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BMS109 Phys/Pharm > The Muscular System > Flashcards

The Muscular System Flashcards

1
Q

What are the functions of the skeletal muscles

A

movement, support, communication, posture

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2
Q

What are the characteristics of skeletal muscle

A

contractility, extensibility, elasticity, conductivity

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3
Q

What are myofibrils rich in

A

blood vessels and nerves

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4
Q

What type of cell are myofibrils

A

multi-nucleate - syncytium

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5
Q

What formed myofibrils

A

fusion of myoblasts

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6
Q

What are t tubules

A

invaginations of muscle fibre membrane in the cytoplasm

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7
Q

What do t tubules allow

A

electric depolarisation of membrane - propagation

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8
Q

What does the myofibril cytoplasm contain

A

bundles of protein and mitochondria

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9
Q

What are sacromeres

A

repeated units in myofibrils

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10
Q

What are sarcomeres responsible for

A

contraction of muscle

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11
Q

What does the dark A band of myofibrils contain

A

myosin filaments

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12
Q

Which band is dense in myofibrils?

A

dark A band

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13
Q

What is the I band in myofibrils composed of

A

actin - thin filament

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14
Q

What does the I band in myofibrils span across

A

sarcomere

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15
Q

How is actin made stable in myofibrils

A

plus ends anchored into the Z line

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16
Q

What does anchoring of actin into the Z line prevent

A

polymerisation at the plus end

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17
Q

What is nebulin

A

large protein

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18
Q

What is nebulin made of

A

repeating actin binding domains

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19
Q

What is the process of muscle contraction driven by

A

myosin heads

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20
Q

What is contraction

A

thick filament of actin moves towards thin filament

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21
Q

What does contraction obtain

A

shortening of sarcomere without changing length of filaments

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22
Q

What is the myosin head normally attached to

A

specific binding site on actin filament

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23
Q

What happens when the actin filament binds ATP

A

change in conformation, myosin head slides along actin filament

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24
Q

What happens when the myosin head attaches to new binding site

A

phosphate is released - change in head conformation - power stroke

25
Q

What does the power stroke allow

A

actin filament to slide against myosin filament

26
Q

What does contraction require

A

energy - ATP

27
Q

How is contraction initiated

A

membrane depolarisation allows entry of calcium

28
Q

What is the starting point of contraction

A

calcium

29
Q

What has the ability to bind calcium

A

troponin

30
Q

What does the binding of calcium allow

A

conformational change - releases tropomyosin

31
Q

What is the function of calcium in contraction initiation

A

unmasks myosin binding sites on thin filament

32
Q

What is the function of releasing tropomyosin

A

unmasks binding site for myosin head

33
Q

What happens when a nerve impulse reaches the nerve terminal

A

Ca2+ released - causes release of ACh by exocytosis

34
Q

When does muscle contraction stop

A

when nerve impulses stop

35
Q

What can toxins cause

A

muscle paralysis

36
Q

What can botulinum toxin cause

A

muscle weakness, paralysis, death

37
Q

What can BOTOX be used for?

A

cosmetically, medically for cross eyedness

38
Q

What does botulinum toxin degrade

A

SNAP25

39
Q

What does botulinum toxin prevent formation of

A

complex needed for fusion of excitatory vesicles with membrane

40
Q

What is the function of SNAP25

A

promotes fusion of excitatory vesicles with membrane

41
Q

What does BOTOX cause to be retained inside the cell

A

ACh

42
Q

What happens if ACh is retained inside the cell

A

X muscle contraction

43
Q

What muscles are fatigue resistant

A

oxidative muscles

44
Q

What is the difference between slow and fast fibres

A

slow fibres - sustain contract for longer periods of time, fast fibres - contract rapidly

45
Q

Which muscle fibres are anaerobic

A

glycolytic

46
Q

Which muscle type has the highest concentration of mitochondria

A

slow oxidative

47
Q

How do cells generate ATP

A

aerobic metabolism in mitochondria

48
Q

What does aerobic muscle metabolism typically stimulate

A

slow fibres

49
Q

What muscle metabolism is anaerobic

A

glycolytic

50
Q

What does anaerobic muscle metabolism rely on

A

degradation of glycogen

51
Q

What does anaerobic muscle metabolism produce

A

lactic acid

52
Q

What is the NET production of anaerobic muscle metabolism

A

2ATP

53
Q

What does anaerobic muscle metabolism stimulate

A

fast fibres

54
Q

What does phosphocreatine allow production of

A

phosphate and ATP

55
Q

What do fast muscle fibres use heavily

A

phosphocreatine

56
Q

What happens to creatine in mitochondria

A

recycled into P-creatine at rest

57
Q

What metabolism do slow fibres use

A

aerobic

58
Q

What metabolism do fast fibres use

A

anaerobic

59
Q

What happens in the muscles during fatigue

A

lactic acid, pH decreases

BMS109 Phys/Pharm (22 decks)

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