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Zoology 242 > Muscle > Flashcards

Muscle Flashcards

1
Q

What are all the functions of muscle?

A
  • provide contractile force
  • circulation
  • digestion
  • respiration
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2
Q

Muscles are controlled by…

A

CNS efferents

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3
Q

What are the 3 types of muscle in the body?

A
  • Smooth
  • cardiac (striated)
  • skeletal (striated)
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4
Q

Describe smooth muscle.

A
  • (organs)
  • single nuclei
  • slow contractions
  • no striations
  • involuntary
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5
Q

Describe cardiac muscle.

A
  • involuntary
  • each cell has nuclei
  • striated
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6
Q

Describe skeletal muscle.

A
  • voluntary movemensts - somatic nervous system
  • dark and light bands
    • striated
  • about 430 muscle pairs of muscle throughout the body
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7
Q
A
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8
Q

Which type of muscle constitutes for 40-50% of body weight?

A

Skeletal

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9
Q

How many pairs of skeletal muscle are responsible for most movements of the body?

A

80

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10
Q

Describe slow twitch muscle.

A
  • type I
  • used for sustained activity (marathon)
  • prefers aerobic conditions
  • high amount of mitochondria and myoglobin present
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11
Q

Describe (general) fast twitch muscles.

A
  • type II
  • type 2a and 2b
  • anaerobic activity possible with these fibres
  • short bursts of activity
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12
Q

What is the difference between type 2a and 2b muscle?

A

2a: intermediate (can use aerobic or anaerobic conditions)
2b: work best under anaerobic conditions

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13
Q

Which type of muscle is white, fatigues very easily and is very powerful?

A

Type 2b

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14
Q

Describe type 2a fibres in detail.

A
  • intermediate
  • can use aerobic conditions
  • contains high concentrations of mitochondria and myoglobin
  • red in colour
  • resistant to fatigue
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15
Q

Describe type 2b fibres in detail.

A
  • white
    • low amounts of myoglobin
  • fatigues easily
  • highest amount of power
  • good for fast/strong activities
    • weight lifting
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16
Q

Myocytes are formed from…

A

the fusion of several myoblasts during development (myogenesis).

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17
Q

What are the part of muscle that are often referred to as muscle fibres?

A

Myofibrils

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18
Q

Why do myofibrils have a parallel arrangement within the muscle?

A

More myofibrils in parallel can generate more force.

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19
Q

A _________, is a single linear continuous stretch of interconnected sarcomeres.

A

Myofibril

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20
Q

In striated muscle cell structure, thick and thin filaments are arranged in?

A

Sarcomeres

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21
Q

What causes the striated appearance (at the cellular level) of muscle?

A

Thick and thin filaments are arranged into sarcomeres - repeated in parallel sequences that are side-by-side across a myocyte.

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22
Q

Describe the structural features of a sarcomeres.

A
  • z-disk
  • a-band (anisotropic)
  • i-band (isotropic band)
  • M-line
23
Q

What two proteins are the workhorses for our bodies?

A

Actin and myosin

24
Q

Actin and myosin are important in…

A
  • cellular movement (vesicles, cytokinesis)
  • muscle contraction
25
Q

What protein is a major component of microfilaments?

A

Actin

26
Q

Describe actin polymerization.

A
  • monomers = g-actin
  • polymers = f-actin
  • can spontaneously assemble/disassemble
27
Q

Muscle myosin = type ____

A

2

28
Q

What is the general organization of myosin?

A

(head, neck, tail)

29
Q

Several _________ molecules come together to form a thick filament.

A

Myosin

30
Q

Describe how properties of isoforms affect contraction.

A
31
Q

Thin filaments are polymers of… and interact with what proteins?

A

α-actin… ends capped by tropomodulin and CapZ to stabilize, proteins troponin and tropomyosin on the outer surface.

32
Q

What are the two muscle auxiliary proteins?

A

Nebulin and titin

33
Q

Describe nebulin.

A
  • along length of thin filament (molecular ruler)
  • may regulate length during development
34
Q

Describe titin.

A
  • giant protein (240 domains)
  • keep thick filament centered in sarcomere
  • attaches thick filament to z-disk
  • responsible for the passive springiness of muscle
35
Q

Neurogenic muscle…

A
36
Q

Show the difference between of vertebrate tonic muscle fibres and arthopod muscle fibres.

A
37
Q

Descibe ACh muscle neurotransmission.

A
  1. acetyl CoA is synthesied in the mitochondria
  2. choline acetyl transferase catalyzes the conversion of cholin and acetyl CoA to ACh
  3. the ACh is packaged into synaptic vesicles
  4. ACh is released into the synapse
  5. ACh binds to its receptor on the postsynaptic cell
  6. Acetylcholinesterase breaks down to ACh into choline and acetate, terminating the signal in the postsynaptice cell
  7. the presynaptic cell takes up and recycles the choline, and the acetate diffuses out of the synapse
38
Q

What is the sole NT for motor division of the somatic system?

A

ACh

39
Q

Muscle contraction that follows the AP…

A
  • neurogenic
    • excited by NTs from motor nerves
    • can have multiple (tonic) or single (twitch) innervation sites
  • receptor is nicotinic
    • ionotropic
  • t-tubules allow rapic spread of the AP throughout the cell
40
Q

How does muscle depolarization follows the AP?

A
  • APs along sarcolemma signal contraction
    • Na+ enterls cell when Na+ channels open
      • depolarization
    • voltage-gated Ca2+ channel open
      • increase in cytoplasmic [Ca2+]
    • Na+ channels close
    • K+ leaves cell when K+ channels open
      • repolarization
    • reestablishment of ion gradients by Na+/K+ ATPase and Ca2+ ATPase
41
Q

Show the t-tubules and SR

A
43
Q

Describe ion movement in myocytes

A
  • AP along sarcolemma conducted down t-tubules
    • depolarization opens DHPR
      • in skeletal muscle, change in DHPR causes RyR to open allowing of Ca2+ from SR
      • DHPR and RyR are physically coupled
44
Q

Describe the importance of Ca2+ release from SR in muscle contraction.

A

AP along sarcolemma conducted down T-tubules. Depolarization opens DHPR…

  • in skeletal muscle, change in DHPR shape causes RyR to open, allowing release of Ca2+ from SR
  • DHPR and RyR are physically coupled
45
Q

Describe what happens with DHPR and RyR during contraction and relaxation.

A
46
Q

Describe muscle contraction.

A
  • Ca allows mypsin to bind to the actin
    • at rest, cytoplasmic [Ca] is low
      • troponin-tropomyosin cover myosin binding sites actin
    • as cytoplasmic [Ca] increases
      • Ca binds TnC (Ca binding site on troponin)
      • troponin-tropimyosin moves, exposing myosin-beinding site on actin
      • myosin binds to acin and cross-bridge cycle begins
      • cycles continue as long as Ca2+ is present
      • cell relaxes when the sarcolemme repolaries and intrecellular Ca2+ returns to resting levels
47
Q

Show the regulation of contraction by Ca2+

A
48
Q

What are the two processes of the sliding filament model?

A

Chemical reaction (myosin binds to actin, cross bridge) and structural change (myosin bends, power stroke).

49
Q

What is meant by the cross bridge cycle (muscle contraction)?

A

Formation of cross-bridge, power stroke, release and extension.

50
Q

What is needed to release and reattach to actin?

A

ATP

51
Q

What are the two factors affect actino-myosin activity?

A
  • Unitary displacement
    • distance myosin steps during each cross-bridge cycle
  • Duty cycle
    • the fraction of the total cross-bridge cycle that mosin spends attached to acin in a fore generating state
52
Q

Unitary displacement is dependent on…

A

Microfilaments, the length of myosin neck and on actin structure.

53
Q

What does contractile force depend on?

A

Overlap of thick and thin filaments.

54
Q

Describe what happens during muscl relaxation.

A

Repolarization of sarcolemma

– Remove Ca2+ from cytoplasm

  • Ca2+ ATPase in sarcolemma and SR
  • Na+/Ca2+ exchanger (NaCaX) in sarcolemma

• Parvalbumin
– Cytosolic Ca2+ binding protein buffers Ca2+

– Ca2+ dissociates from troponin – Tropomyosin blocks myosin binding sites – Myosin can no longer bind to ac1n

Zoology 242 (13 decks)

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