Skeletal Muscle Physiology I Flashcards
sliding filament mechanism
a) Muscle relaxed
b) Partially contracted muscle
- actin move toward each other, sarcomere shortens
- I band and H zone narrow
c) Maximally contracted muscle
- actin ends overlapp
- H zone disappears
Cross Bridge Cycle
- Exposure: Ca2+ binds to troponin, exposes active site. Myosin heads in active state (ADP energy stored, ADP+phosphate bound)
- Cross bridge forms: myosin binds to active sites, phosphate released
- Power stroke: myosin head toward M line, pulls actin. When bent, ADP released.
- Release: ATP binds to head, releases myosin from actin
- Re-energize: ATPase on head turns ATP to ADP and phosphate, cycle starts again
rigor mortis
Stiff muscles in dead bodies
Myosin head stays bound to actin because no ATP being produced to release it
difference between skeletal muscle and nervous resting membrane potential
membrane potential larger in skeletal muscles
- greater K leak channels in
what is a branch of a somatic motor neuron called
branch from somatic motor neuron
neurtotransmitter released in somatic motor neurons
Acetylcholine
portion of sarcolemma that contains neuromuscular junction
motor end plate
function of neuromuscular junction
- AP arrives at presynaptic terminal, opens VG Ca2+ channels
- Ca2+ releases Ach from synaptic vesicles into synaptic cleft via exocytosis
- Ach diffuses across cleft, binds to ligand gated Na+ channels on motor end plate
- chanels open, Na+ into cell
- depolarization
- VG channels right beside continue AP
EPSP or IPSP in muscles?
alwasy EPSP
difference between neuron and skeletal muslce
In muscle ligand gated channels located close to VG channels on postsynaptic membrane
how to stop muscle contraction from continually occuring
- Ach constantly broken down by ACETYLCHOLINEESTERASE into choline and acetic acid
- choline recycled (paired with acetic acid in presynatpic terminal), acetic acid reused by other cells
excitation-contraction coupling
- muscle AP propagated along sarcolemma and into t-tubules
- Ca+ channels in the SR open and calcium is released into sarcoplasm
- Ca+ binds to troponin, movement of tropomyosin off of myosin binding site
- Heads of myosin can bind active sites on actin, cross-bridge forms
how does calcium release from troponin?
via SERCA pumps
- an ATPase
3 places where ATP is needed for skeletal muscle contraction
- Na+ K to reestablish resting membrane potential
- for myosin heads: stored energy and to detach from actin
- calcium pumps