Muscle Tissue Physiology - Key Terms

Vocabulary flashcards covering key terms and concepts in muscle tissue physiology.

Neuromuscular Junction

Region where the motor neuron interacts with a muscle fiber.

Motor Neuron

Nerve cell that sends signals to muscles (or glands).

Axon Terminal

Bulbous end of an axon; contains synaptic vesicles.

Synaptic Vesicles

Membranous sacs in axon terminals that release ACh when triggered by an AP.

Acetylcholine (ACh)

Neurotransmitter stored in synaptic vesicles in the axon terminal.

Synaptic Cleft

Gap between a nerve ending (axonal terminal) and muscle.

Calcium Ion (Ca2+)

Rushes into the axon terminal when triggered by an AP; causes ACh to be released.

Action Potential (AP)

Electrical signal/impulse that travels down neurons and/or muscle cells.

End Plate Potential

Depolarization at the neuromuscular junction caused by ACh binding to gated ion channels.

Repolarization

Voltage across membrane gets MORE negative (moves away from zero).

Depolarization

Voltage across membrane gets LESS negative (moves toward zero).

Refractory Period

After an AP when a cell (muscle fiber or neuron) cannot be stimulated again.

Voltage Gated Ion Channels

Membrane proteins that open to allow Na+ or K+ into/out of the cell; triggered by depolarization.

Sodium Ion (Na+)

Rushes into muscle fiber via voltage-gated channels during an AP.

T Tubule

Tube-like extension of sarcolemma into muscle fiber; AP travels down this.

Sarcoplasmic Reticulum (SR)

Endoplasmic reticulum of muscle cells; releases Ca2+ when triggered by an AP.

Myosin

Protein of thick myofilament.

Actin

Protein of thin myofilament; has sites for thick filament proteins to bind.

Troponin

Holds tropomyosin in place (blocking actin binding sites) when Ca2+ is absent.

Tropomyosin

Rod-shaped protein that blocks the binding sites on actin when Ca2+ is absent.

Cross Bridge

The link between the myosin head and actin during contraction.

Excitation-Contraction Coupling

Process linking muscle fiber excitation to contraction.

Ca2+ Ion

Released by SR; binds to troponin & stops tropomyosin from blocking the binding sites on actin