By definition, the (blank) is the amount of stimulus required to successfully recruit ALL the muscle fibers into developing maximum force.

Answer 21

Maximal voltage

Question 22

A sufficiently strong electrical stimulus applied to an isolated, mounted skeletal muscle induces the development of muscle force, or muscle tension. Which of the following statements concerning this observation is true?

Answer 22

The electrical stimulus mimics acetylcholine release at the neuromuscular junction

Question 23

During a single twitch of a skeletal muscle

Answer 23

Maximal force is never achieved

Question 24

When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as

Answer 24

Wave summation

Question 25

Wave summation is achieved by

Answer 25

Increasing the stimulus frequency (the rate of stimulus delivered to the muscle)

Question 26

Wave summation increased the force produced in the muscle. Another way to increase the force produced by a muscle is to

Answer 26

increase the number of activated motor units

Question 27

Which of the following is NOT one of the ways that the body can increase the force produced by a skeletal muscle?

Answer 27

Application of higher voltages to the whole muscle

Question 28

When a muscle receives a stimulus frequency that causes non-overlapping twitches to follow each other closely in time such that the peak tension of each twitch rises in the stepwise fashion up to a plateau value, the result is known as

Answer 28

treppe

Question 29

Stimulus frequency refers to

Answer 29

The rate that stimulating voltage pulses are applied to an isolated whole skeletal muscle

Question 30

Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus?

Answer 30

Muscle tension increases and decreases during a state on unfused tetanus

Question 31

When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle, the muscle has reached its

Answer 31

Maximal tetanic tension

Question 32

The term tension refers to

Answer 32

Sustained muscle tension due to very frequent stimuli

Question 33

When skeletal muscle twitches fuse so that the peaks and valleys of each twitch become indistinguishable from each other, the muscle is in a state known as

Answer 33

Complete (fused) tetanus

Question 34

A decline in a muscle's ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation is called

Answer 34

Fatigue

Question 35

Which of the following is not thought to be a contributing factor to the development of fatigue

Answer 35

Buildup of Ca2 in the muscle fibers

Question 36

When did the length of the intervening rest period affect the length of time the skeletal muscle can maintain maximum tension once the stimulator is turned on again?

Answer 36

Intercellular concentrations of ADP and Pi declined during the rest period

Question 37

During cross bridge cycling in skeletal muscle, force is created by the

Answer 37

power stroke of the myosin heads

Question 38

The term tetanus refers to

Answer 38

Sustained muscle tension due to repetitive stimuli

Question 39

During fatigue

Answer 39

the number of active cross bridges begins to decline although the rate of stimulus delivery (frequency) remains constant

Question 40

If an intervening rest period is imposed on active skeletal muscle

Answer 40

the development of fatigue will be delayed

Question 41

During isometric contraction

Answer 41

the skeletal muscle is generating force, but it remains at a fixed length

Question 42

The force that results from muscles being stretched is

Answer 42

passive force

Question 43

Active force

Answer 43

is determined by the amount of myosin bound to actin

Question 44

When you generate the isometric length-tension curve, which of the following forces will NOT be indicated?

Answer 44

tetanic force

Question 45

Passive force in skeletal muscle is largely caused by

Answer 45

the protein titin

Question 46

When skeletal muscle is stimulated and generates force but remains at a fixed length

Answer 46

the muscle is contracting isometrically

Question 47

in skeletal muscle, active force stimulated through a range of muscle lengths

Answer 47

will utilize ATP hydrolysis to drive the cross bridge cycle

Question 48

Which of the following is NOT depicted in a typical skeletal muscle isometric length-tension curve?

Answer 48

Time

Question 49

Maximal active tension will be produced in a skeletal muscle fiber when

Answer 49

the fiber is at its resting length

Question 50

During an isotonic concentric contraction, the

Answer 50

force generate by the muscle is greater than the weight of the attached load

Question 51

During an isotonic concentric contraction

Answer 51

the latent period increases with heavier loads

Question 52

During the latent period for an isotonic concentric contraction

Answer 52

cross bridges cycle and when muscle tension exceeds the load, muscle shortening occurs

Question 53

Muscle shortening velocity

Answer 53

decreases with heavier loads

Question 54

An isotonic contraction of a muscle is one in which

Answer 54

the length of the muscle changes

Question 55

When lifting a heavy load

Answer 55

the muscle shortening velocity is decreased in comparison with lighter loads