Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Exercise Physiology > Chapter 8: Skeletal Muscle Structure and Function > Flashcards

Chapter 8: Skeletal Muscle Structure and Function Flashcards

1
Q

from bigger picture to smaller details, describe muscle structure

A

muscle —> fascicles —> muscle fibers (cells) —> myofibrils —> sarcomeres —> thick and thin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how many nuclei do skeletal muscle fibers have

A

many nuclei among the entire length of the muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

where are subsarcolemmel (SS) mitochondria located? purpose?

A

directly beneath the cell membrane; produce cellular energy needed to maintain active transport of ions across sarcolemma (to establish a concentration gradient for action potentials)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

where are intermyofibrillar mitochondria (IMF) located? purpose?

A

located near the myofibrillar (contractile) proteins; provide energy needed to sustain muscle contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

purpose of satellite cells

A

increase number of nuclei in muscle fibers during muscle growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does an increase in # of nuclei allow for muscle fibers?

A

greater protein synthesis, which is important for muscle growth in response to strength training

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

non-endocrine functions of skeletal muscle

A

-force production for locomotion and breathing
-force production for postural support
-heat production during cold stress (shivering thermogenesis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

endocrine functions of skeletal muscle

A

produce myokines and IL-6 during contraction, promote anti-inflammatory environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

purpose of myokines

A

stimulate glucose uptake and fatty acid oxidation, promote blood vessel growth in muscle, promote liver glucose production and triglyceride breakdown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

purpose of IL-6 during exercise

A

anti-inflammatory effects which reduces chronic inflammation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is advantageous about an anti-inflammatory environment induced by exercise?

A

reduces chronic inflammation, reduces risk of heart disease, type 2 diabetes and certain cancers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

muscles that decrease joint angles

A

flexors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

muscles that increase joint angles

A

extensors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe static exercise

A

muscle exerts force without changing length (i.e. pulling against immovable object or postural muscles)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe concentric dynamic exercise

A

muscle shortens during force production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe eccentric dynamic exercise

A

muscle produces force but length increases, this is associated with muscle fiber injury and soreness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define motor unit

A

motor neuron and all the muscle fibers it innervates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

role of somatic motor neurons of the PNS

A

carry neural messages from spinal cord to skeletal muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

define neuromuscular junction

A

junction between motor neuron and muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

define motor end plate

A

pocket formed around motor neuron by the sarcolemma of the muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

describe the sliding filament model

A

muscle shortening occurs due to the movement of the thin filament over the thick filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

during muscle contraction, there is a reduction in distance between the __ lines of the sarcomere

A

Z lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

5 stages of excitation-contraction coupling

A

1) action potential stimulates Ach release from alpha motor neuron at the neuromuscular junction
2) Ach induces an AP in muscle fiber; AP spreads down sarcolemma and T-tubules
3) AP stimulates Ca2+ release from sarcoplasmic reticulum
4) Ca2+ initiates tropomyosin displacement, revealing myosin-binding sites
5) myosin forms cross-bridges with actin, producing force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

7 stages of cross-bridge cycling

A

1) myosin binding sites on the actin molecule are covered in resting fibers
2) the AP releases calcium from SR
3) Ca2+ binds troponin; tropomyosin moves, revealing binding sites
4) cross bridge forms when myosin heads bind actin
5) myosin head pivots, moving actin, ADP and Pi dissociate from myosin head
6) myosin head releases actin when a fresh ATP binds
7) myosin head bends next actin; ATP is cleaved to ADP + Pi and the cycle repeats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is a muscle cramp

A

spasmodic, involuntary muscle contractions often associated with prolonged, high intensity exercise

26
Q

why does the electrolyte depletion and dehydration theory fall short in explaining muscle cramps?

A

dealing with electrolyte imbalance/dehydration is a full body phenomenon that doesn’t necessarily have to do with one single muscle, also stretching/massaging helps relieve cramps

27
Q

describe the altered neuromuscular control theory for muscle cramps

A

there is abnormal spinal reflex activity due to fatigue which results in increased excitatory activity of muscle spindles and reduced inhibitory effect of Golgi tendon organ

28
Q

role of muscle spindles, specifically in regards to muscle cramps

A

muscle spindles detect stretch of the muscle, then sensory neurons conduct APs to the spinal cord and synapse with alpha motor neurons, stimulation of alpha motor neurons causes the muscle to contract to resist being stretched to far (muscle spindle activity is increased during a muscle cramp)

29
Q

role of Golgi tendon organ, specifically with regard to muscle cramps

A

Golgi tendon organs detect tension applied to a tendon, sensory neurons conduct APs to spinal cord and synapse with inhibitory interneurons that synapse with alpha motor neurons, inhibition of the alpha motor neurons causes muscle relaxation, relieving tension (decreased Golgi tendon activity during a muscle cramp)

30
Q

what relieves muscle cramps and why does this work?

A

passive stretching, because it activates the Golgi tendon organ and inhibits motor neurons in the spinal cord, resulting in muscle relaxation

31
Q

type I fibers

A

slow-twitch fibers, slow-oxidative fibers

32
Q

type IIa fibers

A

intermediate fibers, fast-oxidative glycolytic fibers

33
Q

type IIx fibers

A

fast-twitch fibers, fast-glycolytic fibers

34
Q

3 biochemical properties differing between muscle fiber types

A

1) oxidative capacity
2) type of myosin ATPase isoform
3) abundance of contractile proteins

35
Q

what is meant by oxidative capacity? which muscle fiber type has the highest?

A

number of capillaries, mitochondria, and amount of myoglobin; type I has the highest oxidative capacity

36
Q

what does the type of myosin ATPase isoform determine? which muscle fiber type has the fastest isoform?

A

speed of ATP degradation; type IIx

37
Q

which muscle fiber type has the most abundance of contractile proteins?

A

type IIx

38
Q

4 contractile properties differing between muscle fiber types

A

1) speed of contraction (Vmax)
2) maximal force production
3) maximal power output
4) muscle fiber efficiency

39
Q

what is speed of contraction dependent on? which muscle fiber type has the fastest speed of contraction?

A

dependent on rate of SR releasing calcium and ATPase activity, type IIx has the fastest speed of contraction

40
Q

what is maximal force production dependent on? which fiber type has the highest max force production?

A

dependent on the force per unit of cross-sectional area; type IIx has the highest max force production

41
Q

how do men and women differ in terms of muscle mass?

A

men have significantly more skeletal muscle mass than women

42
Q

how do men and women differ in absolute force production?

A

men are stronger than women in terms of absolute force production

43
Q

how to men and women differ in terms of relative force production?

A

there is no apparent sex or age differences in fiber distribution, so men and women have the same relative force production

44
Q

what does maximal power output depend on? what type of muscle fibers have the highest maximal power output?

A

power = force x velocity of shortening
type IIx

45
Q

what is muscle fiber efficiency dependent on? which muscle fiber type is the most efficient?

A

how much ATP is used to generate force (lower ATP, more efficient); type I are the most efficient

46
Q

power athletes such as sprinters generally have higher percentage of

A

fast fibers

47
Q

endurance athletes such as distance runners generally have a higher percentage of

A

slow fibers

48
Q

3 factors that determine the amount of force produced during a muscle contraction

A

1) types and number of motor units recruited
2) initial muscle length
3) nature of the neural stimulation of motor units

49
Q

describe Type S (slow) motor neurons

A

smallest, innervate type I muscle fibers

50
Q

describe Type FR (fast, fatigue resistant) motor neurons

A

innervate type IIa muscle fibers

51
Q

describe type FF (fast, fatigable) motor neurons

A

largest of the motor neurons, innervate type IIx muscle fibers

52
Q

describe the recruitment pattern of motor neurons during graded exercise

A

type S —> type FR —> type FF

53
Q

describe the muscle fiber type recruitment pattern

A

type I —> type IIa —> type IIx

54
Q

what is the size principle with regard to motor neuron recruitment?

A

progressive recruitment of motor units begins with the smallest motor unit and progressively gets to larger motor units

55
Q

how does increasing stimulus affect the motor units recruited?

A

recruits more motor units and thus produces more force

56
Q

describe the length-tension relationship in skeletal muscle

A

there is an “ideal” length for force generation which allows for maximal cross bridge formation; not too much overlap and not too little

57
Q

describe how frequency of stimulation affects the force produced in muscles

A

increasing frequency results in summation of simple twitches until tetanus is finally reached

58
Q

how can force production be additive?

A

increased Ca2+ availability, not enough time to fully resequester it within the sarcoplasmic reticulum

59
Q

what is delayed onset muscle soreness (DOMS) due to? what is it NOT due to?

A

microscopic tears in muscle fibers or connective tissue, not due to buildup of lactic acid

60
Q

timeline of DOMS

A

sarcomere damage (hours to days) —> immune cell infiltration (days) —> satellite cell activation (days to weeks)

61
Q

mechanism of DOMS

A

1) structural damage to muscle fibers
2) membrane damage
3) calcium leaks out of SR
4) protease activation- breakdown of cellular proteins
5) inflammatory response
6) edema and pain

62
Q

describe the repeated bout effect on DOMS

A

following recovery, another bout of the same exercise results in minimal injury (soreness)

Exercise Physiology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions