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systemic physiology > CHAP: 6 CONTRACTION OF SKELETAL MUSCLE > Flashcards

CHAP: 6 CONTRACTION OF SKELETAL MUSCLE Flashcards

1
Q

how many % of the body is skeletal muscle?

A

40%

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2
Q

how many % is smooth & cardiac muscle?

A

10%

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3
Q

state the right statement about the fiber.

A

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

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4
Q

is a thin membrane enclosing a skeletal muscle fiber?

A

Sarcolemma

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5
Q

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

A

plasma membrane Y& polysaccharide

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6
Q

are composed of actin & myosin filaments

A

Myofibrils

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7
Q

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

A

Actin & Myosin filaments

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8
Q

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

A

I bands

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9
Q

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

A

A bands

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10
Q

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

A

Z disc

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11
Q

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

A

sacromere

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12
Q

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

A

Titin filamentous

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13
Q

is the intracellular fluid between myofibrils?

A

Sarcoplasm

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14
Q

sarcoplasm contain large quantities of :

A
  1. potassium
  2. magnesium
  3. phosphate
  4. plus multiple protein enzyme
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15
Q

is a specialized endoplasmic reticulum of skeletal muscle?

A

Sarcoplasmic reticulum

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16
Q

muscle contraction occurs by a what type of mechanism?

A

sliding filament mechanism

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17
Q

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

A

myosin molecule

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18
Q

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

A

tail

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19
Q

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

A

Myosin head

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20
Q

the protruding arms & heads together are called?

A

cross-bridges

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21
Q

each cross-bridge is flexible at 2 points called ?

A

hinges

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22
Q

Actin filaments are composed of :

A
  1. Actin
  2. Tropomysin
  3. Troponin
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23
Q

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.

A

F-actin protein molecule

24
Q

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

A

ADP molecules

25
Q

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.

A

Tropomyosin

26
Q

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

A

Troponin

27
Q

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

A

Troponin-tropomyosin complex

28
Q

this postulated walk-along mechanism for contraction.

A

Walk along theory

29
Q

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

A

Fenn effect

30
Q

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

A

Active tension

31
Q

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

A
  1. Pumping calcium
  2. Pumping sodium
  3. Pumping potassium ions
32
Q

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

A

Pumping sodium & potassium ions

33
Q

what are the several energy for rephosphorylation :

A
  1. phosphocreatine
  2. Glycogen
  3. Oxidative metabolism
34
Q

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

A

Phosphocreatine

35
Q

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

A

5-8 seconds

36
Q

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.

A

glycogen or “glycolysis”

37
Q

what are the 2 importance of glycogen

A
  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
38
Q

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.

A

Oxidative metabolism

39
Q

what are the foodstuffs that is consumed in oxidative metabolism?

A

Carbohydrates, Fat & Protein

40
Q

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

A

95%

41
Q

when the muscle does not shorten during contraction

A

isometric

42
Q

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

A

isotonic

43
Q

what is the characteristics of FAST FIBERS;

A
  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.
44
Q

Characteristics of SLOW FIBER;

A
  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.
45
Q

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

A

Motor unit

46
Q

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

A

Summation

47
Q

summation occurs in 2 ways:

A
  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
48
Q

______ 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.

A

Size principle

49
Q

_______ 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.

A

Staircase effect

50
Q

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.

A

Muscle tone

51
Q

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

A

Rigor mortis

52
Q

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

A

Macromotor units

53
Q

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

A

contracture

54
Q

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.

A

ATROPHY

55
Q
A

systemic physiology (4 decks)

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