Guided Notes for the Muscles Part 1

5 Golden Rules of Skeletal Muscle Activity  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

2. Each of our over 600 muscles is attached to bone or other connective tissue at no less than 2 points. One of the these points, the origin, is attached to the immovable or less movable bone. The insertion is attached to the movable bone. Body movement occurs when muscles contract across joints.

6 Major Body Movements Name of Movement Typical ActionAt which joints? Flexion Decreases the angle of the joint and brings bones closer together Hinge joints and ball-and-socket joints Extension Increases the angle of joints Hinge joints and ball-and-socket joints Rotation Movement of a bone around its longitudinal axis Ball-and-socket joints and the atlas/axis Abduction Moving a limb away from the median plane of the body Ball-and-socket joints

6 Major Body Movements Name of Movement Typical ActionAt which joints? Adduction Movement of a limb toward the body midline Ball-and-socket joints Circumduction The proximal end of a limb remains stationary and the distal end moves in a circle Ball-and-socket joints

7 Special Muscle Movements Name of MovementDescriptionWhere does it occur? Dorsiflexion Lifting the foot so that its superior surface approaches the shin At the foot (ankle) Plantar flexion Depressing the foot so that it is in a straight plane with the leg At the foot (ankle) Inversion Turning the sole medially At the foot (ankle) Eversion Turning the sole laterally At the foot (ankle)

7 Special Muscle Movements Name of MovementDescriptionWhere does it occur? Supination the forearm rotates laterally so that the palm faces anteriorally and the radius and ulna are parallel The wrist Pronation the forearm rotates medially so that the radius and ulna form an X The wrist Opposition Moving the thumb to touch the tips of the other fingers in the same hand Saddle joint between metacarpal 1 and the other metacarpals

5. Origin of the word “muscles”  The latin word mus means “little mouse”. This refers to the flexion of muscles beneath the skin, which looks like mice scurrying beneath the skin

6. The essential function of muscles is contraction, or shortening.

7. All muscle cells are elongated, which is why all muscle cells, regardless of type, are called muscle fibers.

8. Skeletal muscle fibers are cigar-shaped, multinucleate cells, and the largest of the muscle-fiber types.

9. Skeletal muscle is also known as striated muscle because its fibers appear to be striped, and it is also known as voluntary muscle because it is the only muscle type subject to conscious control.

10. Tendons and aponeuroses attach muscles indirectly to bones, cartilages, or connective tissue coverings of each other.

11. Besides acting to anchor muscles, tendons perform several functions. The most important are providing durability and conserving space.

12. Smooth muscle has no striations, and is involuntary, which means that we cannot consciously control it. Smooth muscle is generally found in the walls of hollow visceral organs such as the stomach, bladder, and respiratory passages. The function of smooth muscle is to propel substances along a definite tract within the body.

13. Where is cardiac muscle found?  The heart

14. How is cardiac muscle like skeletal muscle?  It is striated

15. How is cardiac muscle like smooth muscle?  It is involuntary

16. Cardiac muscle tissue contraction is regulated by the heart’s “in-house” pacemaker, but it can also be stimulated by the nervous system to “shift into high gear” for short periods.

Functions of Muscle Tissue  Producing Movement: a result of contraction  Maintaining Posture: counteract the force of gravity to keep our bodies upright  Stabilizing Joints: tendons reinforce joints that have poorly articulating surfaces  Generating Heat: as ATP is used to power muscle activity, ¾ of its energy escapes as heat, which helps maintain body temp.

18. A muscle is fatigued when it is unable to contract even though it is still being stimulated.

19. Muscle fatigue is believed to be a result of the oxygen debt that occurs during prolonged muscle activity.

20. During the recovery period that occurs after activity, an individual breathes rapidly and deeply. This continues until the muscles have received the amount of oxygen needed to get rid of the accumulated lactic acid and make ATP and creatine phosphate reserves.

21. In isotonic contractions, the muscle shortens and movement occurs. Examples include bending the knee, rotating the arms, and smiling.

22. Contractions in which the muscles do not shorten are called isometric contractions. These contractions occur when the muscle is pitted against some more or less immovable object.

23. Muscle tone is a state of continuous partial contractions. It is the result of different motor units throughout the muscle being stimulated by the nervous system in a systematic way.

24. Aerobic exercises result in stronger, more flexible muscles with greater resistance to fatigue. These changes come about because the blood supply to the muscles increases, and the individual muscle cells form more mitochondria and store more oxygen.

25. The bulging muscles of a weightlifter result from resistance, or isometric exercises.