Muscle Structure

Frequency

Number of occurrences of a repeating event per unit time

Amplitude

the height of the wave from baseline to crest

Waveform

The shape and form of a signal

Wavelength

The length from the crest of one peak to the crest of the next peak

Muscle fibers

Individual cells organized into fascicles that makeup skeletal muscle tissue

Upper motor neuron lesions

loss of muscle function as a consequence of strokes damaging neurons in the brain

Excitability

ability to receive and respond to stimuli

Contractility

ability to shorten forcibly when stimulated

Extensibility

ability to be stretched

Elasticity

ability to recoil after being stretched

Direct attachment

periosteum or perichondrium is fused with the muscle's epimysium

Indirect attachment

Tendon or aponeurosis connects muscle to bone

Sacrolemma

plasma membrane of a muscle fiber

Sacroplasm

cytoplasm of a muscle cell

Myoglobin

stores oxygen in muscle cells

Glycosomes

glycogen storage, broken down to supply ATP for energy

Myofibrils

repeating units of sarcomeres

Sarcomeres

smallest contractile units of skeletal muscle fibers

A bands and I bands

striations within sarcomeres

H zone

middle, slightly lighter region of A band

Z line

dark midline region of I band

Actin

thin filaments

myosin

The contractile protein that makes up the thick filaments of muscle fibers

Tropomyosin

covers myosin binding sites on the actin molecules

Troponin

regulatory protein that binds to actin, tropomyosin, and calcium

Titin

elastic filaments holding thick filaments in place and providing flexible recoil to the sarcomere

T-tubules

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

Terminal cisterns

Perpendicular cross channels of sarcoplasmic reticulum that controls calcium levels

Triad

T tubule plus terminal cisterns on either side

Steps of muscle action potential propagation

1. Depolarization makes sarcolemma less negative - end plate potential

2. + sodium ions enter and cause a depolarization wave - muscle action potential

3. sodium channels close and sodium exits, negative potassium channels open and sarcolemma repolarizes