week 6 Flashcards
Basal Ganglia (BG)
Structure
- BG is a collection of 5 anatomical and functionally related grey matter structures
- Caudate + Putamen = striatum
- Globus palidus = Consists of internus (GPi) & externus sections (GPe)
- Substania nigra: Consists of pars compacta (SNpc) and pars reticulata (SNpr)
Basal Ganglia (BG)
Function(s)
1.Goal Directed behaviour loop (non-motor)
2.Social behaviour loop (non-motor)
3.Emotion loop (non-motor)
4.Motor loop (motor)
Basal Ganglia (BG)
Function - Movement control
- Regulates desired and inhibits undesired movements
- Voluntary movement, postural muscles,
rhythmic movements - Sends information back to the motor cortex via thalamus
- Regulates muscle tone (force) and many other thing
Accelerator: Direct movement control
pathway allows movements (white boxes)
Brake: Indirect movement control
pathway prevents undesired movements (black boxes)
Basal Ganglia (BG)
Function - Movement control
what horomone do they rely on
- Relies on dopamine producing neurons the substantia nigra to supply it with dopamine
where are the Dopaminergic producing neurons found
SNpc
Dopamine is a neurotransmitter that:
- Enhances the action of the direct pathway (Accelerator)
- Inhibits the action of the indirect pathway (Brake)
Striatum input and out put
input- From cortical areas
output- Inhibits Gpi (Direct Pathway) & Gpe (indirect pathway)
GPi input and out put
i- Striatum
o- inhibits (via GABBA) Thalamus
GPe input and out put
i-Striatum
o- Inhibits (via GABBA) STN
STN input and out put
i- GPe
o- Excites (via Glutamate) the pallidus internus
SNpc input and output
i- Subcortical structures
o- Dopamine to the striatum
Basal Ganglia (BG) Dysfunction
Hypokinetic movement disorder
Hyperkinetic movement disorder
cerebellum weighs what percent of the brain
10%
how many neurons does the cerebellum have
50% of all neurons in the brain
cerebellum 3 cortical layers from superficial to deep
1.Molecular Layer – few neurons (axons of
granule cells / dendrites of Purkinje’s)
2.Purkinje Cells – single row of huge cells
(unique to cerebellum)
3.Granular Layer – numerous densely packed
neurons
three lobes of cerebeullum called
Anterior
- Posterior
- Flocculonodular
Superior cerebellar Peduncle connects what and function
Midbrain. Primarily cerebellar efferent fibres –via thalamic nuclei to cortex
Middle cerebellar Peduncle connects what and function
Pons. Entirely afferent fibres - Information to cerebellum from cerebrum
Inferior cerebellar Peduncle connects what and function
Medulla. Afferent & efferent fibres – afferents from spinal cord, vestibular apparatus, efferent to vestibular nuclei & reticular formation
cerebellum Blood supply
- Anterior inferior cerebellar artery (AICA)
- Superior cerebellar artery (SCA)
- Posterior inferior cerebellar artery (AICA)
Cerebellum Function(s)
- Coordinates human movement
Works as a comparator – comparing
Maintaining posture and balance - Coordination of voluntary movement
- Motor learning
- Cognitive function
Cerebellum Functional areas
1) Spinocerebellum (Vermis)
2) Vesibulotcerebellum (Flocculonodular)
3) Cerebroerebellum (lateral hemispheres)
Cerebellum Functions: Spinocerebellum
- Located in the vermal and paravermal sections of the cerebellum
- Input
- Movement commands from the cortex
- Activity levels of spinal cord neurons
- Movement or postural adjustments from proprioceptors
- Role in making anticipatory, corrective and responsive adjustments or otherwise movement would be uncoordinated
Cerebellum Functions: Vesitbulocerebellum
Located in the flocculonodular lobe
- Input from ipsilateral vestibular apparatus and ipsilateral vestibular nuclei in the brainstem
- Output to vestibular nuclei and reaches motor neurons via vestibulospinal tracts and tracts coordinating head and eye movement
- Role in head movement and head position
Cerebellum Functions: Cerebrocerebellum
- Located in lateral cerebellar hemispheres (named for extensive connections with cerebral cortex)
- Input – cerebral cortex via pontine nucleus
- Output – motor and premotor cortex via dentate and motor thalamus
- Role in timing movements, planning movements and coordination of voluntary movement
Cerebellum Dysfunction(s) Pathologies include but not limited to
- Stroke
- Tumour
- Degenerative disease
- Trauma (eg TBI)
- Structural / Malformation
- Hereditary
- Toxicity (alcohol, drugs)
- Other: Infection or endocrine or immune mediated
Cerebellum
Dysfunction(s) Ataxia
Posture and Balance impairments
- Dysmetria (undershoot or overshoot of intended position)
- Action tremor (Intention tremor)
- Nystagmus: Eye movement dysfunction
- Dysarthria: Poorly articulated / coordinated speech
Differentiating Cerebellar Vs. Somatosensory Ataxia
- To differentiate between somatosensory and cerebellar ataxia, movement coordination should be compared with eyes open and eyes closed
- Cerebellar lesions cause ataxia regardless of the use of vision.
Vestibulocerebellum dysfunction signs
Unsteadiness
truncal ataxia
nystagmus
Spinocerebellum dysfunction signs
Intention tremor
ataxic gait
dysarthria
dysdiadochokinesia
dysmetria
movement decomposition
Cerebrocerebellum dysfunction signs
Finger ataxia
Dysarthria
Parkinson’s disease (PD) and Huntington’s disease (HD) affects what in CNS
primarily affect the structures within the Basal Ganglia and are progressive neurological disorders
Both disorders result in significant changes to movement including the production of speech, emotion, cognition and functions controlled by the autonomic nervous system
PD parkingtons disease
neurodegenerative disease
gradual onset
subtyypes of PD
parkinsonism
bradykineasia- slowness of movement
hypokinesia- reduced amplitude of movmenet
ridigity- increase resisitance to movement
resting tremou- high frquancy small amplitude
neural structure changes in PD
degeneration of the substantia nigra
substantia nigra synthesis NT dopamine
symptoms of PD develop when 60% of substantia nigra degerenrates
intraneuronal changes in PD
lewy bodies are interneuronal accumulation of protein
resting tremour
hand but may also be in lower limb jaw or leg
rigidity
involuntary resistance to movement int the flexor and extensor muscles
brakykinesia
slow movement and reduced speed and size of movement as a sequence progresses
hypokinesia
reduced size of movement
freezing of gait and festination
walking pattern may come to a stop and difficult to initiate walking again. festiniation describes increase reduction in size of steps in a sequence then may expereince freeze
akinesia
abscence of movement
postural instabiloty
difficulty maintaining equilibrium in standing and mobility
dystonia
prolonged involuntary muscle contraction affecting specific muscle
impaired recall memory and prospective memory
recsll memory is retrieval of imformation from the past.
prospective memory is related to remembering to execute a planned action in the future
reduced attention
ability to selectively attend to something in the neviornement whilst ignoring competing stimuli
difficulties in comprehension of complex sentences
may have difficulty extracting meaning from words that are combined in a particular order
orthostatic hypotension
drop in bp with change in positionc
bladder dysfunction
frequency urgency and nocturia
hyperhidrosis
excessive sweating
sialorroea
excessive salivation
sexual dysfunction
may inc a range of difficulties inc decreased desire
dopamine replacement action of meds
crosees blood brain barrier. converted into dopamine
dopamine agonist action of medication
mimics effects of dopamine
dyskenesia
involuntary continnuous muscle movements of head, trunj or limbs
hallucinations
often visual such as sensation of a person present
impulse control disorder
harmful urger or behavior that may occur
deep brain stimulation
useful for people experiencing debisabiling motor fluctuations, tremours,dyskinesia or dystonia
deep brain stimulation target sites
subthalamic nucleus
globus pallidus internus
venteral intermediate thalamus
death of neuron ins huntingston occurs where
caudate and putamen (striatmen)
structes affected in the brain during HD are
substantia nigra
cerebellum
thalmus
cerebral cortex
