lecture 3 muscle physiology part 2

Vocabulary flashcards covering structural and regulatory components of the sarcomere and skeletal muscle tissue, based on the lecture transcript.

Sarcomere

The smallest contractile unit of a myofibril, spanning from one Z disc to the next Z disc.

Thick Filament

Bundle of myosin molecules that appears dark and forms part of the A band.

Thin Filament

Filament made of actin molecules; interacts with myosin during contraction.

Myosin

Motor protein composing thick filaments; each molecule has a tail and a head that pulls on actin.

Actin

Globular protein that polymerizes into thin filaments and contains binding sites for myosin heads.

Myosin Head

Projection on a myosin molecule that attaches to actin and performs the power stroke.

Myosin-Binding Site

Specific location on an actin molecule where a myosin head attaches during contraction.

Zone of Overlap

Region in a sarcomere where thick and thin filaments overlap; enlarges during contraction.

Sliding Filament Theory

Model stating that muscle contraction occurs as thin filaments slide past thick filaments, shortening the sarcomere.

I Band

Light band containing only thin filaments; shortens during contraction.

A Band

Dark band containing the entire length of thick filaments, including overlap with thin filaments.

H Zone

Central area within the A band that contains only thick filaments and no overlap.

M Line

Middle line of a sarcomere where thick filaments are anchored; defines center of the H zone.

Z Disc (Z Line)

Zig-zag protein structure that anchors thin filaments and marks sarcomere boundaries.

Tropomyosin

Long regulatory protein that winds around thin filaments and blocks myosin-binding sites on actin.

Troponin

Regulatory protein that holds tropomyosin in place over actin's binding sites.

Dystrophin

Protein that anchors the sarcomere to surrounding structures, maintaining alignment.

Titan

Elastic protein that connects the Z disc to the M line, stabilizing and recoiling the sarcomere.

Nebulin

Protein that wraps around thin filaments, helping to align and stabilize them.

Myomesin

Protein that forms the M line and links thick filaments together.

Alpha-Actinin

Protein in the Z disc that binds actin filaments, helping to anchor them.

Fascicle

Bundle of muscle fibers surrounded by perimysium.

Epimysium

Connective tissue sheath that surrounds the entire muscle.

Perimysium

Connective tissue layer that wraps around and separates fascicles.

Endomysium

Thin connective tissue surrounding each individual muscle fiber.

Muscle Fiber

Single skeletal muscle cell; contains many myofibrils and multiple nuclei.

Sarcolemma

Plasma membrane of a muscle fiber.

Myofibril

Rod-like bundle of contractile proteins inside a muscle fiber, composed of repeating sarcomeres.

Sarcoplasmic Reticulum

Specialized endoplasmic reticulum that stores and releases calcium for contraction.

T Tubules

Extensions of the sarcolemma that penetrate the cell and transmit action potentials throughout the fiber.