Question

1. Match each statement with the appropriate nerve.

A. Axillary     B. femoral      C. fibular    D. obturator      E. radial      F. phrenic      G. ulnar

            ______ Forms from the cervical plexus.

            ______ Damage to this nerve would prevent extension at the knee.

            ______ Stimulation of this nerve would trigger adduction at the hip.

            ______ Damage to this nerve might weaken flexion at the wrist.

2. Match each phrase with the appropriate structure associated with the spinal cord.

A. ventral root      B. ventral horn      C. ventral ramus      D. dorsal root      E. dorsal horn   F. dorsal ramus

   

______ Origin of somatic motor neurons.

______ Contains only sensory fibers.

______ Carries only fibers connecting to the central region of the back.

3. What is the reason for the two enlargements in the spinal cord?
4. Describe the distal (inferior) end of the spinal cord and the contents of the vertebral canal below L2.
5. Explain why the crossed extension reflex must accompany a withdrawal reflex of the leg.

Answer 1

Match each statement with the appropriate nerve.   

F. phrenic - Forms from the cervical plexus.

Explanation:- Phrenic Nerve is the nerve of the Cervical Plexus which runs inferiorly through the thorax and supplies both sensory and motor fibers to the diaphragm.

B. femoral - Damage to this nerve would prevent extension at the knee.

Explanation:- Injury to femoral nerve results in weakened hip flexion and loss of knee extension.

D. obturator - Stimulation of this nerve would trigger adduction at the hip.

Explanation:- Injury to obturator nerve results in loss of hip adduction and weakened hip lateral rotators.

  

G. ulnar - Damage to this nerve might weaken flexion at the wrist.

Explanation:- Injury to ulnar nerve results in loss of wrist ulnar deviation, weakend wrist/finger flexion.

Match each phrase with the appropriate structure associated with the spinal cord.

B. ventral horn - Origin of somatic motor neurons.

Explanation:- somatic motor neurons located in the ventral horn of spinal cord.

E. dorsal horn   - Contains only sensory fibers.

Explanation:- The dorsal horn contains axons of sensory neurons whose cell bodies are in the dorsal root ganglion.

D. dorsal root :- Carries only fibers connecting to the central region of the back

Explanation:- dorsal root passes posteriorly through the intervertibral foramne towards the back of the spinal cord.

What is the reason for the two enlargements in the spinal cord?

Answer:- There are two number of enlargements that spinal cord have: cervical and lumbar enlargement.The reason for these two enlargements is the increased number of cell bodies for motor control. The cervical enlargement of the spinal cord that is responsible for innervation of the upper limbs whereas the lumbar enlargement of the spinal cord that is responsible for innervation of the lower limbs.

Describe the distal (inferior) end of the spinal cord and the contents of the vertebral canal below L2.

Answer:- The spinal cord tapers to a point called the medullary cone. Arising from the lumbar enlargement and medullary cone is a bundle of nerve roots that occupy the vertebral canal below L2.Below L2, the spinal canal is occupied by a bundle of spinal nerve roots called Cauda Equina.

Explain why the crossed extension reflex must accompany a withdrawal reflex of the leg.

Answer:- Crossed extensor reflex is the contraction of extensor muscles in the limb opposite from the one that is withdrawn. As if you all the withdrawal, you would be fall over thus the crossed extensor reflex maintains balance and shifts your center of gravity.