Cerebellum + basal ganglia

Question 1

What is the cerebellum?

Answer 1

Structure at back of brain, under occipital + temporal lobes, densely packed with neurons

Comprises 10% of brain space but contains 50% of neurons.

Question 2

What are the main functions of the cerebellum?

Answer 2

• Maintenance of balance/posture
• Coordination of voluntary movements
• Motor learning
• Cognitive function

Question 3

What happens when the cerebellum is damaged?

Answer 3

• Reduced muscle tone
• Impaired balance & motor learning
• Disrupts spatial accuracy
• Disrupts temporal coordination of movement
• Can impair various cognitive functions

Question 4

What is the anatomy of the cerebellum?

Answer 4

Located in posterior cranial fossa, made up of an outer mantle of gray matter, internal white matter, and deep nuclei

Three pairs of deep nuclei: dentate, interposed (globose + emboliform), and fastigial.

Question 5

What are the three symmetrical pairs of tracts that connect the cerebellum to the brain stem?

Answer 5

• Inferior cerebellar peduncle
• Middle cerebellar peduncle
• Superior cerebellar peduncle

• Superior cerebellar peduncle has most output projections from cerebellum, outputs originate from cell bodies in deep nuclei

Question 6

What are folia in the cerebellum?

Answer 6

Parallel convolutions that run horizontally across its surface

Question 7

What are the three lobes of the cerebellum?

Answer 7

• Anterior lobe
• Posterior lobe
• Flocculonodular lobe

Question 8

What is the vermis?

Answer 8

Elevated ridge that connects the 2 lateral hemispheres

Question 9

What are the functions of the fastigial nucleus?

Answer 9

Input from vermis + cerebellar afferents, projects to vestib nuclei + reticular formation

Question 10

What is the role of the interposed nuclei?

Answer 10

Input from intermediate zone + cerebellar afferents, projects to contralateral red nucleus

Question 11

What does the dentate nucleus do?

Answer 11

Largest nucleus, input from lateral hemisphere + cerebellar afferents, projects to contralateral red nucleus + ventrolateral thalamic nucleus (VL)

Question 12

What are the three distinct functional regions of the cerebellum?

Answer 12

• Vestibulocerebellum
• Spinocerebellum
• Cerebrocerebellum

Question 13

What is the function of the vestibulocerebellum?

Answer 13

Helps control balance + eye movements

Made up of flocculonodular lobe, receives input from primary vestibular afferents.

Question 14

What is the spinocerebellum comprised of?

Answer 14

• Vermis
• Intermediate hemispheres

Question 15

What is the role of the vermis in the spinocerebellum?

Answer 15

Projects via the fastigial nucleus to medial descending systems that control proximal muscles

Question 16

What are the two types of spinocerebellar tracts?

Answer 16

• Ventral tract
• Dorsal tract

Question 17

What is the role of the cerebrocerebellum?

Answer 17

Inputs only from cerebral cortex, proposed for planning + performance of complex motor actions + conscious error assessment

Question 18

What are the three layers of the cerebellar circuit?

Answer 18

• Molecular layer
• Purkinje cell layer
• Granular layer

Question 19

What types of neurons are found in the cerebellum?

Answer 19

• Inhibitory: stellate, basket, Purkinje, Golgi
• Excitatory: granule

Question 20

What are mossy fibres?

Answer 20

Originate in SC + brain stem nuclei, carry sensory input from periphery + cerebral cortex, make excitatory connections to granule cells

Question 21

What is the difference between climbing fibres and parallel fibres?

Answer 21

• Climbing fibres: originate in inferior olivary nucleus, wrap around Purkinje cells, cause prolonged Ca2+ conductance
• Parallel fibres: originate from granule cells, provide brief EPP to Purkinje cells

Question 22

What is ataxia?

Answer 22

Group of disorders affecting movement coordination and accuracy

Question 23

What are the symptoms of dysdiadochokinesia?

Answer 23

Inability to perform rapidly alternating movements due to poor coordination + impaired muscle timing

Question 24

What are common causes of cerebellar lesions?

Answer 24

• Multiple sclerosis
• Tumours
• Metabolic diseases

Question 25

What therapies can be used to manage cerebellar disorders?

Answer 25

* Physical therapy * Speech therapy

Question 26

What is the basal ganglia?

Answer 26

Collective name for subcortical, grey matter structures within hemispheres that work as a functional cohesive unit ## Footnote Includes structures like the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus.

Question 27

Describe the caudate nucleus.

Answer 27

C-shaped structure lying deep inside the brain near the thalamus, with 3 parts: wider head at front, tapering to body and tail ## Footnote One caudate nucleus is present in each hemisphere.

Question 28

What is the putamen's relationship to the caudate nucleus?

Answer 28

Continuation of the caudate nucleus, both forming the striatum ## Footnote Mainly composed of GABAergic neurons.

Question 29

What two components divide the globus pallidus?

Answer 29

Divided into GPi (internal) and GPe (external) ## Footnote GPi is medial and GPe is lateral.

Question 30

What type of neurons do the globus pallidus receive from the striatum?

Answer 30

GABAergic axonal terminal arborisations ## Footnote They inhibit thalamic targets using GABAergic neurons.

Question 31

What characterizes the substantia nigra?

Answer 31

High neuromelanin levels in dopaminergic neurons, involved in reward, addiction, and movement ## Footnote Divided into pars compacta (SNpc) and pars reticulata (SNpr).

Question 32

What is the subthalamic nucleus's function?

Answer 32

Only excitatory nucleus in basal ganglia, receives inhibitory input from GPe and excites SNr-GPi complex ## Footnote Preferred target for deep brain stimulation in advanced Parkinson's patients.

Question 33

What happens in the direct pathway of basal ganglia?

Answer 33

Thalamus is disinhibited, leading to activation/excitation inducing muscle movement ## Footnote Inhibition of SNr and GPi by striatum plays a crucial role.

Question 34

What are the effects of dopamine on the direct pathway?

Answer 34

Binds to D1 receptors, facilitating movement ## Footnote D1 is excitatory.

Question 35

What are the effects of dopamine on the indirect pathway?

Answer 35

Binds to D2 receptors, inhibiting movement ## Footnote D2 is inhibitory.

Question 36

What is the motor loop in basal ganglia?

Answer 36

Formed between the motor and premotor cortices including the striatum, regulates motor actions ## Footnote Essential for coordinated movement.

Question 37

What is the associative loop in basal ganglia?

Answer 37

Formed between the dorsolateral prefrontal cortex and central regions of the striatum, regulates cognitive functions ## Footnote Important for decision-making and planning.

Question 38

What is the limbic loop in basal ganglia?

Answer 38

Formed between the orbital and medial prefrontal cortex and striatum, important in emotions and motivation ## Footnote Involved in reward-based behaviors.

Question 39

What are the global functions of the basal ganglia?

Answer 39

Guide all aspects of motor control and form a bridge between cortex and limbic system ## Footnote Dysfunction can lead to diseases like Parkinson's and Huntington's.

Question 40

What characterizes Parkinson's disease in relation to basal ganglia?

Answer 40

Degeneration of dopaminergic neurons in SNc, leading to imbalances in excitation/inhibition of motion ## Footnote Common treatment includes levodopa (dopamine precursor)

Question 41

What causes hyperkinetic disorders?

Answer 41

Small strokes restricted to STN leading to involuntary movements (ballism) ## Footnote Abnormal disinhibition of thalamocortical pathway.

Question 42

What genetic defect is associated with Huntington's disease?

Answer 42

Defect in IT15 gene encoding huntingtin, characterized by unstable and expanded AG repeats ## Footnote Autosomal dominant inheritance.

Question 43

What is the impact of Huntington's disease on the striatum?

Answer 43

Early degeneration in striatum, with preferential loss of indirect neurons leading to uncontrollable muscle movements ## Footnote Results in disinhibition of thalamocortical pathway.