N3 Anatomy and Physiology AY 2023-2024

Activity 2

1. Throwing a baseball overhead

   1. Deltoid

      1. 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.

      2. Innervation: Axillary nerve

   2. Biceps brachii

      1. Action: Flexes forearm at elbow joint, supinates forearm at radioulnar joints, and flexes arm at shoulder joint.

      2. Innervation: Musculocutaneous nerve.

2. Kicking a ball

   1. Popliteus

      1. Action: Flexes leg at knee joint and medially rotates tibia to unlock the extended knee

      2. Innervation: Tibial nerve

   2. Gastrocnemius

      1. Action: Plantar flexes foot at ankle joint and flexes leg at knee joint.

      2. Innervation: Tibial nerve

3. Doing sit-ups

   1. Iliopsoas

      1. 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.

      2. Innervation: Lumbar spinal nerves L2–L3.

   2. Gluteus Maximus

      1. Action: Extends thigh at hip joint and laterally rotates thigh; helps lock knee in extension. RMA: Extends torso.

      2. Innervation: Inferior gluteal nerve.

4. Breathing

   1. Diaphragm

      1. 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. 

      2. Innervation: Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5).

   2. Internal Intercostals

      1. Action: Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.

      2. Innervation: Thoracic spinal nerves T2–T12.

References:

Tortora, G. J., & Derrickson, B. H. (2017). Principles of Anatomy & Physiology. Wiley.