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Bio 66 > Chapter 12 Muscles > Flashcards

Chapter 12 Muscles Flashcards

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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
What are the different Troponin proteins and what do they bind
``` C = binds calcium T = binds tropomyosin I = binds actin ```
26
What does tropomyosin do
blocks myosin binding site on actin
27
What is a sacromere
basic contractile unit in striated muscle structure
28
What characteristics are there for sacromere
``` 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 ```
29
What is the definition of contraction
Activation of the force generating sites in muscle fibers
30
What happens to the Z lines when actin is pulled by the myosin
Come closer together
31
What bands reduces in width when actin is pulled by the myosin
I bands
32
What must occur first in order for a contraction to occur
Corss-bridge in myosin must bind to actin
33
When a muscle is relaxed, what is blocked and by what
Actin is blocked | By tropomyosin
34
What does troponin do
holds tropomyosin in blocking position
35
Explain the stages of a muscle contraction
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
Explain how myosin "cocks"
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
Explain the process of a power stroke
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
What is excitation
Coupling of AP with muscle contraction
39
What does the transverse tubule do
Surrounds myofibrils | Brings AP into fiber
40
What does the sacroplasmic reticulum do
Releases Ca into fiber's sarcoplasm
41
What does Ca bind to in order to stimulate a muscle contraction
Troponin C
42
What is a latent period
Period in between AP and contraction
43
List the pathway of excitation contraction coupling in a muscle (11)
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
What 4 steps follow a muscle contraction
1. Muscle cell membrane repolarises 2. Calcium transported back into sacroplasmic reticulum 3. Tropomyosin covers binding site 4. Therefore muscle relaxes
45
What is tension
Force exerted on an object by a contracting muscle
46
What is load
Force exerted on a muscle by an object
47
What is special between tension and load
They are opposing forces
48
What is Summation
Increase in muscle tension from successive APs occurring during contraction
49
What is recruitment
Activation of more muscle fibers due to increased stimulation e.g. increased voltage
50
What is Tetanus
Maintained contraction due to repetitive stimulation
51
What is a twitch
Single stimulus to a muscle to generate a muscle twitch
52
What is unfused tetanus
Partial dissipation of elastic tension between subsequent stimuli
53
What is fused tetanus
no time for dissipation of elastic tension between rapidly recurring stimuli
54
What are the 2 types of contraction
``` Isometric = same size contraction Isotonic = same tension contraction ```
55
What is an isometric contraction
1. Same size contraction 2. Muscle develops tension but doesnt change length 3. Tension = load
56
What is an isotonic contraction
1. Same tension contraction 2. Tension remains constant and muscle changes length 3. Occurs when tension exceeds load
57
What happens when the sarcomere is short
Actin filaments lack room to slide = little tension can be developed
58
What happens when the sarcomere is optimal length
Lots of actin-myosin overlap = plenty of room to slide = maximum tension
59
What happens when the sarcomere is long
Actin and myosin do not overlap much = little tension can be developed
60
What are the two main ways skeletal muscles can be differentiated
Contraction speed | Pathway used to form ATP
61
Fast twitch fibers have
high ATPase activity
62
Slow twitch fibers have
Low ATPase activity
63
Oxidative fibers have
High capacity for aerobic respiration Are red due to many blood vessels to provide oxygen
64
Glycolytic fiber have
Few mitochondria and blood vessels Anaerobic respiration White due to few blood vessels Larger diameter = more filaments producing force = more tension
65
What are the 3 skeletal muscle fiber types
Type 1 = Slow oxidative fiber Type 2A = Fast Oxidative fiber Type 2X = Fast Glycolytic fiber
66
What is special about Type 1 What does it respond to
``` Fatigue resistant Small diameter Red Many mitochondria Oxidative Low glycoltic ``` Responds well to repetitive stimulation without becoming fatigued
67
What is special about Type 2A What does it respond to
``` Fatigue resistant Large diameter** Red Many mitochondria Oxidative Intermediate glycoltic** ``` Responds quickly and to repetitive stimulation without becoming fatigue
68
What is special about Type 2X What does it respond to
``` Fatigable Large diameter White Few mitochondria High Glycolytic ``` Responds to quick bursts of strong activation
69
Where is maximum tension generated the quickest
Fast twitch
70
The percentage of muscle types depends on what two factors
Genetics | Physical training
71
What is muscle fatigue
Decrease in muscle tension due to previous contractile activity
72
What contributes to muscle fatigue (4)
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
What is a "muscle cramp" What causes it
Involuntary tetanic contraction Due to electrolyte imbalance or dehydration
74
What is hypocalcemic tetany What causes it
Involuntary tetanic contraction Due to low extracellular Ca
75
What is muscular dystrophy
Deterioration of muscle mass
76
What is myasthenia gravis and what causes it
Paralysis due to decreased number of ACh receptors
77
What is special about cardiac muscle (8)
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
What is special about smooth muscle (8)
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
How do the thick filaments in smooth muscle stack
Vertically
80
What is the key difference between smooth muscle and skeletal muscle
Ca mediated changes in thick filaments activate cross bridges There is no troponin C = tropomyosin doesnt block actin
81
What is the process of cross bridge formation in smooth muscle starting from the SR
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
Gap junctions are located in which muscle(s)
Caridac | Smooth
83
Striation occurs in which muscle(s)
Skeletal | Cardiac
84
What is the order of most developed SR to least
Skeletal Cardiac Smooth
85
Which muscle(s) have troponin C
Skeletal | Cardiac
86
What muscles(s) have Ca enter the cytoplasm from the SR AND extracellular fluid
Cardiac | Smooth
87
Which muscle(s) can contract without stimulation
Cardiac | Smooth

Bio 66 (22 decks)

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