Name at least three muscles that actively contracts during the following activities and name its action and innervation:
1. Turning a door knob
- Supinator
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- Action: Supinates forearm at radioulnar joints
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Innervation: Deep radial nerve
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- Pronator teres
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Action: Pronates forearm at radioulnar joints and weakly flexes forearm at elbow joint
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Innervation: Median nerve
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Pronator quadratus
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Action: Pronates forearm at radioulnar joints
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Innervation: Median nerve
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2. Throwing a baseball overhead
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Deltoid
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Action: Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder joint
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Innervation: Axillary nerve
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Pectoralis major
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Action: As a whole, adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head extends flexed arm to side of trunk
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Innervation: Medial and lateral pectoral nerves
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Latissimus dorsi
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Action: Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly. RMA: Elevates vertebral column and torso
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Innervation: Thoracodorsal nerve
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3. Kicking a ball
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Biceps femoris
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Action: Flexes leg at knee joint and extends thigh at hip joint
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Innervation: Tibial and fibular nerves from sciatic nerve
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Rectus femoris
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Action: Extends leg at knee joint; flexes thigh at hip joint
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Innervation: Femoral nerve
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Iliopsoas
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Action: Psoas major and iliacus muscle acting together flex thigh at hip joint, rotate thigh laterally, and flex trunk on hip
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Innervation: Lumbar spinal nerves L2-L3
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4. Doing sit-ups
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Rectus abdominis
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Action: Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column
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Innervation: Thoracic spinal nerves
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External obliques
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Action: Acting together (bilaterally), compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column
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Innervation: Thoracic spinal nerves T7-T12 and the iliohypogastric nerve
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- Iliopsoas
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Action: Psoas major and iliacus muscle acting together flex thigh at hip joint, rotate thigh laterally, and flex trunk on hip
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Innervation: Lumbar spinal nerves L2-L3
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5. Walking
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Vastus medialis
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Action: Extends leg at knee joint
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Innervation: Femoral nerve
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Tibialis anterior
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Action: Dorsiflexes foot at ankle joint and inverts (supinates) foot at intertarsal joints
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Innervation: Deep fibular (peroneal) nerve
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- Iliocostalis cervicis
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Action: Acting together, muscles of each region (cervical, thoracic, and lumbar) extends and maintain erect posture of vertebral column of their respective regions; acting singly, laterally flex vertebral column of their respective regions to same side as contracting muscle
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Innervation: Cervical and thoracic spinal nerves
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6. Breathing
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Diaphragm
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Action: Contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, resulting in inhalation; relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity, resulting in exhalation
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Innervation: Phrenic nerve, which contains axons from cervical spinal nerves (C3-C5)
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External Intercostals
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Action: Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity, resulting in exhalation
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Innervation: Thoracic spinal nerves T2-T12
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Internal Intercostals
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Action: Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation
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Innervation: Thoracic spinal nerves T2-T12
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