Chapter 10 Study Guides

Skeletal Muscle Functions

Movement, posture maintenance, heat production

Skeletal Muscle Characteristics

Striated, voluntary control, long cylindrical fibers, multinucleated

Epimysium

Outer connective tissue surrounding entire muscle

Perimysium

Connective tissue surrounding bundles of muscle fibers (fascicles)

Endomysium

Connective tissue surrounding each individual muscle fiber

Sarcolemma

Cell membrane of a muscle fiber

Sarcoplasmic Reticulum

Specialized smooth ER that stores and releases calcium ions

T-Tubule

Tunnel-like extension of sarcolemma that carries signals deep into muscle fiber

Triad

One T-tubule between two terminal cisternae of sarcoplasmic reticulum; allows rapid calcium release for contraction

Sarcomere

Basic functional unit of muscle contraction

I Band

Light band containing only thin (actin) filaments

A Band

Dark band containing thick (myosin) filaments and overlapping thin filaments

H Zone

Center of A band containing only thick filaments

M Line

Proteins in center of sarcomere holding thick filaments together

Z Disk

Boundary of sarcomere; anchors thin filaments

Actin

Thin filament protein myosin binds to during contraction

Myosin

Thick filament protein that pulls actin during contraction

Motor Unit

One motor neuron and all muscle fibers it controls

Synaptic Knob

End of motor neuron that releases neurotransmitters

Excitation-Contraction Coupling

Process where nerve signal triggers calcium release and contraction

Crossbridge Formation

Myosin head binds to actin

Powerstroke

Myosin pulls actin toward center of sarcomere

Crossbridge Release

ATP binds myosin causing it to detach from actin

Reset

Myosin head re-cocks using ATP

Relaxation

Calcium pumped back into sarcoplasmic reticulum; contraction stops

Acetylcholine (ACh)

Neurotransmitter released by motor neuron to start contraction

Calcium Role

Binds troponin to expose actin binding sites for myosin

Troponin

Protein that binds calcium and moves tropomyosin

Tropomyosin

Protein that blocks myosin binding sites on actin when muscle is relaxed

Glycolysis

Fast ATP production without oxygen; low yield

Creatine Phosphate

Immediate ATP source for short bursts

Aerobic Respiration

Uses oxygen to produce large amounts of ATP

Oxidative Fibers

Fibers that use oxygen and resist fatigue

Glycolytic Fibers

Fibers that generate energy quickly and fatigue fast

Isometric Contraction

Muscle tension without changing length

Isotonic Contraction

Muscle changes length while contracting

Concentric Contraction

Muscle shortens during contraction

Eccentric Contraction

Muscle lengthens during contraction

Cardiac Muscle

Striated muscle under involuntary control found in the heart