Chapter 6 The Muscular System—Part C

1. Chapter 6 The Muscular System—Part C

2. Muscles and Body Movements • Movement is attained due to a muscle moving an attached bone • Muscles are attached to at least two points • Origin • Attachment to an immoveable bone • Insertion • Attachment to a movable bone • During contraction, insertion moves toward origin

4. Muscles and Body Movements

5. Types of Ordinary Body Movements • Flexion • Decreases the angle of the joint • Brings 2 bones closer • Ex: hinge joints like knee & elbow • Ex: ball & socket joints like hip & shoulder • Extension • Opposite of flexion • Increases the angle between two bones • Ex: Straightening knee or elbow

7. Types of Ordinary Body Movements • Hyperextension • Line of appendage is over 180° when straightened • Ex: Tip head posteriorly

8. Types of Ordinary Body Movements • Rotation • Movement of bone around its longitudinal axis • Common in ball & socket joints • Ex: Move atlas around the axis (shake your head “no”)

9. Types of Ordinary Body Movements • Abduction • Movement of a limb away from the midline • Adduction • Opposite of abduction • Movement of a limb toward body midline • Circumduction • Combination of flexion, extension, abduction, adduction = circular • Common in Ball & socket joints

10. Special Movements • Dorsiflexion – • Lifting the foot so that the superior surface approaches the shin • Plantar flexion • Depressing the foot (pointing the toes)

11. Special Movements • Inversion • Turn sole of foot medially • Eversion • Turn sole of foot laterally

12. Special Movements • Supination • Forearm rotates laterally so palm faces anteriorly • Radius & Ulna are parallel • Pronation • Forearm rotates medially so palm faces posteriorly • Radius & Ulna form “X” shape

13. Special Movements • Opposition • Move thumb to touch the tips of other fingers on the same hand

14. Types of Muscles • Prime Mover – muscle with the major responsibility for a certain movement • Antagonist – muscle that opposes or reverses a prime mover • Muscle can be both: • Biceps – prime mover flexes elbow • Triceps – prime mover extends elbow • Synergist – muscle that aids a prime mover in a movement and helps prevent rotation • Fixator – stabilizes the origin of a prime mover • Allows all tension to move insertion bone

15. Naming of Skeletal Muscles • Based on direction of muscle fibers • Example: Rectus (straight) • Based on relative size of the muscle • Example: Maximus (largest) Minimus – smallest Longus - long • Based on location of the muscle • Example: many muscles are named for bones Temporalis(temporal bone)

16. Naming of Skeletal Muscles • Based onnumber of origins • Example: Triceps (three heads) • Bi – 2 • Quad -4 • Based on location of the muscle’s origin and insertion • Example: sterno (on the sternum)

17. Naming of Skeletal Muscles • Based on the shape of the muscle • Example: deltoid --triangular • Based on the action of the muscle • Examples: flexor and extensor --flexes or extends a bone

18. Arrangement of Fascicles Figure 6.14

19. Fascicles • Circular – rings of muscle that open and close areas • Sphincters • Orbicularisoris – around mouth • Convergent – muscles come together to a single insertion point—usually a tendon • Fan or triangle shaped • Pectoralis major • Parallel – length runs parallel to long axis of muscle • Straplike

20. Fusiform – spindle shaped, long • Biceps brachii • Pennate – fascicles attach obliquely (at a slanted position) to central tendon

21. Head and Neck Muscles • Facial muscles • Frontalis—raises eyebrows • Orbicularisoculi—closes eyes, squints, blinks, winks • Orbicularisoris—closes mouth and protrudes the lips • Buccinator—flattens the cheek, chews • Zygomaticus—raises corners of the mouth • Chewing muscles • Masseter—closes the jaw and elevates mandible • Temporalis—synergist of the masseter, closes jaw

22. Head and Neck Muscles • Neck muscles • Platysma—pulls the corners of the mouth inferiorly • Sternocleidomastoid—flexes the neck, rotates the head

23. Head and Neck Muscles Figure 6.15

24. Muscles of Trunk, Shoulder & Arm • Anterior muscles • Pectoralis major—adducts and flexes the humerus • Intercostal muscles • External intercostals—raise rib cage during inhalation • Internal intercostals—depress the rib cage to move air out of the lungs when you exhale forcibly

25. Anterior Muscles of Trunk, Shoulder, Arm Figure 6.16

26. Muscles of Trunk, Shoulder, Arm • Muscles of the Abdominal Girdle: • Rectus abdominis—flexes vertebral column and compresses abdominal contents (defecation, childbirth, forced breathing) • External and internal obliques—flex vertebral column; rotate trunk and bend it laterally • Transversusabdominis—compresses abdominal contents

27. Anterior Muscles of Trunk, Shoulder, Arm Figure 6.17

28. Muscles of Trunk, Shoulder, Arm • Posterior muscles: • Trapezius—elevates, depresses, adducts, and stabilizes the scapula • Latissimusdorsi—extends and adducts the humerus • Erector spinae—back extension • Quadratuslumborum—flexes the spine laterally • Deltoid—arm abduction

29. Muscles of Posterior Neck, Trunk, Arm

30. Muscles of Posterior Neck, Trunk, Arm

31. Muscles of the Upper Limb • Biceps brachii—supinates forearm, flexes elbow • Brachialis—elbow flexion; lifts ulna • Brachioradialis—weak muscle • Triceps brachii—elbow extension (antagonist to biceps brachii)

32. Anterior Muscles of Trunk, Shoulder, Arm

33. Muscles of the Lower Limb • Gluteus maximus—hip extension • Gluteus medius—hip abduction, steadies pelvis when walking • Iliopsoas—hip flexion, keeps the upper body from falling backward when standing erect • Adductor muscles—adduct the thighs

34. Muscles of the Pelvis, Hip, Thigh Posterior view of hip and thigh

35. Muscles of the Lower Limb • Muscles causing movement at the knee joint: • Hamstring group—thigh extension and knee flexion • Biceps femoris • Semimembranosus • Semitendinosus

36. Muscles of the Lower Limb • Muscles causing movement at the knee joint • Sartorius—flexes the thigh • Quadriceps group—extends the knee • Rectus femoris • Vastus muscles (three)

37. Muscles of the Pelvis, Hip, Thigh Anterior view of pelvic & thigh muscles

38. Muscles of the Lower Limb • Muscles causing movement at ankle and foot: • Tibialis anterior—dorsiflexion and foot inversion • Extensor digitorumlongus—toe extension and dorsiflexion of the foot • Fibularis muscles—plantar flexion, everts the foot • Soleus—plantar flexion

39. Muscles of the Lower Leg

40. Muscles of the Lower Leg

41. Superficial Muscles: Anterior

42. Superficial Muscles: Posterior

43. Developmental Aspects • Nervous system must mature before muscle control can be achieved. • Gross movements develop before precise control is possible. • Maximum development of nervous system achieved in mid-teens—athletes often notice an increased level of performance.

44. Homeostatic Imbalances • Muscular Dystrophy – group of inherited muscle-destroying diseases that affect specific muscle groups • Muscles enlarge due to fat and connective tissue deposits, but muscle fibers degenerate • Caused by lack of the protein dystrophin that is found in the sarcolemma • Duchenne’s Muscular Dystrophy • Primarily affects males • Do not live beyond young adult

45. Homeostatic Imbalances • Myasthenia gravis • Characterized by drooping of eyelids, difficulty in swallowing and talking, generalized muscle weakness • Shortage of acetylcholine receptors at the neuromuscular junction • Autoimmune disease

46. Homeostatic Imbalances • Effects of Aging • Connective tissue increases, muscle mass decreases • Body weight decreases • Strength decreases • These effects can be countered by regular exercise, including weight training