Basal Ganglia and cerebellum Flashcards
What is the role of both the basal ganglia and cerebellum?
They both improve the accuracy of movement by creating loops with the motor and sensory areas of the cerebral cortex and impact the upper motor neurons.
What is the effect of damage to the cerebellum?
Uncoordinated gait with ataxia
What is the effect off damage to the basal ganglia?
Issues with speech, movement and posture.
What is the cerebellum?
It is a structure in the hind brain that contains 50% of all neurons in the CNS. It has a high surface area due to its folia and lobules.
What is the function of the cerebellum?
It co-ordinates muscles for balance and muscle tone and movement. It has a comparator function by modifying motor movement for accurary based on sensory input from the cortex. It is responsible for motor memory of muscles.
What is the vestibulocerebellum?
It consists of the flocculus and the nodules. Receives input from the vestibular nuclei. Controls the muscles for balance.
What is the spinocerebellum?
Receives input from the spinal cord. Lateral part controls distal muscles and medial portion controls axial muscles.
What is the cerebrocerebellum?
Receives input from the cerebral cortex and responsible for skilled movement such as speech.
What are the peduncles?
Stalks which connect the cortex to the midbran. Consists of the superior, middle and inferior cerebellar peduncles.
What is the superior cerebellar peduncles?
They are an efferent pathway which arises from the white matter of the cerebellum to act on the red nuclei and thalamus. This includes communication with the dendate nuclei for motor execution control.
What is the middle cerebellar peduncles?
They are an afferent pathway which arises from the pons. The pons has a relay neuron that receives input from the cerebrum to communicate motor input to the cerebellum. It is contralateral because it decassates and allows motor input for movement.
What is the inferior cerebellar peduncles?
They are both an afferent and efferent pathway. They allow communication between the spinal cord and medulla oblaganta to the cerebellum to allow for sensory input such as propioception to modulate.
What is the motor input into the cerebellum?
Middle cerebellar peduncles.
What is the sensory input to the cerebellum?
Inferior cerebellar peduncles.
What is the inferior olive?
Part of the medulla oblaganta that communciates to the cerebullum motor timing and planning.
What is the deep cerebellar nuclei?
Imbedded structures in the white matter which are the main ouputs from the cerebellar cortex to the midbrain and cerebral cortex.
What is the ventral lateral complex?
Thalamus which receives input from the cerebellum and midbrain to project onto the cerebral cortex and influence movement.
What is the output to the cerebellum?
Deep cerebellar nuclei.
What is the role of the fastigial nuclei?
Cerebellar nuclei of the archicerebellum which creates a lateral descending pathway to control motor execution.
What is the role of the intersposed nuclei?
Cerebellar nuclei of the spinocerebellum which creates a medial descending pathway to control motor execution.
What is the role of the dendate nuclei?
Cerebellar nuclei of the cerebrocerebellum which is involved in motor plannning.
What is the vestibular nuclei?
Group of 4 nuclei present in the pons, medulla and the flocculonodular lobe that is involved in balance and gait.
What cells are present in the cerebellar cortex?
Glial, granule, stellate and golgi cells which act as the interneurons for mossy fibre afferents.
What is the input to the cerebellar cortex?
Via either the mossy fibres or the climbing fibres.
What is the output to the cerebellar cortex?
Purkinje fibres which act on the deep cerebellar nuclei by releasing the inhibitory neurotransmitter GABA to reduce action.
What are the interneurones in the cerebellar cortex?
Golgi, stellate, basket and Granule cells which are the interneurons between the mossy fibres and the Purkinje fibres by creating parallel T fibres to synpase.
What are the climbing fibres?
Input from the inferior olives of the medulla due to error in motor action and act on Purkinje fibres to correct movement. A single climbing fibre wraps around the dendrite of multiple Purkinje fibres to generate a large depolarisation.
What are the mossy fibres?
Motor or sensory input from the spinal cord, medulla oblaganta or cerebral cortex which synapses with interneurons in the granule layer of the cerebellum.
What is the Purkinje fibres?
Output from the cerebellar cortex which act on the deep cerebellar nuclei by releasing the inhibitory neurotransmitter GABA.
What are the layers of the cerebellar cortex?
Molecular layer, Purkinje layer, Granule layer and the white matter
What is the consequences of cerebellar injury?
Leads to unbalanced and uncoordinated ataxic gait.
What is the blood supply to the cerebellum?
Anterior potion-> superior cerebellar artery
Posterior portion-> Posterior inferior cerebellar artery
Lesion to caudal vermis
Reduced oculomotor control and trunk ataxia.
Lesion to rostral vermis
Posture and gait ataxia
Lesion to medial/lateral zone
Upper limb ataxia and dysarthria
What is the consequences of lesion to the vestibulocerebellum?
Reduced balance and posture of the lower limb
What is the consequences of lesion to the spinocerebellum?
Reduced motor execution of the upper limbs for co-ordination of the muscles
What is the consequences of lesion to the cerebrocerebellum?
Reduced motor execution
What is cerebellar ataxia?
Uncontrolled, uncoordinated gait
What is dyssnergia?
Reduced simultaneous movement of multiple muscles
What is dysmetria?
Inability to determine distance of objects
What is dysdiadochokinesia?
Difficulty with sequence of alternating movements.
How does alcohol affect the cerebellum?
Acts on the rostral vermis to cause ataxia of the lower limbs and reduced gait and posture but the caudal and medial vermis are preserved and upper limb movements are normal
How is the cerebellum influence planned movements?
It sends information to the somatosensory cortex to influence the sensitivity of the motor cortex.
What is the basal ganglia?
A group of 4 nuclei wrapped around the thalamus above the amygdala. These are the subtantia nigra, putamen, caudate and the global pallidus.
What is the striata?
The caudate and putamen nuclei of the basal ganglia which act as the input from the cerebral cortex.
What is the pars reticulata?
The substantia nigra and the globus pallidus of the basal ganglia for output from the cerebellum
What is the significance of the parietal lobe?
Sensory association area and somatosensory cortex
What is the function of the basal ganglia?
Modulates motor movement from the cerebral cortex following input via the corticalstriatal pathway.
What are the inputs to the basal ganglia?
Corticostriatal pathway which uses glutamate as an excitatory neurotransmitter to send motor movement to the striata.
What is the corticostriatal pathway?
The input pathway from the cerebral cortex to the striata.
What is the substantia nigra pars compacta?
A complex in the midbrain which is involved in the nigrostriatal pathway to initiate movement.
What is the nigrostriatal pathway?
Input structure from the substantia nigra pars compacta to the striata and uses the inhibitory neurotransmitter dopamine to modulate voluntary movement.
What are the medium spiny neurons?
Input neurons of the basal ganglia
What is the role of the substantia nigra compacta?
It releases the neurotrnasmitter dopamine to stimulate either the direct or indirect pathway for thalamus stimulation via D1/D2 receptors and regulates ocular movement
What is the role of the globus pallidus?
It inhibits the thalamus for projection to the cerebral cortex for regulation of voluntary movement of the limbs and trunk.
What is the corticostriatal loop direct pathway?
Decreases the inhibiton of the thalamus. The corticostriatal pathway excites the striata and inhibits the globus pallidus internal segment which leads to reduced inhibiton of the thalamus. The substantia nigra compacta releases dopamine which acts on D1 receptors to further increase its effects.
What is the corticostriatal loop indirect pathway?
Increases the inhibition of the thalamus. Corticostriatal pathway inhibits the external segment of the globus pallidus. The internal segment of the globus pallidus and the subthalamic nucleus act to increase the thalamic inhibition of projection to the cortex. Substantia nigra compacta releases dopamine which acts on D2 receptors to reduce thalamic inhibition.
What is Parkinson’s disease?
Hypokinetic disorder caused by the degeneration of the substantia nigra. Characteristic tremors, rigidity, postural problems and akinesia.
How does Parkinson’s disease affect the dorsal cortical loop pathway?
Absence of dopamine means lack of regulation of the direct and indirect pathway so thalamic inhibiton continues uninterrupted.
How can Parkinson’s disease be treated?
Dopamine agonist, foetal cell transplant of mesenchyme and stimulation with electrodes to the substantia nigra or remvoal of parts of the globus pallidus or the thalamus.
What is Huntington’s disease?
Mutation on chromosome 4 which leads to reduced input to the globus striata for inhibition of the subthalamic nucleus. This leads to chorea (overexcessive movements). To treat this, deplete dopamine levels using tetrabenazide.
What is hemiballismus disease?
Caused by a lesion in the subthalamic nucleus which causes reduced inhibiton leading to jerky movements on one side of the body/.
