L5.4.2: Interactions of Skeletal Muscles in the Body

• PRIME MOVER

  ● Major responsibility for causing a particular movement
• ANTAGONISTS

  ● Muscles that oppose or reverse a movement

  ● When a prime mover is active, its antagonist is stretched and relaxed

  ● Can be prime movers in their own right, but for different actions

  ● Ex: Biceps brachii and brachialis muscles of the arm (prime movers of the elbow flexion) are antagonized by the triceps brachii (a prime mover of elbow extension)
• SYNERGISTS

  ● Syn- “together”

  ● Erg- “work”

  ● Help prime movers by producing the same movement or by reducing undesirable movements

  ● Ex: Flexor muscles of the fingers cross both the wrist and the finger joints. You can make a fist without bending your wrist because synergist muscles stabilize the wrist joints and allow the prime mover to act on you finger joints
• FIXATORS

  ● Are specialized synergists

  ● Hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone

  ● The postural muscles that stabilize the vertebral column are fixators, as are the muscles that anchor the scapulae to the thorax