Microscopic Anatomy of Skeletal, Cardiac, and Smooth Muscle

sarcolemma

cell membrane

sarcoplasm

cytoplasm of muscle cells

sarcolemma

cell membrane

sarcoplasm

cytoplasm of muscle cells

sarcoplasmic reticulum

smooth ER

what are the two main structures unique to muscle fibers

T-tubules and Sarcoplasmic Reticilum

Transverse Tubules

deep invaginations of the sarcolemma that extend into the sarcoplasm

what do T-tubules do

Carry impulses from sarcolemma to help stimulate muscle contraction

sarcoplasmic reticulum

internal membrane complex that stores calcium

what are the two types of myofilaments

thick and thin filaments

thick filaments

hundreds of bundled myosin molecules

myosin heads

the binding site for actin

thin filaments

2 strands of actin twisted around each other

what are the two regulatory proteins that are also part of the thin filament

tropomyosin and troponin

tropomyosin

rope like protein; at rest covers myosin binding site

troponin

binding site for calcium; attached to tropomyosin

sarcomeres

structural and functional unit within a myofibril; many thick and thin filaments

i-band

only thin filaments; lightest band of color

a-band

anywhere with thick filaments

h-zone

region at the center of the A band where there are only thick filaments

m-line

midline of sarcomere

during contraction, thin filaments slide past

thick filaments