1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slides 6.1 – 6.17 Seventh Edition Elaine N. Marieb Chapter 6 The Muscular System: Anatomy Lecture Slides in PowerPoint by Jerry L. Cook

3. Characteristics of Muscles  Muscle cells are elongated (muscle cell = muscle fiber)  Contraction of muscles is due to the movement of myofilaments  All muscles share some terminology  Prefix myo refers to muscle  Prefix mys refers to muscle  Prefix sarco refers to flesh

4. Smooth Muscle Characteristics  Has no striations  Spindle-shaped (fusiform) cells  Single nucleus  Involuntary – no conscious control  Found mainly in the walls of hollow organs (digestive, respiratory, reproductive, circulatory, urinary, endocrine*, integumentary*)

5. circular layer longitudinal layer Smooth muscle surrounding a blood vessel

6. Cardiac Muscle Characteristics  Has striations  Usually has a single nucleus  Joined to another muscle cell at an intercalated disc  Involuntary  Found only in the heart Figure 6.2b intercalated disc

7. Skeletal Muscle Characteristics  Most are attached by tendons to bones  Cells are multinucleate  Striated – have visible banding  Voluntary – subject to conscious control  Cells are surrounded and bundled by connective tissue

8. Connective Tissue Wrappings of Skeletal Muscle  Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers Figure 6.1

9. Connective Tissue Wrappings of Skeletal Muscle  Epimysium – covers the entire skeletal muscle  Fascia – on the outside of the epimysium Figure 6.1

10. Skeletal Muscle Attachments  Epimysium “blends” into a connective tissue attachment  Tendon – cord-like structure; usually connect muscle to bone  Aponeurosis – flat, sheet-like tendon  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

11. Nerves in Muscle Motor Neurons 1.AKA Efferent Neurons 2.Form neuromuscular junctions 3.Initiate muscle contraction Proprioceptors 1.Sense stretch 2.From “proprio,” one’s own or belonging to self, and “cep,” to take 3.AKA Afferent Neurons 4.Found in muscle spindle within skeletal muscle a.Capsule of fibrocartilaginous tissue surrounds a group of 8-15 thin muscle fibers b.Nerves that innervate and spiral around muscle spindles sense stretch 5.Also found in tendons

12. Microscopic Anatomy of Skeletal Muscle  Cells are multinucleate  Nuclei are just beneath the sarcolemma

13. Microscopic Anatomy of Skeletal Muscle  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum (SR)– specialized smooth endoplasmic reticulum (surrounding each myofibril)

14. Microscopic Anatomy of Skeletal Muscle  Myofibril  Bundles of myofilaments  Myofibrils are aligned to give distinct bands  I band = light band (only actin)  A band = dark band (actin and myosin)

15. Microscopic Anatomy of Skeletal Muscle  Sarcomere  Contractile unit of a muscle fiber  Z discs separate one sarcomere from the next

16. Microscopic Anatomy of Skeletal Muscle  Organization of the sarcomere  Thick filaments = myosin filaments  Composed of the protein myosin  Has ATPase enzymes  Extend entire length of dark (A) band

17. Microscopic Anatomy of Skeletal Muscle  Organization of the sarcomere  Thin filaments = actin filaments  Composed of the protein actin  Anchored to Z discs  Light (I) band is made up of only actin filaments

18. Microscopic Anatomy of Skeletal Muscle  H zone (Bare zone):  Central region of sarcomere where there is only myosin (no actin)  During contraction, actin filaments slide together and bare zones disappear  M line is in middle of H zone

20. Microscopic Anatomy of Skeletal Muscle  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat Figure 6.3d

21. Microscopic Anatomy of Skeletal Muscle  At rest, there is a bare zone that lacks actin filaments

24. Microscopic Anatomy of Smooth Muscle  Uses same contractile filaments as skeletal muscle (actin & myosin), however they are arranged in a crisscross pattern around each smooth muscle cell.

25. Microscopic Anatomy of Cardiac Muscle  Uses same contractile filaments as skeletal muscle (actin & myosin), and are arranged in the same banding pattern Presence of intercalated discs help to transmit the action potential and coordinate contractions.