Anatomy Chapter 6 Flashcards

Muscle Anatomy and Function

• Origin and Insertion: The origin is the fixed point of muscle attachment, while the insertion is attached to the movable bone. Muscle contraction pulls the insertion toward the origin.
• Muscle Contraction: Body movements occur when muscles contract across joints.

Types of Movements

• Flexion: Decreases the joint angle, bringing bones closer; typical in hinge joints (e.g., bending the knee).
• Extension: Increases the angle between two bones or parts; hyperextension occurs beyond 180 degrees.
• Rotation: Movement of a bone around its axis, common in ball-and-socket joints (e.g., shaking the head "no").
• Dorsiflexion: Lifting the foot so the top approaches the shin (standing on heels).
• Plantar Flexion: Pointing the toes down.
• Abduction: Movement away from the body's midline (e.g., lifting arm sideways).
• Adduction: Movement toward the midline of the body.
• Circumduction: Circular limb movement, combining flexion, extension, abduction, and adduction.
• Inversion: Turning the sole of the foot medially.
• Eversion: Turning the sole of the foot laterally.
• Supination: Turning the palm up, involving lateral rotation of the forearm.
• Pronation: Turning the palm down, involving medial rotation of the forearm.
• Opposition: Thumb movement to touch the tips of other fingers.
• Elevation: Upward movement of body structures (e.g., raising arms).
• Depression: Downward movement of body structures.

Muscle Roles

• PUSH vs. PULL: Muscles can only pull, never push.
• Antagonistic Pairs: Muscles that oppose each other; one contracts while the other relaxes (e.g., biceps and triceps).
• Prime Mover: The main muscle responsible for a specific movement.
• Antagonist: Muscle that opposes the prime mover.
• Synergist: Aids the prime mover and stabilizes the joint during movement.
• Fixator: Specialized synergist that stabilizes a bone's origin to focus force on moving the insertion.

Naming Skeletal Muscles

• Muscles are named based on:
  • Direction of Fibers: e.g., "rectus" for straight, "oblique" for slanted.
  • Relative Size: e.g., "maximus" (largest), "minimus" (smallest), "longus" (long).
  • Location: Named after bones they are associated with (e.g., temporalis overlying the temporal bone).
  • Number of Origins: e.g., biceps (two origins), triceps (three).
  • Location of Origin and Insertion: e.g., sternocleidomastoid indicating its attachment sites.
  • Shape: e.g., deltoid (triangular).
  • Action: e.g., flexor, extensor, adductor.

Muscle Structure

• Fascicles: Bundles of muscle fibers; arrangement affects the muscle’s power and range of motion.
• Powerful Arrangements: Bipennate and multipennate muscles are thick and powerful, packing many fibers.

Anabolic Steroids

• Definition: Synthetic derivatives of testosterone, used to enhance muscle mass and strength.
• Originally Developed for: Treatment of conditions like muscle-wasting diseases, anemia, and muscle atrophy.
• Athlete Usage: Claims of enhanced performance through increased muscle mass, strength, and aggressive behavior.
• Risks: Physical and mental issues include infertility, liver damage, psychiatric problems, and drastic personality changes.

Notable Muscular Conditions

• Duchenne Muscular Dystrophy: A fatal condition characterized by muscle weakness, emphasizing genetic causes.
• Muscle Injury: High-risk movements can lead to muscle pulls, such as hamstring injuries from improper extension.
• Emergency Surgery: Surgical knowledge about underlying muscle structures prevents unnecessary damage.

Miscellaneous

• Muscle Actions: Anteriorly positioned muscles lead to flexion, posteriorly lead to extension, laterally facilitate abduction, and medially enable adduction.
• Muscle Attachments: Understanding origin and insertion is critical for predicting movement dynamics.

Test your knowledge of muscle anatomy and the significance of origin and insertion points in Chapter 6. This quiz focuses on understanding body movements and muscle contractions, helping you grasp essential concepts in human anatomy.