https://padlet.com/carhol926/pahr9f7ghnyi Made with charisma en-us 2019-03-08 13:18:08 UTC 2025-11-20 21:56:37 UTC hello@padlet.com carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276662 Step 1: The brain sends an action potential through the motor unit down to a neuromuscular junction.
Step 2: The action potential causes voltage gated calcium ion channels to open, which allow calcium ions to enter the neuron.  This increase in calcium stimulates the release of the neurotransmitter, ACh, which is released into the cleft.
Step 3: ACh binds to an ACh receptor sight and activates voltage gated sodium channel, which pumps Na+ in and K+ out. More Na+ is pumped into the muscle cell than K+ is pumped out causing the cell interior to become less negative.
Step 4: Initial depolarization spreads to adjacent areas, opening voltage gated Na+ channels and eventually initiating an action potential that moves along the lengths of the sarcolemma.
Step 5: Na+ concentrations, caused by depolarization, stimulate a change in membrane permeability by opening voltage-gated K+ pumps which allow K+ to diffuse across the sarcolemma out of the muscle fiber.  This is known as repolarization.]]> 2019-03-08 13:21:19 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276662 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276699 Step 1:  The action potential moves down the sarcolemma and down the T tubules. 

 

]]> 2019-03-08 13:21:24 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276699 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276718 Step 2: Transmission of the action potential along the T tubules cause the adjacent sarcoplasmic reticulum to release Ca2+ which flows into the cytosol. ]]> 2019-03-08 13:21:29 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276718 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276768 Step 3: Ca2+ combines with troponin and removes the blocking action of tropomyosin by changing the shape of the actin so that the myosin binding site are exposed.
Step 4: Myosin binds to actin forms cross bridges and contraction begins.

]]> 2019-03-08 13:21:39 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276768 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276793 Step 1: Cross bridge formation: high-energy myosin head attaches to actin myofilaments forming a cross bridge.

]]> 2019-03-08 13:21:44 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276793 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276857 Step 2: Working (power) stroke: myosin head pivots and pulls actin filament toward M line. ]]> 2019-03-08 13:21:55 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276857 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276891 Step 3: Cross bridge detachment: ATP attaches to myosin head, causing bridge to detach. ]]> 2019-03-08 13:22:00 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276891 carhol926 https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276919 Step 4: Cocking of myosin head: energy from hydrolysis of ATP "cocks" myosin head into high-energy state. ]]> 2019-03-08 13:22:05 UTC https://padlet.com/carhol926/pahr9f7ghnyi/wish/339276919