basal ganglia and cerebellum

Question 1

basal ganglia- what is it and parts of it

Answer 1

it’s extrapyramidal ie not part of corticospinal tract include caudate nucleus (like a tadpole, anteriorly has a head, posteriorly has a tail), lentiform nucleus (putamen and external globus pallidus- separated from caudate by internal capsule), subthalamic nucleus (beneath thalamus), substantia nigra (not part of ganglia but in midbrain, projecting to basal ganglia) then there are structure loosely connected to basal ganglia, including ventral pallidum (dopaminergic neurones), claustrum (thin layer of gray matter with unknown function), nucleus accumbens (reward centre) and nucleus basalis of meyner (important for memory)

Question 2

basal ganglia structure DIAGRAM

Answer 2

anterior (pic on right) we have caudate on left of right pic, putamen on right (caudate and putamen are linked) and nucleus accumbens at bottom on 2nd pic to right caudate and putamen still present, but small structure just below is external globus pallidus- these 3 structures known as striatum on pictures to left, in blue is thalamus

Question 3

lateral basal ganglia structures DIAGRAM

Answer 3

caudate and putamen near septum, with nucleus accumbens

Question 4

medial basal ganglia structures DIAGRAM

Answer 4

caudate almost disappeared, but thalamus not present with mamilllary body

Question 5

functions of basal ganglia

Answer 5

coordinate associated movements eg swinging arms when walking, smiling when happy ie important for emotions perform movements in order

Question 6

basis of parkinsons DIAGRAM

Answer 6

involves breaking down of dopaminergic neurones in the substantia nigra that project to the striatum in pic, on left is normal- black line in middle is dopaminergic neurones in substantia nigra- on right is missing black line in a parkinsons patient

Question 7

nigrostriatal pathway DIAGRAM

Answer 7

nigro striatal fibres go from nigra in midbrain to striatum (putamen)

Question 8

main motor signs of parkisons

Answer 8

BLOOD HORRIBLE RATS

bradykinesia- slow movements eg doing buttons

hypomimic face- expressionless (can’t show emotions)

rigidity- high muscle tone

akinesia- difficulty initiating movements

tremor at rest- starts in hand and spreads

shuffling gait

Question 9

brain in huntingtons disease DIAGRAM

Answer 9

on left you have caudate, putamen and occumbens, but caudate on right is nearly gone

Question 10

basis of huntingtons disease

Answer 10

genetic disorder due to CAG repeats on chromosome 5 (autosomal dominant) leads to degeneration of GABAergic neurons in striatum

Question 11

motor signs of huntingtons

Answer 11

choreic movements ie rapid jerky movements, starting with hands and face then legs speech impairment and dysphagia unsteady gait (abnormal walking) later decline in cognition/dementia

Question 12

where is cerebellum DIAGRAM

Answer 12

cerebellum posterior to pons, with transverse fibres anteriorly, which connects to cerebllum

Question 13

layers of cerebellum, inputs and outputs DIAGRAM

Answer 13

3 layers- molecular layer (not many cells), purkinje cell layer and granule cell layer

there are 2 inputs (fibre types) and 1 output- inferior olive (nucleus in medulla) projects to purkinje cells via climbing fibres, mossy fibres then parallel fibres go to granule cells, then output is from purkinje ells to nuclei in white matter

Question 14

divisions of cerebellum 1 DIAGRAM

Answer 14

vestibulocerebellum controls posture and gait, as well as matching head with eye movements (vestibulo-ocular reflex)

Question 15

divisions 2 DIAGRAM

Answer 15

spinocerebellum for coordinating speech, coordinating limb movements and refining muscle tone spinal cord involved, and goes via inferior cerebellar peduncle to cerebellum

Question 16

divisions 3 DIAGRAM

Answer 16

cerebrocerebellum coordinates skill movement, needed for emotional control and cognitive function

Question 17

types of cerebellar dysfunction

Answer 17

vestibulocerebellar syndrome- tumour causes syndrome= gait ataxia and tendency to fall spinocerebellar syndrome associated with chronic alcohol drinking- abnormal gait and stance, affecting mainly legs cerebrcerebellar movement affect skilled movements and speech

Question 18

main symptoms of cerebellar dysfunction

Answer 18

can only tell when moving ataxia (drunken gait), dysmetria (inappropriate force/distance for target-directed movements like reaching a cup, your hand goes too far), intention tremor (thiking about doing a movement causes a tremor), dysdiadokinesia (can’t do rapidly alternating movements like pronation and supination) and scanning speech (staccato- speech separated by pauses)

DADIS