1. The muscular system 36-2

2. Muscles  Makes up 40% of the mass of an average person.  Power every movement of the body, from the blink of an eye to regulating blood pressure.  There are 3 different types of muscle tissue.

3. #1 :Skeletal muscle  Are usually attached to bones. Have a striped (striated) appearance.  Under the conscious control of the central nervous system.  Cells are 1mm-30cm long, have multiple nuclei.  Called muscle fibers, many are bundled together.

4. Muscle Contraction The thin filaments (actin) slide over the thick filaments (myosin), shortening the fiber. Bundles of muscle fibers together exert a lot of force, using ATP for energy. The thin filaments (actin) slide over the thick filaments (myosin), shortening the fiber. Bundles of muscle fibers together exert a lot of force, using ATP for energy.

5. How does a muscle work?  They work by contracting  Muscles work in pairs: when one shortens, the other lengthens

6. # 2. Smooth muscle  Spindle-shaped, not striated.  Lines the hollow organs: stomach, blood vessels, intestines, pupils.  Not under voluntary control.  Pump food, blood, dilate/constrict pupils. Smooth muscle in longitudinal and cross section

7. #3. Cardiac muscle  Found only in the heart.  Striated like skeletal muscle, but the cells are smaller.  Like smooth muscle, it’s under the direct control of the central nervous system.

8. Control of muscle contraction  Motor nerves stimulate muscles to contract, in response to impulses from the brain.  If an object is light, few cells will be activated.  For maximum effort, all muscle cells will respond.

9. Interactions: muscles and bones  Tendons (connective tissue) attach muscles to bones.  Tendons pull on bones, making them work like levers.  Several muscles surround a joint to move it in different directions.

10. Exercise and health  Regular exercise is important in maintaining muscular strength and flexibility.  Aerobic: helps heart and lungs be more efficient.  Resistance: increases muscle mass.  Regular exercise also strengthens bones.  “Use it or lose it”: both muscles and bones will atrophy if not used regularly.

11. Copyright Pearson Prentice Hall Skeletal muscles are joined to bones by tough connective tissue called Skeletal muscles are joined to bones by tough connective tissue called ligaments.ligaments. tendons.tendons. filaments.filaments. bursae.bursae.

12. Copyright Pearson Prentice Hall Muscle cells that are large, have many nuclei, and striations are Muscle cells that are large, have many nuclei, and striations are skeletal muscle cells.skeletal muscle cells. smooth muscle cells.smooth muscle cells. cardiac muscle cells.cardiac muscle cells. involuntary muscle cells.involuntary muscle cells.

13. Copyright Pearson Prentice Hall Muscle that is found in the walls of blood vessels and intestines is Muscle that is found in the walls of blood vessels and intestines is skeletal muscle.skeletal muscle. smooth muscle.smooth muscle. cardiac muscle.cardiac muscle. striated muscle.striated muscle.

14. Copyright Pearson Prentice Hall The filaments found in skeletal muscle cells are The filaments found in skeletal muscle cells are actin and myosinactin and myosin myosin and myofibrilsmyosin and myofibrils actin and Z linesactin and Z lines actin and sarcomeresactin and sarcomeres

15. Copyright Pearson Prentice Hall The type of muscle found only in the heart is The type of muscle found only in the heart is skeletal muscle.skeletal muscle. striated muscle.striated muscle. cardiac muscle.cardiac muscle. smooth muscle.smooth muscle.

16. Iris Kyle, Miss Olympia, 2012Phil Heath, Mr. Olympia 2012 Review: