1. Review Questions begin on page 198
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

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. Categorizing muscles Microscopically Nonstriated (no lines)
Microscopically
Nonstriated (no lines)
Striated (lines running through)
micro.magnet.fsu.edu/

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.

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

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
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…

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. Squinting Stimulus Receptor Light reduced Effectors Regulator
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
Bozeman Science—Muscles

20. Animations

21. 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
Animation of entire process…

22. 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.

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

24. Musculature terms Origin—fixed end (proximal end of bone)
Insertion—moveable end (distal end of bone)

25. 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.

26. 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.

27. 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.

28. 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

29. 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

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

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

32. Body Movements Depressor—produce a downward movement
Levatator—provide an upward movement
Sphincter—decreases the size of an opening

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

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

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

36. Muscular System
Pathologies

37. 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.

38. Strain Most common muscle ailment
An injury due to overworking the muscle’s force on the joints.
Injury to the tendon or muscle tissue

39. 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.

40. Contusion
Bruising of the muscle

41. Muscle Spasms
Involuntary, abnormal contractions of a muscle or muscle group
Caused by a wide range of medical conditions

42. 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

43. 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

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

45. 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

46. 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!

47. 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

48. 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

49. 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.

50. 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