Activity 2
Name at least two muscles that actively contracts during the following activities and name its action and innervation:
1. Throwing a baseball overhead - Biceps brachii and Triceps brachii
Biceps brachii
Action: Flexes forearm at elbow joint, supinates forearm at radioulnar joints, and flexes arm at shoulder joint.
Innervation: Musculocutaneous nerve
Triceps brachii
Action: Extends forearm at elbow joint and extends arm at shoulder joint
Innervation: Radial nerve
2. Kicking a ball - Biceps femoris, Gluteus maximus
Biceps femoris
Action: Flexes leg at knee joint and extends thigh at hip joint
Innervation: Tibial and fibular nerves from sciatic nerve.
Gluteus maximus
Action: Extends thigh at hip joint and laterally rotates thigh;
Innervation: Inferior gluteal nerve
3. Doing sit-ups action - Transversus Abdominis and Rectus Abdominis
Transversus Abdominis
Action: Compresses abdomen
Innervation: Thoracic spinal nerves T8–T12, iliohypogastric nerve, and ilioinguinal nerve
Rectus Abdominis
Action: Flexes vertebral column, especially lumbar portion.
Innervation: Thoracic spinal nerves T7–T12
4. Breathing - Diaphragm and External intercostal muscles
Diaphragm
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.
Innervation: Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5)
External intercostal
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
Innervation: Thoracic spinal nerves T2–T12
Reference:
Tortora, G. & Derrickson, B. (2017). Chapter 11: The Muscular System. Principles of Anatomy and Physiology (15th ed.). Wiley.