Muscular System and Muscle Contraction

Flashcards covering key terms and concepts related to the muscular system and muscle contraction.

Sarcolemma

The cell membrane of muscle cells, featuring a phospholipid bilayer plus proteins and carbohydrates.

Resting Membrane Potential (RMP)

The net charge difference across the sarcolemma at rest, typically around -95 mV.

Sodium-Potassium Pump

A membrane protein that uses ATP to move 3 Na+ out and 2 K+ into the cell, contributing to the charge difference.

T-tubules

Invaginations of the sarcolemma that facilitate signal delivery for muscle contraction into the fiber.

Myofibrils

Cylindrical organelles in muscle fibers that contain thick and thin filaments and enable contraction.

Myosin

A contractile protein that forms thick filaments, with heads that bind to actin during contraction.

Actin

A contractile protein that makes up thin filaments and has binding sites for myosin.

Tropomyosin

A regulatory protein that covers myosin binding sites on actin in a resting muscle.

Troponin

A regulatory protein attached to tropomyosin, containing a binding site for Ca2+.

Sarcomeres

The repeating units of thick and thin filaments that form the functional contractile unit of the muscle.

Excitation-Contraction Coupling

The sequence of events linking the muscle action potential in the sarcolemma to muscle contraction.

Crossbridge Cycling

The process in which myosin heads attach to actin, pivot, and detach, resulting in muscle contraction.

Motor Unit

A single motor neuron and all the muscle fibers it innervates, crucial for muscle contraction.

Neuromuscular Junction

The synapse between a motor neuron and a muscle cell, where signal transmission occurs.

Acetylcholine (ACh)

The neurotransmitter released at the neuromuscular junction that binds to receptors on the muscle cell.

Voltage-Gated Calcium Channels

Channels that open in response to an action potential, allowing Ca2+ to enter the sarcoplasm for contraction.

Power Stroke

The action in which myosin heads pull thin filaments towards the center of the sarcomere, leading to contraction.

ATP Hydrolysis

The process by which ATP is broken down to ADP + Pi, providing energy for muscle contraction.

Calcium ions (Ca2+)

Ions that trigger muscle contraction by binding to troponin and causing conformational changes in tropomyosin.