Neuro 10 - Basal Ganglia and Cerebellum Flashcards
What is the collective term given to the basal ganglia and cerebellum?
Extrapyramidal system
Broadly speaking, what is the role of this system>?
checks the movement selected by the motor cortex
Where is the basal ganglia located?
white matter in the middle of the brain
What are the different parts of the basal ganglia?
Striatum = caudate and putamen
Globus pallidus = external and internal
Substantia nigra
Subthalamic nucleus
What is the function of the basal ganglia?
involved in planning and coordinating movement
plans associated movements
Describe the structure of the direct pathway in the basal ganglia?
Motor cortex – striatum – putamen – globus pallidus internal segment – substantia nigra pars reticulata
Describe the structure of the indirect pathway in the basal ganglia.
motor cortex – striatum – putamen – globus pallidus external segment – subthalamic nucleus – globus pallidus internal segment
What is the difference in function of the direct and indirect pathways?
direct = excitatory on the motor cortex
indirect = inhibitory on the motor cortex
What extra component modulates the function of the direct and indirect pathways?
Nigro-striatal pathway
Where do the projections fo to after leaving the basal ganglia?
thalamus
then go to the cortex - supplementary and primary motor areas
Describe how the basal ganglia are involved in choosing the correct motor programmes to carry out particular functions.
form a processing loop
enable motor commands via direct pathway
inhibit commands via indirect pathway
Connections with which parts of the brain allow the basal ganglia to have a role in enabling various cognitive, executive and emotional programmes?
prefrontal association cortex
Limbic cortex
What causes Parkinson’s?
neuronal degeneration of dopaminergic neurones in the substantia nigra pars compacta
progressive depletion of dopaminergic neurones
What are the consequences of the loss of dopaminergic neurones in the substantia nigra pars compacta?
connection between the striatum and the substantia nigra pars compacta is lost
so direct pathway is reduced and so excitation of motor cortex reduced
State the main signs of Parkinson’s?
bradykinesia pill rolling tremor akinesia hypomimic face rigidity
Describe the Parkinsonian gait.
walking slowly, small steps, shuffling feet
stooped posture
What is Huntington’s disease caused by?
Abnormality on Chromosome 4
degeneration of GABAergic neurones in the striatum
What are the consequences of loss of GABAergic neurones in the striatum?
inhibitory effect of the indirect pathway is no longer in place
direct pathway is unopposed so the motor cortex is hyperexcitable
What are the main signs of Huntington’s disease?
Choreic movements - rapid jerky
hands and face affected first
chorea increased over time until patients totally incapacitated
State the 3 lobes of the cerebellum.
Anterior
Posterior
Flocculonodular
The cerebellum is divided sagittally into 3 zones. What are they?
Vermis
Intermediate hemisphere
Lateral hemisphere
State the three layers of the cerebellar cortex?
Granule cell layer
Purkinje cells
molecular layer
Name 3 deep nuclei that are involved in the connections of the cerebellum with other parts of the body.
Fastigial - control of balance and connected with the vestibular nuclei
Interposed and Dentate - both involved in voluntary movement and are connected to the thalamus
What are the three sources of input into the cerebellum and what do they connect with?
Mossy fibres - from cortex and pons
mossy fibres - from spinocerebellar tract
Climbing fibres - from the inferior olive
Functionally the cerebellum is divided into three, What are these divisions.
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
What is the role of the vestibulocerebellum?
flocculonodular lobe
connected with vestibular nuclei
involved in balance, posture, gait
also coordinating head and eye movements
Which parts of the cerebellum are part of the spinocerebellum?
Vermis and intermediate hemispher
From where does the spinocerebellum receive inputs?
afferent from axial - vermis
afferent from limbs - intermediate hemisphere
What are the roles of the spinocerebellum?
coordination of speech
adjustment of tone
coordination of limb movement
Which part of the cerebellum is part of the cerebrocerebellum?
Lateral hemisphere
From where does the cerebrocerebellum receive inputs from?
Cortex
- function is for cognitive function, attention and coordiination of skilled movement
In summary what are the main functions of the cerebellum?
maintenance of balance and posture
coordination of voluntary movements
motor learning
cognitive functions
State 3 syndromes causes by dysfunction of different parts of the cerebellum.
Vestibulocerebellar syndrome
Spinocerebellar syndrome
Cerebrocerebellar syndrome
symptoms associated with functions obviously
What behavioural habit is spinocerebellar syndrome associated with?
Chronic alcoholism
Describe the symptoms of spinocerebellar syndrome?
abnormal gait and wide based stance
Describe the symptoms of cerebrocerebellar syndrome?
arms affected
affects coordinated movements
What are the main signs of cerebellar disorders?
ataxia - general impairments in movement
dysmetria - inappropriate force and distance
intention tremor - nose finger tracking
dysdiadochokinesia - inability to perform rapid alternating movements
Scanning speech - staccato
State a hereditary and acquired cause of the symptoms listed?
hereditary - friedreich’s ataxia
acquired - multiple sclerosis
