Lecture 8.1: Motor Cortex, Cerebellum and Basal Ganglia Flashcards
What parts of nervous system are involved in active moving? (4)
Motor cortex –> thalamus –> Pyramidal system –> Lateral corticospinal tract
What part of the brain is involved in coordination of movement?
Cerebellum
What part of the brain differentiates between correct vs incorrect mechanisms of moving?
Basal Ganglia
Cycle of Planning Movement in Brain (4)
- Posterior Cortex provides sensory information to
frontal cortex - Prefrontal cortex plans movements
- Premotor cortex organises movement sequences
- Motor cortex produces specific movements
Pyramidal vs Extra-Pyramidal Tracts
- Pyramidal tracts: Conscious control of muscles from
the cerebral cortex to the muscles of the body and
face - Extrapyramidal tracts: Originate in the brainstem,
carrying motor fibres to the spinal cord
What is the Basal Ganglia?
A group of subcortical nuclei responsible primarily for motor control, as well as other roles such as motor learning, executive functions and behaviours, and emotions
What structures are included in the Basal Ganglia?
- Caudate
- Putamen
- Globus pallidus
- Substantia nigra (midbrain)
- Subthalamic nuclei (ventral thalamus)
Do Basal Ganglia project directly to the spinal cord?
They do not project directly to the spinal cord
How does the Basal Ganglia influence activity movement?
By regulating activity of UMNs
What can happen if there are defects in the basal ganglia? (3)
- Cause inability to control movement
- Problems when switching between commands
- Problems initiating and terminating movements
The Cerebellum is also know as the…?
- ‘Little Brain’
- Hindbrain
How does the Cerebellum influences movements?
By interaction with UMNs rather than projecting directly to LMNs
The Cerebellum is involved in feedback loops with …..?
the motor cortex and brain stem nuclei
Where is the Cerebellum found?
Found infratentorial below the tentorium cerebelli in the posterior fossa
How does the Cerebellum connect to the brainstem (pons and medulla)?
Via 3 peduncles – superior, inferior and middle
What is the Structure of the Cerebellum?
- Consists of 2 hemispheres joined in the middle by
the vermis - Has an outer cerebellar cortex and subcortical
cerebellar nuclei
What is the white matter of the Cerebellum called?
Arbor vitae
What are the predominant cell types in the Cerebellum? (2)
Purkinje and Granule Cells
Role of Cerebellum? (4)
- Coordinates smooth skeletal muscle movements
- Balance
- Learning and memory
- Processes sensory information to monitor the
course of movement/feedback
Inputs to the Cerebellum (3)
- Cerebral Cortex
- Brainstem
- Ascending Pathways – JPS, muscle length/tension
Outputs to the Cerebellum (3)
- Brain Stem Nuclei
- Thalamus
- Cerebral Cortex
What is Dysdiadochokinesis?
The inability to perform and sustain a series of repeated movements
What is Ataxia?
- Gross incoordination of movements
- Gait / rebound
What is Nystagmus?
Repetitive, involuntary oscillation of the eyes
What is Intention Tremor
A wide tremor when performing voluntary movements
What is Slurred Speech?
Speech may be imprecise slow and distorted
What is Hypotonia?
The patient may have muscle weakness
What is Pass Pointing (Dysmetria)?
The patient overshoots when touching the examiners finger
Pyramidal Tracts
- Corticospinal & corticobulbar tracts
- Travel through the pyramids of the medulla
oblongata - Chief organiser and executor of motor function
Extrapyramidal Tracts
- Rubrospinal/ vestibulospinal/ reticulospinal/
tectospinal/ basal ganglia/cerebellum - Essentially beyond voluntary control
Signs of Extrapyramidal Lesions (5)
- Impair the regulation of voluntary movement
without affecting strength - Absence of UMN signs
- Abnormal, involuntary movements - hyperkinesia
- Reduced movements – hypokinesia
- Tremor – a rhythmic oscillatory movement
Signs of Extrapyramidal Lesions (7)
- Chorea
- Hemiballismus
- Dystonia
- Bradykinesia
- Tics
- Athetosis
- Tardive Dyskinesia
What is Chorea?
- Rapid irregular, unpredictable, involuntary muscle
jerks - Nearly always abnormal
What is Hemiballismus?
Unilateral, usually violent, chorea
What is Dystonia?
Excessive or inappropriate muscle contractions/ spasm
What is Bradykinesia?
- Slowness of movement
- Can go onto akinesia (absence of movement)
What is Tics?
- Fleeting purposeless actions
- Can be normal (stress, childhood)
What is Athetosis?
Involuntary slow writhing movements hands or face
What is Tardive Dyskinesia?
- An iatrogenic cause of parkinsonism-like effects
- Oral grimaces, sucking, chewing
Signs of UMN Lesions (5)
- Weakness / spastic paralysis
- Increased tone - spasticity
- Increased tendon reflexes
- Hyperreflexia
- Extensor plantars (Babinski reflex)
Signs of LMN Lesions (5)
- Weakness / flaccid paralysis
- Reduced tone (flaccidity)
- Loss of tendon reflexes
- Wasting
- Fasciculations
What is Multiple Sclerosis (MS)?
Chronic central nervous system demyelinating disease
Pathophysiology of MS
- Autoimmune disease caused by myelin-reactive T cells in the peripheral circulation that become activated by a trigger
- Invade the central nervous system and cause
destruction of myelin and axons directly and by
initiating the release of various inflammatory
mediators - There is often ineffective or no repair of damage
How does MS Present Clinically? (6)
- Visual: loss, dim, blurred (49%)
- Oculomotor: impaired eye movements, nystagmus
(42%) - Paresis: unilateral, mono-, paraparesis (42%)
- Incoordination: extremity, gait, tremor (23%)
- GU/bowel: incontinence, retention (10%)
- Cerebral: cognitive impairment (4%)
Treatment of MS Exacerbations (3)
- Methylprednisolone 500-1000mg qd x 5 +/- oral
taper Oral high dose steroids - Plasma exchange
- Intravenous immunoglobulin
Treatment of MS: Refractory Relapsing Remitting Disease (4)
- High dose methylprednisolone pulse therapy
- IVIG –intravenous immunoglobulin
- Plasma exchange
- Immunosuppressives (mitoxantrone,
cyclophosphamide, azathioprine, methotrexate)
What Disease Modifying Agents can be used to treat MS?
- INTERFERONS: (Beta interferon-1a: Avonex, Rebif
Beta interferon-1b: Betaseron) - GLATIRAMER ACETATE: Copaxone
