Sliding Filament Theory

Question 1

In what ORDER does the SLIDING FILAMENT THEORY OCCUR?

Answer 1

Resting Phase—> Excitation Phase—> Contraction Phase—> Recharge Phase—> Relaxation Phase

Question 2

Describe the RESTING PHASE

Answer 2

• No action potential from Motor Neuron
• So muscle is at rest

Question 3

Describe the EXCITATION PHASE

Answer 3

• Ca2+ released into Myofibrils & binds to Troponin
• Causes Tropomyosin to move, exposing Binding sites on Actin
• ATP on the Myosin Head hydrolyses and binds to Actin, forming Crossbridge

Question 4

Describe the CONTRACTION PHASE

Answer 4

• Myosin Cross Bridges perform a Power Stroke
• Energy released from hydrolyses of ATP is required for this process

Question 5

Describe the RECHARGE PHASE

Answer 5

• ATP Resynthesised & Myosin Head detaches from Actin
• This process will continuously occur so long as there is sufficient Ca2+ to bind to Troponin & ATP for C—B & Pstroke

Question 6

Describe the RELAXATION PHASE

Answer 6

• Motor Neurone stop firing impulses & Ca2+ is removed from Myofibrils
• Ca2+ moves back to Sarcoplasmic Reticulum
• Tropomyosin recovers and blocks binding sites on Actin=no more C—B
• Muscle is relaxed and returns to resting length

Question 7

Describe what is meant by POWER STROKE

Answer 7

• Sarcomere shortens
• Actin and Myosin filaments overlap
• Z-Lines move closer to each other