Quiz 132 · Cerebellum

Answers to Quiz 131 · Basal Ganglia

1. The principal output nucleus of the basal ganglia is the:

   Answer: Internal segment of the globus pallidus

   Output leaves through the globus pallidus internus, to the ventral lateral, ventral anterior and centromedian thalamic nuclei. GPe and the subthalamic nucleus are relays inside the indirect pathway, not exits. Revise basal ganglia: circuits and functions

2. The striatum, or neostriatum, is made up of the:

   Answer: Caudate nucleus and putamen

   Caudate plus putamen is the striatum, the part that receives nearly all the input. Putamen plus globus pallidus is the lenticular nucleus, which is the tempting second option. Revise basal ganglia: circuits and functions

3. In the direct pathway, the projection from striatum to globus pallidus internus is:

   Answer: Inhibitory and GABAergic

   Striatum to GPi is GABAergic and inhibitory, as is GPi to thalamus. Glutamate is the transmitter of the cortex to striatum step, and dopamine of the nigrostriatal projection. Revise basal ganglia: circuits and functions

4. Stimulating the striatum ends up exciting the thalamus through the direct pathway because:

   Answer: Two inhibitory synapses in series disinhibit the thalamic neurons

   An active striatum silences the GPi, and the GPi was itself inhibiting the thalamus, so the thalamus is released. That is disinhibition: the GPi output is inhibitory, not excitatory. Revise basal ganglia: circuits and functions

5. Which link in the indirect pathway is excitatory?

   Answer: Subthalamic nucleus to globus pallidus internus

   The subthalamic nucleus drives the GPi; the other three links are inhibitory. That single excitatory step is what makes the indirect pathway suppress the thalamus. Revise basal ganglia: circuits and functions

6. The dopaminergic projection from pars compacta of the substantia nigra to the striatum:

   Answer: Excites the direct pathway and inhibits the indirect pathway

   Dopamine presses the accelerator and eases the brake, so both of its actions favour movement. Losing it leaves the indirect pathway dominant, which is the hypokinesia of Parkinsonism. Revise basal ganglia: circuits and functions

7. The limbic system projects mainly to which zone of the striatum?

   Answer: Striosomes

   Striosomes take limbic input and serve limbic functions; the matrix takes motor cortex input and serves motor functions. Pars reticulata belongs to the substantia nigra. Revise basal ganglia: circuits and functions

8. Which of the following is NOT a function of the basal ganglia?

   Answer: Relaying sensory impulses from the spinal cord to the cerebral cortex

   Unlike the cerebellum, the basal ganglia get no direct sensory input from the periphery or cord, so they relay nothing sensory. Their neurons fire before a movement starts, which is the evidence for planning. Revise basal ganglia: circuits and functions

9. The tremor of Parkinsonism has a frequency of about:

   Answer: 8 per second

   Antagonists contract alternately at roughly 8 per second. It is present at rest and stops once the patient begins to move, hence resting tremor. Revise parkinson’s and huntington’s disease

10. MPP, the toxin found in high concentration in the Parkinsonian brain, is formed from MPTP by:

    Answer: Monoamine oxidase B

    MAO-B converts MPTP to MPP, which piles up in basal ganglia neurons and destroys them. That is exactly why deprenyl, an MAO-B inhibitor, is used in treatment. Revise parkinson’s and huntington’s disease

11. L-dopa is given rather than dopamine itself in Parkinsonism because:

    Answer: Dopamine cannot cross the blood-brain barrier but L-dopa can

    The barrier admits the precursor but not dopamine, so L-dopa is the drug of choice and is converted to dopamine centrally. Lowering striatal acetylcholine is what the anticholinergics do, not L-dopa. Revise parkinson’s and huntington’s disease

12. Which finding is NEVER seen in the rigidity of Parkinsonism?

    Answer: Sudden loss of resistance while the rigid limb is being moved

    The give-way is clasp-knife spasticity, which belongs to upper motor neuron paralysis. Parkinsonian rigidity is lead-pipe, sometimes cogwheel, with both agonists and antagonists overactive. Revise parkinson’s and huntington’s disease

13. In Huntington's disease the pathway that degenerates is the:

    Answer: GABAergic striatonigral projection

    Loss of the striatal GABA neurons removes inhibition of the globus pallidus, thalamic activity falls and chorea results. Degeneration of the nigrostriatal dopamine fibres is Parkinsonism instead. Revise parkinson’s and huntington’s disease

14. A 34-year-old man has dancing involuntary movements, slurred speech and worsening dementia; his father died of the same illness at 45. The defective gene lies on:

    Answer: Chromosome 4, inherited as an autosomal dominant

    Huntington's disease is autosomal dominant, from a chromosome 4 gene coding the abnormal protein huntingtin. It begins at 30 to 40 years and kills within 10 to 15 years, and there is no definite treatment. Revise parkinson’s and huntington’s disease

15. A hypertensive man suddenly develops violent flailing movements of the right arm and leg. The likely site of the haemorrhage is the:

    Answer: Left subthalamic nucleus

    Hemiballism follows bleeding into the subthalamic nucleus of the opposite side. Damage to the caudate nucleus gives chorea and damage to the striatum gives the slow writhing of athetosis. Revise parkinson’s and huntington’s disease

15 questions on chapter 132. Pick one answer for each, then save. Your answers stay in this browser, and the right ones are shown on your results page.

1. Which pairing of a cerebellar peduncle with what it connects the cerebellum to is correct?

Middle peduncle – medullaSuperior peduncle – ponsMiddle peduncle – ponsInferior peduncle – midbrain

2. Compared with the cerebral cortex, the cerebellum has:

About a quarter of its surface area and a quarter of its weightAbout 10% of its surface area but about 75% of its weightAbout 75% of its surface area but only about 10% of its weightAbout half of its surface area and about half of its weight

3. The flocculonodular lobe of the cerebellum is concerned with:

Equilibrium, and learned changes in the vestibulo-ocular reflexPlanning and programming of movement with the cortexSkilled voluntary movement of the distal limb musclesPosture, through the axial and proximal limb muscles

4. The paravermal region of the spinocerebellum projects to brainstem nuclei that act on:

Axial and proximal limb muscles, so it controls postureExtraocular muscles, so it keeps the eyes on a targetDistal limb muscles, so it controls skilled voluntary movementMuscles of the larynx and tongue, so it shapes speech

5. Which division of the cerebellum is also called the corticopontocerebellum?

Spinocerebellum, the vermis and paravermal stripCerebrocerebellum, the two hemispheresVestibulocerebellum, the flocculonodular lobeOnly the vermal part of the spinocerebellum

6. The interneurons of the molecular layer of the cerebellar cortex are:

Purkinje cells and basket cellsGolgi cells and stellate cellsBasket cells and stellate cellsGranule cells and Golgi cells

7. Mossy fibres entering the cerebellum end mainly on:

Basket cellsDeep cerebellar nucleiGranule cellsPurkinje cells

8. Climbing fibres reach the cerebellum from:

The inferior olivary nucleus, and end on Purkinje cellsThe lateral cuneate nucleus, and end on Golgi cellsThe vestibular nuclei, and end on the fastigial nucleusThe pontine nuclei, and end on granule cells

9. Which cell carries the output of the cerebellar cortex to the deep cerebellar nuclei?

The granule cellThe Purkinje cellThe Golgi cellThe basket cell

10. Nucleus interpositus is made up of which nuclei, and what feeds it?

The fastigial nucleus alone; the flocculonodular lobeGlobose and emboliform nuclei; the paravermal spinocerebellumThe dentate nucleus alone; the neocerebellumFastigial and dentate nuclei; the vermis

11. The signs of a cerebellar lesion appear on the same side as the lesion because:

The deep cerebellar nuclei project only to the thalamus of the same sideThe cerebellum has no crossed connections with the brainstem at allThe cerebellar outflow crosses in the midbrain and the corticospinal tract crosses again in the medullaThe Purkinje cells inhibit the deep cerebellar nuclei of the same side

12. Which of these is NOT a feature of a cerebellar lesion?

Intention tremor on the affected sideSpastic paralysis with a positive Babinski signHypotonia of the limbs on the affected sideA pendular knee jerk on the affected side

13. A patient flexes the elbow against the examiner's pull; the pull is released suddenly and the forearm flies up and strikes his chest. This is:

An exaggerated inverse stretch reflexThe clasp-knife response of spasticityThe lead-pipe rigidity of ParkinsonismThe rebound phenomenon of a cerebellar lesion

14. In a patient with cerebellar ataxia, Romberg's test shows:

Swaying only when the head is turned to the affected sideNo swaying at all, because tone is reducedSteady standing until the eyes close, when the patient sways or fallsSwaying with the eyes open that is little worse when they are closed

15. A 7-year-old cannot sit or stand steadily and has nystagmus, yet coordination of the limbs is almost normal. The lesion is most likely in the:

Flocculonodular lobe and vermisPosterior limb of the internal capsuleAnterior horn cells of the cervical cordOne cerebellar hemisphere and its dentate nucleus

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