Neuromuscular Junction and Muscle Cell Excitation

Neuromuscular Junction

• The initial neurotransmitter released at the neuromuscular junction is acetylcholine.

Muscle Cell Membrane

• Depolarization of the muscle cell membrane occurs at the motor end plate.

Muscle Fiber

• The T-tubules (transverse tubules) spread the action potential into the muscle fiber.

Sarcoplasmic Reticulum

• The depolarization of the T-tubules stimulates the release of calcium ions from the sarcoplasmic reticulum.

Calcium Ions

• Calcium ions bind to the troponin protein in muscle cells.

Muscle Contraction

• The binding of calcium ions to troponin causes a conformational change in the troponin-tropomyosin complex, which exposes the binding sites on actin.

Cross-Bridge Formation

• ATP provides energy for myosin heads during cross-bridge formation.

Muscle Contraction Process

• Myosin heads are responsible for pulling actin filaments toward the center of the sarcomere.

Sarcoplasmic Reticulum Function

• The sarcoplasmic reticulum releases stored calcium ions into the cytoplasm of the muscle cell.

Neuromuscular Junction Communication

• Acetylcholine binds to receptors on the muscle cell membrane at the neuromuscular junction.

Action Potential Generation

• The binding of acetylcholine to its receptors is responsible for generating an action potential that spreads along the sarcolemma and into the muscle fiber.