Skeletal muscle Flashcards

1
Q
A
  1. Nerve impulse comes through axon and depolarized calcium channel at end of axon. Calcium causes release of acetylcholine
  2. Acetylcholine causes ligand dependent Na channel to open and Na moves into sarcoplasm, depolarizing cell.
  3. Depolarized sarcoplasm opens Na voltage gated channel and further depolarizes.
  4. Voltage gated Ca channel in sarcoplasm opens which opens calcium channel (dihydropyridine, DHP) in Sarcoplasmic reticulum. (this is where T-tubule is depolarized here)
  5. Calcium moves from SR into sarcoplasm which contracts cell.
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2
Q

muscle fiber

A
  • aka muscle cell
  • are post mitotic
    • do not replicate, just get bigger
  • each cell can have multiple nuclei
  • cells get bigger by growing more nuclei
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3
Q

muscle from gross to molecular

A
  • muscle
  • muscle fasciculus (single cell)
  • myofibril
    • A band, I band, z disc
  • sarcomere
  • myofilaments
    • Actin
    • myosin filament
      • myosin molecule (the grabber golf club)
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4
Q

troponin

A
  • covers the actin sites
  • requires Ca++ to move off actin site so myosin molecule can grab on to actin.
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5
Q

myosin head action

A
  1. ATP binds to myosin head, causing it to let go of actin
  2. ATP becomes ADP and myosin head repositions (With ADP & P)
  3. myosin head grabs hold of actin, causing release of P
  4. realease of P triggers “flick” that moves actin and myosin filaments relative to one another. ADP is released.
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6
Q
A

more overlap of the myosin and actin, the stronger the contraction.

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7
Q

isotonic system

A

muscle retraction against resistance where length changes

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8
Q

isometric system

A
  • generate force without changing length
    • much harder
    • difficult to get blood flow b/c muscles are contracted
      • leads to anaerobic metabolism
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9
Q

slow oxidative muscles

A
  • low myosin ATPase activity (speed of myosin release and reposition)
  • slow speed of contraction
  • high fatigue resistance
  • high oxidative capacity (gets O2, makes ATP, good as long as it has fuel)
  • low anaerobic enzyme content
  • many mitochondria (needed to make ATP)
  • many capillaries (to deliver O2)
  • high myoglobin
  • Red fiber color (dark)
  • low glycogen content (constantly refueling)
  • small fiber diameter
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10
Q

tetanization

A

sustained muscle contraction when action potentials are emitted at high rate

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11
Q

lever system

A
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12
Q

muscle damage and repair

A
  1. muscle experiences trauma, which injurs muscle
  2. progenitor cell attach to injured fiber
  3. myofiber is regenerated, a bit bigger

**Stem cells make more nuclei

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13
Q

t-tubules

A
  • communicate with outside of the cell membrane
  • lies next to the ends of SR tubules
  1. Ca leaves SR, depolarizing sarcoplasm and membrane.
  2. depolarization travels along membrane and down t-tubule to center of large muscle cell
  3. depolarization of t-tubule triggers voltage gated SRs along T-tubule in center of cell to open, releasing Ca and allowing entire muscle to contract
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14
Q

Golgi tendon organ

A
  • stretch gauge of tendon
  • tells brain how much force tendon is under
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15
Q

interfusal fibers

A
  • spindle shaped, found between normal muscle fibers
  • measures how much stretch spindle is getting
    • relays to brain the change in muscle length constantly
  • this is what controls fine motor
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16
Q

motor pathways

corticospinal

A
  • starts in cerebral cortex, ends in spine
  • (decussates) crosses at medulla
17
Q

Motor pathways

Rubrospinal

Reticulospinal

A
  • starts in red nucleus/reticula formation, ends at muscle plate
  • decussates (crosses over) at substantia nigra
    • problems with this synapse cause parkinsons
18
Q

sensory pathways

DCML

(dorsal column medial lemniscus)

A
  • fine touch and kinesthesis
  • first neuron starts at fingertip (or toe, etc.) and goes all the way to medula. Then continues up to cortex.
  • dessucation (crosses over) at medulla
19
Q

Sensory pathway

spinothalamic

A
  • pain and temperature
  • dessucates (crosses over) immediately in spine before continueing up to brain stem
20
Q

dorsal horn

A
  • spot in spine where spinothalamic “information” has first synaps and dessucates.
    • these synapses can be blocked by opiods so the pain sensation never gets to brain
21
Q

DHP

A

dihydropyridine

voltage gated channel that opens the ryanodine receptor that releases the Ca out of the SR

22
Q

creatine cycle

A
  1. creatine in mitochondria turned into creatine phosphate (by ATP in mito)
  2. creatine phosphate comes back and gives its phosphate to ADP
  3. making it now an ATP
  4. ATP binds to the myosin head (allowing it to release from the actin)
23
Q

plasma enzyme changes after MI

order of appearance

A
  1. myoglobin
  2. ck-MB
  3. CK
  4. LDH