[03] Muscle Contraction and Relaxation Flashcards
What are the key stages of muscle contraction?
- Signal initiation
- Propagation of action potential
- Calcium ion release
- Cross-bridge cycle
- Contraction
What initiates a muscle contraction?
A signal from the nervous system
What is an “Action Potential”?
A rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane
How does an action potential propagate in a muscle fiber?
It travels along the sarcolemma and down the T-tubules.
What role do “Calcium Ions” play in muscle contraction?
They bind to troponin, exposing the myosin-binding sites on actin.
What is the “Cross-Bridge Cycle”?
It’s the process where myosin heads bind to actin, perform a power stroke, and detach, leading to muscle contraction.
How does a muscle contract?
Myosin heads bind to actin, pull the actin filaments towards the center of the sarcomere, then detach and repeat the process.
What happens during muscle relaxation?
- Calcium ions are pumped back into the sarcoplasmic reticulum
- Troponin returns to its original shape
- Myosin-binding sites are covered again
- Myosin heads can no longer attach to actin
What role does ATP play in muscle contraction and relaxation?
- Provides energy for the power stroke during contraction
- Facilitates detachment of myosin heads during relaxation
What is the “Sliding Filament Theory”?
It’s the explanation of how muscle fibers contract and lengthen by actin and myosin sliding past each other.
What is “Troponin”?
A protein that regulates muscle contraction by binding calcium ions and uncovering the myosin-binding sites on actin.
What is the “Sarcolemma”?
The cell membrane of a muscle fiber.
What are “T-Tubules”?
Extensions of the sarcolemma that penetrate into the muscle fiber and help propagate the action potential.
What is the “Sarcoplasmic Reticulum”?
A specialized form of endoplasmic reticulum that stores and releases calcium ions in muscle cells.
What is the “Power Stroke”?
The action of myosin pulling actin towards the center of the sarcomere, resulting in muscle contraction.
