3. (2) Neuron & Muscle
• Cause:
– Conscious decision to move
– Homeostatic response
• Nervous System Sends a Message to the
Effector Organ:
– Neurotransmitter released (ACh, acetylcholine)
– ACh binds to sarcolemma of muscle fiber
– ACh initiates opening of sodium-potassium
channels
4. (3) Depolarization
• Cause:
– Binding of ACh to sodium-potassium channels
– Opening of channels + Movement of Na-K+
across sarcolemma
• Involves the Movement of Charges:
– More Na+ moves in, Than K+ moves out
– Imbalance of charges electrical current
(action potential)
5. (4) Sarcoplasmic Reticulum &
Calcium
• Cause: Depolarization
• Action Potential across the Sarcoplasmic
Reticulum causes the release of Calcium:
– Ca+ released from membrane of sarcoplasmic
reticulum.
– Ca+ binds with troponin:
• Troponin-Tropomyosion conformation changes
• Troponin & Tropomyosin no longer cover Actin
• Actin is exposed
6. (5) Myosin interacts with Actin:
• Cause:
– Troponin & Tropomyosin unveils Actin
– Actin exposed
• Myosin releases Inorganic Phosphate + ADP
– Pi + ADP = ATP
– Myosin changes conformation
– Myosin binds to Actin
– Myosin and Actin slide towards each other
– WE HAVE A CONTRACTION! WOO WOO!
7. (6) Relaxation
• ATP binds back with myosin…
–Myosin detaches and moves away from
Actin
–Troponin & Tropomyosin cover up Actin
–Ca+ moves back into Sarcoplasmic
Reticulum
–Repolarization Sarcolemma stable
again
8. (7) Why is it called the Sliding
Filament Theory?
• Movement of myofilaments causes
contraction
• Myosin grabs actin & SLIDES them
towards the center
9.
10. (1-2) Depolarization of
Sarcolemma & Generation of
Action Potential
(3) Calcium Ions
released from
Sarcoplasmic Reticulum
(4-6) Calcium binds to troponin,
tropomyosin moves, actin exposed
(7-8) Myosin attaches to actin, Myosin moves actin, ATP
released
(9) Calcium removed by active transport
(10) Everything moves back &
contraction done!
