Lecture 8 Brainstem and motor disorders Flashcards
Ears
Cerebral peduncles
Eyebrows
Substantia nigra that releases dopamine
Eyes
Red nucleus
Tears
Ascending sensory pathways
- medial lemniscus pathway - dorsal column
- spinothalamic tract
Nose
Occulomotor nucleus
Edinger Westphal nucleus
Motor nucleus
- for accommodation reflex
Mouth
Cerebral aqueduct connecting the third and fourth ventricle
Around the mouth
Peri-aqueductal grey matter Function: - pain perception - contains progesterone receptors that alter pain tolerance during menstruation - urinary continence
Double chin
Tectum of the midbrain contains colliculi for vision and hearing
Lentiform nucleus
Putamen and globus pallidus
Striatum
Putamen and caudate nucleus
What shape in the caudate nucleus
C shaped due to the lateral ventricles which are also C shaped due to the temporal horn that goes into the temporal lobe
Parts of the cerebellum
Cerebellar peduncles - connects the cerebellar to the brain stem
- superior - midbrain
- middle - pons
- inferior - medulla
Vermis - midline structure between the cerebellar hemispheres that control the trunk
Cerebellar tonsil - can compress the medulla during a rise in intracranial pressure
Basal ganglia function
Decide the most appropriate set of movements from a motor plan provided by the prefrontal cortex
Act via:
- Direct pathway
- Indirect pathway
Direct pathway
Causes excitation of the cerebral cortex to facilitate motor movements
Indirect pathway
Inhibits the cerebral cortex to inhibit motor movements
Role of dopamine
Acts as a kick starter
- acts on D1 receptors of the direct pathway which causes excitation of the direct pathway
- acts on D2 receptors of the indirect pathway which inhibits the indirect pathway
Role of the cerebellum
Using proprioception input via the spinocerebellum tract, determines an appropriate sequence to conduct the motor plan
Parkinson’s disease triad
Tremor - pill rolling tremor
Lead pipe rigidity - resistance to full range of movement
Bradykinesia
+/- psychiatric features such as depression
Micrographia - small handwriting
Hypophonia
Dementia (Lewy body)
Bradykinesia
Slowness of movement
Mask like face
Trouble stopping and starting with destinations gait
Walk slow
Cause of Parkinson’s disease
Degeneration of the substantia nigra therefore less dopamine release
Decreased inhibition of the indirect pathway therefore increased movements
Decrease stimulation of the direct pathway
Causes of huntington’s disease (chorea)
Decreased activity of the indirect pathway therefore decreased inhibition of the globus pallidus external segment resulting in increased movements
Chorea
Abnormal involuntary movement does order
Features of Huntington’s disease
Autosomal dominant
- choreiform movements
- dystonia
- incoordination
- psychiatric features
Dystonia
Uncontrollable muscle contraction causing twisting, abnormal posture or repetitive movements
Hemiballismus
Destruction of subthalamic nucleus therefore less excitation of the globus pallidus internal segment
Causes increased movement
- ballistic movements on one side
Ballistic movements
- no one side
- rotating
Basal ganglia lesions
Affects the contralateral side
Cerebellar lesions
Affects the ipsilateral side
Symptoms of cerebellar lesions
Dysdiadochokinesis Ataxia Nystagmus Intention tremor Slurred speech (dysarthria) Hypotonia
Lesion in the vermis
Affect the trunk e.g. trunk ataxia
When sitting down, one falls to one side
Dysdiadochokinesis
Difficulty with rapidly alternating movements
Nystagmus
Flickering movements of the eyes that are fast phase towards the side of the lesion
How to test for intention tremor
Finger nose test
- past pointing - go beyond finger
Cerebellar pathway
- Proprioception receptors in the muscle spindle send afferent a to the ipsilateral cerebellar hemisphere viabthe dorsal spinocerebellar pathway
- Motor innervation from the precentral gyrus has efferents that travel to the pontine nucleus via the corticospinal pathway
- From the pontine nucleus where is synapses, it desuccates to the CONTRALATERAL cerebellar hemisphere
- Collating the data, the cerebellum sends axons to the CONTROLATERAL primary motor cortex via the cerebellum-thalamo- cortical pathway but first synapses at the thalamus
- Motor efferent are sent to the effector muscle via the corticospinal pathway after decussating
