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. 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

8. Physiology of muscle • Contraction is achieved by the simultaneous shortening of all the sarcomeres within a cell. • Three stages: • Neural stimulation • Contraction • Relaxation.

9. 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

10. 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

11. 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/...

12. 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

13. 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.

14. 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.

15. Myosin crossbridges at work…

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

17. 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).

18. Stimulus Squinting Receptor Sensory Nerves Light reduced Motor Nerves Effectors Regulator

19. Video links • http://www.hippocampus.org/Biology search for Biology for AP/Skeletal Muscle contraction • Crash course—Muscles http://www.youtube.com/watch?v=jqy0i1KXUO4 • Bozeman Science—Muscles http://www.youtube.com/watch?v=mejCXr7p37U&list=PLCC2DB523BA8BCB53&index=17

20. Animations • http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2904 • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#

21. 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.

22. 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.

23. 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

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

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

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

27. Special Movements • Pronator—motion of palm downward • Supinator—palm moves upward

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

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

30. Muscular System Pathologies

31. 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.

32. 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

33. 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

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

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

36. 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

37. 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

38. 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

39. 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

40. Tetany • Calcium imbalance disease that causes extended periods of spasms in the arm and leg muscles. • Do NOT confuse this with the bacterial disease tetanus!

41. Cachexia • Type of muscle loss associated with diseases such as AIDS and cancer. • Also found in starvation and a common consequence of anorexia and bulimia www.aids-images.ch

42. Cachexia • A slower form is a normal consequence of aging b/c the body reduces its ability to rebuild muscle structure as you age. • Brought about by sedentary lifestyles—resulting from other age related illnesses • Neural stimulation also is lessened as you age; important for muscle upkeep

43. Nutritional issues with muscle loss • Protein turnover: muscles need lots of protein to maintain their integrity • Malnutrition and undernutrition as we age greatly affects protein turnover. • Can be caused by poor diets or income levels • Lack of appetite as we age is another contributing factor • As we age, our digestive system can’t absorb some of the impt amino acids needed for muscle cell growth/maintenance.

44. Muscle atrophy—other causes • Decline in sex hormones and other chemical messages needed for muscle cell growth, maintenance and repair. • Insulin-like growth factor-1: known to lessen with maturity • Cytokines cause muscle atrophy and are known to increase with age