Chapter 6: Contraction of Skeletal Muscle

Question 1

how many percent of the body is skeletal muscle

Answer 1

40%

Question 2

how many percent is smooth
and cardiac muscle in the body?

Answer 2

10%

Question 3

The sarcolemma consists of a true cell membrane, called
the?

Answer 3

plasma membrane

Question 4

outer coat made
up of a thin layer of polysaccharidematerial that
contains numerous thin collagen fibrils

Answer 4

plasma membrane

Question 5

turn collect into bundles to form the muscle tendons thatthen insert into the bones.

Answer 5

tendon fibers

Question 6

Each muscle fiber contains
several hundredto several thousand

Answer 6

myofibrils

Question 7

Each myofibril is composed
of about?

Answer 7

1500 myosin filaments and 3000 actin filaments

Question 8

The light
bands contain only actin filaments and are called?

Answer 8

I bands

Question 9

dark bands contain

Answer 9

myosin filaments

Question 10

ends of the actin filaments where they
overlap the myosin, and are called?

Answer 10

A bands

Question 11

the small projections from the sides of the
myosin filaments

Answer 11

cross-bridges

Question 12

ends of the
actin filaments are attached to a so-called?

Answer 12

Z-discs

Question 13

composed of
filamentous proteins different from the actin and
myosin filaments

Answer 13

Z disc

Question 14

The portion of the myofibril (or of the whole
muscle fiber) that lies between two successive Z
discs is called a?

Answer 14

sarcomere

Question 15

at
this length the muscle is capable of generating its greatest force of contraction called

Answer 15

sarcoplasm

Question 16

sarcoplasm surrounding the myofibrils
of each muscle fiber is an extensive reticulum called the ?

Answer 16

sarcoplasmic reticulum

Question 17

This
reticulum has a special organization that is extremely important in controlling muscle contraction

Answer 17

sarcoplasmic reticulum

Question 18

achieved by a large number of filamentous molecules
of a protein called?

Answer 18

titin

Question 19

acts on a local area of the
musclefiber membrane to open multiple
“acetylcholine-gated
”cation channels through
protein molecules floating inthe membrane

Answer 19

acetylcholine

Question 20

initiate attractive forces
between the actin and myosin filaments, causing them to slide along side each other, which is
the contractile process

Answer 20

calcium ions

Question 21

the Z discs have been
pulled bythe actin filaments up to the ends of
the myosin filaments. Thus, muscle contraction
occurs by a

Answer 21

sliding filament mechanism

Question 22

what causes the actin filaments to slide
inward among the myosin filaments?

Answer 22

caused by forces generated by interaction of the
cross-bridges from the myosin filaments with the
actin filaments.

Question 23

The backbone of
the actin filament is a double-stranded

Answer 23

F-actin protein molecule

Question 24

Each strand of the double F-actin helix is
composed of polymerized

Answer 24

G actin molecules

Question 25

the active sites on the actinfilaments with which the cross-bridges of the myosin filaments interact to cause muscle contraction

Answer 25

ADP molecules

Question 26

Attached to one end of each tropomyosin molecule is a

Answer 26

troponin

Question 27

The actin filament also contains another protein

Answer 27

tropomyosin

Question 28

Attached intermittently along the sides of the tropomyosin molecules are still other protein molecules called

Answer 28

troponin

Question 29

has a strong affinity for actin

Answer 29

troponin I

Question 30

subunits for tropomyosin

Answer 30

troponin T

Question 31

subunits for tropomyosin

Answer 31

troponin T

Question 32

subunits for calcium ions

Answer 32

troponin C

Question 33

The new alignment of forces causes the head to tilt toward thearm and to drag the actin filament along with it

Answer 33

power stroke

Question 34

the greater the amount of work performed by the muscle, the greater the amount of ATP that is cleaved

Answer 34

fenn effect

Question 35

the increase in tension that occurs during contraction

Answer 35

active tension

Question 36

contracts rapidly when it contracts against no load—to a state of full contraction in about 0.1 second for the average muscle

Answer 36

skeletal muscle

Question 37

When a muscle contracts against a load, it performs

Answer 37

work

Question 38

The second important source of energy, which is used to reconstitute both ATP and phosphocreatine

Answer 38

glycolysis

Question 39

third and final source of energy. means combining oxygen with theend products of glycolysis and with various other cellular foodstuffs to liberate ATP

Answer 39

oxidative metabolism

Question 40

3 sources of energy for muscle contractions

Answer 40

1. phosphocreatine 2. glycolysis 3. oxidative metabolism

Question 41

what do you call of muscle contraction when the muscle does not shorten during contraction

Answer 41

isometric

Question 42

when it does shorten but thetension on the muscle remains constant throughout the contraction

Answer 42

isotonic

Question 43

Muscles that react rapidly, including anterior tibialis

Answer 43

fast muscle fibers

Question 44

muscles such as soleus that respond slowly but with prolonged contraction

Answer 44

slow fibers

Question 45

Slow Fibers (Type 1, Red Muscle)

Answer 45

(1) Smaller fibers (2)Also innervated by smaller nerve fibers (3) More extensive blood vessel system and capillaries to supply extra amount of oxygen (4) Greatly increased numbers of mitochondria,also to support high levels of oxidative metabolism (5) Fiber Contain large amounts of myoglobin, an iron-containing protein similar to hemoglobin in red blood cells

Question 46

The myoglobin gives the slow muscle a reddish appearance andthe name?

Answer 46

red muscle

Question 47

Fast Fibers (Type II, White Muscle)

Answer 47

(1) Large fibers for great strength of contraction (2) Extensive sarcoplasmic reticulum for rapid release of calcium ions to initiate contraction (3) Large amounts of glycolytic enzymes for rapid release of energy by the glycolytic process (4) Less extensive blood supply because oxidative metabolism is of secondary importance (5) Fewer mitochondria, also because oxidative metabolism is secondary

Question 48

A deficit of red myoglobin in fast muscle gives it the name

Answer 48

white muscle

Question 49

All the muscle fibers innervated bya single nerve fiber are called a

Answer 49

motor unit

Question 50

means the adding together of individual twitch contractions to increase the intensity ofoverall muscle contraction

Answer 50

summation

Question 51

Summation occurs in two ways;

Answer 51

✓ multiple fiber summation ✓ frequency summation

Question 52

increasing the number of motor units contracting simultaneously

Answer 52

multiple fiber summation

Question 53

increasing the frequency of contraction

Answer 53

frequency summation

Question 54

frequency summation can lead to?

Answer 54

tetanization

Question 55

When the frequency reaches acritical level, the successive contractions eventually become so rapid that they fuse together and the whole muscle contraction appears to be completely smooth and continuous

Answer 55

tetanization

Question 56

the strength of contractionincreases to a plateau, a phenomenon called the?

Answer 56

staircase effect or treppe

Question 57

Even when muscles are at rest, a certain amount of tautness usually remains. This is called?

Answer 57

muscle tone

Question 58

study of different types of muscles, lever systems, and their movements is called?

Answer 58

kinesiology

Question 59

total mass of a muscle increases

Answer 59

muscle hypertrophy

Question 60

total mass of a muscle decrease

Answer 60

muscle atrophy

Question 61

causing enlargement of the individual muscle fibers

Answer 61

simple fiber hypertrophy

Question 62

occurs to a much greater extent when themuscle is loaded during the contractile process

Answer 62

hypertrophy

Question 63

The pathway that appears to account for much of the protein degradation in a muscle undergoing atrophy is the

Answer 63

ATP dependent ubiquitin- proteasome pathway

Question 64

increase in fiber number

Answer 64

fiber hyperplasia

Question 65

fibrous tissue that replaces the muscle fibers during denervation atrophy also has a tendency to continueshortening for many months, which is called

Answer 65

contracture

Question 66

causes large motor units

Answer 66

macromotor units

Question 67

muscles of the body go into a state of contracture called? that is, the muscles contract and become rigid

Answer 67

rigor mortis