Nervous System Disorders and Clinical Correlations

1. Parkinson's Disease

• Pathology: Loss of dopaminergic neurons in substantia nigra → nigrostriatal dopamine deficiency
• Symptoms: Resting tremor (pill-rolling), rigidity, bradykinesia, postural instability
• Treatment: L-DOPA (crosses BBB, converted to dopamine)

2. Multiple Sclerosis (MS)

• Pathology: Autoimmune destruction of CNS myelin (oligodendrocytes) → demyelination plaques
• Symptoms: Variable — weakness, sensory loss, optic neuritis, ataxia, relapsing-remitting
• Relevance: Directly tests saltatory conduction: destruction of myelin → slowed conduction

3. Myasthenia Gravis

• Pathology: Autoantibodies against nicotinic ACh receptors at NMJ → failure of neuromuscular transmission
• Symptoms: Muscle weakness worsening with use, ptosis (drooping eyelid), diplopia (double vision)
• Treatment: Acetylcholinesterase inhibitors (increase ACh availability)

4. Organophosphate Poisoning

• Mechanism: Irreversible inhibition of acetylcholinesterase → ACh accumulation
• Symptoms: SLUDGE (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis) + muscle spasm
• Treatment: Atropine (blocks muscarinic receptors) + pralidoxime (reactivates AChE)

5. Glaucoma

• Pathology: Increased intraocular pressure → optic nerve compression → peripheral vision loss
• Pattern: Open-angle (gradual, painless) vs angle-closure (acute, painful)
• Treatment: Beta-blocker eye drops (e.g., timolol) to reduce aqueous humour production

6. Night Blindness (Nyctalopia)

• Cause: Vitamin A deficiency → inadequate rhodopsin synthesis → rods cannot function in dim light
• Relevance: Directly links nutrition (Vitamin A) to neural function (rhodopsin in rods)

Pharmacological Principles