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Physiology Exam 2 > Muscles > Flashcards

Muscles Flashcards

1
Q

What are the 4 properties of muscles?

A

Contractility
Excitability
Extensibility
Elasticity

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2
Q

What is muscle contractility?

A

Ability of a muscle to shorten with force

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3
Q

What is muscle excitability?

A

Capacity of a muscle to respond to a stimulus

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4
Q

What is muscle extensibility?

A

Muscle can be stretched to its normal length and beyond to a limited degree

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5
Q

What is muscle elasticity?

A

Ability of muscle to recoil to original resting length after stretched

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6
Q

What three things are muscles organized into?

A

Location
Structure
Mode of control

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7
Q

What are the two modes of control of muscles?

A

Voluntary
Involuntary

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8
Q

What are the two types of muscle structure?

A

Striated
Smooth

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9
Q

What are the three types of muscle location?

A

Skeletal
Cardiac
Visceral (gut)

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10
Q

What are muscle cells

A

muscle fibers

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11
Q

What is a myofibril?

A

rod-like organelle of muscle cell

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12
Q

What are myofilaments?

A

Actin
Myosin

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13
Q

Where are myofilaments located?

A

Myofibrils

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14
Q

What myofilament is connected to z disks?

A

Actin

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15
Q

What is thick filament?

A

bundle of Myosin

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16
Q

What is thin filament?

A

Actin

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17
Q

Which myofilament slides?

A

Myosin slides along actin

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18
Q

What two binding sites exist on myosin head?

A

Actin binding site
ATPase site

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19
Q

What is the structure of an actin filament?

A

Actin monomer in 2-strand helix
Tropomysoin
Troponin

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20
Q

What are the steps of the power stroke?

A

Myosin binds to actin
Phosphate is released
Power stroke happens
ADP is released
ATP binds
Myosin unbinds from actin
ATP is hydrolyzed

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21
Q

How does myosin rotate during the power stroke?

A

Four sequential bonds, each stronger
ADP leaves and ATP binds

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22
Q

How is muscle contraction regulated?

A

Tropomysosin and Troponin

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23
Q

What is the role of tropomyosin and troponin in actin?

A

Tropomysoin blocks myosin binding sites
Calcium binds to troponin which moves tropomyosin, revealing myosin binding site

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24
Q

What concentration does calcium remove inhibition of cross bridges?

A

10^-7 M

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25
Q

What is calcium concentration controlled by?

A

Sarcoplasmic reticulum

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26
Q

How is calcium released from the sarcoplasmic reticulum?

A

Muscle action potential

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27
Q

What is the funciton of T tubules?

A

allows action potentials to go inside cell

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28
Q

What is the structure of t tubules?

A

formed from sarcolemma (muscle plasma membrane)
Open to extracellular environment

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29
Q

What are the steps of excitation-contraction coupling?

A

ACh release
Na+ initiates action potential
Action potential in T-tubes opens DHP receptor which opens calcium release channels in SR
calcium enters cytoplasm
Calcium binds to troponin
Myosin-actin binding
Power stroke
Actin filament slides
Calcium pumped back into SR
Troponin returns to original position

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30
Q

Where and what releases ACh during excitation-contraction coupling?

A

Neuro-muscular junction
Somatic motor neurons

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31
Q

Where does Na+ go to initiate a muscle action potential?

A

Entry into ACh recpetors

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32
Q

How do t-tubules open DHP receptor?

A

Action potential in t-tube alters conformation of receptor

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33
Q

What is titin?

A

Titin proteins stabilize myosin, located between actin and myosin, bound to myosin at various points

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34
Q

What is a motor unit?

A

All muscle fibers connected to one motor neuron

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35
Q

Are motor unit contractions all or nothing?

A

Yes

36
Q

How do muscles vary contraction force and duration?

A

Recruitment of differet types and amount of motor units

37
Q

What is tension control?

A

The more motor units recruited, the greater the force generated

38
Q

What are the two types of movement control?

A

Fine and coarse

39
Q

What is fine motor control?

A

1:1 nerve fiber

40
Q

What is an example of fine motor control?

A

finger tips

41
Q

What is coarse motor control?

A

1: 2000 nerve to fiber

42
Q

What is an example of coarse motor control?

A

Leg muscles

43
Q

What is isotonic muscle contraction?

A

Muscle changes length

44
Q

What is isometric muscle contraction?

A

Constant muscle length

45
Q

Does isotonic or isometric muscle contractions have more tension?

A

Isometric

46
Q

What are two components of muscle elasticity?

A

Parallel Elastic Component
Series Elastic Component

47
Q

What is Parallel Elastic Component?

A

passive elasticity derived from muscle membranes

48
Q

What is series Elastic Component?

A

passive elasticity derived from tendons when a tensed muscle is stretched

49
Q

What is the difference between the series elastic components in isometric and isotonic contractions?

A

Isometric- SEC compensates for changes in contractile component- doesn’t change length
Isotonic- Not as much compensation, does change length

50
Q

What is a twitch?

A

Brief increase in tension due to cross-bridge activity

51
Q

What does the active state of muscles require?

A

Calcium

52
Q

What is tetanus?

A

Activate state of muscle persists, many action potentials
Maximal internal and external tension

53
Q

What happens when Maximal internal and external tension is reached in muscles?

A

Tetanus

54
Q

When is tension in the muscle the highest?

A

Relaxed muscle, a little bit of overlap, room for sliding

55
Q

What are the three metabolic pathways that supply ATP for muscle activity?

A

Creatine phosphate
Glycolysis
Oxidative phosphorylation

56
Q

Where does energy come from in the first 30 minutes of exercise?

A

Creatine phosphate
Glycogen
Glucose
Fatty acids from bloodstream

57
Q

Where does energy come from after 30 minutes of exercise?

A

Only fatty acids from blood stream

58
Q

What type of fibers are red fibers?

A

Slow

59
Q

What type of fibers are white fibers?

A

fast

60
Q

What are slow fibers?

A

Small, dark, fatigue resistant

61
Q

What are fast fibers?

A

Large, light, easily fatigued

62
Q

Where are smooth muscles found in the body?

A

GI, lining of blood vessels

63
Q

What is the role of smooth muscles?

A

Homestatic- Control fluids, sphincters
Support tubes
Move prodcuts

64
Q

What type of contractions are used in smooth muscle?

A

Slow
Little fatigue, low O2

65
Q

What is multi unit smooth muscle?

A

Individual cells with several neuron

66
Q

What is single unit smooth muscle?

A

Gap junctions between cells with fewer neurons

67
Q

What are multi unit smooth muscles used for?

A

Fine control
Respiratory airways, large arteries

68
Q

What are single unit smooth muscles used for?

A

GI tract
Uterus

69
Q

Do action potentials spread from cell to cell in multi or single unit smooth muscle?

A

Single unit

70
Q

What do some visceral muscles exhibit?

A

Autorhythmic contractions

71
Q

What is true about smooth muscle tension?

A

Relatively constant tension

72
Q

How does the amplitude of contraction change in smooth muscle?

A

Remains constant despite muscle length changes

73
Q

What in smooth muscles is analogous to z-lines in striated muscle?

A

Dense bodies

74
Q

What are dense bodies?

A

connect to actin in smooth muscles, analogous to z-lines

75
Q

What is the mechanism of smooth muscle contraction?

A

Calcium increases from SR and from outside cell
Calcium binds to calmodulin
Activates MLCK in myosin head
MLCK phosphorylates myosin heads and increases myosin ATPase activity
Binds to actin
Power stroke

76
Q

What does calcium bind to in smooth muscle contraction?

A

Calmodulin

77
Q

Is troponin present in smooth muscle?

A

No

78
Q

Is tropomyosin present in smooth muscle?

A

Yes but function unknown

79
Q

What is the mechanism of smooth muscle relaxation?

A

Calcium leaves cytoplasm into SR or out of cell
Calcium unbinds calmodulin
Myosin phosphotase inactivates myosin

80
Q

What are unique characteristics of smooth muscle contraction?

A

Slow prolonged contractile activity
Low energy requirements
Response to stretch

81
Q

What is phasic contraction?

A

Brief stimulation, quick calcium elevation, quick loss of phosphorylation

82
Q

What is tonic contraction?

A

continued stimulation, continued calcium elevation, continued phosphorylation latch stage

83
Q

What is a similar smooth muscle event to tetanus in skeletal muscle?

A

Tonic contraction

84
Q

What smooth muscles are normally contracted?

A

Sphincters

85
Q

What smooth muscles are normally partially contracted?

A

Blood vessels
Airways

86
Q

What smooth muscles are normally relaxed?

A

Esophagus
Bladder

87
Q

What smooth muscles are phasically active?

A

Stomach
Intestines

Physiology Exam 2 (5 decks)

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