Knowledge of the Central Nervous System and Cranial Nerves

Knowledge of the Central Nervous System and Cranial Nerves

The following article provides detailed information on the structure and function of the central nervous system and cranial nerves, and explains their salient features through questions and answers.

1. Spinal cord compression due to a fracture of the sacral spine:

Question: A 40-year-old patient suffers from sacral cord compression due to a fracture of the spine. The spine may be fractured at:

A. Lumbar spine, at the level of the first lumbar vertebra.

B. Lower lumbar spine, at the levels of the third and fourth lumbar vertebrae.

C. Sacral spine.

D. The junction of the lumbar and sacral spine.

Answer: C

Explanation: The sacral cord is located at the end of the spinal cord, corresponding to the sacral vertebrae. Therefore, a fracture of the sacral spine will directly affect the sacral cord.

2. Sensation least affected by an intramedullary tumor:

Question: A patient with an intramedullary tumor (affecting the area around the central canal) will have which of the following sensations in the neck, trunk, and limbs least or not affected:

A. Touch.

B. Pain.

C. Temperature.

D. Proprioception.

Answer: D

Explanation: Proprioception is the ability to sense the position and movement of the body, controlled by receptors in muscles, tendons, and joints. Intramedullary tumors primarily affect the sensory pathways for touch, pain, and temperature, so proprioception is less affected.

3. Correct description of the spinal cord:

Question: The correct description of the following descriptions of the spinal cord is:

A. The inferior end of the adult spinal cord is at the upper margin of the third lumbar vertebra.

B. The spinal nerves in the different segments or vertebrae of the spinal cord are the same length.

C. The cervical enlargement of the spinal cord is located in the segment of the spinal cord that gives rise to spinal nerves C1 to IV.

D. A lumbar puncture between the spinous processes of the third and fourth or fourth and fifth lumbar vertebrae will avoid puncturing the spinal nerves.

Answer: D

Explanation: The adult spinal cord ends at the level of the first and second lumbar vertebrae, not the third. The spinal nerves in the different segments of the spinal cord have different lengths, and the cervical enlargement of the spinal cord is located in the segment of the spinal cord that gives rise to spinal nerves C5 to VIII. Puncture between the spinous processes of the third and fourth or fourth and fifth lumbar vertebrae is a safe technique to avoid puncturing the spinal nerves.

4. Incorrect description of the spinal cord:

Question: The following descriptions of the spinal cord are all correct EXCEPT:

A. The inferior end of the spinal cord tapers abruptly into the conus medullaris.

B. There is more gray matter in the cervical and lumbosacral enlargements of the spinal cord.

C. All spinal nerves exit the vertebral canal below their corresponding vertebra.

D. The anterior median fissure of the spinal cord contains the anterior spinal artery.

Answer: C

Explanation: The spinal cord only ends at the level of the first and second lumbar vertebrae, while the spinal nerves in the sacral and coccygeal segments still exit the vertebral canal below their corresponding vertebrae.

5. Correct description of the gray matter of the spinal cord:

Question: Of the following descriptions of the gray matter of the spinal cord, the correct one is:

A. The lateral horn is present in the cervical and upper thoracic segments.

B. All nerve fibers in the posterior root of the spinal nerve end in the posterior gray horn.

C. The anterior horn contains the cell bodies of motor neurons whose axons go to skeletal muscles.

D. Preganglionic parasympathetic motor neurons are located in the intermediolateral cell column.

Answer: C

Explanation: The lateral horn of the gray matter of the spinal cord is only present in the thoracic and lumbar segments, where it contains the preganglionic sympathetic motor neurons. The posterior horn contains sensory neurons, and the anterior horn contains motor neurons that innervate skeletal muscles.

6. Incorrect description of the gray matter of the spinal cord:

Question: The following descriptions of the gray matter of the spinal cord are all correct EXCEPT:

A. The descending motor tracts from the brain end in the anterior horn.

B. The posterior horn is the origin of the ascending sensory tracts.

C. The gray matter of the spinal cord is surrounded by a layer of white matter with uniform thickness from top to bottom.

D. The gray matter in the cervical segment contains the phrenic nucleus.

Answer: C

Explanation: The white matter of the spinal cord surrounds the gray matter, but its thickness varies depending on the location, being thicker in the cervical and lumbosacral enlargements.

7. Incorrect description of the oculomotor nerve:

Question: The following descriptions of the oculomotor nerve are all correct EXCEPT:

A. It contains both somatic motor fibers and autonomic (parasympathetic) fibers.

B. It passes through the superior orbital fissure into the orbit.

C. It innervates the superior oblique muscle.

D. It innervates the inferior oblique and inferior rectus muscles.

Answer: C

Explanation: The oculomotor nerve innervates the superior rectus, medial rectus, inferior rectus, and inferior oblique muscles, but not the superior oblique muscle.

8. Incorrect description of the nerves to the extraocular muscles:

Question: The following descriptions of the nerves to the extraocular muscles are all correct EXCEPT:

A. The trochlear nerve originates from a nucleus in the midbrain.

B. The abducens nerve nucleus is located in the pons, near the floor of the fourth ventricle.

C. The abducens nerve passes through the cavernous sinus.

D. The abducens nerve exits the skull through the inferior orbital fissure.

Answer: D

Explanation: The abducens nerve exits the skull through the superior orbital fissure, not the inferior orbital fissure.

9. Correct description of cranial nerves III, IV, and VI:

Question: Of the following descriptions of cranial nerves III, IV, and VI, the correct one is:

A. The autonomic fibers in cranial nerve III dilate the pupil.

B. Cranial nerve IV exits the brain in the region of the posterior perforated substance.

C. Cranial nerve VI innervates the lateral rectus muscle.

D. Cranial nerve III is unlikely to be compressed by a cerebral aneurysm.

Answer: C

Explanation: Cranial nerve VI innervates the lateral rectus muscle, while cranial nerve III innervates the medial rectus, superior rectus, inferior rectus, and inferior oblique muscles. The autonomic fibers in cranial nerve III constrict the pupil, not dilate it.

10. Correct description of the trigeminal nerve:

Question: Of the following descriptions of the trigeminal nerve, the correct one is:

A. It consists of two roots that emerge from the anterolateral pons, the motor root being lateral to the sensory root.

B. The sensory fibers from the trigeminal ganglion end in the midbrain nucleus.

C. The mandibular nerve is a mixed nerve.

D. The spinal trigeminal nucleus only receives fibers from the trigeminal ganglion.

Answer: C

Explanation: The trigeminal nerve consists of three branches: ophthalmic, maxillary, and mandibular. The mandibular branch is a mixed nerve, containing both motor and sensory fibers. The sensory fibers from the trigeminal ganglion end in the pontine nucleus, not the midbrain nucleus.

11. Correct description of the ophthalmic branch of the trigeminal nerve:

Question: Of the following descriptions of the ophthalmic branch of the trigeminal nerve, the correct one is:

A. All three terminal branches of it pass through the common tendinous ring of the recti muscles.

B. The ciliary ganglion of the nasociliary nerve supplies all the sensory fibers to the eyeball.

C. The anterior ethmoidal nerve of the nasociliary nerve supplies sensation to the posterior part of the lateral wall and septum of the nose.

D. The frontal nerve of the ophthalmic nerve contains sensory fibers from the forehead and upper eyelid.

Answer: D

Explanation: The frontal nerve of the ophthalmic nerve contains sensory fibers from the forehead and upper eyelid, not the anterior ethmoidal nerve.

12. Incorrect description of the maxillary branch of the trigeminal nerve:

Question: The following descriptions of the maxillary branch of the trigeminal nerve are all correct EXCEPT:

A. It gives off the posterior superior alveolar nerve before becoming the infraorbital nerve.

B. Its pterygopalatine branches are the pathway for postganglionic fibers from the pterygopalatine ganglion to the maxillary nerve.

C. It passes through the foramen rotundum to enter the pterygopalatine fossa.

D. The infraorbital nerve only contains sensory fibers from the face.

Answer: D

Explanation: The infraorbital nerve contains both sensory fibers from the face and autonomic fibers to the pterygopalatine ganglion.

13. Correct description of the maxillary branch of the trigeminal nerve:

Question: Of the following descriptions of the maxillary branch of the trigeminal nerve, the correct one is:

A. It passes through the inferior orbital fissure with the maxillary artery.

B. It supplies sensation to the entire nasal cavity.

D. It supplies sensation to the bridge of the nose and upper eyelid.

C. It is not associated with the pterygopalatine ganglion.

Answer: A

Explanation: The maxillary branch passes through the inferior orbital fissure with the maxillary artery. It supplies sensation to the anterior part of the nasal cavity, not the entire nasal cavity.

14. Correct description of the mandibular nerve:

Question: Of the following descriptions of the mandibular nerve, the correct one is:

A. It contains motor, sensory, and autonomic fibers.

B. It passes through the foramen ovale into the infratemporal fossa.

C. The trunk of the mandibular nerve lies in the upper head of the lateral pterygoid muscle.

D. It innervates four muscles.

Answer: C

Explanation: The trunk of the mandibular nerve lies in the upper head of the lateral pterygoid muscle, and it innervates more than four muscles.

15. Incorrect description of the mandibular nerve:

Question: The following descriptions of the mandibular nerve are all correct EXCEPT:

A. It usually has two branches to the temporalis muscle.

B. The auriculotemporal branch of the facial nerve joins the lingual branch of the mandibular nerve.

C. The buccal branch of the nerve innervates the skin and mucosa of the cheek.

D. It does not supply sensation to the auricle.

Answer: D

Explanation: The mandibular nerve supplies sensation to the auricle, not that it does not.

16. Incorrect description of the branches of the mandibular nerve:

Question: The following descriptions of the branches of the mandibular nerve are all correct EXCEPT:

A. The inferior alveolar nerve contains fibers that innervate the mylohyoid muscle.

B. The mental nerve is a terminal branch of the inferior alveolar nerve.

C. The auriculotemporal nerve accompanies the superficial temporal artery into the skin of the temporal region.

D. The lingual nerve supplies sensation to the posterior 1/3 of the tongue.

Answer: D

Explanation: The lingual nerve supplies sensation to the anterior 2/3 of the tongue, not the posterior 1/3 of the tongue.

17. Correct description of the facial nerve:

Question: Of the following descriptions of the facial nerve, the correct one is:

A. It is the only nerve that passes through the petrous bone.

B. It divides into its terminal branches after emerging from the parotid gland.

C. It lies below the vestibulocochlear nerve as it passes through the internal auditory meatus.

D. The geniculate ganglion is located at the angle between the labyrinthine and tympanic segments.

Answer: D

Explanation: The geniculate ganglion is located at the angle between the labyrinthine and tympanic segments. The facial nerve passes through the internal auditory meatus, not below the vestibulocochlear nerve.

18. Incorrect description of the facial nerve:

Question: The following descriptions of the facial nerve are all correct EXCEPT:

A. It contains sympathetic fibers.

B. Its sensory fibers originate from the geniculate ganglion.

C. It gives off the chorda tympani branch just before exiting the petrous bone through the stylomastoid foramen.

D. Within the parotid gland, it lies lateral to the external carotid artery.

Answer: A

Explanation: The facial nerve does not contain sympathetic fibers.

19. Correct description of the branches of the facial nerve:

Question: Of the following descriptions of the branches of the facial nerve, the correct one is:

A. The greater petrosal nerve contains sensory fibers from the tongue.

B. The chorda tympani nerve contains autonomic fibers to the submandibular ganglion.

C. The branch to the stapedius muscle originates at the level of the geniculate ganglion.

D. The posterior auricular nerve innervates the occipitalis muscle.

Answer: B

Explanation: The chorda tympani nerve contains autonomic fibers to the submandibular ganglion. The branch to the stapedius muscle originates at the level of the tympanic segment of the facial nerve.

20. Correct description of the facial nerve:

Question: Of the following descriptions of the facial nerve, the correct one is:

A. The geniculate ganglion is the location of the cell bodies of the sensory neurons.

B. The motor fibers go directly from the facial nerve motor nucleus to the pontine sulcus.

C. The facial nerve crosses the face medially to the stylomastoid foramen before entering the parotid gland.

D. The autonomic fibers of the facial nerve originate from the inferior salivatory nucleus.

Answer: A

Explanation: The geniculate ganglion is the location of the cell bodies of the sensory neurons. The motor fibers of the facial nerve go from the facial nerve motor nucleus to the pontine sulcus, not directly.

21. Correct description of the vestibulocochlear nerve:

Question: Of the following descriptions of the vestibulocochlear nerve, the correct one is:

A. It travels within the facial nerve canal with the facial nerve.

B. The peripheral processes of the vestibular ganglion neurons branch to the saccule, utricle, and ampullae of the semicircular canals.

C. The vestibular ganglion is located at the external end of the external auditory meatus.

D. The vestibular nerve nuclei are not located in the brainstem.

Answer: A

Explanation: The vestibulocochlear nerve travels within the facial nerve canal with the facial nerve. The vestibular ganglion is located at the internal end of the internal auditory meatus.

22. Incorrect description of the vestibulocochlear nerve:

Question: The following descriptions of the vestibulocochlear nerve are all correct EXCEPT:

A. A tumor of the vestibulocochlear nerve can compress the facial nerve.

B. Within the internal auditory meatus, the cochlear nerve lies below the facial nerve.

C. The vestibulocochlear nerve enters the brain at the pontine sulcus.

D. The cochlear nerve fibers terminate in the solitary nucleus.

Answer: D

Explanation: The cochlear nerve fibers terminate in the cochlear nuclei, not the solitary nucleus.

23. Incorrect description of the glossopharyngeal nerve:

Question: The following descriptions of the glossopharyngeal nerve are all correct EXCEPT:

A. The sensory fibers in this nerve terminate in the solitary nucleus and the spinal trigeminal nucleus.

B. It is the sensory nerve for the pharynx, posterior 1/3 of the tongue, tympanic cavity, carotid sinus, and carotid body.

C. Its auricular branch contains sensory fibers.

D. It innervates the stylopharyngeus muscle.

Answer: C

Explanation: The auricular branch of the glossopharyngeal nerve contains motor fibers, not sensory fibers.

24. Correct description of the glossopharyngeal nerve:

Question: Of the following descriptions of the glossopharyngeal nerve, the correct one is:

A. Its sensory fibers do not terminate in the solitary nucleus.

B. Its motor fibers innervate the digastric muscle.

C. Its autonomic fibers originate from the inferior salivatory nucleus.

D. It exits the brain at the anterior pontine sulcus.

Answer: C

Explanation: The autonomic fibers of the glossopharyngeal nerve originate from the inferior salivatory nucleus.

25. Correct description of the vagus nerve:

Question: Of the following descriptions of the vagus nerve, the correct one is:

A. The dorsal (posterior) vagal nucleus is the origin of the motor fibers to the muscles of the palate and pharynx.

B. The superior and inferior ganglia are enlargements along the course of the vagus nerve, containing the cell bodies of the sensory neurons.

C. The superior laryngeal branch of the vagus nerve innervates most of the laryngeal muscles.

D. The vagus nerve passes through the posterior part of the jugular foramen.

Answer: B

Explanation: The superior and inferior ganglia are enlargements along the course of the vagus nerve, containing the cell bodies of the sensory neurons.

26. Incorrect description of a branch of the vagus nerve:

Question: The following descriptions of the branches of the vagus nerve are all correct EXCEPT:

A. The pharyngeal branch of the vagus nerve contains motor fibers to the muscles of the palate and pharynx.

B. The vagus nerve gives off branches that innervate the heart.

C. The recurrent laryngeal branch innervates the muscles of the larynx.

D. The terminal branches of the vagus nerve innervate the pelvic viscera.

Answer: D

Explanation: The terminal branches of the vagus nerve innervate the thoracic and abdominal viscera, not the pelvic viscera.

27. Incorrect description of the relationship of the vagus nerve:

Question: The following descriptions of the relationship of the vagus nerve are all correct EXCEPT:

A. The left vagus nerve does not cross the left subclavian artery.

B. The right recurrent laryngeal nerve is longer than the left recurrent laryngeal nerve.

C. The vagus nerve travels in the neck alongside the internal carotid and common carotid arteries.

D. The vagus nerves lie behind the pulmonary hilum.

Answer: B

Explanation: The left recurrent laryngeal nerve is longer than the right recurrent laryngeal nerve.

28. Incorrect description of the accessory nerve:

Question: The following descriptions of the accessory nerve are all correct EXCEPT:

A. The accessory nerve is the most inferior of the three nerves that exit from the posterior pontine sulcus.

B. The cranial root of the accessory nerve exits the skull through the foramen magnum to join the spinal root.

C. The fibers in the cranial root of the accessory nerve originate from the nucleus ambiguus.

D. The accessory nerve passes through the posterior triangle of the neck.

Answer: B

Explanation: The cranial root of the accessory nerve exits the skull through the foramen magnum, not the foramen magnum.

29. Correct description of cranial nerve XII:

Question: Of the following descriptions of cranial nerve XII, the correct one is:

A. Cranial nerve XII exits the brain at the posterior pontine sulcus.

B. Cranial nerve XII exits the skull through the foramen magnum.

C. Those fibers of cranial nerve XII that originate from spinal nerve C1 do not pass through the hypoglossal canal.

D. Cranial nerve XII gives off the inferior root of the ansa cervicalis.

Answer: C

Explanation: Those fibers of cranial nerve XII that originate from spinal nerve C1 do not pass through the hypoglossal canal.

30. Correct description of the external surface of the medulla:

Question: Of the following descriptions of the external surface of the medulla, the correct one is:

A. The furrow between the pyramids becomes indistinct at the decussation of the pyramids.

B. The roots of the hypoglossal nerve emerge from the posterior pontine sulcus.

C. The olives on either side lie adjacent to the posterior median sulcus.

D. The superior medullary velum lies on the surface of the medulla.

Answer: A

Explanation: The furrow between the pyramids becomes indistinct at the decussation of the pyramids.

31. Incorrect description of the medulla:

Question: The following descriptions of the medulla are all correct EXCEPT:

A. The medulla is the relay station for the first and second stages of the conscious proprioceptive pathway of the neck, trunk, and limbs.

B. The medulla contains all the ascending sensory tracts from the spinal cord to the brain.

C. The medulla contains the centers that regulate vital functions of the body.

D. The nucleus ambiguus is located inferior to the area postrema.

Answer: D

Explanation: The nucleus ambiguus is located superior to the area postrema.

32. Incorrect description of the pons:

Question: The following descriptions of the pons are all correct EXCEPT:

A. The pontine base contains the pontine nuclei.

B. The corticospinal tract passes through the pontine base.

C. The pons contains the relay station for the cerebello-cortical pathway.

D. The abducens nerve nucleus is located in the pontine base.

Answer: D

Explanation: The abducens nerve nucleus is located in the tegmentum of the midbrain.

33. Correct description of the pons:

Question: Of the following descriptions of the pons, the correct one is:

A. The pons contains the terminal nuclei for the cochlear nerve fibers.

B. All the sensory fibers of cranial nerve V terminate in nuclei in the pons.

C. The facial nerve motor nucleus is located in the pontine base.

D. The tentorium cerebelli lies in the pontine base.

Answer: A

Explanation: The pons contains the terminal nuclei for the cochlear nerve fibers.

34. Incorrect description of the midbrain:

Question: The following descriptions of the midbrain are all correct EXCEPT:

A. The superior colliculus is the center for reflexes related to vision.

B. The inferior colliculus is part of the auditory pathway.

C. The descending and ascending tracts in the midbrain are separated by the red nucleus.

D. The tentorium cerebelli lies behind the substantia nigra, lateral to the red nucleus.

Answer: C

Explanation: The descending and ascending tracts in the midbrain are separated by the substantia nigra, not the red nucleus.

35. Incorrect description of the temporal lobe:

Question: The following descriptions of the temporal lobe are all correct EXCEPT:

A. There is no sulcus separating the temporal lobe from the occipital lobe.

B. It borders all four other lobes of the brain.

C. It is located on all three surfaces of the cerebral hemisphere.

D. It contains one of the horns of the lateral ventricle.

Answer: C

Explanation: The temporal lobe is located on the superolateral and inferior surfaces of the cerebral hemisphere, not all three surfaces.

36. Correct description of the frontal lobe:

Question: Of the following descriptions of the frontal lobe, the correct one is:

A. It is separated from the cingulate gyrus by the supplementary motor area.

B. The general sensory area of the body is located in the frontal lobe.

C. It is located just anterior to the postcentral gyrus of the parietal lobe.

D. Its inferior surface lies on the middle cranial fossa.

Answer: B

Explanation: The general sensory area of the body is located in the frontal lobe.

37. Incorrect description of the parietal lobe:

Question: The following descriptions of the parietal lobe are all correct EXCEPT:

A. It does not lie on the inferior surface of the hemisphere.

B. It is located on the superolateral and medial surfaces of the cerebral hemisphere.

C. It borders the frontal, occipital, temporal, and limbic lobes.

D. On the superolateral surface, it is bordered by the postcentral sulcus, the parieto-occipital sulcus, and the lateral sulcus.

Answer: D

Explanation: On the superolateral surface, the parietal lobe is bordered by the postcentral sulcus, the parieto-occipital sulcus, and the lateral sulcus, not the lateral sulcus.

38. Correct description of the limbic lobe:

Question: Of the following descriptions of the limbic lobe, the correct one is:

A. It is located on all three surfaces of the hemisphere.

B. It consists of three parts: hippocampus, cingulate gyrus, and parahippocampal gyrus.

C. It is surrounded by the sulci: Cingulate, supplementary motor, and subparietal.

D. It is susceptible to injury in a depressed skull fracture.

Answer: C

Explanation: The limbic lobe is surrounded by the sulci: Cingulate, supplementary motor, and subparietal.

39. Artery damaged in a cerebral infarction causing complete loss of sensation and motor function of the right half of the body:

Question: A patient suffers from complete loss of sensation and motor function of the right half of the body due to a cerebral infarction. The artery likely to be damaged in the following arteries is:

A. Left anterior cerebral artery.

B. Cortical branch of the left middle cerebral artery.

C. Lenticulostriate branches of the left middle cerebral artery.

D. Left posterior cerebral artery.

Answer: C

Explanation: The lenticulostriate branches of the left middle cerebral artery supply the sensory and motor cortex of the right half of the body.

40. Information about the medulla:

Question: Regarding the medulla:

A. It is the relay station for the conscious proprioceptive pathway.

B. It is the site of decussation of most corticospinal fibers.

C. It contains only the nuclei of cranial nerves IX to XII.

D. It contains the auditory and visual centers.

Answer: D

Explanation: The medulla contains the auditory and visual centers. It is also the relay station for the conscious proprioceptive pathway and the site of decussation of most corticospinal fibers.

41. Information about the pons:

Question: Regarding the pons:

A. It contains the main sensory nuclei of cranial nerve V.

B. It contains nuclei that give rise to fibers that go to the cerebellum.

C. The facial nerve motor nucleus is not located in the pons.

D. The vestibular nuclei are located in both the pons and medulla.

Answer: B

Explanation: The pons contains nuclei that give rise to fibers that go to the cerebellum. It also contains the main sensory nuclei of cranial nerve V. The facial nerve motor nucleus is located in the pons. The vestibular nuclei are located in the pons and medulla.

42. Information about the midbrain:

Question: Regarding the midbrain:

A. The midbrain does not contain nuclei of cranial nerve V.

B. The substantia nigra separates the motor and sensory tracts in the midbrain.

C. The oculomotor nerve nucleus lies on a cross section through the superior colliculus.

D. The red nucleus is located anterior to the substantia nigra.

Answer: B

Explanation: The substantia nigra separates the motor and sensory tracts in the midbrain. The oculomotor nerve nucleus lies on a cross section through the inferior colliculus. The red nucleus is located posterior to the substantia nigra.

43. Information about the gray matter of the spinal cord:

Question: Regarding the gray matter of the spinal cord:

A. The posterior gray horn is the termination site of all fibers in the posterior root of the spinal nerve.

B. The axons in the posterior white column of the spinal cord do not originate from the posterior gray horn of the spinal cord.

C. The anterior horn of the gray matter is the origin of a small fraction of fibers in the anterior root of the spinal nerve.

D. Axons from the intermediolateral cell column (of the lateral horn) go to all sympathetic and parasympathetic ganglia in the periphery.

Answer: B

Explanation: The axons in the posterior white column of the spinal cord do not originate from the posterior gray horn of the spinal cord. The posterior gray horn is the termination site of sensory fibers in the posterior root of the spinal nerve, and the anterior horn is the origin of motor fibers in the anterior root of the spinal nerve.

44. Information about the white matter of the spinal cord:

Question: Regarding the white matter of the spinal cord:

A. The anterior white commissure connects the two halves of th