Essentials of Anatomy and Physiology

B Bundles of

muscle cells

Muscle cells (fibers)

Myofibril

Fascia and

connective tissue

Myofibrils

C Muscle fiber

Sarcomere

Z line

Myosin filaments

Myosin cross bridges

Troponin

Tropomyosin

Myosin-binding

site

E Muscle filaments

D Sarcomere

Titin

filament

Actin

filament

Z line

Myosin filament

Transverse

tubule

Sarcoplasmic

reticulum

Sarcolemma

A Entire muscle

Actin

Figure 7–3. Structure of skeletal muscle. (A) Entire muscle. (B) Bundles of muscle cells

within a muscle. (C) Single muscle fiber, microscopic structure. (D) A sarcomere.

(E) Structure of muscle filaments.

QUESTION:What is the unit of contraction of a muscle fiber?

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