BIOL 2401
Study Points Handout Chapter 13
1 What portion of the spinal cord connects with nerves of the upper limbs?
The cervical enlargement connects with sensory and motor nerves of the upper limbs.
2 What is the difference between a horn and a column in the spinal cord?
A horn is an area of gray matter, and a column is a region of white matter in the spinal cord.
3 Why are all spinal nerves classified as mixed nerves?
All spinal nerves are classified as mixed because their posterior roots contain sensory axons and their anterior roots
contain motor axons.
4 Why does complete severing of the spinal cord at level C2 cause respiratory arrest?
Severing the spinal cord at level C2 causes respiratory arrest because it prevents descending nerve impulses from
reaching the phrenic nerve, which stimulates contraction of the diaphragm, the main muscle needed for breathing.
5 What three important nerves arise from the brachial plexus?
The axillary, musculocutaneous, radial, median, and ulnar nerves are five important nerves that arise from the brachial
plexus.
Critical Thinking: Sunil has developed an infection that is destroying cells in the anterior gray horns in the lower cervical
region of the spinal cord. What kinds of symptoms would you expect to occur?
The anterior gray horns contain cell bodies of somatic motor neurons and motor nuclei that are responsible for the
nerve impulses for skeletal muscle ontraction. Because the lower cervical region is affected (brachial plexus, C5-C8), you
would expect that Sunil may have trouble with movement in his shoulder, arm, and hand on the affected side.