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BPK 142 - Lecture > 4 - Skeletal Muscle & Function > Flashcards

4 - Skeletal Muscle & Function Flashcards

1
Q

muscle cells are the only cells in the body that have the property of _______, which allows them to shorten and develop tension

A

contractility

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2
Q

what are the three types of muscle tissue?

A
  • skeletal
  • cardiac
  • smooth
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3
Q

what are the defining characteristics of skeletal muscle?

A
  • striated

- voluntary control

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4
Q

what are the defining characteristics of smooth muscle?

A
  • non-striated

- involuntary control

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5
Q

what are the defining characteristics of cardiac muscle?

A
  • striated

- involuntary control

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6
Q

what are 4 examples of skeletal muscle function?

A
  1. maintain posture and body position
  2. breathing
  3. generate heat and maintain body temperature
  4. chewing food and talking
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7
Q

what criteria is used to name muscles? (6)

A
  1. shape
  2. action
  3. location
  4. divisions
  5. size relationships
  6. direction of fibers
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8
Q

def: bundles of muscle fibers

A

fasciculi

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9
Q

if fasciculi run parallel to long axis of muscle they give…

A

greater range of motion, less strength

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10
Q

if fasciculi insert diagonally(pennate), into a tendon running the length of the muscle they give….

A

smaller range of motion, greater strength

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11
Q

def: all fasciculi insert on one side of a tendon

A

unipennate, semimembranosus

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12
Q

def: fasiciculi insert on both sides of tendon

A

bipennate, rectus femoris

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13
Q

def: convergence of several tendons

A

multipennate, deltoid

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14
Q

def: fasciculi run parallel to the long axis of the muscle

A

longitudinal, sartorius, rectus abdominus

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15
Q

def: fibers ran out from a single attachment

A

radiate, pectoralis major

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16
Q

def: a muscle whose contraction is primarily responsible for a particular movement

A

prime mover

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17
Q

def: muscles that oppose one another upon contraction - biceps and triceps

A

antagonists

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18
Q

def: muscles that immobilize a bone or joint near the origin of the primer mover so that the prime mover can act more efficiently

A

fixators/stabilizers

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19
Q

def: less movable end of a muscle, usually proximal

A

origin

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20
Q

def: more movable end of a muscle, usually distal

A

insertion

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21
Q

def: widest portion of a muscle, between its origin and insertion

A

belly

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22
Q

T or F: all muscles insert on bones

A

false, some face muscles insert into skin

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23
Q

what are the three layers of connective tissue?

A
  1. endomysium
  2. perimysium
  3. epimysium
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24
Q

def: extensions beyond the end of muscle

A

tendons

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25
Q

which is stronger: tendons or muscles?

A

tendons

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26
Q

within each muscle cell are many ______.

A

myofibrils

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27
Q

each repeated array of contractile proteins is called a _______

A

sarcomere

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28
Q

what are the two major contractile proteins of the sarcomere?

A

actin (thin) and myosin (thick)

29
Q

what is the most prominent theory of muscle contraction?

A

the sliding filament theory

30
Q

describe the sliding filament theory?

A
  1. when muscle is activated, protruding cross bridges on myosin attach to actin
  2. with ATP, the cross bridge microstructure can rotate
  3. shortens the thin actin filament to slide over myosin
  4. sarcomere shortens
31
Q

on average, how many capillaries are there surrounding each muscle fiber of a sedentary person?

A

3-4

32
Q

when muscle force increases, so does _________

A

intramuscular pressure

33
Q

training can induce ________ ________, resulting in up to 7 capillaries per muscle fiber

A

capillary angiogenesis

34
Q

what are the two extremes in muscle fiber activation?

A

max force or max velocity

35
Q

def: a functional unit of a muscle, consisting of a motor neuron and all the muscle fibers that motor neuron innervates

A

motor unit

36
Q

what does the axon do when it is close to the muscle?

A

separates many times (bifurcates) to innervate all the muscle fibers of that particular motor unit

37
Q

how many muscle fibers will the average motor unit innvervate?

A

200 muscle fibers

38
Q

if the cell body of the motor neuron receives a strong enough stimulus, an ________ _________ is generated

A

action potential

39
Q

what law do action potentials follow?

A

all-or-none law

40
Q

what percent of muscles in legs and arms are slow twitch fibers?

A

45% - 55%

41
Q

T or F: all the muscle fibers in a given motor unit will have identical contractile and metabolic properties

A

true

42
Q

what are the two classifications of motor units?

A

slow twitch & fast twitch

43
Q

what are the three metabolic characteristics of muscles?

A

slow twitch oxidative - type I
fast twitch oxidative-glycolytic - type IIa
fast twitch glycolytic - type IIx

44
Q

who has a higher proportions of slow twitch muscle fibers: endurance athletes or power athletes?

A

endurance athletes

45
Q

can slow twitch fibers and fast twitch fibers be inter-converted by physical training?

A

no

46
Q

can FOG and FG fibers be inter-converted by physical training?

A

yes

47
Q

what are the two methods by which a muscle can control force production?

A
  • multiple motor unit summation

- frequency or wave summation

48
Q

def: when a muscle activates a certain number of motor units depending on the amount of force needed. more force = more motor units

A

multiple motor unit summation

49
Q

def: frequency of action potentials controlling the force.

A

frequency or wave summation

50
Q

how is a muscle maximally activated?

A

when all motor units are activated and they are all activated at a high firing rate

51
Q

as the muscle force requirement increases, motor units with progressively ______ _____ are recruited

A

larger axons

52
Q

during light to moderate effort, which motor units are used?

A

slow twitch motor units with the lowest activation threshold are selectively recruited

53
Q

which motor units are used during rapid, powerful movements?

A

FOG motor units and then FG until all the motor units of all types are activated

54
Q

when can an isolated muscle exert its maximal force or tension?

A

while in a resting stretched position

55
Q

as a muscle shortens, ____ tension can be exerted

A

less

56
Q

what do sarcomeres do when a muscle is stretched or shortened?

A

their length also increases or decreases

57
Q

within the range of sarcomere lengths there is an ______ ______ at which provides the greatest possible number of cross bridge formations

A

optimal length

58
Q

little cross-bridges or too many cross-bridges results in…?

A

reduced active force production

59
Q

when velocity is positive, then the muscle is shortening which is called?

A

concentric contraction

60
Q

when the velocity is negative, then the muscle is lengthening, which is called?

A

eccentric contraction

61
Q

when the velocity of shortening is zero, there is no change in muscle length?

A

isometric contraction

62
Q

power is the product of ______ X _______

A

force X velocity

63
Q

when does max muscle power output occur?

A

one half of max velocity and one third of max concentric force

64
Q

how does muscle activity change at joint angles greater than 90 degrees?

A
  • magnitude of rotational component of the muscle pull force decreases
  • magnitude of stabilizing component of the force increases
65
Q

what are the three factors that affect the expression of strength by a muscle?

A
  • the initial length of the muscle fibers
  • the speed of shortening
  • the angle of pull of the muscle on the bony skeleton
66
Q

def: the age related loss of skeletal muscle mass, strength, and function

A

sarcopenia

67
Q

what are the physical characteristic of old age?

A
  • significant decline in skeletal muscle mass and strength
  • decreased physical activity
  • decreased food intake
68
Q

what are the causes of sarcopenia?

A
  • neural apoptosis (cell death)
  • imbalance of muscle protein synthesis/degradation
  • physical inactivity
  • hormonal imbalance
  • food intake (insufficient protein)
69
Q

what are 4 ways to prevent sarcopenia?

A
  • strength training
  • hormonal therapy
  • dietary intervention
  • reduction in sedentary time

BPK 142 - Lecture (14 decks)

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