Chapter 8 Skeletal Muscle And Function

Front 1

The human body contains over _____ skeletal muscles, which constitutes 40-50% total body weight.

Back 1

400

Front 2

Skeletal muscle performs three important functions:
1. Force generation for ________ and _______.
2. Force generation for _______ support
3. Heat production during long periods of ______ stress.

Back 2

locomotion, breathing
postural
cold

Front 3

Muscles that decrease joint angles are called _______, and muscles that increase joint angles are called _______.

Back 3

flexors
extensors

Front 4

Individual muscle fibers are separated from each other and held in position by connective tissue called ______.

Back 4

fascia

Front 5

The outermost layer that surrounds the entire muscle is called the ___________.

Back 5

epimysium

Front 6

As we move inward from the epimysium, connective tissue called the _________ surronds individual bundles of muscle fibers.

Back 6

perimysium

Front 7

These individual bundles of muscle fibers are called a ________.

Back 7

fascicle

Front 8

Each muscle fiber within the fasciculus is surrounded by connective tissue called the ___________.

Back 8

endomysium

Front 9

Just below the endomysium and surrounding each muscle fiber is another layer of protective tissue called the ________ ________.

Back 9

external lamina

Front 10

Unlike other cells in the body, muscle cells are ___________ (have many nuclei).

Back 10

multinucleated

Front 11

Each individual muscle fiber is a thin, elongated cylinder that generally extends the length of the muscle. The cell membrane surrounding the muscle fiber cell is called the ____________.

Back 11

sarcolemma

Front 12

Located above the sarcolemma and below the external lamina are a group of muscle precursor cells called _______ cells. These are undifferentiated cells that play a key role in muscle growth and repair.

Back 12

Satellite

Front 13

True/False If muscle fiber cells are destroyed they cannot be replaced by cell division.

Back 13

True

Front 14

Satellite cells can contribute to growth during ________ ________ by dividing and contributing nuclei to existing muscle fibers. Increasing the number of nuclei within muscle fibers enhances the fibers' ability to synthesize ________ and, therefore, assists in muscle growth.

Back 14

strength training
proteins

Front 15

In a _________ _______, there is a certain volume of cytoplasm surrounding each nucleus. To keep this constant, new nuclei are incorporated into skeletal muscle fibers during growth, this occurs in hypertrophy and atrophy.

Back 15

myonuclear domain

Front 16

Beneath the sarcolemma lies the ________, which contains the cellular proteins, organelles and myofibrils.

Back 16

sarcoplasm

Front 17

________ are numerous threadlike structures that contain the contractile proteins and are composed of two major types of protein filaments: thick and thin.

Back 17

myofibrils

Front 18

Thick filaments are composed of the protein ______ and thin filaments are composed of the protein _____.

Back 18

myosin
actin

Front 19

Located on the actin molecule itself are two additional proteins, _______ and ___________.

Back 19

troponin and tropomyosin

Front 20

Myofibrils can be further subdivided into individual segments called __________.

Back 20

sarcomeres

Front 21

Sarcomeres are divided from each other by a thin sheet of structure proteins called a __ line or __ disk.

Back 21

Z

Front 22

Mysosin filaments are located primarily within the (light/dark) portion of the sarcomere, which is called the ___ band, while actin filaments occur primarily in the (light/dark) portion of the sarcomere called ___ bands.

Back 22

dark A
Light I

Front 23

In the center of the sarcomere is a portion of the myosin filament with no overlap of the actin. This is the __ line.

Back 23

H

Front 24

Within the sarcoplasm of muscle is a network of membranous channels that surrounds each myofibril and runs parallel with it. These channels are called the __________ ________ and are storage sites for calcium, which plays an important role in muscular contraction.

Back 24

sarcoplasmic reticulum

Front 25

Another set of membranous channels called the _________ _______ extends inward from the sarcolemma and passes completely through the fiber.

Back 25

Transverse tubules

Front 26

These transverse tubules pass between two enlarged portions of the sarcoplasmic reticulum called the _________ __________.

Back 26

Terminal cisternae

Front 27

Each skeletal muscle is connected to a nerve fiber branch coming from a nerve cell. These nerve cells are called ______ _______, and they extend outward from the spinal cord.

Back 27

motor neurons

Front 28

The motor neuron and all the muscle fibers it innervates are called a _____ _____.

Back 28

motor unit

Front 29

Stimulation from motor neurons initiates the contraction process. The site where the motor neuron and muscle cell meet is called the ____________ _______.

Back 29

neuromuscular junction

Front 30

At this junction the sarcolemma forms a pocket that is called the ______ ____ ______.

Back 30

motor end plate

Front 31

The end of the motor neuron does not physically make contact with the muscle fiber, but is separated by a short gap called the neuromuscular _____.

Back 31

cleft

Front 32

When a nerve impulse reaches the end of the motor nerve, the neurotransmitter ______________ is released and diffuses across the synaptic cleft to bind with _________ _____ on the motor end plate.

Back 32

acetylcholine
receptor sites

Front 33

This causes an increase in the permeability of the sarcolemma to ______, resulting in a ___________ called the ___-______ potential

Back 33

sodium
depolarization
end-plate

Front 34

Muscular contraction is a complex process involving a number of cellular proteins and energy production systems. The final result is a sliding of ______ over ______, which causes the muscle to shorten and therefore develop tension.

Back 34

actin
myosin

Front 35

The process of muscular contraction is best explained by the _______ _________ _______ of contraction.

Back 35

sliding filament model

Front 36

True/False Actin and myosin myofilaments do not change length during contraction.

Back 36

True

Front 37

During contraction, ______ myofilaments at each end of the sarcomere slide past the ______ myofilaments toward eachother. As a result the __ disks are brought closer together, and the sarcomere shortens.

Back 37

actin
myosin
Z

Front 38

As the actin myofilaments slide over the myosin filaments, the __ zones and the ___ bands narrow. The __ bands, which are equal to the length of the myosin myofilaments, do not narrow, because the length of myosin myofilaments does not change.

Back 38

H
I
A

Front 39

Myosin _____ _______ are are always attached to actin, but the strength of the attachment varies from "weak" bond to a "strong" bond.

Back 39

cross bridges

Front 40

The "pulling" of actin over the myosin molecule results in muscle (shortening/lengthening) and the generation of ______.

Back 40

shortening
force

Front 41

The term _______/_________ _______ refers to the sequence of events in which a nerve impulse (action potential) reaches the muscle membrane and leads to muscle shortening by cross-bridge activity.

Back 41

excitation-contraction coupling

Front 42

The energy for muscular contraction comes from the breakdown of ___ by the enzyme _______ _____.

Back 42

ATP
myosin ATPase

Front 43

Myosin ATPase is located on the "____" of the myosin cross-bridge.

Back 43

head

Front 44

The first step in the process of muscular contraction begins with a nerve impulse arriving at the ____________ _______.

Back 44

neuromuscular junction

Front 45

The action potential from the motor neuron causes the release of __________ into the synaptic cleft of the neuromuscular junction, and ATC binds to receptors on the _____ _____ ______, producing an end plate potential that leads to depolarization of the muscle cell.

Back 45

acetycholine
motor end plate

Front 46

This depolarization is conducted down the _______ _________deep into the muscle fiber.

Back 46

transverse tubules

Front 47

When the action potential reaches the ___________ __________ and from the lateral sac, calcium is released and diffuses into the muscle to bind to a protein on the actin filament called _________.

Back 47

sarcoplasmic reticulum
troponin

Front 48

As calcium binds to troponin, there is a position change in _________ such that the active sites on the actin are uncovered. This permits the strong binding of a "cocked or energized" myosin cross bridge on the actin molecule.

Back 48

tropomyosin

Front 49

The strong cross-bridge binding initiates the release of _____ stored within the myosin molecule producing an angular movement of each cross-bridge on the actin molecule.

Back 49

ATP

Front 50

True/False ATP is needed to break the strong binding state of the myosin cross bridges after muscle shortening has occurred.

Back 50

True

Front 51

What is needed to repeat the contraction cycle and if it is lost leads to fatigue?

Back 51

Calcium

Front 52

The signal to stop contraction is the absence of the nerve impulse at the _____________ ________. When this occurs, an energy-requiring Ca++ pump located within the sarcoplasmic reticulum begins to move Ca++ back into the sarcoplasmic reticulum.

Back 52

neuromuscular junction

Front 53

The percentage of fast vs. slow fiber types contained in skeletal muscles can be influenced by _______, blood levels of ________, and the exercise habits of the individual.

Back 53

genetics
hormones

Front 54

In general, the two key biochemical characteristic of muscle that are important to muscle function are (1) the _________ capacity and (2) the type of _______ isoform.

Back 54

oxidative
ATPase

Front 55

The oxidative capacity is determined by the number of _________, the number of _________ surrounding the fiber and the amount of ________ within the fiber.

Back 55

mitochondria
capillaries
myoglobin

Front 56

The importance of ATPase isoforms is the _______ that they degrade ATP.

Back 56

speed

Front 57

In comparing contractile properties of muscle fiber types, three performance characteristics are important (1) maximal ______ production (2) speed of _________, (3) muscle _____ efficiency

Back 57

force
contraction
fiber

Front 58

Maximal force production is described as the force per unit of _____-sectional area.

Back 58

cross

Front 59

The contraction speed of muscle fibers is compared by measuring the maximal shortening ______ of individual fibers. _____ represents the highest speed at which a fiber can shorten.

Back 59

velocity
Vmax

Front 60

The efficiency of a muscle fiber is made by dividing the amount of ____ used by the amount of force produced.

Back 60

ATP

Front 61

______ __ fibers (also called slow-oxidative or slow-twitch fibers) contain large numbers of oxidative enzymes like mitochondria and are surrounded by more capillaries than any of the fibers as well as high concentrations of myoglobin.

Back 61

Type I

Front 62

True/False Type I fibers produce a FASTER Vmax compared to fast fibers and are LESS efficient than fast fibers.

Back 62

False

Front 63

______ ___ fibers (sometimes called fast-twitch fibers or fast-glycolytic fibers) have a relatively small number of mitochondria, have a limited capacity for aerobic metabolism, and are less resistant to fatigue than slow fibers. However, these fibers are rich in glycolytic enzymes which provide them with a large anaerobic capacity.

Back 63

Type IIx

Front 64

Type IIx fibers are less efficient than all other fiber types. This low efficiency is due to the high myosin ________ activity, which results in a greater energy expenditure per unit of work performed.

Back 64

ATPase

Front 65

A second type of fast fiber is the ______ ___ fiber (also called intermediate fibers or fast-oxidative glycolytic fibers) and contain biochemical and fatigue characteristics that are between type IIx and type I fibers.

Back 65

Type IIa

Front 66

The specific tension of type IIx fibers is greater than type __ fibers.

Back 66

I

Front 67

Long distance runners utilize which fiber type more: Type I, Type IIx and IIa?

Back 67

Type I

Front 68

Track sprinters utilize which fiber type more: Type I, Type IIx and IIa?

Back 68

Type IIx and IIa

Front 69

Strength training can lead to an increase in muscle size through ___________ and force production.

Back 69

hypertrophy

Front 70

Endurance exercise does not increase muscle size or strength but results in an increase in muscle ________ capacity (mitochondrial number increases)

Back 70

oxidative

Front 71

What type of training can convert fast fiber types to slow fiber types?

Back 71

Endurance training

Front 72

Research has proven that during the first ____ days of muscle disuse, most of the initial atrophy occurs due to increased muscle protein breakdown.

Back 72

2

Front 73

___% of muscle mass is lost between the ages of 25-50 years.

Back 73

10

Front 74

Additional ___% of muscle is lost between ages of 50-80 years

Back 74

40

Front 75

As aging occurs, what type of fibers are lost and which ones are gained?

Back 75

Fast fibers lost, slow fibers gained

Front 76

__________ muscle action is referred to as a static exercise such as a plank.

Back 76

Isometric

Front 77

Exercise that involves movement of body parts is called dynamic exercise or ________ exercise.

Back 77

isotonic

Front 78

A muscle action that results in muscular shortening with movement of a body part is called _________ action.

Back 78

concentric

Front 79

An _________ action occurs when a muscle is activated and force is produced but the muscle lengthens.

Back 79

eccentric

Front 80

If a muscle is given a single stimulus, such as a brief electrical shock applied to the nerve innervating it, the muscle responds with a simple _____.

Back 80

twitch

Front 81

During a muscle twitch there are three periods. Name them and their respective time periods.

Back 81

Latent period ~5 ms
Contraction 40 ms
Relaxation 50 ms

Front 82

Is the speed of shortening greater in fast fibers or in short fibers?

Back 82

fast fibers

Front 83

The amount of force generated during muscular contraction is dependent on the following factors:
1. types and number of motor _____ recruited
2. the ______ muscle length
3. the nature of the motor unit's ______ stimulation

Back 83

units
initial
neural

Front 84

The addition of muscle twitches is termed _________.

Back 84

summation

Front 85

When the frequency of neural stimulation to a motor unit is increased, individual contractions are fused in a sustained contraction called a _______.

Back 85

tetanus

Front 86

The peak force generated by muscle (increases/decreases) as the speed of movement increases. However, the amount of power generated by a muscle group _______ as a function of movement velocity.

Back 86

decreases
increases