Muscular System Activity 2
- Throwing a baseball overhead
a) Deltoid
Action: Lateral fibers abduct the arm at the shoulder joint, anterior fibers flex and medially rotate the arm at the shoulder joint, and posterior fibers extend and laterally rotate the arm at the shoulder joint
Innervation: Axillary nerve
b) Pectoralis major
Action: Adduct and medially rotate 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
Innervation: Medial and lateral pectoral nerves - Kicking a ball
a) Gluteus maximus
Action: Extend the thigh at the hip joint and laterally rotate the thigh, and help to lock the knee in extension
Innervation: Inferior gluteal nerve
b) Rectus femoris
Action: Extend the leg at the knee joint and flex the thigh at the hip joint
Innervation: Femoral nerve - Doing sit-ups
a) Rectus abdominis
Action: Flex the vertebral column (especially the lumbar portion), and compress the abdomen to aid in defecation, urination, forced exhalation, and childbirth.
Innervation: Thoracic spinal nerves T7-T12
b) External oblique
Action: Acting bilaterally with the internal oblique, compress the abdomen and flex the vertebral column; acting unilaterally, laterally flex the vertebral column (especially the lumbar portion), and rotate the vertebral column
Innervation: Thoracic spinal nerves T7-T12 and iliohypogastric nerve - Breathing
a) Diaphragm
Action: Contracts (flattens and increases the vertical dimension of thoracic cavity) during inhalation, relaxes (moves superiorly and decreases the vertical dimension of thoracic cavity) during exhalation
Innervation: Phrenic nerve (contains axons from cervical spinal nerves C3-C5)
b) External intercostals
Action: Contracts (elevates ribs and increases the anteroposterior and lateral dimensions of the thoracic cavity) during inhalation, relaxes (depresses ribs and decreases the anteroposterior and lateral dimensions of the thoracic cavity) during exhalation
Innervation: Thoracic spinal nerves T2-T12