Question

1. Describe the blood brain barrier

2. Describe the pathophysiology of parkinson's disease

3. Describe the mechanism of action of the dopaminergic medications to treat parkinson's. How do these medications reduce symptoms? Is there a cure for parkinson's

4. Describe the pathophysiology of Alzheimer's Disease

5. Describe the mechanism of action of the drugs for cognitive impairment (page 193). How do these medications achieve a therapeutic effect in Alzheimer's disease.

6. Describe the pathophysiology of multiple sclerosis

7. Describe the mechanism of action of the disease modifying drugs used to treat MS

8. Discuss 3 major nursing implications to medication used to treat MS and how these would be attended to

9. Describe the 5 ways in which antiepileptic drugs (AEDs) work to reduce seizures

10. Discuss two teaching points for a patient that is starting phenytoin

11. How do centrally acting muscle relaxants work to relieve spasticity?

Answer 1

Ans) 1) The blood–brain barrier (BBB) is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS).

- The BBB has several important functions: Protects the brain from "foreign substances" in the blood that may injure the brain. Protects the brain from hormones and neurotransmitters in the rest of the body. Maintains a constant environment for the brain.

2) The pathophysiology of Parkinson's disease is death of dopaminergic neurons as a result of changes in biological activity in the brain with respect to Parkinson's disease. There are several proposed mechanisms for neuronal death in PD; however, not all of them are well understood.

3) As the substantia nigra degenerates in Parkinson's disease (PD), the nigrostriatal pathway is disrupted, reducing striatal dopamine and producing PD symptoms.

- Although dopamine does not readily cross the blood-brain barrier, its precursor, levodopa, does. Levodopa is absorbed in the small bowel and is rapidly catabolized by aromatic-L-amino-acid decarboxylase (AADC) and catechol-O-methyltransferase (COMT).

- Because gastric AADC and COMT degrade levodopa, the drug is given with inhibitors of AADC (carbidopa or benserazide), and inhibitors of COMT will also enter clinical use.

- Although the exact site of decarboxylation of exogenous levodopa to dopamine in the brain is unknown, most striatal AADC is located in nigrostriatal dopaminergic nerve terminals. Newly synthesized dopamine is stored in the terminals and then released, stimulating postsynaptic dopamine receptors and mediating the antiparkinsonian action of levodopa.

- Dopamine agonists act directly on postsynaptic dopamine receptors, thus obviating the need for metabolic conversion, storage, and release.

4) Pathophysiology of Alzheimer's disease:

The 2 pathologic hallmarks of Alzheimer disease are

• Extracellular beta-amyloid deposits (in senile plaques)
• Intracellular neurofibrillary tangles (paired helical filaments)
• The beta-amyloid deposition and neurofibrillary tangles lead to loss of synapses and neurons, which results in gross atrophy of the affected areas of the brain, typically starting at the mesial temporal lobe.

- The mechanism by which beta-amyloid peptide and neurofibrillary tangles cause such damage is incompletely understood. There are several theories.

- The amyloid hypothesis posits that progressive accumulation of beta-amyloid in the brain triggers a complex cascade of events ending in neuronal cell death, loss of neuronal synapses, and progressive neurotransmitter deficits; all of these effects contribute to the clinical symptoms of dementia.

- Prion mechanisms have been identified in Alzheimer disease. In prion diseases, a normal cell-surface brain protein called prion protein becomes misfolded into a pathogenic form termed a prion. The prion then causes other prion proteins to misfold similarly, resulting in a marked increase in the abnormal proteins, which leads to brain damage. In Alzheimer disease, it is thought that the beta-amyloid in cerebral amyloid deposits and tau in neurofibrillary tangles have prion-like, self-replicating properties.