Muscle Tissue Review Flashcards

Flashcards covering key terms and concepts related to muscle tissue.

Connective Tissue Layers

The layers of connective tissue from superficial to deep: epimysium, perimysium and endomysium

Aponeurosis

A thin, flattened sheet of regular tissue.

Sarcomere Structure

Includes the M line, I band, A band, and Z discs.

Thick Filaments

Consist of bundles of many myosin protein molecules; myosin head points towards end of filament.

Thin Filaments

Twisted strands of actin; has a myosin binding site where myosin heads attach; tropomyosin and troponin are present.

Connectin & Dystrophin

Stabilizes thick filaments and has a spring-like property, anchors some myofibrils to sarcolemma proteins.

Functions of Skeletal Muscle

Move the body, maintain posture, protect and support, regulate elimination of materials, and produce heat.

Cardiac Muscle Cells

Short branching fibers with one or two nuclei, striated and contain sarcomeres, many mitochondria, intercalated discs join ends of neighboring fibers, contractions started by heart autoarrhythmic pacemaker cells, heart rate and contraction force influenced by autonomic nervous system, and have thick and thin filaments.

Slow Oxidative Fibers (Type I)

Contractions are slower and less powerful, high endurance since ATP supplied aerobically, about half the diameter of other fibers, red in color due to myoglobin, and have a lot of mitochondria.

Isometric Contraction

Increase in tension with an insufficient ability to overcome resistance; muscle length stays the same.

Motor Unit

A motor neuron and all the muscle fibers it controls; small motor units allow for precise control of force output; large motor units allow for production of large amount of force, but not precise control; fibers in motor units are dispersed throughout the muscle.

Concentric Contraction

Muscle shortens as it contracts.

Sarcoplasm

Has typical organelles plus contractile proteins and other specializations.

Transverse Tubule (T-tubule)

Contain voltage-sensitive calcium channels.

Troponin

Regulatory proteins; trigger cross-bridge cycling when calcium binds to it.

Myosin

A protein molecule; myosin heads point toward the ends of filament and attach to binding site of G actin.

Isotonic Contraction

When the muscle tension results in movement, the muscle shortens and lengthens as the movement occurs; during eccentric contraction, muscle maintains tension while becoming longer.

Structure of Skeletal Muscle Fiber

Includes the sarcolemma, opening to tubules, myofibril, nucleus, and sarcoplasmic reticulum.

Sarcomere

Repeating unit of myofilaments; overlapping thin and thick filaments; delineated at both ends by Z discs; position of thin and thick filaments give rise to alternating I bands and A bands.

I Bands

Light-appearing regions that contain only thin filaments; bisected by Z discs; get smaller when muscles contract and can disappear with maximal contraction.

A Band

Dark-appearing region that contains thick filaments and overlapping thin filaments; contains the H zone and M line; makes up the central region of the sarcomere.

Crossbridge Cycling

When calcium binds to troponin, it triggers cross-bridge cycling; troponin and tropomyosin move so actin is exposed; myosin head attaches to exposed binding site on actin; myosin head pulls thin filament toward center of sarcomere; ADP and phosphate are released; Z line moves toward the M line, shortening contracting sarcomere; ATP binds to myosin head causing it to release from actin; ATP is split into ADP and phosphate by myosin ATPase providing energy to recock the myosin head.

Events of Muscle Contraction

Motor neuron releases acetylcholine (ACH); ACH binds to receptors on sarcolemma; action potential (AP) travels through T tubule; calcium released from sarcoplasmic reticulum; Calcium binds to troponin, tropomyosin moves; Myosin binds actin, cross bridge forms, power stroke occurs; ATP binds myosin, myosin reactivates ATP hydrolysis; Nerve signal stops, ACH broken down, calcium pumped back into SR, myofilaments relax to resting state.

Connective Tissue Layers

The layers of connective tissue from superficial to deep: , , and