TANILON, Pauline Joy B.
ACTIVITY 2
Name at least three muscles that actively contracts during the following activities and name its action and innervation:
1. Turning a door knob
a. Extensor carpi radialis longus
• Action: Extends and abducts hand at wrist joint (ulnar deviation).
• Innervation: Radial nerve
b. Pronator quadratus
• Action: Pronates forearm at radioulnar joints.
• Innervation: Median nerve.
c. Supinator
• Action: Supinates forearm at radioulnar joints.
• Innervation: Deep radial nerve.
2. Throwing a baseball overhead
a. Deltoid
• 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.
• Innervation: Axillary nerve.
b. Teres major
• Action: Extends arm at shoulder joint and assists in adduction and medial rotation of arm at shoulder joint.
• Innervation: Lower subscapular nerve.
c. Latissimus dorsi
• Action: Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly. RMA: Elevates vertebral column and torso.
• Innervation: Thoracodorsal nerve.
3. Kicking a ball
a. Rectus femoris
• Action: Extend leg at knee joint; rectus femoris muscle acting alone also flexes thigh at hip joint.
• Innervation: Femoral nerve.
b. Semitendinosus
• Action: Flexes leg at knee joint and extends thigh at hip joint.
• Innervation: Tibial nerve from sciatic nerve.
c. Iliopsoas (Psoas major)
• Action: Psoas major and iliacus muscles acting together flex thigh at hip joint, rotate thigh laterally, and flex trunk on hip as in sitting up from supine position.
• Innervation: Lumbar spinal nerves L2–L3.
4. Doing sit-ups
a. Rectus abdominis
• 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.
• Innervation: Thoracic spinal nerves T7–T12.
b. External oblique
• Action: Acting together (bilaterally), compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column.
• Innervation: Thoracic spinal nerves T7–T12 and the iliohypogastric nerve.
c. Internal oblique
• Action: Acting together, compress abdomen and flex vertebral column; acting singly, laterally flex vertebral column, especially lumbar portion, and rotate vertebral column.
• Innervation: Thoracic spinal nerves T8–T12, the iliohypogastric nerve, and ilioinguinal nerve.
5. Walking
a. Tibialis anterior
• Action: Dorsiflexes foot at ankle joint and inverts (supinates) foot at intertarsal joints.
• Innervation: Deep fibular (peroneal) nerve.
b. Biceps femoris
• Action: Flexes leg at knee joint and extends thigh at hip joint.
• Innervation: Tibial and fibular nerves from sciatic nerve.
c. Gluteus maximus
• Action: Extends thigh at hip joint and laterally rotates thigh; helps lock knee in extension. RMA: Extends torso.
• Innervation: Inferior gluteal nerve.
6. Breathing
a. 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).
b. External intercostals
• 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.
c. Internal intercostals
• Action: Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.
• Innervation: Thoracic spinal nerves T2–T12.
References:
Tortora, G. J., & Derrickson, B. (2014). Principles of Anatomy and Physiology (14th ed.). Wiley.