1. Throwing a baseball overhead
|
Muscle |
Action |
Innervation |
|
Pectoralis major |
As a whole, adducts and medially rotates the arm at the shoulder joint; the clavicular head flexes the arm, and the sternocostal head extends the flexed arm to the side of the trunk. |
Medial and lateral pectoral nerves. |
|
Deltoid |
Lateral fibers abduct the arm at the shoulder joint; anterior fibers flex and medially rotate the arm at the shoulder joint; posterior fibers extend and laterally rotate the arm at the shoulder joint. |
Axillary nerve.
|
2. Kicking a ball
|
Muscle |
Action |
Innervation |
|
Quadriceps femoris |
All four heads extend the leg at the knee joint; the rectus femoris muscle acting alone also flexes the thigh at the hip joint.
|
Femoral nerve.
|
|
Rectus femoris |
All four heads extend the leg at the knee joint; the rectus femoris muscle acting alone also flexes the thigh at the hip joint. |
Femoral nerve.
|
3. Doing sit-ups
|
Muscle |
Action |
Innervation |
|
Rectus Abdominis |
Flexes the vertebral column, especially the lumbar portion, and compresses the abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column. |
Thoracic spinal nerves T7–T12.
|
|
Transversus abdominis |
Compresses abdomen.
|
Thoracic spinal nerves T8–T12, iliohypogastric nerve, and ilioinguinal nerve.
|
4. Breathing
|
Muscle |
Action |
Innervation |
|
External intercostals
|
Contraction elevates ribs and increases anteroposterior and lateral dimensions of the thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of the thoracic cavity, resulting in exhalation. |
Thoracic spinal nerves T2–T12.
|
|
Diaphragm
|
Contraction of the diaphragm causes it to flatten and increases the vertical dimension of the thoracic cavity, resulting in inhalation; relaxation of the diaphragm causes it to move superiorly and decreases the vertical dimension of the thoracic cavity, resulting in exhalation. |
Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5).
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