Muscular System

1. Muscular System Read Ch 6 Review Questions begin on page 198 S/A #2, 7, 10, 12, 18, 20, 21 At the Clinic #2, 5, 6

2. Overview • Over ½ of body’s mass is muscle—90% of that is skeletal muscle • These contractile cells have high energy needs, so it’s common to see an ample blood supply associated with muscles http://www.edukshun.info/wp-content/uploads/2008/04/big-muscles.jpg

3. Overview con’t: • Blood provides glucose and oxygen while removing metabolic waste products • Muscles (and nervous tissue) consume almost 70% of the food energy taken into your body daily • Muscle is as intensive a consumer of calcium as is the skeletal system—much of the Ca stored in bones is made available for the muscles’ needs.

4. http://phelafel.technion.ac.il/~tamarh/website/images/different-kinds-of-muscles-2.jpghttp://phelafel.technion.ac.il/~tamarh/website/images/different-kinds-of-muscles-2.jpg micro.magnet.fsu.edu/ Categorizing muscles Microscopically • Nonstriated (no lines) • Striated (lines running through)

5. Categorizing muscles Controllability • Involuntary (no control) • Voluntary (control)

6. Categorizing muscles Location • Cardiac: Involuntary, only found in heart • Smooth: Involuntary, lines digestive organs • Skeletal: voluntary muscles found attached to bones

7. Cardiac Muscle • Involuntary, striated muscle • Have two nuclei per cell • These branched cells communicate with one another with intercalated disks • Cardiac cells have a natural contraction cycle called the intrinsic beat • Intercalated disks help synchronize the intrinsic beat so all cardiac muscles act in unison

8. Smooth muscle • Non-striated, involuntary muscle • Location: found in the lining of blood vessels, digestive organs, urinary system and parts of the respiratory system

9. Smooth muscle • These cells produce weak involuntary contractions that can last for long periods of time • Assist with dilation and constriction of the bv and respiratory system • In the digestive tract, they produce pulsating contractions called peristalsis (moves food and wastes though system)

10. Skeletal muscle—our focus • Voluntary, striated muscles • Provides movement of the bones and joints • Skeletal muscle is composed of many individual cells that have fused together into a long fiber. (have many nuclei in each one)

11. Muscle cell structure • Sarcomere—the contractile unit of a muscle cell (there are thousands of these in one cell) • Myofibril—long chains of sarcomeres. Each muscle fiber is made up of many bundled myofibrils running parallel to one another for the length of the cell Video of sarcomere shortening

12. http://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gifhttp://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gif Muscle cell structure • Sarcolemma—the membrane of the muscle cell • Bands of proteins called myofilaments • Thick (myosin) • Thin (actin, tropomyosin and troponin)

13. Myofilament arrangement • Thick (myosin) and thin (actin, troponin, tropomyosin) arrange to form an overlapping pattern w/in a sarcomere. • Thin myofilaments are attached to the Z-line • In between these thin myofilaments are the thick myosin filaments which appear to be floating within the cell.

14. http://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gifhttp://media-2.web.britannica.com/eb-media/36/2836-004-C63246A5.gif

15. Myofilament arrangement • Surrounding each sarcomere is an organelle called the sarcoplasmic reticulum (a system of tubes transporting Ca needed for contraction) http://media-2.web.britannica.com/eb-media/41/2841-004-8EA13F0E.gif

16. Functions of the Muscular System • Movement of body parts—by pulling on bones. Bones act as levers, joints as the fulcrum. • Guard entrances and exits • Posture • Stabilizing joints • Create heat

17. Muscle cell Function • Contraction is achieved by the simultaneous shortening of all the sarcomeres within a cell. • Three stages: Neural stimulation, contraction, relaxation.

18. Neural Stimulation • Takes place at the neuromuscular junction. • The nerve cell releases a neurotransmitter • neurotransmitter—a chemical used for cell to cell communication. http://www.freewebs.com/soaring_sphincter_travel_agency/nerve%20impulse2.bmp

19. Neural Stimulation • Muscles respond to the neurotransmitter acetylcholine (Ach). • Ach binds to receptors on the sarcolemma. • The binding of Ach affects the transport of ions across the sarcolemma www.cells.de/.../Neuromuscular-junction.jpg

20. Neural Stimulation • In a resting muscle, the concentration of sodium ions is normally higher in the fluid outside the muscle cell while the concentration of potassium ions is higher inside the cell. • Sodium/potassium pumps maintain these unequal ion concentrations. upload.wikimedia.org/wikipedia/commons/thumb/...

21. Neural Stimulation • This imbalance produces an unstable condition. When stimulated by Ach the membrane loses its ability to maintain the imbalance. • Once the membrane is stimulated, it opens the ion channels permitting the free flow of sodium into the muscle cell and potassium out of the cell. • In turn, calcium stored in the sarcoplasmic reticulum is released to begin the contraction phase

22. Muscle Contraction www.cvphysiology.com • When calcium (released by the sarcoplasmic reticulum) binds to the troponin, contraction begins. • Troponin sits on tropomyosin on the same region where actin binds to myosin.

23. Muscle Contraction • Ca bumps troponin off the binding site, permitting myosin to attach to actin. • Troponin also transmits info that activates ATP synthesis around the myosin. The ATP provides energy for the myosin head to swivel and pull the myosin toward the actin.

24. http://www.patrickcarlberg.dk/images/thinfilament.jpg

25. Muscle Relaxation • Relaxation occurs when there are no more neural stimulations exciting the sarcolemma. The sodium and potassium ion levels are completely recovered • The sarcoplasmic reticulum has retrieved most of the Ca, causing the release of the myosin heads from the actin. • There is no mechanism for the muscle cell to lengthen (so we’ll discuss how that happens later in the lecture).

26. Review • Nerve impulse arrives at muscle cell • Ca+2 released from SR into sarcoplasm • Ca+2 combines with troponin molecules in the thick filaments of myofibrils (Myosin) • Troponin without Ca+2 doesn’t interact like this • Myosin interacts with Actin and pulls toward center • Contraction of muscle • Video of contraction occurring… • Animation of entire process…

27. Other factors found in muscle fibers ensuring adequate muscle contractions: • Creatine Phosphate: stores energy in muscle cells. It collects this energy from ATP and is capable of storing it for long periods of time. • Glycogen (stored form of glucose) can supply glucose when muscles cells need it to produce ATP • Myoglobin is a chemical that stores oxygen for certain muscle cells. This O2 permits muscle cells to provide large amounts of ATP during continuous or heavy work.

28. Muscle Attachment Fibers • Tendons—connect muscle to bone (cordlike) • Aponeuroses—connect muscles to muscles (sheetlike)

29. Musculature terms • Origin—fixed end (proximal end of bone) • Insertion—moveable end (distal end of bone) www.scielo.cl/.../ijmorphol/v25n4/fig37-01.jpg

30. Skeletal Muscle Action • Muscle cells either contract or don’t…so we get graded effects based on contraction of more individual fibers at the same time. • Strength is achieved by stimulating more individual fibers to fire • Endurance is achieved by producing contraction and relaxation groups working together.

31. Skeletal Muscle Action • Antagonistic effects occur when one muscle opposes or resists the action of another muscle.—if nothing else, your muscles are acting against the antagonistic force of gravity • The antagonistic actions are essential for pulling the relaxed muscle cells back to their original length.

32. Skeletal Muscle Action • Synergistic effects occur when muscles work together to produce a common end result…the muscles of the forearm work synergistically with the muscles of the fingers to produce a fist. http://www.dkimages.com/discover/previews/779/76289.JPG

33. 5 golden rules of skeletal muscle • All muscles cross at least one joint • Typically the bulk of the muscle lies proximal to the joint crossed • All muscles have at least two attachments, the origin and the insertion • Muscles can only pull; they never push • During contraction, the muscle insertion moves toward the origin http://www.omnism.com/om/images/golden-rule.jpg

34. Body Movements • Flexor—decreases the angle of the joint by bringing the bones closer together • Extensor—extends a joint by increasing the angle between the bones

35. Body Movements • Rotator—movement around an axis (partway around) • Tensor—important posture/positioning muscles that make a body part more rigid or tense.

36. Body Movements • Abduction—moving away from the midline • Adduction—moving toward the midline

37. Body Movements • Depressor—produce a downward movement • Levatator—provide an upward movement • Spincter—decreases the size of an opening www.mda.org www.cescg.org

38. Body Movements • Pronator—motion of palm downward • Supinator—palm moves upward

39. Special Movements • Inversion—turning the sole of your foot medially • Eversion—turning the sole of your foot laterally

40. Special Movements • Dorsiflexion—pointing your toes up toward your shin • Plantar Flexion—pointing your toes downward

41. Muscular System Pathologies

42. Rigor Mortis • Calcium leakage out of the sarcoplasmic reticulum into the sarcomere. Common after death. Eventually, the muscle cells structures start to decay, causing the muscles to become soft and loose.

43. Strain • Most common muscle ailment • An injury due to overworking the muscle’s force on the joints. • Injury to the tendon or muscle tissue http://www.nlm.nih.gov http://www.fairview.org

44. Sprain • A sprain is an injury to a ligament. (A ligament is a thick, tough, fibrous tissue that connects bones together.) • Ligaments prevent abnormal movements. When too much force is applied to a ligament they can be stretched or torn. www.eorthopod.com

45. Contusion • Bruising of the muscle www.bruisepatch.com

46. Muscle Spasms • Involuntary, abnormal contractions of a muscle or muscle group • Caused by a wide range of medical conditions www.cure-back-pain.org

47. Muscle Cramp • Painful contraction of a muscle • Extreme muscle exertion is the most common cause of cramps, although certain poisons and bacterial infections can also cause muscle cramping www.answers.com

48. Paralysis • Complete failure of a muscle function • Rigid paralysis—excessive muscle stiffness • Flaccid paralysis—complete lack of muscle contraction • Many causes…including spinal injury and poisoning • Eg: Tetanus--Caused by soil bacteria that produces poisons that cause rigid paralysis

49. Dermatomyositis • Inflammation of the muscle and overlying skin. • Cause: unknown, but it can be treated with drugs (to reduce inflammation) and sun avoidance www.nytimes.com

50. Muscular dystrophies • Group of conditions that involve progressive weakness in the voluntary muscles. • Usually due to the inability of the nervous system to stimulate muscle action • Eventually results in muscle atrophy and wasting. esciencenews.com