NCERT Skeletal Muscle (17.2)

sarcolemma

plasma membrane of muscle fibre

sarcoplasm

cytoplasm of muscle fibre

syncitium means

sarcoplasm contains many nuclei

STOREHOUSE of Ca^+2 ions

sarcoplasm

Characteristic feature of muscle fibre (cell)

presence of myofilaments or MYOFIBRILS

what are large no. of parallelly arranged filaments in sarcoplasm

myofibrils

_____ has alternate light and dark bands on it

myofibril

the striated appearance is due to the distribution pattern of which PROTEINS

Actin $ Myosin

Light band - I band - isotropic band

contains

Actin

Dark band - A band - anisotropic band

contains

myosin

priteins are arranged parallel to______ axis of myofibril

longitudinal

Z line

elastic FIBRE. bisects I band

I band

actin only

A band

extend to length of MYOSIN

M line

Z line

H zone

THIN fibrous membrane.- bisects A band

ELASTIC fibrous membrane - bisects I band

cental part of thick filament not overlapped by thin filament— MYOSIN only

Sarcomere

functional unit of contraction

portion of myofibril between 2 —Z lines

arrangement of both proteins

rod like structure

parallel to each other

parallel to longitudinal myofibril axis

fascicles

muscle bundle

make skeletal muscle

fascia

collagenous connective tissue layer b|w muscle bundles

contains a number of muscle fibre

each fascicle

fascicle -fascia (connects)- fascicle——>muscle fibres——> sarcolemma ,sarcoplasm, syncitium ———>Actin thin , Myosin thick

I band actin — A band myosin —

[Z cuts I ]— [M cuts A]—

H has only myosin —I has only actin-

sarcomere is between Z-Z