Cells of the Central Nervous System
They are classified into two different types:
Glial cells: These are further divided into:
Astrocytes
Oligodendrocytes
Ependymal cells
Macrophages
Glial Cells
Astrocytes
These are star-shaped cells.
IHC stain: glial fibrillary acidic protein marker.
Functions
Formation of the Blood-Brain Barrier (BBB).
Involved in the repair mechanism.
B. Oligodendrocytes
Formation of the myelin sheath (helps in fast conduction of impulses) in the CNS.
Special stain for myelin: Luxol fast blue.
C. Ependymal cells Also read: Detailed Pathology of Brain Tumors: Types, Grading, and Diagnosis
Response to Injury
Astrocytes become giant and pink (gemistocytes).
Alzheimer (no memory loss) astrocytes seen in Type 1 progressive multifocal leukoencephalopathy.
Alzheimer's (no memory loss) is found in Type 2 hepatic encephalopathy (damage by ammonia).
Rosenthal fibers:
Not specific
Made of ubiquitin, alpha-beta crystallin, heat shock protein, and GFAP.
They are seen in:
Also read: Important Pathology Questions on Cell Injury – MCQs & Key
Prion Diseases
Pathogenesis
Normal prion proteins are found in nerve cells (alpha-helical)
↓Misfolding
Sc · Formation of PrP (beta-pleated configuration)
↓
Mainly occurs due to the polymorphism at codon 129
Diseases
Creutzfeldt-Jakob disease
Fatal familial insomnia (FFI)
Kuru disease-PAS & Congo red positive
Scrapie disease (sheep)
Bovine spongiform encephalopathy (animal association)
Mink transmissible encephalopathy (animal association)
All these show spongiform changes except FFI.
Codons
Prion disease: caused by the mutation of codon 129.
Aflatoxin (p53 gene) due to the mutation of codon 249.
BRAF V600 E
JAK2 V617F: Polycythemia
Also read: Plasma Cell Dyscrasia & Flow Cytometry in Hematology
Neuro-degenerative Disorders
1. Alzheimer's Disease
Element of dementia .
Seen in old age people (>70 years).
The Amyloid Precursor Protein (APP) gene is present in chromosome 21.
APP gene has two pathways:
Amyloidogenic pathway
Has beta-secretase activity (A β 40 and Aβ 42)
Gamma-secretase enzyme activity
Non-amyloidogenic pathway
Has alpha-secretase activity
Gamma-secretase enzyme activity
A β42-key initiator of Alzheimer's disease
↓
βplaque
↓
Meyernet Nucleus
↓ Reduced acetylcholine levels
↓
Dementia
Genetics of Alzheimer's Disease
APP gene:
Trisomy 21: more APP leads to presenile Alzheimer's disease.
Presenilin 1 gene
Present in chromosome 14
Increases the levels of gamma-secretase activity
Presenilin 2 gene
Present in chromosome 1
Activity of gamma-secretase enzyme is increased
ApoE4 gene
Present in chromosome 19
Early onset of Alzheimer's disease
Pathology of Alzheimer's Disease
Neuritic plaques:
Core of Amyloid (Aβ 42) in the center.
Damaged nerves are accumulated (dystrophic nerve fibers)
Bielschowsky stain is used to observe the neuritic plaques.
Neurofibrillary Tangles
Flame cells
Made of hyperphosphorylated Tau protein
Cerebral amyloid angiopathy:
Blood vessels present in the brain are affected due to Aβ 40.
Granula-vascular degeneration:
Hirano bodies:
Needle-shaped body
Made of actin
Also read: Comprehensive Overview Of Lung Pathology Images
ii.Parkinson's Disease
Decrease in dopaminergic neurons.
Decrease in melanin (pale substantia nigra).
Symptoms: Tremors, rigidity, slow movement (bradykinesia).
Genetics of Parkinson's Disease Mutations :
Alpha-synuclein
Gain-of-function
Forms Lewy bodies
LRRK2
PINK
Parkin
iii. Huntington's disease/Huntington's chorea:
Purposeless jerky movements
CAG repeats on the exon of chromosome 4
Proteins: Increase in Polyglutamate, Huntintin, and Ubiquitin proteins
↓
Accumulates in the caudate nucleus
↓
Chorea ↓ Purposeless jerky movements
iv. Amyotrophic Lateral Sclerosis
Involves both upper motor neuron and lower motor neuron.
Presence of bunina bodies.
SOD 1 gene mutations.
Also read: Blood Groups and Storage in Blood Banking
Overview: Most Expected Questions Disease Summary Alzheimer's Disease - APP (Chromosome: 21) - PS 1 (Chromosome: 4) - PS 2 (Chromosome: 1) - APOE4 - Hirano bodies: Made of Actin Parkinson's Disease - Parkin and pink gene mutation - Lewy bodies: Made of alpha-synuclein ALS - Mutations of SOD1 - Bunina bodies Huntington disease - CAG repeat, chromosome 4 - Increase of Huntingtin and Ubiquitin proteins
Proteins & Diseases Protein Disease Aβ Alzheimer's disease Alpha-synuclein Parkinson's disease Polyglutamine aggregates Huntington's disease FUS Frontotemporal lobar degeneration TDP43 Frontotemporal lobar degeneration Tau (Tau pathies—CCAPP) - Frontotemporal lobar degeneration - Cortico-basal encephalopathy - Chronic traumatic encephalopathy - Alzheimer's disease - Parkinson's disease - Progressive supranuclear palsy
FTLD-TDP: Expansion of a hexanucleotide repeat of C9orf72
Also read: Acute Lymphoblastic Leukemia: Symptoms, Causes and Treatments
Important questions
Q. How is myelin sheath formed in PNS? Ans: Schwann cells
Q. What are the brain changes in HIV-positive individuals? Ans: Microglial nodules
Q. In which condition rod-shaped cells are found? Ans: Neurosyphilis (Tertiary syphilis)
Q. In which condition neuronophagia occurs? Ans: Polio and Rabies
Q. What are globoid bodies? And in which condition are they found? Ans: These are small clusters found in lysosomal storage disorders (Krabbe's disease)
Q. In which disease Lewy bodies are found? Ans: Parkinson's disease
Q. What is a Lewy body made up of? Ans: Alpha-synuclein
Q. What stain is used to identify Flame cells? Ans: Bielschowsky Stain
Q. What gives the cells a flaming appearance to the cells? Ans: Hyperphosphorylated Tau protein
Q. How are Rosenthal fibers made? Ans: They are made of ubiquitin, alpha-beta crystallin, HSP and GFAP (In In P P)
Also read: NEET PG High Yield Questions for Pathology
Multiple Choice Questions
Q. Ubiquitin deposition is seen in which of the following conditions?
Alzheimer's disease
Huntington's disease
Meningioma
FTLD
Q. Lewy bodies are composed of?
Tau protein
Alpha-synuclein
Beta plaques
Actin
Q. Hirano bodies are composed of?
Tau protein
Alpha-synuclein
Beta plaques
Actin
Q. Which of the following is/ are seen in Alzheimer's disease?
CAA
Granulovacuolar degeneration
Flame cells
Hyperphosphorylated tau proteins
Hirano bodies
Neuritic plaques
1,2,4,5
1,2,4,5,6
1,2,3,4,5,6
2,3,4,5,6
Access Video Lectures, digital notes, QBank, and Mock Tests for FREE to start with the Best NEET PG Coaching Online .
Download PrepLadder's best app for neet pg preparation for Android
Download PrepLadder's best app for neet pg preparation for ios