Muscular System - Physiology of Muscle Contraction

Flashcards covering key concepts from the muscular system lecture on muscle contraction physiology.

What are striations in skeletal muscle cells and why are they significant?

Striations are vertical light and dark bands along a muscle fibre, corresponding to regions of overlapping thick and thin myofilaments, crucial for contraction.

What is the smallest functional unit of a muscle cell?

The sarcomere, defined by the distance from one Z disc to the next.

Describe the role of calcium in muscle contraction.

Calcium binds to troponin, causing tropomyosin to shift and expose actin's binding sites for myosin to attach, enabling contraction.

What initiates muscle contraction at the neuromuscular junction?

The arrival of an action potential at the axon terminal, leading to the release of acetylcholine (ACh) which depolarizes the sarcolemma.

What are the four phases of excitation-contraction coupling?

Phase 1: Depolarization at the neuromuscular junction; Phase 2: Action potential spreads along the sarcolemma and T-tubules; Phase 3: Calcium is released from the sarcoplasmic reticulum; Phase 4: Binding of calcium to troponin and muscle contraction begins.

What is the cross-bridge cycle?

The series of events where myosin heads pull thin filaments toward the center of the sarcomere during muscle contraction.

Define hypertrophy and hyperplasia in muscle context.

Hypertrophy is the increase in size of muscle fibers; hyperplasia refers to an increase in the number of muscle fibers.

What are the three types of muscle fibers, and how do they differ?

Fast Glycolytic (FG) fibers are used for short bursts of strength; Slow Oxidative (SO) fibers are used for endurance; Fast Oxidative (FO) fibers share characteristics of both.

Explain how ATP is used in muscle contraction.

ATP is essential for the binding of myosin heads to actin, facilitating contraction and relaxation by breaking cross-bridges.

What happens during the sliding filament mechanism of muscle contraction?

Thin filaments slide past thick filaments, increasing overlap without changing their lengths, leading to muscle shortening.