Skeletal muscle Flashcards
1
Q
A
- Nerve impulse comes through axon and depolarized calcium channel at end of axon. Calcium causes release of acetylcholine
- Acetylcholine causes ligand dependent Na channel to open and Na moves into sarcoplasm, depolarizing cell.
- Depolarized sarcoplasm opens Na voltage gated channel and further depolarizes.
- Voltage gated Ca channel in sarcoplasm opens which opens calcium channel (dihydropyridine, DHP) in Sarcoplasmic reticulum. (this is where T-tubule is depolarized here)
- Calcium moves from SR into sarcoplasm which contracts cell.
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
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)
4
Q
troponin
A
- covers the actin sites
- requires Ca++ to move off actin site so myosin molecule can grab on to actin.
5
Q
myosin head action
A
- ATP binds to myosin head, causing it to let go of actin
- ATP becomes ADP and myosin head repositions (With ADP & P)
- myosin head grabs hold of actin, causing release of P
- realease of P triggers “flick” that moves actin and myosin filaments relative to one another. ADP is released.
6
Q
A
more overlap of the myosin and actin, the stronger the contraction.
7
Q
isotonic system
A
muscle retraction against resistance where length changes
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
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
10
Q
tetanization
A
sustained muscle contraction when action potentials are emitted at high rate
11
Q
lever system
A
12
Q
muscle damage and repair
A
- muscle experiences trauma, which injurs muscle
- progenitor cell attach to injured fiber
- myofiber is regenerated, a bit bigger
**Stem cells make more nuclei
13
Q
t-tubules
A
- communicate with outside of the cell membrane
- lies next to the ends of SR tubules
- Ca leaves SR, depolarizing sarcoplasm and membrane.
- depolarization travels along membrane and down t-tubule to center of large muscle cell
- 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
14
Q
Golgi tendon organ
A
- stretch gauge of tendon
- tells brain how much force tendon is under
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
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
