Sliding Filament Theory

Biomotion Notes

a) Muscle contraction:

As the message reaches the end of the nerve it releases a molecule called acetylcholine which then goes through the gap between the nerve and the muscle

b) Muscle contraction: Action Potential on T-Tubule:

After the receptors grab the acetylcholine it causes the muscle to become more positively charged which continues the message to the T-Tubule 

c) Muscle contraction: Calcium Release

The message causes the release of calcium

d) Muscle contraction: Troponin Binding

The calcium then binds to Troponin signaling to tropomyosin to move off of the binding sight

e) Muscle contraction: Powerstroke

The energized myosin heads bond to the open binding site, forming a cross bridge. After the cross bridge forms the head rotates which releases the ADP. As the actin slides past the myosin it creates the power stroke

f) Actin-Myosin Detachment

After the power stroke the myosin head stays connected until a new ATP connects to the myosin head, then releasing the head from the binding site

Videos

Amoeba Sisters

  • Actin-thin filaments

  • Myosin- thick filaments

  • Z lines- are where the actin is connected to

  • In the middle there are m lines that connect the myosin 

  • When muscles contract the actin filaments slide further over the myosin making the over all length shorter

  • Myosins have myosin heads which bind to the actin 

  • The ADP holds it to the heads to the actin

  • The new ATP then breaks the cross bridge

  • If you are relaxed there are things that block the binding sights for the heads

  • When your brain tells it to contract it releases calcium unblocking the binding sites so they can bind


Tech PE

  • When there is a nerve impulse it releases a chemical called acetylcholine 

  • The acetylcholine in the muscle releases calcium 

  • The calcium reacts with troponin to unblock the reaction sites

  • The calcium then binds to Tropomyosin/ Troponin Complex changing its shape so it moves the Complex from the attachment site

  • The head then attaches to the binding site causing a cross bridge to form

  • The breakdown of the ATP releases energy allowing the myosin to pull the actin inwards 

  • When another ATP connects to the myosin head releases

  • It can then break down the ATP and connect to another binding site further down the actin filament

  • This pulling is known as the ratchet mechanism

  • The contraction of the muscle can last for as long as there is ATP 

  • Once the nerve impulse stops the heads go to the resting position causing the muscle to lengthen 


Step-by-Step

  1. Nerve impulses reach the end of the nerve

  2. They release acetylcholine

  3. The acetylcholine goes across the gap

  4. It connects with the receptors on the muscle and causes the muscle to be more positively charged

  5. Action potential (message) spreads through the t-tubules

  6. This message releases calcium into the muscle

  7. The calcium bonds to the binding site blockers moving them out of the way

  8. Energized myosin heads then connect to the binding site

  9. This causes a cross bridge to form 

  10. The myosin head then turns to the center of the sarcomere while breaking down the ATP to give it energy (This is when the ADP is shed)

  11. When a new ATP attaches to the head it can then release and relax or connect to another binding site farther down the actin