CSGD Quiz 1 2010

1

Which one of the following statements about the organizat ion of the nervous system is correct?


  The boundary between frontal and parietal lobes lies between the primary somatosensory cortex in the precentral gyrus and the primary motor cortex in the postcentral gyrus.

  The temporal lobe is separated from the frontal and most of the parietal lobe by the longitudinal fissure.

  The cerebellum lies in the angle between the occipital lobe and brainstem and is connected to the occipital lobe.

  The longitudinal fissure divides the cerebrum into two hemispheres.

  The thalamus lies in the midbrain.


A is incorrect: The postcentral gyrus is the primary somatosensory cortex, and the precentral is the primary motor cortex. B is incorrect: The temporal lobe is separated by the lateral fissure. C is incorrect: The cerebellum has no direct connection to the occipital lobe. D is correct. E is incorrect: The thalamus sits above the midbrain and underneath the cortex.

2

Which one of the following statements about the development of the nervous system is correct?


  The nervous system is derived from the mesoderm.

  In the developing spinal cord, cells identify their function by "reading" their location on a gradient of signalling molecules released from the dorsal and ventral surfaces of the tube.

  The neuroepithelium of the neural tube is initially a single cell layer thick but increases to many cells thick because stem cells migrate to the outer (pial) surface where they divide.

  The sequence of neural tube closure occurs from the head to the tail.

  During development, glial cells tend to appear before neurons.


A is incorrect: The nervous system is derived from the ectoderm. B is correct: This gradient is between Shh ventrally and TGF-β family (e.g. BMP4, BMP5, BMP7) dorsally. C is incorrect: The stem cells divide on the inner (apical or ventricular) surface. D is incorrect: Primary neurulation closes the neural tube first in the centre, then progresses outwards both cranially and caudally. E is incorrect: The opposite is true; neurons tend to appear before glial cells.

3

Which one of the following is correct? A hemisection on the right side of the spinal cord extending from segment C3 to segment C6 results in:


  An up-going plantar reflex (Babinski sign) on the left side.

  Increased tendon reflexes for the right biceps brachii.

  Decreased temperature sensation from the right shoulder.

  Decreased position sense at the left ankle.

  Decreased pain sensation from the right calf.


A is incorrect: Motor neurons do not decussate in the spinal cord, therefore the Babinski sign would be on the same side as the lesion. B is incorrect: Exaggerated reflexes are a UMN sign. Hemisection from C3 to C6 would produce LMN signs for the biceps brachii. C is correct. D is incorrect: As for A, touch and position sense nerves do not decussate in the spinal cord, therefore decreased position sense would be observed on the right ankle. E is incorrect: Pain and temperature sensory nerves decussate within several spinal segments after entry into the spinal cord; therefore this would be observed on the left calf.

4

Which one of the following statements about pain is correct?


  C fibres from nociceptors terminate in both lamina I and lamina V of the dorsal horn.

  Hyperalgesia and allodynia only occur in regions of skin that are injured or damaged.

  Action potentials propagating backward down the axon into nociceptor terminals release glutamate.

  Glutamate released by nociceptor terminals in the dorsal horn activates AMPA type receptors but not NMDA type receptors.

  Enkephalin releasing interneurons in the dorsal horn of the spinal cord produce both pre-synaptic and post-synaptic inhibition.

5

Which one of the following bones does not contribute to the configuration of sutures at the pterion?


  Frontal bone.

  Ethmoid bone.

  Sphenoid bone.

  Parietal bone.

  Temporal bone.


The ethmoid bone is located on the cranial floor anteromedially.

6

Joseph has a somatosensory deficit on the left side of his face. Neurological examination also finds that when he protrudes his jaw it deviates to his left. On testing the corneal reflex, there is no response to touching the left cornea and both eyes blink when the right cornea is touched. Other cranial nerves and all limb functions are normal to examination. MRI shows a lesion in the posterior fossa. Which one of the following best explains the most likely location of the lesion?


  Left cerebello-pontine angle because the seventh cranial nerve innervates facial movements and is efferent for the corneal reflex.

  Right cerebello-pontine angle because somatosensory and motor pathways decussate in the brainstem.

  Inside the brainstem on one side because the abnormalities are all left-sided and affect multiple cranial nerve nuclei.

  Adjacent to the pons laterally because the fifth cranial nerve is affected, and there are no signs of damage to tracts inside the brainstem.

  Adjacent to the pons medially because both fifth and sixth cranial nerves on one side are abnormal.

7

Which one of the following structures is located in the rostral midbrain (level of the superior colliculi)?


  Inferior olivary nucleus.

  Dorsal cochlear nucleus.

  Nucleus cuneatus.

  Motor trigeminal nucleus.

  Oculomotor nucleus.

8

Which one of the following statements about cranial nerves is correct?


  The stapedius muscle (middle ear) is innervated by a branchial motor branch of cranial nerve seven (trigeminal nerve).

  The nervus intermedius provides autonomic innervation to the parotid gland and lacrimal gland.

  The corneal blink ref lex is mediated by motor and sensory branches of the fifth cranial nerve (Trigeminal).

  The tensor tympani (middle ear) is innervated by a motor branch of the fifth cranial nerve (trigeminal nerve).

  Both the trigeminal and the facial nerves mediate taste sensation from the anterior two thirds of the tongue and soft palate.

9

With regard to myelin production, which one of the following is correct?


  Only astrocytes produce myelin.

  Only oligodendrocytes produce myelin.

  Neurons can produce myelin after injury.

  Only Schwann cells produce myelin.

  Both oligodendrocytes and Schwann cells produce myelin.


A is incorrect: Astrocytes do not produce myelin at all. B is incorrect: Both oligodendrocytes and Schwann cells produce myelin. C is incorrect: Neurons do not produce myelin; this is done by glial cells. D is incorrect: Same as for B. E is correct.

10

With regard to voltage-activated sodium channels in a neuron, which one of the following is correct?


  They are not present in the cell body.

  They occur mainly in axons and dendrites.

  Their function is unknown.

  They are present in highest numbers at the axon hillock.

  Once triggered, they remain open for 100 milliseconds.


A is incorrect: VASCs are located in most parts of the neuron. B is incorrect: Dendrites do not have VASCs (in theory); they are signal collectors only. C is incorrect: Their function is integral to action potential generation and propagation. D is correct. E is incorrect: VASCs close much faster than this; they generally close at the peak of the action potential (after about 1ms).