Motor System and Muscle Contraction

These flashcards cover key vocabulary related to the motor system, muscle contraction, and neuromuscular junctions.

Muscle Fiber

A muscle cell that is long and fibrous, composed of myofibrils.

Myofibril

The basic rod-like unit of a muscle cell that contains sarcomeres.

Sarcomere

The functional unit of a muscle fiber, defined by Z lines.

Sarcolemma

The membrane of a muscle cell.

T-tubules

Extensions of the cell membrane that penetrate into the muscle cell, involved in action potential transmission and calcium regulation.

Sarcoplasmic Reticulum

Internal calcium store in muscle cells, releases calcium to trigger contraction.

Neuromuscular Junction (NMJ)

The synapse between a motor neuron and a muscle cell where neurotransmitter ACh is released.

Acetylcholine (ACh)

The neurotransmitter at the neuromuscular junction that stimulates muscle contraction.

Motor Unit

A motor neuron and the skeletal muscle cells it innervates.

Motor Pool

The group of motor neurons in the spinal cord that innervate a single muscle.

Cross-Bridge Cycle

A cyclical process in muscle contraction where myosin heads bind and detach from actin filaments, powered by ATP.

Motor End-Plate

The part of the muscle cell membrane at the NMJ, with receptors for ACh.

Diad

Association of one T-tubule with one terminal cistern in cardiac muscle.

Triad

Association of one T-tubule with two terminal cisternae in skeletal muscle.

Central Pattern Generator (CPG)

A neural circuit that generates rhythmic patterns of motor outputs.

Monoamines

Neuromodulators like dopamine, serotonin, and norepinephrine that modulate motor neuron activity.

Excitatory Postsynaptic Potential (EPSP)

A voltage change in a postsynaptic neuron that makes it easier to generate an action potential.