0 The human body contains> 400 skeletal muscles (40 % of B. wt)
while smooth & cardiac muscles are (1 0% of B. wt.)
D Skeletal muscles are under voluntary control (somatic N.S .)
D Skeletal muscle contraction depends on its nerve supply. ... _
0 Functions (4):
• Locomotion & breathing .
• Heat production.
• Ma;ota;o;og po,toce & 'tabmty Thldl ftlamMta~
• Help venous return . <myooln)
Thlnfl ..ment.
---
-
lband
...
TIQ
A~nd I~
:
411
{ IK'tln) ... - •
\ m u •cle fibers z line a:=.. ~ z lne
• bun dled I n sh e ath
::1
H
ii ~ , q~ Actin Myosin
Z- line magnified
(structure}
Muscle fibers:
0 Bundled together by C.T.
0 Arranged in parallel fascicles between the tendinous ends.
0 Each muscle fiber is a single cell which is closely enveloped by sarcolemma
(a glycoprotein containing sheath , outside the true cell membrane)
0 Each muscle fiber is made of many parallel myofibrils embedded in its cytoplasm
(sarcoplasm) in between a complex tubular system.
Myofibrils
0 Thread-like structures that contain 2 types of interdigitating protein filaments.
jThick filaments c:> the protein (myosin) this arrangement gives
Filaments the striated appearance
Thin filaments c:> the protein (actin) of the skeletal muscles
0 Myofibrils are divided into functional units (sarcomeres) by Z lines c::> attach all
myofibrils together in a single muscle fiber.
47
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