1.
a) infraspinatus
- action: laterally rotates arm at shoulder joint
- innervation: suprascapular nerve
b) teres minor
- action: laterally rotates and extends arm at shoulder joint
- innervation: axillary nerve
2.
a) gastrocnemius
- action: plantar flexes foot at ankle joint and flexes leg at knee joint
- innervation: tibial nerve
b) tibialis anterior
- action: dorsiflexes foot at ankle joint and inverts (supinates) foot at intertarsal joints
- innervation: deep fibular (peroneal nerve)
3.
a) rectus abdominis
- action: compresses abdomen
- innervation: thoracic spinal nerves T7-T12
b) transversus abdominis
- action: compresses abdomen
- innervation: thoracic spinal nerves T8-T12, iliohypogastric nerve, ilioinguinal nerve
4.
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