Such an injury could eradicate output through the phrenic nerve, which arises from the cervical nerve plexus. Such nerve damage would result in respiratory depression or paralysis.
Signals for deep touch and limb position below that level ascend the ipsilateral side of the spinal cord in the gracile fasciculus and do not decussate until they get to the medulla oblongata. Therefore, an injury to the left gracile fasciculus would block the transmission of these types of signals from the left (ipsilateral) side of the body below the injury. Signals for pain and heat, however, decussate in the spinal cord near the point of entry and travel up the contralateral side of the cord in the spinothalamic tract. An injury to the left spinothalamic tract would thus block the transmission of these signals from the right (contralateral) side of the body.
A stab wound in this area can damage the sciatic nerve, which gives rise to numerous branches (table 14.6) that supply the hamstrings, gastrocnemius, and other major muscles of hip, knee, ankle, and foot movements.
It is virtually impossible to raise the left foot without losing contact with the wall on the right. The lifting of one foot normally includes lateral flexion of the waist so that the body weight is supported on the contralateral foot, but in this experiment, the wall prevents waist flexion.
Removal of the median nerve abolishes sensation from the lateral two-thirds of the hand and motor control of anterior forearm flexors, thenar muscles, and first and second lumbrical muscles. The result would be inability to flex the wrist and fingers, inability to grip objects, loss of other thumb movements (abduction, flexion, and opposition), and inability to extend the interphalangeal joints.
