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Pharmacology > Muscles & Skin > Flashcards

Muscles & Skin Flashcards

1
Q

What are the muscular system functions?

A 
Body movement (locomotion)
Maintenance of posture
Heart beat
Respiration 
Vasoconstriction
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2
Q

What are skeletal muscles attached to?

A

Bones

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3
Q

What are skeletal muscles responsible for?

A

Locomotion, facial expression, posture, respiratory movements + body movement

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4
Q

What are skeletal muscles controlled by?

A

Somatic motor neurons

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5
Q

Are skeletal muscles voluntary in action?

A

YES

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6
Q

What are the cardiac muscles controlled by?

A

Involuntarily controlled by endocrine + autonomic nervous system

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7
Q

Where are smooth muscles found?

A

Hollow organs, blood vessels, eyes, uterus + skin

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8
Q

What are some functions of smooth muscles?

A

Propel urine, mix food in digestive tract, dilating/constricting pupils + regulating blood flow

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9
Q

What are smooth muscles controlled by?

A

Involuntarily by endocrine + autonomic nervous systems

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10
Q

What is a muscle?

A

Soft tissue which cells are rich in actin + myosin that slide past one another, producing contraction

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11
Q

What is a syncytium?

A

Multinucleated cell that can result from multiple cell functions of uninuclear cells

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12
Q

What is an example of a structural syncytium?

A

Skeletal muscle

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13
Q

What is an example of a functional syncytium?

A

Cardiac or smooth muscle

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14
Q

Describe the structure of myofiber

A 
Membrane = sarcolemma 
T-tubules 
Multinucleated 
Myofibrils assembled into myofibers 
Fibres surrounded + bundled by connective tissue
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15
Q

Describe structure of cardiomyocyte

A 
Single centrally located nucleus 
Branching structure 
Mitochondria
Abundant reserve of myoglobin 
Each cell in contact with adjacent cells
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16
Q

Why do cardiomyocytes have a large reserve of myoglobin?

A

To store O2

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17
Q

Why do cardiomyocytes have each cell in contact with adjacent cells?

A

Have membrane modification to increase SA

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18
Q

What are electrical coupling (intercalated discs)?

A

Specialised intracellular attachment of cardiac muscle cells compromising gap junctions

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19
Q

What are gap junctions?

A

Intracellular channels that allow for direct chemical communication between adjacent cells through diffusion of ions + small molecules without contact with extracellular fluids

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20
Q

What are desmosomes?

A

Fasteners through plasma membrane of adjacent cells by means of intermediate filaments, compassed of keratin or desmin to form dense plaque

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21
Q

What is a sacromere?

A

Repeating functional unit of myofibrils or cardiomyocyte

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22
Q

What is A-band (dark) made up of?

A

Thick myosin filament

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23
Q

What is the I-band (light)?

A

From Z discs to end of thick filaments

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24
Q

What is the M line?

A

Protein which thick filaments attach

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25
Q

What is the H-zone?

A

Thick filaments with NO thin

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26
Q

What are the Z discs?

A

Filamentous network of protein, attaches actin filament

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27
Q

What are thin filaments?

A

Elastic chains of polypeptides

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28
Q

Describe myosin

A

Thick, fibrillar protein

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29
Q

Describe actin

A

Thin, globular protein

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30
Q

What colour is a slow twitch muscle?

A

Red

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31
Q

What colour is a fast twitch muscle?

A

White

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32
Q

What is the density of capillaries in slow twitch fibres?

A

High

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33
Q

What is the density of capillaries in fast twitch fibres?

A

Low

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34
Q

What is the density of mitochondria in slow twitch fibres?

A

High

35
Q

What is the density of mitochondria in fast twitch fibres?

A

Low

36
Q

What is the density of myoglobin in slow twitch fibres?

A

High

37
Q

What is the density of myoglobin in fast twitch fibres?

A

Low

38
Q

What type of energy is released in slow twitch fibres?

A

Aerobic (oxidative phosphorylation)

39
Q

What type of energy is released in fast twitch fibres?

A

Anaerobic (glycolysis)

40
Q

What type of fuel for slow twitch fibres?

A

Fats or carbohydrates

41
Q

What type of fuel for fast twitch fibres?

A

Carbohydrates-glucose

42
Q

What are the dynamics of slow twitch fibres?

A

Slow, lasts for long time with little fatigue

43
Q

What are the dynamics of fast twitch fibres?

A

Fast, fatigue develops quickly

44
Q

What type of force for slow twitch fibres?

A

Little

45
Q

What type of force for fast twitch fibres?

A

Powerful

46
Q

Describe the muscle contraction mechanism

A 
ATP hydrolysed
ADP + Pi bind to myosin head
Ca2+ binds to troponin = exposes myosin binding site
Myosin head binds to actin
Power stroke occurs
Sarcomere contracts
ADP + Pi dissociate from myosin
New ATP bind to myosin 
= detachment of myosin from actin 
Hydrolysis of ATP ----> ADP + Pi
= recocks head
47
Q

Describe what happens in contraction

A 
Stimulate Na+ channel to open
= stimulates Ca2+ channels to open
DEPOLARIZATION 
Ca2+ conc +
= Ca2+ release from Ryanodine receptors
Ca2+ stimulate contractile apparatus
48
Q

Describe what happens in relaxation

A

Ca2+ reuptake into SR
Withdrawal of Ca2+ to extracellular media
Active transport
Exchange of Ca2+ for 3Na+ with Na+/Ca2+ exchanger
Then 3Na+ exchanged for 2K+ with Na+/K+-ATPase
Activation of K+ channels
REPOLARIZATION

49
Q

What are examples of vascular smooth muscles?

A

Arteries, veins + lymphatic vessels

50
Q

What are examples of visceral smooth muscles?

A

Airways, GI tract + urinary system

51
Q

What does it mean smooth muscles are strated?

A

No sarcomeres

52
Q

Describe smooth-muscle contraction

A

Excitation-depolarisation = opening of voltage-gated L-type Ca2+ channels
Ca2+ released from ER/SR via RYR = increases [Ca2+]
Ca2+ binds to calmodulin (CaM)
Ca2+-CaM complex activates myosin light chain kinase (MLCK)
MLCK phosphorylates myosin head + stimulates contraction

53
Q

What is importance of Ca2+?

A

Responsible for depolarisation + propagation of excitation
Activation of contraction of muscles
Ca2+ important signal molecule + 2nd messenger

54
Q

What is the excitation for skeletal muscles?

A

Voltage-gated Na+ channels

55
Q

What is the contraction for skeletal muscles?

A

Ca2+ release from internal stores (SR)

56
Q

Why do skeletal muscles have short latent period?

A

Need fast response

57
Q

What is the excitation for cardiac muscles?

A

Voltage-gated Ca2+ channels

58
Q

What is the contraction for cardiac muscles?

A

External Ca2+ influx released from internal stores

59
Q

Why are cardiac muscles latent period not as fast as skeletal muscles?

A

Still must be fast to push blood to circulation system

60
Q

Why do cardiac muscles have long action potential?

A

Increases absolute refractory period

= decreases probability of arrhythmia

61
Q

What is the excitation for smooth muscles?

A

Voltage-gated Ca2+ channels

62
Q

What is the contraction for smooth muscles?

A

Extend Ca2+ influx + partly Ca2+ release from internal store (SR)

63
Q

Why do smooth muscles have long latent period?

A

Slow to contract

64
Q

What is latent period?

A

Time between stimulus + muscle contraction

65
Q

What is a twitch in muscle excitation?

A

Single contractile action

66
Q

What is a wave summation in muscle excitation?

A

Muscle does not relax between stimulations

Fibre re-stimulated while there is still some contractile activity

67
Q

What is a incomplete tetanus in muscle excitation?

A

Frequency of stimulation increases, contractions fuse into total contraction with partial relaxations between events

68
Q

What is a complete tetanus in muscle excitation?

A

Frequency of stimulation is maximal + separate events fuse into smooth, continuous contraction with no relaxation

69
Q

What happens due to force of contraction rises with frequency of stimulation, in tetanus?

A

Increases Ca2+ around myofibril with Ca2+ ATPase are unable to manage intracellular Ca2+

70
Q

What are the functions of skin?

A 
Regulates body temp
Stores blood
Protects body
Detects cutaneous sensations
Excretes + absorbs substances
Synthesises vitamin D
71
Q

What is stratum basale?

A

Contains basale keratinocytes that form basal lamina + attach to dermis
These keratinocytes proliferate + regenerate epidermis

72
Q

What is stratum spinosum?

A

Contain suprabasal keratinocytes that differentiate + produce different types of keratin

73
Q

What is the “spinous” appearance of keratinocytes caused by?

A

Desmosomes

74
Q

What is stratum granulosum?

A

Keratinocytes start losing their nuclei + cytoplasm appears granular
Lipids released from cells to contribute to cornified envelop

75
Q

What is stratum lucidum?

A

Clear or translucent layer only found in palms + soles

76
Q

What is stratum corneum?

A

Outermost layer of 10-30 flattened cells without nucleus or other organelles
Cells surrounded by keratin, lipids + other crosslinked proteins forming barrier

77
Q

What happens to dead cells?

A

Exfoliated requiring constant regeneration of epidermis

78
Q

What are holocrine glands?

A

Secretions are released by rupture of plasma membrane, which destroys the cell + results in secretion + cell remnants into lumen

79
Q

What is an example of a holocrine gland?

A

Sebaceous glands

80
Q

What are merocrine cells?

A

Secretions are released by exocytosis

81
Q

What is exocytosis?

A

Fusion of secretory vesicles with cell membrane + release of product to outside the cell

82
Q

What is an example of a merocrine gland?

A

Sweat glands

83
Q

What are apocrine glands?

A

Secretions released by budding off the apical portion of cells including the secreted product

84
Q

What is an example of an apocrine gland?

A

Mammary gland

Pharmacology (40 decks)

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