The Spine

Reflexes Many of the body’s reflexes allow for testing of nervous system integrity.

Patellar (Knee-Jerk) Reflex This commonly tested reflex is accomplished by tapping the patellar tendon, which stretches the quadriceps muscle, stimulating that muscle’s stretch receptors.

Patellar (Knee-Jerk) Reflex (cont.) A nerve signal is sent to the spinal cord, which reflects back through a motor neuron to the quadriceps and causes contraction. Quadriceps contraction causes the lower leg to extend.

Flexor (Withdrawal) Reflex This reflex is usually activated in response to some potentially injurious stimulus, such as stepping on a sharp or hot object. Usually the evaluator will “poke” the bottom of the foot with something sharp – not enough to break the skin.

Flexor (Withdrawal) Reflex (cont.) A receptor located in the skin responds to pain. A nerve signal is sent to the spinal cord, where it reflects through a motor neuron to flexor muscles such as the leg’s hamstrings, causing the limb to pull away from the stimulus.

Plantar Reflex Tests the integrity of the lower spinal cord. A reflex hammer is pulled along the sole of the foot with pressure applied. The normal response is a curling of the toes.

Plantar Reflex (cont.) If damage is present, an abnormal reflex response is a spreading of the toes and lifting of the big toe, also known as Babinski’s sign.

Nervous System Anatomy Although other cells help with support and nourishment, the only cell that can communicate impulses to other cells is the neuron.

Gray and White Matter Gray matter consists mostly of neuron cell bodies. White matter consists mostly of myelinated nerve fibers.

Gray and White Matter (cont.) Gray matter is found in the center of the spinal cord and is surrounded by white matter. In the brain there is an additional outer gray matter layer, the cerebral cortex.

Spinal Injuries Trauma to the spine can produce devastating injuries, including paralysis and death.

Jaw-Thrust Maneuver This is the safest method to restore breathing when neck injury is suspected. The mandible is brought forward by placing fingers behind the jaw angle and lifting.

Intervertebral Disc Herniation A structural defect in which the softer nucleus pulposus protrudes through the tough annulus fibrosus