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Bio 66 > Chapter 12 Muscles > Flashcards

Chapter 12 Muscles Flashcards

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Biology 101 flashcards
1
Q

What are the 3 types of muscle cell

A

Skeletal - attached to bones
Smooth - organs and skin
Cardiac - heart

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2
Q

What characteristics in skeletal

A

Striated
Voluntary
Somatic

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3
Q

What characteristics in smooth

A

Non-striated
involuntary
Autonomic

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4
Q

What characteristics in cardiac

A

Striated
Involuntary
Autonomic

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5
Q

What is a skeletal muscle cell known as

A

Muscle fiber

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6
Q

Characteristics of muscle fiber

A

Multiple nuclei in fiber due to fusion of multiple cells (myoblasts)
Can be up to 20cm long
Fibers usually shorter than entire muscle

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7
Q

What is a muscle

A

multiple skeletal muscle fibers bound together with connective tissue

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8
Q

What is muscle attached to the bone by

A

tendons = bundles of connective tissue consisting of collagen fibers

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9
Q

What do each muscle fibers contain

A

myofibrils which contain myofilaments

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10
Q

What gives the striated appearance

A

Alternating dark [A BANDS] and light [I BANDS]

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11
Q

“A” bands are

A

Dark
Thick filaments
Myosin

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12
Q

“I” bands are

A

Light
Thin filament
Actin

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13
Q

What is a neuromuscular junction

A

Location where muscle fiber and neuron meet

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14
Q

List the pathway of a AP in a muscle

A

Stimulation of a neuron inititates AP in muscle

  1. AP causes acetylcholine release into neuronmuscular junction
  2. ACh binds to Nicotinic Ach receptor in muscle fiber and initiates AP in muscle fiber
  3. Contraction of fiber
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15
Q

What is a motor unit

A

1 motor neuron + many muscle fibers

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16
Q

What do smaller motor units allow

A

finer muscle control

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17
Q

What is recruitment

A

Process of increasing the number of motor units that are active in a muscle at any given time in order to increase the strength of contraction

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18
Q

What are the two ways of recruitment

A
  1. Activation of more motor neurons

2. Summation

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19
Q

What is contained within skeletal muscle fibers

A

Myofibrils

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20
Q

What is contained within myofibrils

A

Myofilaments
Actin
Myosin

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21
Q

Myofibrils are…

A

bundle of myofilaments

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22
Q

What are the different sections of a myofibril called

A

sacromeres

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23
Q

The think dark filament has…

It forms…

A

Myosin

Forms cross bridges which contact thin filaments during muscle contraction

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24
Q

The thin light filament has…

and…

A

Actin

Regulatory proteins:
Troponin
Tropomyosin

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25
Q

What are the different Troponin proteins and what do they bind

A 
C = binds calcium
T = binds tropomyosin
I = binds actin
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26
Q

What does tropomyosin do

A

blocks myosin binding site on actin

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27
Q

What is a sacromere

A

basic contractile unit in striated muscle structure

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28
Q

What characteristics are there for sacromere

A 
Section of myofibril
Pattern of thick and thin filaments
Z lines at each end
Actin is anchored to Z lines
Myosin is anchored in place by titin fibers
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29
Q

What is the definition of contraction

A

Activation of the force generating sites in muscle fibers

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30
Q

What happens to the Z lines when actin is pulled by the myosin

A

Come closer together

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31
Q

What bands reduces in width when actin is pulled by the myosin

A

I bands

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32
Q

What must occur first in order for a contraction to occur

A

Corss-bridge in myosin must bind to actin

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33
Q

When a muscle is relaxed, what is blocked and by what

A

Actin is blocked

By tropomyosin

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34
Q

What does troponin do

A

holds tropomyosin in blocking position

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35
Q

Explain the stages of a muscle contraction

A
  1. Muscle fiber depolarised
  2. Signal travels down transverse tubules
  3. Causes release of Ca from sarcoplasmic reticulum
  4. Ca binds to Troponin C
  5. Troponin T changes shape
  6. Tropomyosin moves out the way
  7. Myosin cross-bridge with actin
36
Q

Explain how myosin “cocks”

A
  1. ATP binds to myosin head
  2. Hydrolysis of ATP
  3. Myosin changes shape to become cocked
  4. Myosin head binds to actin via cross-bridge
  5. Power stroke
37
Q

Explain the process of a power stroke

A
  1. ATP hydrolysis = myosin cocked
  2. Binding of myosin to actin releases energy
  3. Release in energy causes power stroke
  4. Actin pulled towards center of sarcomere
  5. A new ATP must then attach to the myosin in order to break bond between myosin and actin
38
Q

What is excitation

A

Coupling of AP with muscle contraction

39
Q

What does the transverse tubule do

A

Surrounds myofibrils

Brings AP into fiber

40
Q

What does the sacroplasmic reticulum do

A

Releases Ca into fiber’s sarcoplasm

41
Q

What does Ca bind to in order to stimulate a muscle contraction

A

Troponin C

42
Q

What is a latent period

A

Period in between AP and contraction

43
Q

List the pathway of excitation contraction coupling in a muscle (11)

A
  1. ACh released in somatic motor neuron
  2. Binds to nicotinic ACh in Sarcolemma
  3. Opens channels, Na diffuses in
  4. AP produced
  5. AP travels along T tubules
  6. T tubules bring AP into skeletal muscle fiber
  7. Depolarise membrane close to sarcoplasmic reticulum
  8. AP opens voltage-gated Ca channels
  9. Stimulates release of calcium ions
  10. Calcium readily diffuses into sarcoplasm to all of the troponin C binding sites
  11. Calcium troponin complex pulls tropomyosin out of the way in myofibril
44
Q

What 4 steps follow a muscle contraction

A
  1. Muscle cell membrane repolarises
  2. Calcium transported back into sacroplasmic reticulum
  3. Tropomyosin covers binding site
  4. Therefore muscle relaxes
45
Q

What is tension

A

Force exerted on an object by a contracting muscle

46
Q

What is load

A

Force exerted on a muscle by an object

47
Q

What is special between tension and load

A

They are opposing forces

48
Q

What is Summation

A

Increase in muscle tension from successive APs occurring during contraction

49
Q

What is recruitment

A

Activation of more muscle fibers due to increased stimulation
e.g. increased voltage

50
Q

What is Tetanus

A

Maintained contraction due to repetitive stimulation

51
Q

What is a twitch

A

Single stimulus to a muscle to generate a muscle twitch

52
Q

What is unfused tetanus

A

Partial dissipation of elastic tension between subsequent stimuli

53
Q

What is fused tetanus

A

no time for dissipation of elastic tension between rapidly recurring stimuli

54
Q

What are the 2 types of contraction

A 
Isometric = same size contraction
Isotonic = same tension contraction
55
Q

What is an isometric contraction

A
  1. Same size contraction
  2. Muscle develops tension but doesnt change length
  3. Tension = load
56
Q

What is an isotonic contraction

A
  1. Same tension contraction
  2. Tension remains constant and muscle changes length
  3. Occurs when tension exceeds load
57
Q

What happens when the sarcomere is short

A

Actin filaments lack room to slide = little tension can be developed

58
Q

What happens when the sarcomere is optimal length

A

Lots of actin-myosin overlap = plenty of room to slide = maximum tension

59
Q

What happens when the sarcomere is long

A

Actin and myosin do not overlap much = little tension can be developed

60
Q

What are the two main ways skeletal muscles can be differentiated

A

Contraction speed

Pathway used to form ATP

61
Q

Fast twitch fibers have

A

high ATPase activity

62
Q

Slow twitch fibers have

A

Low ATPase activity

63
Q

Oxidative fibers have

A

High capacity for aerobic respiration

Are red due to many blood vessels to provide oxygen

64
Q

Glycolytic fiber have

A

Few mitochondria and blood vessels

Anaerobic respiration

White due to few blood vessels

Larger diameter = more filaments producing force = more tension

65
Q

What are the 3 skeletal muscle fiber types

A

Type 1 = Slow oxidative fiber
Type 2A = Fast Oxidative fiber
Type 2X = Fast Glycolytic fiber

66
Q

What is special about Type 1

What does it respond to

A 
Fatigue resistant
Small diameter
Red
Many mitochondria
Oxidative
Low glycoltic

Responds well to repetitive stimulation without becoming fatigued

67
Q

What is special about Type 2A

What does it respond to

A 
Fatigue resistant
Large diameter**
Red
Many mitochondria
Oxidative
Intermediate glycoltic**

Responds quickly and to repetitive stimulation without becoming fatigue

68
Q

What is special about Type 2X

What does it respond to

A 
Fatigable
Large diameter
White
Few mitochondria
High Glycolytic

Responds to quick bursts of strong activation

69
Q

Where is maximum tension generated the quickest

A

Fast twitch

70
Q

The percentage of muscle types depends on what two factors

A

Genetics

Physical training

71
Q

What is muscle fatigue

A

Decrease in muscle tension due to previous contractile activity

72
Q

What contributes to muscle fatigue (4)

A
  1. Increased extracellular K+ after many APs
  2. Lactic acid build up = denatures proteins
  3. Reduced ability for SR to release Ca prevents excitation-contraction coupling
  4. Depletion of fuel
73
Q

What is a “muscle cramp”

What causes it

A

Involuntary tetanic contraction

Due to electrolyte imbalance or dehydration

74
Q

What is hypocalcemic tetany

What causes it

A

Involuntary tetanic contraction

Due to low extracellular Ca

75
Q

What is muscular dystrophy

A

Deterioration of muscle mass

76
Q

What is myasthenia gravis and what causes it

A

Paralysis due to decreased number of ACh receptors

77
Q

What is special about cardiac muscle (8)

A
  1. Found in heart only
  2. Involuntary
  3. Contracts spontaneously - pacemaker cells
  4. Striated - sarcomeres
  5. Similar functions with troponin and tropomyosin
  6. Sliding filament mechanism
  7. Single nucleus
  8. Cardiac muscle cells join end to end at intercalated disks
78
Q

What is special about smooth muscle (8)

A
  1. Not striated
  2. Single nucleus
  3. Arranged in layers
  4. Surrounds hollow structures
  5. Involuntary
  6. Uses cross bridge movements to generate force
  7. Calcium ions control cross bridge activity
  8. Different organisation of filaments and excitation-contraction coupling
79
Q

How do the thick filaments in smooth muscle stack

A

Vertically

80
Q

What is the key difference between smooth muscle and skeletal muscle

A

Ca mediated changes in thick filaments activate cross bridges

There is no troponin C = tropomyosin doesnt block actin

81
Q

What is the process of cross bridge formation in smooth muscle starting from the SR

A
  1. Ca binds to Calmodulin
  2. Ca regulated enzyme phosphorylates myosin
  3. Phosphorylated myosin binds to actin
  4. Cross bridge activation
  5. Cross bridge generates force as long as myosin is phosphorylated
82
Q

Gap junctions are located in which muscle(s)

A

Caridac

Smooth

83
Q

Striation occurs in which muscle(s)

A

Skeletal

Cardiac

84
Q

What is the order of most developed SR to least

A

Skeletal
Cardiac
Smooth

85
Q

Which muscle(s) have troponin C

A

Skeletal

Cardiac

86
Q

What muscles(s) have Ca enter the cytoplasm from the SR AND extracellular fluid

A

Cardiac

Smooth

87
Q

Which muscle(s) can contract without stimulation

A

Cardiac

Smooth

Bio 66 (22 decks)

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