The Nervous System

The Nervous System

Clinical Case Study

Bob Bingen is a 24 year-old college student taking an anatomy and physiology class. As part of his lab for the class, Bob had his deep tendon reflexes tested. His class was taught to use this grading scale to report the strength of the reflexes. Bob's deep tendon reflexes were found to be "2" throughout.

Bob's deep tendon reflexes (also called stretch reflexes) were tested in a physical examination. Deep tendon reflexes are a good way to review the monosynaptic reflex arc. In this arc, afferent impulses travel along sensory neurons to the spinal cord (integrating center) and stimulate motor neurons. Efferent impulses travel along motor neurons to the muscle and cause muscle contraction.

Look at the illustration to see this arc.

Different reflexes test the integrity of nerve fibers and spinal cord segments at various levels.

Place the names of the reflexes next to the spinal cord segments with which they are associated.

Description of Current Illness:

On his way home from school one day, Bob was involved in a motorcycle accident and suffered multiple fractures and a spinal cord transection. His doctors determined that Bob suffered from quadriplegia. While he was able to breathe and speak on his own, he was unable to voluntarily move his arms, trunk, or legs.

Questions

Given Bob's ability to breathe but his inability to move his arms or legs, at what spinal level would you place his spinal cord injury?

The diaphragm is innervated by the phrenic nerve, which has fibers from spinal levels C3-5. The arms are controlled by nerves containing fibers from spinal levels C5-T1. Therefore, Bob's spinal cord lesion is probably around C5.

2. Did Bob's spinal cord lesion involve the integrating centers for the biceps-jerk or knee-jerk? Explain your answer.

The reflex (integrating) center for the biceps jerk is at C5-6. Because this was damaged, Bob's biceps jerk was absent. The reflex center for the knee jerk is...