Basal ganglia
Terms
undefined, object
copy deck
- How is the basal ganglia involved in motor function?
- It modulates motor output: in essence it decides which movement will be performed given a range of stimuli.
- What five structures make up the basal ganglia?
-
1.Caudate
2.Putamen
3.Globus pallidus
4.Subthalamus
5.Substantia nigra - Other than motor signals from the cortex, what are three kinds of information the basal ganglia receives?
-
1.Sensory information
2.Motivational state
3.Emotional state - What are the major outputs from the globus pallidus? What neurotransmitter dominates these pathways?
-
*to the thalamus and subthalamus
*GABA - What are the major outputs from the caudate and putamen? What neurotransmitter dominates these pathways?
-
*to the globus pallidus and substantia nigra
*GABA - What are the major inputs to the caudate and putamen? What neurotransmitters dominate these pathways?
-
*from the cerebral cortex and substantia nigra to the caudate and putamen
*from the substantia nigra - dopamine
*from the cortex - glutamate - What three neurotransmitters dominate basal ganglia circuits? Are they inhibitory or excitatory?
-
1.GABA - inhibitory
2.Dopamine - excitatory
3.Glutamate - excitatory - How is output from the basal ganglia similar to output from the cerebellar cortex?
- They both are all inhibitory
- Name the 4 dyskinesias seen with damage to the basal ganglia.
-
1.Bradykinesia
2.Resting tremor
3.Chorea
4.Rigidity - What is the incidence of PD in the general population? In adults over age 70? What percentage of PD patients are under age 50?
-
*1:1000
*1:100
*4% - Are men and women equally affected by PD?
- No - men are twice as likely to have PD than women.
- Give 4 of the characteristic symptoms of PD.
-
1.Bradykinesia
2.Resting tremor
3.Rigidity
4.Masking
5.Characteristic gait - short steps, stooped posture, little arm movement
6.Dementia - What neurons degenerate in PD?
- The dopaminergic neurons of the substantia nigra.
- What is the cause of the majority of PD cases? Name some environmental factors postulated to be at play. With what lifestyle has PD been associated?
-
*most cases have an idiopathic etiology
*exposure to carbon monoxide, carbon disulfide, cyanide, manganese
*farming and well water - Two classes of medication are used to alleviate the symptoms of PD. What are these and what symptoms does each alleviate?
-
1.Dopaminergic agonists - alleviate bradykinesia, slow gait, rigidity
2.Cholinergic antagonists - alleviate resting tremor - Why is the effectiveness of medication limited in PD patients?
- Patients develop tolerance and require larger and larger doses. Eventually the size of the dose eclipses the margin of safety. Also there are significant side effects associated with these drugs.
- Name two surgical techniques aimed at alleviating the symptoms of PD.
-
1.Specific lesioning of the globus pallidus (pallidotomy)
2.Transplant of fetal or stem cell dopaminergic neurons. - MPTP has been shown to destroy dopaminergic neurons in the substantia nigra and cause a syndrome almost identical to PD. In what way is this condition different from PD?
- Rather than the gradual onset seen in PD patients, individuals who have been administered MPTP show sudden destruction of neurons and dramatic onset of symptoms.
- Typically, what are the first signs of HD? How does this frequently lead to misdiagnosis?
-
*emotional lability and disorders in mood
*often misdiagnosed as a psychiatric illness - What are the motor symptoms of HD? How do these symptoms contribute to the death of these patients?
-
*chorea
*progressive inability to walk, speak, and swallow
*bacterial pneumonia secondary to aspiration - What is the incidence of HD? Are men and women equally affected?
-
*5-10:100,000
*men are twice as likely to have HD than women - What is "anticipation" as seen in HD? How was this phenomenon explained biochemically?
-
*age of onset decreases and severity of symptoms increases with successive generations
*the number of CAG triplet repeats increases with successive generations - Though HD patients eventually show widespread degeneration of brain tissue, where does this pathology generally begin?
- With destruction of GABA-nergic (medium spiny neurons) in the caudate and putamen.
- Is the genetic mutation that causes HD recessive or dominant? How is this mutation expressed in the affected genome?
-
*autosomal dominant
*expansion of CAG triplet repeats in the huntingtin gene from 10-35 to 40-100 - It is known that the genetic mutation in HD causes an accumulation of an insoluble polyprotein, but why does this fail to explain the pathology seen in the disease?
- The effects of polyglutamine on neurons is not known. Also, this gene is expressed throughout the body but only the GABA-nergic neurons in the caudate and putamen are affected.