Skeletal muscle Excitation-Contraction Cycle Flashcards
- In order for a skeletal muscle to contract…
it must get a signal from the nervous system.
- An action potential will travel down the motor neuron allowing…
Ca+ channels to open so Ca+ can move into the membrane.
- The presence of Ca+ in the membrane allows…
the motor neuron to release neurotransmitters Acetylcholine (ACh)
- The ACh will cross the synaptic cleft and bind to…
ACh (nicotinic) receptors on the motor end plate of the skeletal muscle.
- The Na+ channels open, allowing Na+ ions to pass into…
the muscle cell fiber. K+ ions also flow out.
- This inflow of Na+ and outflow of K+ results in…
depolarization along the muscle fiber and creates motor end plate potential.
- Once ACh binds, it can’t stay there or else it will…
keep muscle in constant state of contraction.
- ACh is broken down by…
Acetylcholinesterase, and stimulation stops.
- The increase in Na+ ions inside the muscle cells results in…
an action potential along the sarcolemma.
- The Action Potential moves down the sarcolemma into the T tubules and stimulates…
the release of Ca+ from the terminal cisternae and SR.
- Once Ca+ is released, it binds to troponin, this pulls…
tropomyosin off the active site of Actin.
- When Ca+ binds, it opens the active site on Actin, which allows…
myosin cross-bridge to bind to that active site.
- ATP must be broken down so that…
Myosin cross-bridges can ratchet.
- As long as ACh is stimulating the muscle fiber, the active site will stay open and the myosin will…
continue to ratchet along the myosin, brining the Z-lines closer together, causing muscle contraction.
- ATP also provides the energy to pump Ca+ back into the SR which allows….
the muscle to relax.
