. Parkinson’s disease (PD) is chronic progressive nervous system disorder that a
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Question
. Parkinson’s disease (PD) is chronic progressive nervous system disorder that affects movements. Describe: a) The major motor symptoms of PD. (1 mark) b) The major causes of PD. (1 mark) c) How dopaminergic neurons in substantia nigra are thought to control the direct and indirect pathways of the basal ganglia (2 marks) and what is overall effect of dopaminergic neurons in the substantia nigra on the basal ganglia outflow in normal individuals? (1 mark) d) In patients with Parkinson’s disease that have akinesia, describe the changes that occur in nigrostriatal pathways (1 mark); and in the direct & indirect pathways of the cortex-basal ganglia-cortex motor loop, underlying this motor symptom. (3 marks) e) List the major pharmacological therapies for PD patients. (1 mark)
Explanation / Answer
(a) The major symptoms of Parkinson's Disease are:
(1) Tremor of hands even when the body is at rest.
(2) Head remains held forward.
(3) Open mouth with salivary drooling along with drooping eyelids.
(4) Slow gait which leads to short steps and slow movement.
(b) The major cause of Parkinson's disease is the damage or destruction of the nerve cells in the brain called Substantia nigra. The substantia nigra is responsible for the production of Dopamine. Dopamine is responsible for controlled and smooth body movement. In a person with PD the nerve cells are damaged so there is a lack of dopamine which causes these slow movement and tremors.
(c) Dopaminergic neurons in substantia nigra definitely control the direct and indirect pathways of the basal ganglia. D1 receptors on the dopaminergic neurons that is the neurons of the pars compacta excite the neurons of the direct pathway. Therefore we can say that Dopaminergic neurons excite the direct pathway of the basal ganglia. In case of Dopamine D2 receptors the striatal neurons is inhibited by dopamine. So we can say that dopaminergic neurons inhibit the neurons of the indirect pathway.
The overall effect of dopaminergic neurons in the substantia nigra on the basal ganglia outflow in normal individuals is that the Substantia nigra in case of normal individuals is bigger compared to patients with PD. Also in normal individuals there is no loss of dopaminergic neurons of the substantia nigra pars compacta.
(d) In patients with PD that have akinesia there is a loss of dopaminergic neurons of the substantia nigra which leads to the degeneration of the nigostriatal pathways.
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