Anatomy of the Basal Ganglia and the Cerebellum Flashcards
Label the cerebellum
Label the brainstem and its attachments to the cerebellum
Label the cerebellum
What three layer is the cerebellum divided into?
Molecular layer (outer)
Purkinje cell layer (middle)
Granule cell layer (inner)
What is the function of the Granular layer of the cerebellum?
The Granular Layer receives Afferent Projections (inputs) mainly from:
- Spinal cord, from somatic proprioceptors and pressure receptors.
- Cerebral cortex (relayed via the pons).
- Vestibular apparatus via the vestibular nuclei.
What is the function of the Purkinje cell layer of the cerebellum?
Efferent Projections of the Cerebellum (outputs), from all three lobes of the cerebellum:
the only output is via the axons of Purkinje cells which mainly synapse on neurons of the deep cerebellar nuclei and subsequently contribute to coordinating the functions all of the motor tracts of the brainstem and spinal cord (corticospinal, vestibulospinal, rubrospinal tracts).
Most efferent axons of the deep cerebellar nuclei cross the midline and synapse in the thalamus. The thalamus in turn sends fibres to the motor cortex.
Describe the clinical effects of a unilateral Cerebellar hemisphere lesion
Cerebellar hemispheres influence the ipsilateral side of the body, therefore lesions also lead to ipsilateral signs and symptoms (contrast with lesions of motor or sensory cortex).
Unilateral hemispheric lesion: Disturbance of coordination in limbs. Can result in intention tremor and unsteady gait in the absence of weakness or sensory loss.
Describe the clinical effects of bilateral cerebllar dysfunction
Bilateral cerebellar dysfunction: Results in slowed, slurred speech (dysarthria), bilateral incoordination of the arms and a staggering, wide based gait (cerebellar ataxia).
What kind of cerebellar dysfunction will acute alcohol poisoning cause?
Acute alcohol exposure typically results in bilateral cerebellar hemisphere dysfunction and presents with cerebellar ataxia.
What clinical effects would a midline cerebellar lesion cause?
Midline lesion:
Disturbance of postural control. Patient will tend to fall over when standing or sitting despite preserved limb coordination.
What are the basal ganglia, list the main 5
Basal Ganglia A number of masses of grey matter located near the base of each cerebral hemisphere
- Caudate Nucleus
- Putamen
- Globus Pallidus
- Subthalamic nucleus
- Sibstantia Nigra
What are the main functions of the Basal Ganglia?
To facilitate purposeful movement.
Inhibit unwanted movements.
Role in posture and muscle tone.
Label the group names associated with the basal ganglia
Label the schematic of the basal ganglia system
Label the shematic of basal ganglia and cerebellar interactions
label the axial section
Label the coronal section
Through which part sturcture is this section? Label it
Mesencephalon (midbrain)
Looking at the substantia nigra, how can parkinson’s disease be indentifed and why?
degeneration of dopaminergic neurons of the substantia nigra, it therefore looses its black clour.
The black pigment is neuromelanin, a by product of dopamine neurotransmitter production
Which basal ganglia does the direct pathway concern, and what does it do?
Direct Pathway: Enhances outflow of thalamus, enhancing the desired movement (inhibition of thalamus inhibition)
Cortex - Putamen - Internal Globus Pallidus - Thalamus - Putamen
(Clever People Get Top Prizes)
Which basal ganglia does the Indirect Pathway concern, and what does it do?
TBasal Ganglia Work With the Motor Cortex via the indirect pathway to Supress Unwanted Movement (inhibiting the inhibition of the excitory neurone that stimulates the neurone inhibiting the thalamus)
Cortex - Putamen - External globus pallidus - Subthalamic nucleus - Internal globus Pallidus - Thalamus
(Can People Eat So I Talk)
Which side of the body will unilateral lesions of the basal ganglia affect?
The contralateral side
What motor signs do lesions of the basal ganglia produce?
changes in muscle tone
dyskinesias (abnormal, involuntary movements) including: tremor (sinusoidal movements),
chorea (rapid, asymmetrical movements usually affecting distal limb musculature)
myoclonus (muscle jerks).
What motor signs do lesions of the basal ganglia NOT produce?
Generally do not cause
- paralysis
- sensory loss
- loss of power
- ataxia
What is the pathophysiology of Parkinson’s, and what are its signs?
Pathology: degeneration of dopaminergic neurons of the substantia nigra
Signs: akinesia, rigidity and resting tremor
What is the pathophysiology and genetic trait of Huntington’s disease (chorea) and what are its signs?
Genetics: autosomal dominant disorder
Pathology: progressive degeneration of the basal ganglia and cerebral cortex
Signs: chorea and progressive dementia
Describe the changes in basal ganlia pathways in Parkinson’s and Huntington’s chorea
