Musculo-Skeletal Anatomy Making the body move!

Goals Important muscle groups to know Review muscle functions, types, and general anatomy In-depth look at skeletal muscle: –Connective tissue covering –Skeletal muscle fibers –Neuromuscular junction

Three types of muscle 1.Skeletal 2.Cardiac 3.Smooth

The Anterior (see handout) Anterior = “Front”

The Posterior (See handout) Posterior = “back”

Functions of Muscle Producing movement. Maintaining posture. Stabilizing joints. Generating heat.

Characteristics of Muscles (some review, some *new*!) Muscle cells are elongated (*muscle cell = muscle fiber) *Contraction of muscles is due to the movement of microfilaments *All muscles share some terminology –Prefix myo refers to muscle –Prefix mys refers to muscle –Prefix sarco refers to flesh

Skeletal Muscle Characteristics *Most are attached by tendons to bones Cells have many nuclei Striated – have visible banding Voluntary – subject to conscious control *Cells are surrounded by and bundled by connective tissue

Skeletal Muscle Striated, long, cylindrical, multi- nucleated. Attached to bones Voluntarily controlled * Range of contractile speed

Cardiac Muscle Striated, one nucleus, branching chains of cells, intercalated discs (= dark bands) Found only in the heart. Involuntary contraction. *Slow speed of contraction. *Rhythmic contraction.

Smooth Muscle One nucleus, no striations. *Found along the walls of blood vessels and digestive canals. Involuntary contraction. *Very slow contraction.

Skeletal Muscle Attachments What structures do muscles attach to? –Bones –Cartilages –**extensions of connective tissue coverings

Connective tissue coverings Layers of connective tissue enclose and separate all parts of a skeletal muscle 1.Fascia 2.Epimysium 3.Perimysium 4.Endomysium Friends Enjoy Protecting Each other

Fascia layers of connective tissue that separate individual skeletal muscles from each other –hold muscles in position –May extend beyond muscle to form: Tendon – cord-like structure Aponeuroses – sheet-like structure

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

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

How does the structure of the coverings arrangement allow the muscles to function? Structure: layers of connective tissue enclose and separate all parts of a skeletal muscle Function: –allows parts to move somewhat independently –Blood vessels and nerves pass through the layers  allows for blood/nutrient supply and stimulation

Review Produce movement Maintain posture Stabilize joints Generate heat Connective tissue coverings ?

Overall structure of muscle Muscle Fascicles (bundles) Muscle fibers (cells) Myofibrils Thick and thin filaments

Modeling Activity In pairs, using the available materials, create a model of a muscle (include fiber, fascicles, muscle fibers, fascia, epimysium, perimysium, endomysium)

Muscle fibers Definition: single cell that contracts in response to stimulation, relaxes when stimulation ends Thin, elongated cylinder that could extend full length of muscle

Muscle fibers Cells are multinucleate Nuclei are just beneath the sarcolemma

Microscopic Anatomy of Skeletal Muscle Sarcolemma – specialized plasma membrane Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6.3a

Figure 6.3b Microscopic Anatomy of Skeletal Muscle Myofibril –Bundles of myofilaments –Myofibrils are aligned to give distinct bands I band = light band A band = dark band Bands make muscle look STRIATED

Microscopic Anatomy of Skeletal Muscle Sarcomere –Contractile unit of a muscle fiber –From Z disc to Z disc Figure 6.3b

Microscopic Anatomy of Skeletal Muscle sarcomere organization (Section of myofibrils) –Thick filaments = myosin filaments = dark band Composed of the protein myosin Has ATPase enzymes (for contraction) Figure 6.3c

Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere –Thin filaments = actin filaments = light band Composed of the protein actin Figure 6.3c

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

Microscopic Anatomy of Skeletal Muscle At rest, there is a bare zone that lacks actin filaments Sarcoplasmic reticulum (SR) – for storage of calcium Figure 6.3d

Modeling activity In pairs, using the available materials, create a model of a myofibril segment between 2 M lines. Include/indicate sarcomere, actin, myosin, 2 M lines, I band, and A band