1. Bell Ringer Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle
Functions
Produce movement
Maintain posture
Stabilize joints
Generate heat

2. Topic 6 The Muscular System Microscopic Anatomy of skeletal muscle
Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Topic 6 The Muscular System
Microscopic Anatomy of skeletal muscle
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. Microscopic Anatomy of Skeletal Muscle
Cells are multinucleate
Nuclei are just beneath the sarcolemma
Figure 6.3a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Microscopic Anatomy of Skeletal Muscle
Sarcolemma – specialized plasma membrane
Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum (Store calcium and release it on demand when contraction is needed)
Figure 6.3a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5. Microscopic Anatomy of Skeletal Muscle
Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distrinct bands
I band = light band
A band = dark band
Figure 6.3b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. Microscopic Anatomy of Skeletal Muscle
Sarcomere (Segment of a myofibril)
Contractile unit of a muscle fiber
Figure 6.3b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Figure 6.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin
Figure 6.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. Microscopic Anatomy of Skeletal Muscle
Myosin filaments have heads (extensions, or cross bridges)
Link the thick and thin filaments during contraction
Myosin and actin overlap somewhat
Figure 6.3d
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings