The Corticospinal Tract And The Internal Capsuel

Question 1

These cells, whose axons terminate directly on skeletal muscle fibers are also known as ‘lower motor neurons.’
A. True.
B. False.

Answer 1

Yes, All commands, conscious or unconscious, arising in the cortex or brain stem must be conveyed to a single target, the large alpha motor neurons. Therefore, the ventral horn cell is the final common pathway to the muscles.

Question 2

What deficit(s) result from interrupting these neurons in area 4?
A. Spasticity.
B. Hypertonia.
C. Hyperreflexia.
D. Pathological reflexes.
E. All of the above.

Answer 2

All of the above.

All of these deficits occur with upper motor neuron pathology. Upper motor neurons are located in the cerebral cortex. This Golgi impregnated section of the cerebral cortex shows cells bodies and dendrites of pyramidal cells.

Question 3

Which limb of the internal capsule contains cortical afferents?
A. Anterior limb.
B. Posterior limb.
C. Both.
D. Neither.

Answer 3

Both limbs contain cortical afferents. The well known sensory radiations, from VPM and VPL, are located in the posterior limb. The anterior limb also has afferents from thalamic nuclei that have connections with the cerebellum and basal ganglia. This sagittal section allows you to see both limbs. The frontal pole is to the left.

Question 4

All of the following are sensory radiations from this structure EXCEPT:
A. Olfactory radiations.
B. Optic radiations.
C. Auditory radiations.
D. Somatosensory radiations

Answer 4

Olfactory radiations

Axons from the olfactory bulb do NOT pass through the thalamus on their way to the olfactory cortex. Olfactory cortex is located in the region of the uncus. The thalamus is seen here in a horizontal section.

Question 5

A lesion placed in which the following would have the most devastating clinical effects to the patient?
A. The precentral gyrus of the cerebral cortex.
B. The anterior limb of the internal capsule.
C. The posterior limb of the internal capsule.
D. The anterolateral system.
E. The postcentral gyrus of the cerebral cortex

Answer 5

The posterior limb of the internal capsule.

A lesion of the posterior limb of the internal capsule would be very severe, compromising most of the somatosensory radiations and motor pathways. This is a coronal section through the posterior limb of the internal capsule.

Question 6

Which of the following is not correct?
A. The center for lateral gaze is in the pons.
B. The center for vertical gaze is in the pretectal area.
C. Looking upward is not dependent on the mlf.
D. Looking upward is not dependent on the pons.
E. The lateral and vertical gaze centers are located near each other in the pons.

Answer 6

The lateral and vertical gaze centers are located near each other in the pons.

Question 7

Cortical afferents in the internal capsule have their cell bodies located in:
A. The dorsal horn.
B. The dorsal column nuclei.
C. The thalamic nuclei.
D. The cerebral cortex.

Answer 7

The thalamic nuclei

Most thalamic nuclei project to the cerebral cortex. A large number of axons in the internal capsule are efferent, particularly for motor behavior. Their cell bodies are in the cortex.

Question 8

The role of the corpus callosum can best be defined as
A. Association cortical connections from all areas.
B. Intracortical connections between homotopic areas of each hemisphere.
C. A dorsal extension of the internal capsule.
D. A pathway for interhemispheric transfer from the nondominant to the dominant hemisphere.
E. A pathway to insure that the same information goes to each hemisphere

Answer 8

Intracortical connections between homotopic areas of each hemisphere.