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Chapter 8

Chapter 8. The Muscular System. I. Introduction. A. There are over 600 skeletal muscles in the body. B. 40-50% of your body weight is skeletal muscle. C. Muscles , along with the skeleton, determine the form and contour of the body. QUESTION….

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Chapter 8

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  1. Chapter 8 The Muscular System

  2. I. Introduction • A. There are over 600 skeletal muscles in the body. • B. 40-50% of your body weight is skeletal muscle

  3. C. Muscles, along with the skeleton, determine the form and contour of the body

  4. QUESTION…. • Two people wear the exact same size in clothing. One of the two has 15% body fat (meaning they have 85% muscle) and the other person has 29% body fat. Who weighs more?

  5. The person with the larger amount of muscle percentage will weight more. Muscle density is 1.06 g/ml and fat density is (about) 0.9 g/ml. Thus, one liter of muscle would weight 1.06 kg and one liter of fat would weight 0.9 kg. In other words, muscle is about 18% more dense than fat.

  6. D. Skeletal Muscles are organs • E. Function of muscles • 1. Movement • 2. Heat production • 3. Posture

  7. II. How muscles are named • A. Muscles are named using one of more of the following features • 1. Location (ie:subscapularis) • 2. Function (adductor muscle)

  8. 3. Shape (deltoid) • 4. Direction of the fibers or muscle cells – (ie: “rectus” of rectus abdominus means “straight”)

  9. 5. Number of heads or divisions (ie: biceps, triceps, quadriceps) • 6. Size of the muscle (ie: gluteus maximus, gluteus medius, gluteus minimus)

  10. 7. Attachment of muscles • Origin—point of attachment that does not move when muscle contracts • Insertion—point of attachment that moves when muscle contracts

  11. Location • Arm • Leg • Abdomen • Back • Head • Brachialis • Femoris • Abdominal • Dorsi • Capitis

  12. Function Adductor Abductor Supinator Flexor Extensor • Adducts • Abducts • Supinates • Flexes • Extends Slide 12

  13. Shape Deltoid Linea Trapezius • Triangle • Line • trapezoid Slide 13

  14. Number of Heads Biceps Triceps Quadriceps • Two • Three • Four Slide 14

  15. Direction of Fibers Oblique Rectus Transverse Circular Spiral • Diagonal • Straight • Transverse • Around • Spiral Slide 15

  16. Points of Attachment • Sternum • Clavicle • Mastoid processes of the temporal bone Examples: • sternocleidomastoid

  17. Relative Size • Large • Largest • Small • Smallest • Long • Short • Very wide • Very long • Very large • Vast or huge • Major • Maximus • Minor • Minimus • Longus • Brevis • Latissimus • Longissimus • Magnus • Vastus

  18. Examples: Flexor carpiradialis Brachioradialis Three headed arm muscle Straight upper leg muscle Flexor pollicuslongus Vast side muscle of upper leg Adductor brevis Adductor magnus • Function/insertion/origin • Location/insertion • Triceps brachii • Rectus femoris • Long muscle that flexes the thumb • Vastuslateralis • Short muscle that adducts the leg • Largest muscle that adducts the leg Slide 18

  19. III. Important Skeletal Muscles

  20. A. Muscles of facial expression • —unique in that at least one point of attachment is to the deep layers of the skin over the face or neck • 1. Corrugatorsupercilii(AKA: frontal muscle) – wrinkles forehead when frowning, and lifts eyebrows in surprise

  21. 2.Orbicularis oculi– encircles the eye and closes it 3. Zygomaticus major– draws the corner of the mouth upward (smiling or laughing)

  22. 4.Obicularis oris– puckers the mouth and presses the teeth to inside cheek (commonly referred to as the “kissing muscle”) 5. Buccinator – works with the above muscle to produce the kissing motion

  23. B. Muscles of Mastication (chewing) • 1. Masseter – closes jaw • 2. Temporalis – this works with the above muscle to close the jaw • 3. Pterygoids – grates teeth

  24. C. Muscles that move the head • Muscles that move the head —paired muscles on either side of the neck are responsible for head movements • 1. Sternocleidomastoid • 2. Trapezius • 3. Splenius capitis • 4. Semispinaliscapitis

  25. C. Muscles of the Thorax • 1. External intercostals– elevated ribs for inhalation • 2. Internal intercostals– depresses ribs for exhalation

  26. 3. Diaphragm – enlarges thorax causing inspiration. Singers train this muscle so the viscera is pushing down which gives the lungs more room to expand. The can hold notes longer and have to inhale less often.

  27. D. Muscles of the Abdominal Wall • 1. External obliques– outermost layer • 2. Internal obliques– middle layer • 3. Transversus abdominus– innermost layer

  28. 4. Rectus abdominus– midline of the abdomen. “6 pack, washboard stomach” Muscles used to “push” in childbirth.

  29. Aponeurosis –layers of flat, broad tendons

  30. E. Muscles of the Back • Muscles of the back —bend or stabilize the back • Allow for rotation

  31. 2 “cap” muscles 3 muscles that move the scapula 4 muscles on the scapula 2 serratus muscles 1 errector muscle 2 gluteal muscles

  32. E. Muscles of the Upper Limb • 1. Deltoid • 2. Rotator cuff muscles (SITS muscles): • a. Supraspinatus • b. Infraspinatus • c. Teres minor • d. Subscapularis

  33. 3. Pectoralis major • 4. Opponens pollicus– thumb muscles which allow thumb to be drawn across the palm • 5. Biceps brachii • 6. Triceps brachii

  34. F. Muscles of the Lower Limb • 1. Gluteal group – posterior buttocks • a. Gluteus maximus • b. Gluteus medius • c. Gluteus minimus

  35. 2. Quadriceps group– anterior thigh • 3. Hamstring group– posterior thigh • 4. Gastrocnemius– calf muscles • 5. Soleus – underneath gastrocnemius

  36. Other Muscles“Involuntary Muscles”

  37. A. Cardiac • 1. The heart • 2. It is extremely striated with a series of intercalated discs…..these are unique dark bands where the plasma membrane of other cardiac fibers come in contact with each other. The nature of the fibers helps the heart contract as a unit.

  38. B. Smooth • 1. These form the muscles of the hollow organs (such as the intestines) • 2. The cells of smooth muscles are tapered at each end and have a single nucleus. They have no striations which gives them the appearance of being “smooth”.

  39. V. Muscle Fiber Types Each muscle contains both types of muscle fibers in varying proportions

  40. A. Slow (red) fibers • 1. These contain large amounts of myoglobin (oxygen storage molecules), which give it its red color (red meat vs. white meat in animals). • 2. “Slow” means they are slow to fatigue

  41. 3. Postural muscles that hold up a skeleton for prolonged periods have greater amounts of slow red fibers. • 4. Studies show that marathon runners have a greater amount of red fibers than the general population

  42. B. Fast (white) fibers • 1. Muscle fibers that contain little myoglobin (hence the word white) • 2. These muscles contract rapidly • 3. But the price of rapid contraction is rapid depletion of ATP. • 4. Sprinters have a greater amount of white fibers than the general population

  43. VI. Muscle Contraction A. Requires Energy

  44. B. Comes from catabolism • Requires these two ingredients • 1. Glucose(from food) – quick burst fuel needed for muscle contraction • 2. Oxygen • a. Aerobic respiration– produces maximum amount of energy using oxygen

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