Muscle Contraction and Cross Bridge Cycle

Cross Bridge Cycle

The mechanical events where myosin and actin interact to generate muscle tension.

Myosin Head Function

Binds to actin to form cross-bridges, which creates muscle tension.

Actin Filament Structure

Contains a specific binding site for the myosin head.

Myosin-Actin Bond

The physical connection formed between the myosin head and actin binding site.

Myosin Energy Source

Myosin is energized through ATP and phosphate.

Myosin ATP Binding

Myosin binds ATP, which undergoes hydrolysis during the cycle.

Myosin ATPase

The enzyme that hydrolyzes ATP and transfers energy to the myosin molecule.

Power Working Stroke

The phase where ADP and Pi are released from the myosin head, causing movement.

Myosin Low Energy State

The state of myosin after ADP and Pi are released during the power stroke.

Cross Bridge Detachment

The process where ATP binds, causing the myosin head to detach from actin.

Detached Myosin State

Myosin is in a low energy state immediately following cross bridge detachment.

Cocking of Myosin Head

When ATP is hydrolyzed to ADP and Pi, returning myosin to its cocked position.

Role of ATP in Contraction

ATP helps break the cross-bridge and energizes the myosin head.

Calcium Regulation

The process managed by the sarcoplasmic reticulum to control intracellular calcium levels.

Sarcoplasmic Reticulum

The intracellular storage tank for calcium in muscle cells.

T Tubules

Structures that dive deep down into the muscle fiber.

Skeletal Muscle Excitation

The process of activating skeletal muscle fibers.

Exocytosis

The cellular process by which cells excrete substances.

Motor End Plate

The area where the neuromuscular junction meets the muscle fiber.

Prestroke Myosin Position

The high-energy or cocked position of the myosin head after ATP hydrolysis.

ADP and Pi Release

Released from the myosin head during the power working stroke.

Cross-Bridge Breakage

Requires ATP binding to break the bond between myosin and actin.

Calcium Storage

Handled by the sarcoplasmic reticulum acting as an intracellular calcium tank.

Muscle Fiber Depth

Reached by T tubules diving deep down in the muscle fiber.

Neuromuscular Junction Region

Includes the motor end plate where muscle meets nerves.

Cross Bridge Formation (Slide 6)

Energized myosin head attaches to an actin myofilament.

The Power Stroke (Slide 6)

ADP and Pi are released, causing the myosin head to pivot and pull the actin filament toward the M line.

Cross Bridge Detachment (Slide 6)

ATP attaches to myosin, weakening the link and causing the myosin head to detach.

Cocking of the Myosin Head (Slide 6)

As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy position.

Rigor Mortis (Slide 6)

Occurs in the absence of ATP when myosin heads will not detach from actin.