Figure 12.1 Microscopic Anatomy of Skeletal Muscle

1 (dark pink band)

A-band, contains both myosin and actin filaments

2 (white band)

I-band, contains only actin filaments

3

muscle fiber, muscle contraction

4

nuclei, regulate cell’s activities

5

sarcolemma, protects muscle fiber

6

mitochondrion, produces ATP

7

myofibril, makes up bulk of muscle cell, contains actin and myosin

8

nucleus, regulates cell’s activities 

9

I-band, contains only actin filaments

10

A-band, contains both actin and myosin

1

Z-disc, border of sarcomere

2

H-zone, contains only myosin filaments

3

actin filament, gets pulled by myosin during muscle contraction

4

myosin, pulls actin towards M-line during muscle contraction

5

I-band, contains only actin filaments

6

A-band, contains both actin and myosin

7

sarcomere, functional contractile unit of muscle cell

8

M-line, center of sarcomere

9

Z-disc, border of sarcomere

11

actin, gets pulled by myosin during muscle contraction

12

titin filaments, provides elasticity

13

myosin, pulls actin towards M-line during muscle contraction

14

I-band, contains only actin filaments

15

H-zone, contains only myosin filaments

16

outer edge of A-band, myosin and actin overlap