7. A tumor pressing against the spinal cord blocks action potential propagation

Question

7. A tumor pressing against the spinal cord blocks action potential propagation in the white matter. You find that all somatosensory modalities from the arms remain intact. The patient feels no pain in the right leg and no fine touch in the left leg. (Sensory information enters the spinal cord from the arms in the cervical region and from the legs in the lumbar region.) You can conclude that the tumor is located on the:

a. right side of the spinal cord below) the lumbar region.

b. left side of the spinal cord above the cervical region.

c. left side of the spinal cord between the lumbar and cervical regions.

d. right side of the spinal cord between the lumbar and cervical regions.

e. on the ventral aspect of the spinal cord.

8. In some neurodegenerative diseases the lower motor neuron cell bodies die and the remaining lower motor neurons sprout process that innervate the neuromuscular synapses vacated by the dead lower motor neurons. In these muscles, the size of the motor unit ____________ and the strength of the muscle contraction generated by the activation of each of the motor neurons _____________.

a. decreases, decreases

b. decreases, increases

c. increases, decreases

d. increases, increases

9. You would predict that electrical stimulation of two neighboring neurons in the right precentral gyrus would cause:

a. muscle contractions in widely different areas of the left side of the body.

b. sensory sensations perceived as coming from widely different areas on the right side of the body.

c. sensory sensations perceived as coming from nearly the same area on the right side of the body.

d. muscle contractions in nearly the same region on the left side of the body.

e. muscle contractions in nearly the same region of the body on the left and right sides of the body.

Explanation / Answer

7. right side of the spinal cord between the lumbar and the cervical region .

8. decreases , decreases

9 muscles contraction in nearly the same region on the left side of the body

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