Week 13 Content Flashcards
What are the two distinct pathways to the thalamus
- Direct pathway
- Indirect pathway
Direct pathway order
- Cerebral cortex
- Striatum
- Globus pallidus internus
- Thalamus
- Cerebral cortex
Direct pathway purpose
Increases thalamus output to the cerebral cortex
- The accelerator
Indirect pathway order
- Cerebral cortex
- Striatum
- Globus pallidus externus
- Subthalamic nucleus
- Globus pallidus internus
- Thalamus
- Cerebral cortex
Indirect pathway purpose
Decreases thalamus output to the cerebral cortex
- The brake
Where does dopamine come from
Substantia nigra pars compacta
What is the effect that dopamine has on the pathways
- Striatal neurons for direct pathway are excited by dopamine
- Striatal neurons for indirect pathway are inhibited by dopamine
- More accelerator
- Less brake
Inputs to the substantia nigra pars compacta that can increase dopamine
- Frontal cortex
- Amygdala
- Peduncle pontine nucleus
- Serotonin
- Striatum
Possible basal ganglia functions
- Affects contralateral movements
- Reinforces/facilitates internally-triggered movement
- Predictive control over movement
- Adjusts tone/speed/amplitude of muscles activity
- Coordinates trunk movements with limb movements
Parkinson’s disease cause
Caused by the degeneration of dopaminergic neurons in the substantia nigra pars compacta
- >85% of degeneration occurs before the disease manifests
- Unknown cause for degeneration (idiopathic)
Parkinson’s disease impact (who and how)
- Adults primarily 40 to 70 years old
- Progressive disorder
- Initially unilateral, may progress to be bilateral
- Affects the contralateral side
What causes Parkinson’s disease (related to pathways)
No dopamine being released due to degeneration of the substantia nigra pars compacta
- Not enough gas and too much brake
Hallmark symptoms of Parkinson’s disease
- Bradykinesia
- Resting tremor
- Rigidity (lead pipe or cogwheel)
- Postural instability
What is bradykinesia
Intended movements are small and slow
What is resting tremor
Involuntary shaking only at rest (3-5hz)
What is rigidity
- Stiffness caused by increased muscle tone
- Rate and force independent
What is postural instability
Sense of imbalance resulting in an unsteady gait
Other Parkinson’s disease symptoms
- Stooped posture
- Shuffling gait
- Diminished arm swing while walking
- Freezing of gait in initiation
- Expressionless face
- Micrographia
What is another name for expressionless face
Masked faces
What is micrographia
When handwriting becomes small and condensed
What is the Hoehn and Yahr scale
A scale used to asses the severity of Parkinson’s disease symptoms
Hoehn and Yahr scale
- Unilateral symptoms; no postural instability
- Bilateral symptoms; no postural instability
- Bilateral symptoms with postural instability
- Considerably impaired walking or balance
- Wheelchair-bound or walking only with assistance
Treatments for Parkinson’s Disease
- Drug replacement of dopamine
- Surgical removal of basal ganglia nuclei
- Deep brain stimulation
- Replacing deteriorated cells
What do all treatments for Parkinson’s Disease not help
Postural instability and subsequent falls
Drug replacement of dopamine
- Levodopa used (precursor to dopamine)
- Can cross blood brain barrier
Drug replacement of dopamine problems
Sensitization after long-term use causes on-off swings
- Under = symptoms return
- Over = dyskinesias
What is dyskinesias
Abnormal movement
Surgical removal of basal ganglia nuclei
Removing:
- Globus pallidus (pallidotomy)
- Thalamus (thalamotomy)
Why would a thalamotomy be performed
When tremors are severe
Surgical removal of basal ganglia nuclei problems
- Collateral damage
- Irreversible
Deep brain stimulation
Inserting a fine wire electrode that will be implanted in either the globus pallidus or subthalamic nuclei then using magnetic stimulation to make it work properly
- Can be tuned with a pacemaker connected to electrode
Replacing deteriorated cells
Deteriorating cells in the substantia nigra pars compacta replaced with new cells that can produce dopamine
- Fetal cell transplants
- Stem cells
Fetal cells do not work –> likely placebo effect
Huntington’s Disease (what and how)
- Caused by genetics
- Onset from 30 to 50 years old
- No known cure
- Degeneration of striatal cells (caudate and putamen)
- Cells for the indirect pathway are mostly affected (no brake and too much gas)
What does Huntington’s Disease cause deficits in
- Motor channel for movements
- Oculomotor channel for eye movements
- Prefrontal channel for cognition
- Limbic channel for emotional processing
Huntington’s Disease symptoms
- Huntington’s Chorea
- Dystonia
- Abnormal eye movement
- Dementia
- Emotional disorders
What is Huntington’s chorea
Frequent, non-rhythmic, involuntary movements with fluid or jerky quality
What is dystonia
Abnormal, sustained positions of limbs, trunk, or face
Huntington’s Disease treatments
- Anti-dopaminergic medication
- Lesions (thalamotomy)
- Deep brain stimulation
Is Parkinson’s hypo or hyper kinetic
Hypokinetic
Is Huntington’s hypo or hyper kinetic
Hyperkinetic
What is athetosis
Writhing, twisting movements of the limbs, face, and trunk
What is Ballismus
Movements of the proximal limb muscles with a larger-amplitude, more rotatory or flinging quality
Tourette Syndrome (when and how)
- Onset in early childhood
- 4:1 male: female
- Genetic component
- Affects striatal cells/receptors
Tourette Syndrome symptoms
- Involuntary motor and vocal tics
- Non-purposeful, sudden, repetitive, non-rhythmic movements, and vocalizations
- Varies with stress/concentration
Tourette Syndrome treatment
- No known cure
- Psychotherapy
- Dopamine blockers (neuroleptics)
- Deep brain stimulation
