Lecture 9 & 10 - Basal Ganglia & Cerebellum Flashcards
The Corpus Striatum consists of
Lentiform Nucleus + Caudate Nucleus
What four nuclei make up the Basal Ganglia?
- Subthalamic Nuclei (STN)
- Globus Pallidus internal/external (GPi, GPe)
- Striatum (Caudate + Putamen; STR)
- Substantia Nigra (SNc, SNr)
The Ventral Striatum is also known as the___which is___
Nucleus Accumbens
not part of the basal ganglia
The Basal Ganglia are responsible for ____ (x2) by ____
- FACILITATING voluntary movement
- SUPPRESSING involuntary movement
- by modulating the functions of PYRAMIDAL and EXTRAPYRAMIDAL tracts.
The basal ganglia receive and send input/output to the ____ via the ____ and ___ have direct contact with the spinal cord.
- motor cortex
- thalamus (VL, VA)
- do not
Damage to the BASAL GANGLIA may result in __ (x2)
- Huntington’s disease (excessive involuntary movement)
- Parkinson’s Disease (suppressed voluntary movement)
which cortical motor area does the Basal ganglia work closely with?
SMA
What are the major INPUT and OUTPUT nuclei of the Basal Ganglia loop?
- Input = Striatum (caudate + putamen)
- output = GPi + SNr
All of the nuclei of the Basal Ganglia LOOP use ___ neurotransmitters, except for _____(x2) which use ____ neurotransmitters.
- GABAergic (inhibitory)
- STN, PFC, Thalamus
- Glutamatergic (excitatory)
The thalamus is under _____
chronic inhibition
The DIRECT pathway involves :
PFC -> striatum -> (Gpi + SNr) -> Thalamus -> SMA
(+) (-) (-) (+)
The INDIRECT pathway involves:
PFC -> STR -> GPe -> STN -> (Gpi + SNr) -> Thal. -> SMA
(+) (-) (-) (+) (-) (+)
The direct pathway DISINHIBITS the _____and INCREASES _____ to FACILITATE voluntary movement.
- thalamocortical tract
- thalamocortical tone
The indirect pathway ____ thalamocortical tone thus _____ INVOLUNTARY movement.
- inhibits
- suppressing
What is the role of the SNc in the Basal Ganglia Loop?
facilitating movement
How does the SNc facilitate voluntary movement?
- by sending dopaminergic neurotransmitters to the STRIATUM,
- where D1 receptors (+) EXCITE the disinhibiting function of the DIRECT pathway and
- D2 receptors (-) INHIBIT the inhibiting function of the INDIRECT pathway (inhibit + inhibit = facilitation)
a reduction in Dopaminergic neurons in the SNc leads to (x2)
- Hypokinesia (reduced/slow movement)
- Akinesia (lack of movement)
The pedunculopontine nucleus (PPN) is located in the ____ and in humans, it is the centre/part of the _____.
- Ponto-mesencephalic tegmentum
- midbrain motor centre
The DESCENDING projection (output) of the Basal Ganglia is to the _____, for control of ______.
- PPN
- Locomotor function
ASCENDING fibres from the PPN project to the ____ (x2) for regulating _____.
- thalamus, cortex
- arousal
The PPN consists of ____neurons
cholinergic
The basal ganglia INDIRECTLY influence spinal motor neurons via (x2)
- PPN
- Reticulospinal Tract
Ventral striatum receive dopaminergic input from ___ for _____ and dorsal striatum receive from ____ for ____.
- Ventral tegmental area (VTA - midbrain)
- reward feelings
- SNc (midbrain)
- initiating reward-predicting movements
Explain Reward-Based Learning (reinforcement)
When the motor cortex sends a set of motor commands to the Basal Ganglia, the SNc aids in selecting best movements that will result in a reward.
What is the HYPERDIRECT pathway?
It is used for FAST inhibition of movement, by direct input from the cortex to the STN -> GPi + SNr -> THAL.
Chorea Huntington is caused by ____
Hemiballism is caused by _____
- degeneration of the STRIATUM (suppressed function of indirect pathway)
- degeneration of the STN (
what are dyskinesia and Bradykinesia?
- excessive involuntary movement
- Reduced voluntary movement
Parkinson’s Disease is mainly caused by?
- overactivity of the Indirect pathway and underactivity of the direct pathway due to degeneration of dopaminergic input from the SNc to the Striatum
What can be done to reduce Parkinson’s Disease symptoms?
- lesion of the STN or GPi
- DBS (deep brain stimulation) - electrodes inserted into GPi, STN or PPN to modulate their functions)
The two cerebellar hemispheres are separated by the _____.
vermis
The cerebellum LACKS what types of fibres?
commissural (no interhemispheric connections)
association (no inter-lobe connections)
the cerebellum contains which lobes?
- anterior, posterior, flocculonodular lobe
The anterior and posterior lobes are separated by the
primary fissure
the posterior and flocculonodular lobes are separated by the
posterolateral fissure
The superior and inferior lobes of the cerebellum are divided by the
horizontal fissure
The superior half of the cerebellum is supplied by the __
The inferior half is supplied by the _____
superior cerebellar arteries
anterior/posterior inferior cerebellar arteries
The superior cerebellar and Anterior Inferior cerebellar arteries branch off the _____
the Posterior inferior cerebellar arteries (PICA) branch off the _____
- Basilar artery
- vertebral arteries
The superior cerebellar peduncles (SCP) contain __
MCP contain___
ICP contain ____
- axons to/from the midbrain (dentatothalamic, dentatorubral tracts)
- axons FROM the pons (pontocerebellar tract)
- axons to/from the medulla
The cerebellum contains which nuclei?
- 2 dentate (most laterally)
- 2 fastigial (most medially)
- interposed (between dentate and fastigial)
- 2 emboliform, 4 globose
The cerebellar cortex contains ___layers which are ___
- 3
- Molecular
- Purkinje (GABAergic)
- Granular (contains most cell bodies)
longitudinally, the cerebellum can be divided into ___
vermis, intermediate (paravermal), lateral hemispheres
The cerebellum is an error detector and corrector. Explain this concept.
- the cerebellum COMPARES sensory feedback with motor actions,
- DETECTS errors between motor actions and sensory feedback
- CORRECTS errors in motor actions
- hence COORDINATES all body movements.
Damage to the cerebellum can cause which disorder?
ataxia (lack of coordinated movement)
explain the input and output of/to the cerebellum in terms of the types of neurotransmitters used.
- ALL afferent fibres to the cerebellar CORTEX are EXCITATORY
- collateral copies of AFFERENT fibres are ALWAYS given to the cerebellar NUCLEI
- ALL efferent fibres from the CORTEX to the cerebellar NUCLEI are INHIBITORY (GABAergic) and arise from the Purkinje layer.
- EFFERENT fibres from the cerebellar NUCLEI that EXIT the cerebellum are MOSTLY EXCITATORY.
What are functional classifications of the cerebellum and respective components?
- Pontocerebellum/cerebrocerebellum
(lateral hemispheres, dentate nuclei) - spinocerebellum
(anterior lobe, vermal & paravermal regions, interposed & fastigial nuclei) - vestibulocerebellum
(flocculonodular lobe, fastigial nuclei)
The Vestibulocerebellum is the __ part of the cerebellum
- oldest (archicerebellum)
Describe the functions and related nuclei of the Vestibulocerebellum (x3)
- sends output/receives input from vestibular nuclei and vestibular nerve (output via fastigial nuclei)
- by mediating medial and lateral vestibulospinal tracts
- for error correction of reflexes:
- vestibulospinal reflex (equilibrium via lateral vestibular pathway)
- vestibulocervical reflex (head stability via medial vestibulospinal tract)
- vestibulo-ocular reflex (gaze stability via medial vestibulospinal tract)
describe the spinocerebellum and major constituents (x5)
- an old part of the cerebellum (paleocerebellum)
- involves ant. lobe, vermis & paravermis, interposed & fastigial nuclei
- receives INPUT from IPSILATERAL spinal cord via POST. SPINOCEREBELLAR & CUNEOCEREBELLAR tracts for UNCONSCIOUS PROPRIOCEPTION & CUTANEOUS SIGNALS (skin)
- sends output to RETICULO, VESTIBULO & RUBROspinal tracts via FASTIGIAL & INTERPOSED nuclei
- mediates MUSCLE TONE, POSTURE & BALANCE of whole body
Describe the Cerebrocerebellum/pontocerebellum
- new system (neocerebellum)
- consists of DENTATE nuclei & LATERAL hemispheres
(cerebro-):
- receives input from CONTRALATERAL NEOCORTEX
- sends output to CONTRALATERAL MOTOR CORTEX via DENTATE nuclei -> THALAMUS (VL) & RED NUCLEUS
(ponto-):
- receives input from CONTRALATERAL PONTINE nuclei
- coordinates FAST & ALTERNATING movements (especially HAND)
Pontine nuclei receive ____ input from the cortex, but send ____ to the cerebellum via the ____.
- ipsilateral
- contralterally
- pontocerebellar tracts (MCP)
truncal ataxia is caused by ___
Limb ataxia is caused by ___
- lesion to SPINO & VESTIBULOcerebellum
- lesion to CEREBROcerebellum
the molecular layer of the cerebellum contains:
- parallel axons of granule cells
- purkinje cell dendrites
The Purkinje cell layer contains
- pukinje cell bodies
- climbing fibres (from Inf. Olivary Nucleus) which excite purkinje cells to convey error signals
- parallel axons of granule cells
The granule cell layer contains
- granule cells
- mossy fibres (all afferent fibres terminate in granule layer)
Why are Purkinje cells flat?
so that they only synapse ONCE with each parallel axon of a granule cell.
How are copies of motor commands sent to the Cerebellum and how are errors corrected?
the motor cortex sends a copy of the command to the INFERIOR OLIVARY NUCLEUS which sends CLIMBING FIBRES to the cerebellum.
axons of climbing fibres synapse multiple times with a purkinje cell to highly excite and thus inhibit their functions for the purpose of error correction.
