CHAP: 6 CONTRACTION OF SKELETAL MUSCLE

Question 1

how many % of the body is skeletal muscle?

Answer 1

40%

Question 2

how many % is smooth & cardiac muscle?

Answer 2

10%

Question 3

state the right statement about the fiber.

Answer 3

2% of the fiber, each fiber is usually innervated by only one nerve ending, located near the middle of the fiber.

Question 4

is a thin membrane enclosing a skeletal muscle fiber?

Answer 4

Sarcolemma

Question 5

Sarcolemma consist of a true cell membrane called ______ & a outer coat made up of a thin layer of _______ that contains numerous thin collagen fibers.

Answer 5

plasma membrane Y& polysaccharide

Question 6

are composed of actin & myosin filaments

Answer 6

Myofibrils

Question 7

this are large polymerized protein molecules that are responsible for the actual muscle contraction.

Answer 7

Actin & Myosin filaments

Question 8

is a light bands contain only acting filaments & are called ____, because they are isotropic to polarized light,

Answer 8

I bands

Question 9

is a dark bands contain myosin filaments as well as the ends of actin filaments where they overlap the myosin & are called?

Answer 9

A bands

Question 10

______, which itself is composed of filamentous proteins different from the actin & myosin filaments, passes crosswise across the myofibril & also crosswise from myofibril to myofibril.

Answer 10

Z disc

Question 11

The portion of the myofibril that lies between 2 successive Z disc is called?

Answer 11

sacromere

Question 12

_______ this is one of the largest protein molecules; it’s a very springy; keep the myosin & actin filaments in place.

Answer 12

Titin filamentous

Question 13

is the intracellular fluid between myofibrils?

Answer 13

Sarcoplasm

Question 14

sarcoplasm contain large quantities of :

Answer 14

1. potassium
2. magnesium
3. phosphate
4. plus multiple protein enzyme

Question 15

is a specialized endoplasmic reticulum of skeletal muscle?

Answer 15

Sarcoplasmic reticulum

Question 16

muscle contraction occurs by a what type of mechanism?

Answer 16

sliding filament mechanism

Question 17

is composed of 6 polypeptide chains (2 heavy chains & 4 light chains )

Answer 17

myosin molecule

Question 18

the 2 heavy chains wrap spirally around each other to form a double helix, which is called?

Answer 18

tail

Question 19

one of the end of each of these chains is folded bilaterally into a globular polypeptide structure called a ?

Answer 19

Myosin head

Question 20

the protruding arms & heads together are called?

Answer 20

cross-bridges

Question 21

each cross-bridge is flexible at 2 points called ?

Answer 21

hinges

Question 22

Actin filaments are composed of :

Answer 22

1. Actin
2. Tropomysin
3. Troponin

Question 23

the backbone of the actin filament is a double-stranded _______ represented by the 2 strands that are wound in a helix in the same manner as the myosin molecule.

Answer 23

F-actin protein molecule

Question 24

_______ are the active sites on the actin filaments w/ which the cross-bridges of the myosin filament interact to cause muscle contraction.

Answer 24

ADP molecules

Question 25

in the resting state, the ______ molecule lie on top of the active sites of the actin strands so that attraction cannot occur between the actin & myosin filaments to cause contraction.

Answer 25

Tropomyosin

Question 26

These _____ are actually complexes of 3 loosely bound protein subunits, plays a specific role in controlling muscle contraction.

Answer 26

Troponin

Question 27

a pure actin filament without the prescence of this _______ the binding of myosin & actin will not take place.

Answer 27

Troponin-tropomyosin complex

Question 28

this postulated walk-along mechanism for contraction.

Answer 28

Walk along theory

Question 29

the greater the amount of work performed by the muscle the greater the amount pf ATP that is cleaved, this is called?

Answer 29

Fenn effect

Question 30

_______ decrease as the muscle is stretched beyond it's normal length, it's called?

Answer 30

Active tension

Question 31

Most of energy is actuate the walk-along mechanism, but small amounts are used for:

Answer 31

1. Pumping calcium 2. Pumping sodium 3. Pumping potassium ions

Question 32

pumping this ____ through the muscle fiber membrane to maintain appropriate ionic environment for propagation of muscle fiber action potentials.

Answer 32

Pumping sodium & potassium ions

Question 33

what are the several energy for rephosphorylation :

Answer 33

1. phosphocreatine 2. Glycogen 3. Oxidative metabolism

Question 34

this is the first source of energy, which carries a high-energy phosphate bond similar to the bonds of ATP, therefore it instantly cleaved & it releases energy caused bonding of a new phosphate ion to ADP to reconstitue the ATP

Answer 34

Phosphocreatine

Question 35

phosphocreatine in the muscle is capable of causing maximal muscle contraction for only how many second?

Answer 35

5-8 seconds

Question 36

this is the second source of energy, it's stored in the muscle cells & rapid enzymatic breakdown of this ______ to pyruvic acid & lactic acid liberates energy that is used to convert ADP to ATP.

Answer 36

glycogen or "glycolysis"

Question 37

what are the 2 importance of glycogen

Answer 37

1. glyocolytic reaction can occur even without the prescence of oxygen, so muscle contraction can be sustained for how many second 2. rate of formation of ATP by the glycolytic process is about 2.5x as rapid as ATP

Question 38

this is the final source of energy; this means combining oxygen with the end product of glycolysis & w/ various other cellular foodstuffs to liberate ATP.

Answer 38

Oxidative metabolism

Question 39

what are the foodstuffs that is consumed in oxidative metabolism?

Answer 39

Carbohydrates, Fat & Protein

Question 40

more than _____ of all energy is used by the muscle for sustained, long term contraction.

Answer 40

95%

Question 41

when the muscle does not shorten during contraction

Answer 41

isometric

Question 42

when the muscle does shorten, but the tension of the muscle remains constant throughout the contraction.

Answer 42

isotonic

Question 43

what is the characteristics of FAST FIBERS;

Answer 43

1. Larger for great contraction 2. Extensive sarcoplasmic reticulum is present for rapid release of calcium ions to initiate contraction 3. Large amount of glycolytic enzymes are present for rapid release of energy by the glycolytic process 4. Has less extensive blood supply because oxidative metabolism is secondary importance 5. Have fewer mitochondria because oxidative metabolism is secondary. 6. Deficit of red myoglobin, gives it name the white muscle.

Question 44

Characteristics of SLOW FIBER;

Answer 44

1. Smaller fiber 2. Innervated by smaller nerve fibers 3. Have a more extensive blood vessel system & more capillaries to supply extra amount of oxygen 4. Has greatly increased nu,ber of mitochondria to support high levels of oxidative metabolism 5. It contains large amount of myoglobin, gives the slow fiber the reddish appearance thus called red muscle.

Question 45

All the muscle fibers innervated by a single nerve fiber are called?

Answer 45

Motor unit

Question 46

______ means the adding together of individual twitch contraction to increase the intensity of overall muscle contraction.

Answer 46

Summation

Question 47

summation occurs in 2 ways:

Answer 47

1. By increasing number of motor units contracting simultaneously called MULTIPLE FIBER SUMMATION 2. By increasing the frequency of contraction which is called FREQUENCY SUMMATION & can lead to TETANIZATION

Question 48

______ allows the gradations of muscle force during weak contraction to occur in small steps, whereas the steps become progressively greater when large amount of force are required.

Answer 48

Size principle

Question 49

_______ is believed to be caused primarily by increasing Ca+ ions in the cytosol because of the release of more & more ions in S. reticulum w/ each successive muscle action potential & failure of the S. reticulum to recapture the ions immediatley.

Answer 49

Staircase effect

Question 50

Normal skeletal muscle fiber do not contract without an action potenial this ______ results entirely from a low rate of nerve impulses coming from the spinal cord.

Answer 50

Muscle tone

Question 51

several hours after death, all the muscle of the body go into a state of contracture called?

Answer 51

Rigor mortis

Question 52

_______ contains as many as 5x the normal number of muscle fivers for each motorneuron coming from the spinal cord.

Answer 52

Macromotor units

Question 53

the fibrous tissue that replaces the muscle fibers during denervation atrophy has a tendency to continue shortening for many months which is called?

Answer 53

contracture

Question 54

when a muscle loses it's nerve supply; it can no longer recieves the contractile signals that are required to maintain normal muscle size, therefore this ______ begins.

Answer 54

ATROPHY