Physiology: Skeletal Contraction

Action Potential

A rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane.

Action Potential travels along motor never to muscle fiber ending

The beginning of the process of muscle contraction

Acetylcholine

After the action potential moves to the motor nerve to the muscle fiber ending, this is secreted on from the nerve endingd

Acetylcholine-gated cation channels

Acetylcholine binds on this which is located in the muscle fiber membrane, leading to an influx of Na ions

Sodium Influx

This influx causes depolarization of the muscle fiber membrane, which opens voltage-gated sodium channels, propagating the action potential along the muscle fiber.

Sarcoplasmic Reticulum

a specialized endoplasmic reticulum in muscle cells that stores calcium ions (Ca2+).

Action potential

Driver of the SR to release calcium ions to the cytoplasm of the muscle fiber

Actin, Myosin

The increase in intracellular calcium concentration initiates the interaction between

Actin, Myosin

e two primary proteins involved in muscle contraction.

troponin- tropomyosin complex

The released calcium ions bind to this, causing a conformational change that uncovers the active sites on the actin filaments.

Cross bridging

Myosin heads, which are part of the thick filaments, attach to these active sites on the actin filaments, forming

ATPase

The binding of myosin to actin activates the enzyme in the myosin head, which hydrolyzes ATP into ADP and inorganic phosphate (P), releasing energy.

Power Stroke

The energy released from ATP hydrolysis is utilized in this, where the myosin head tilts and pulls the actin filament toward the center of the sarcomere.

Sliding Filament Theory

The process of actin sliding over myosin is known as the

ADP + P

After the power stroke, the myosin head releases

Calcium Ions

pumped back into the sarcoplasmic reticulum by calcium pumps, leading to a decrease in intracellular calcium concentration and cessation of muscle contraction

Acetylcholine

A neurotransmitter that transmits signals frommotor neuronstomuscle fibers, initiating muscle contraction.

Sarcoplasmic Reticulum

A specialized form of endoplasmic reticulumin muscle cells thatstores and releases calcium ions.

Troponin-tropomyosin complex

A regulatory protein complex that controls the interaction between actin and myosin by blocking or exposing active sites on actin.

Cross bridging

The connection formed when myosin heads attach to activesitesonactin filaments during muscle contraction.

Power Stroke

The movement of the myosin head that pulls the actin filament during contraction, powered by the hydrolysis of ATP.

Sliding Filament Theory

A model explaining muscle contraction, where actin andmyosinfilaments slide past each other to shorten the muscle fiber.