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Histopathology > Nervous System > Flashcards

Nervous System Flashcards

Week 5

1
Q

Neurons

A

Most metabolically active cell in the body

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2
Q

Neuroglia

A

Glia, astrocytes, Schwann cell

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3
Q

Central Nervous System

A

Meninges, BBB, cerebellum, spinal cord, gray matter, specialized glia

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4
Q

Peripheral Nervous System

A

Nerves

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5
Q

Sensory stimuli

A

Feed into afferent division of PNS then to CNS
Highly myelinated

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6
Q

Visceral stimuli

A

Feed into afferent division of PNS then to CNS
Unmyelinated

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7
Q

Neuron Cell Body Histology

A

Euchromatic Nucleus: indicates high level of gene expression, prominent nucleolus
Perinuclear cytoplasm:
- abundant rER + free ribosomes
- Nissl Bodies: stack of rER
- mitochondria, neurofilaments, prominent Golgi
Metabolically active tissue: prominent nucleolus

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8
Q

EM of Neuron

A

Nucleolus: black dot
Nucleus: black dot + white surroundings
Organelles: abundant rER, Golgi, mitochondria, lysosomes

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9
Q

Junctions of Neurons

A

Specialized junctions between neurons
Visualizing: dark connection point (proteins, receptors, etc)
Presynaptic neurons: transmission of impulses and collection of secretory vesicles
Post-synaptic neuron: receives the signal
Synaptic button

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10
Q

Clear Vesicles

A
  • Chemical transmitters: acetylcholine, GABA, dopamine, serotonin, histamine, etc (not proteins)
  • Produced via enzymatic reactions
  • Released and degraded in synapse
  • Local-action and fast acting
  • V: small black outlined circles
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11
Q

Dense Core Vesicles

A
  • Neuropeptides (neurohormones): insulin, orexin, vasopressin
  • proteins (G-protein receptors)
  • encoded for in the genome
  • (potentially) distant action and slower acting
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12
Q

Peripheral Nerves

A
  • Clustered with artery, vein, nerve
  • Mostly myelinated axons
  • Mixed autonomic, motor, and sensory neurons
  • Perineurium and Endoneurium both connective tissue
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13
Q

Spinal and cranial nerves

A

Spinal comes from spine
Cranial comes from brain

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14
Q

Spinal Cord and Nerves

A

Meninges, dorsal root ganglion (sensory?), and sympathetic ganglion chain

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15
Q

Spinal Cord Anatomy

A

Dorsal Horn: afferent neurons
Lateral Horn: autonomic efferent fibers
Ventral Horn: somatic efferent neurons - motor neurons

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16
Q

Peripheral Nerves Components

A

Epineurium -> Perineurium -> Endoneurium
Capillaries, Axons (light pink, flat), Myelin, Schwann cells (sit around axons)
A bundle of neurons is a fascicle

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17
Q

Peripheral Nerves

A

Blood-Nerve Barrier: allows for ECF environment optimal for neural conductance (tight junction)
- Perineurium with extensive basal lamina - cells contain pumps, receptors for optimal ionic composition
- Endothelial cells with basal lamina

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18
Q

Ganglia are cell bodies of Peripheral Nerves

A

Ganglia: clusters of peripheral cell bodies
- surrounded by connective tissue continuous with the epineurium
- surrounded by satellite cells: small cuboidal cells that nourish the cells and maintain the extracellular environment

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19
Q

Dorsal Root Ganglion

A

Contains cell bodies of sensory neurons
Thick fibers, centrally located axon surrounded by myelin sheath, myelin sheath surrounded by neurilemma

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20
Q

Sympathetic Ganglion

A

Lightly- or un-myelinated
Fibers are thinner than the dorsal root ganglion

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21
Q

Schwann Cells and Myelin Sheath Cells

A

Schwann Cells secrete myelin
- Isolate axon from extracellular compartment
- Does not cover axon hillock and nodes of Ranvier

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22
Q

Unmyelinated nerve fibers

A

Many demyelinated diseases: genetic + autoimmune
Nerve fibers can be found in Schwann cell grooves, act to support neurons
??

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23
Q

Central Neuroglia

A

Astrocytes, microglial cells, ependymal cells, oligodendrocyte, sensory neuron with Schwann cells and satellite cells

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24
Q

Protoplasmic Astrocytes

A
  • Largest of the neuroglia
  • Modulate many neuronal activities:
    Maintains the microenvironments by modulating K+ levels
    Helps maintain the blood-brain barrier
    Plays an active role in regulating physiology (sleep)
  • Protoplasmic: located in outer covering the brain (gray matter)
  • Fibrous: located in the inner core of the brain (white matter)
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25
Q

Fibrous Astrocytes

A

White matter: inner core of the brain
- gatekeeper to regulate fluid in the brain (ions, drugs, larger molecules)

26
Q

Oligodendrocytes

A
  • Produces myelin in the CNS
  • LM: small cells with few processes
  • Often aligned in rows between axons
  • A single oligodendrocyte may myelinate numerous nearby axons
  • Looks like fibrocartilage
27
Q

Microglia

A
  • phagocytic cells
  • proliferate and become more active during times of infection/injury (local inflammatory response)
  • small elongated nuclei, short twister processes
  • Immunoreactive for IBA-1
28
Q

Ependymal Cells

A
  • Function: Lines fluid-filled cavities and spinal cord
  • Visualization: cuboidal-columnar cell type with apical surface containing cilia+microvilli
  • Feature(s): choroid plexus - cluster of ependymal cells and capillaries; secretes CSF???
  • controlled via circadian rhythm
28
Q

Blood-Brain Barrier

A
  • Develops early - astrocytes and endothelial cells signal to one another (during development)
  • High expression of tight junctions (endothelial cells)
  • Astrocyte foot processes (outside of basement membrane) associate with endothelial cells
  • pericyte: surrounds capillary completely
  • Thin capillary for diffusion
  • Need to use EM
29
Q

Spinal Cord

A

Cervical: 8
Thoracic: 12
Lumbar: 5
Sacral: 5
Gray Matter: inside, connected by gray commissure
- Doral Horn: Sensory neurons
- Ventral Horn: motor (efferent) neurons; recognizable by LM, prominent Nissl bodies, euchromatic nuclue
White matter: outside, arranged into tracts
Central Canal: CSF

30
Q

Meninges Structure

A
  • Dura Mater: dense irregular connective tissue
  • Arachnoid Layer: delicate collagen and elastic fibers, looks like spiderweb (loose connective tissue)
  • Pia Mater: thin transparent connective tissue; adheres to brain/spinal cord; composed of collagen and elastic fibers
31
Q

Meningitis

A

Inflammation of the meninges caused by bacteria

32
Q

Encephalitis

A

Infection of the brain cause by virus

33
Q

Meningitis and encephalitis lead to

A

Meningoencephalitis

34
Q

Santiago Ramon and Cajal (1852-1934)

A

Layers of cerebral cortex

35
Q

Layers of Cerebral Cortex

A

Outermost region of the brain
Gray Matter: Cell Bodies, axons, dendrites, glia
1) Plexiform Layer: fibers running parallel to surface, neuroglia
2) Small pyramidal cell layer
3) Medium pyramidal cell layer
4) Granular layer: stellate cells
5) Large pyramidal cells
6) Polymorphic cells: diverse shape
White matter: myelinated axons and glia

36
Q

1) Plexiform Layer

A
  • Nerve fibers (axons/dendrites)
  • Numerous neuroglial cells: appear primarily as nuclei with no obvious cytoplasm
  • Horizontal cells of Cajal
37
Q

2) Small Pyramidal Layer

A
  • Many small pyramidal cells are present
  • Granular cells are also numerous
38
Q

3) Medium Pyramidal Layer

A

Slightly large pyramidal cells

39
Q

4) Granular Layer

A
  • Most cells are granule cells
  • Neuroglial cells are prominent
  • Capillaries evident
40
Q

5) Large pyramidal layer

A

Largest pyramidal cells

41
Q

6) Polymorphic Cell Layer

A
  • Diverse shape of the cells in this region: pyramidal cells, fusiform cells, granule cells, Martinotti cells (short dendrites and send axons up to layer 1)
42
Q

White Matter of brain

A

Neuroglial cells: small round nuclei
- densely packed aggregation of nerve fibers

43
Q

Cerebellum

A

Functions:
- Balance/eye movement
- Timing and coordination of muscle contractions
- planning and initiating voluntary movement

44
Q

Cerebellum Layers

A

1) Molecular Layer: axons of granular cells and dendrites of Purkinje cells
2) Purkinje Layer
3) Granular Layer: Densely packed with granular cells sending their projections into the molecular layer
White matter

45
Q

Purkinje Cells

A
  • Largely inhibitory motor neurons that release the neurotransmitter GABA
  • Inhibit other neurons for motor control
46
Q

Granule cells

A
  • Most numerous neuron type in brain
  • Function as sensory integration allowing the brain to distinguish a vast # of inputs
  • Synapse onto Purkinje cells
47
Q

Parkinson’s

A

Affects 1-2% of people older than 60 years
- Characterized by motor symptoms: rigidity, tremor at rest, slowness of voluntary movement, stooped posture, a shuffling, small-step gait, difficulty with balance
- Nonmotor symptoms: an expressionless face, soft voice, olfactory loss, mood disturbances, dementia, sleep disorders, and autonomic dysfunction
- When cells die, loss of inhibitory output

48
Q

Substantia Nigra

A

Region of brain affected by Parkinson’s disease

49
Q

Parkinson’s mechanism of action

A

Toxic protein aggregates & interaction with potential neurotoxic proteins & Lewy bodies leading to chaperone depletion -> dopamine neuron death -> motor impairment

50
Q

Lewy bodies

A

Pigment in cell bodies

51
Q

Alzheimer’s

A

Commonly found in hippocampus
Key Features:
- most common cause of dementia, accounting for 50-70 percent of all cases
- hallmark symptom: impairment in ability to remember new information
- May be associated with early impairment in language and visuaspatial or executive function
Brain Images:
- increase hippocampal and overall brain atrophy
Histopathology:
- Plaques composed of Beta-amyloid core (magenta color on H&E)
- Dystrophic neurites containing neurofibrillary tangles made of tau protein
Video notes!!

52
Q

Peripheral Neuropathy

A

1) autoimmunity
2) vasculitis (CT disease)
3) systemic illness (diabetes)
4) cancer
5) infection (diphtheria, leprosy, lyme disease, AIDS, herpes zoster)
6) Dysproteinemia (myeloma, cryoglobulinemia)
7) Nutritional deficiencies and alcoholism
8) Compression and trauma
9) Toxic industrial agents and drugs
10) Inherited neuropathies

53
Q

Peripheral Neuropathy

A

Pathological Progressions:
1) Wallerian degeneration
2) Distal axonopathy
3) Segmental demyelination

54
Q

Wallerian Degeneration

A
  • Axonal changes: fragmentation/loss of myelin and axons
  • Changes of the neuronal body:
    • rEr disaggregates and the neuronal body balloons
    • cytoplasm becomes smooth and the nucleus is displaced toward the periphery of the cell: central chromatolysis
      • Reflected activation of protein synthesis in order to regenerate the axon
55
Q

Distal Axonopathy

A
  • Degeneration of axon and myelin develops first
  • Neurofilaments and organelles accumulate in the degenerating axon
  • Eventually, the axon becomes atrophic and breaks down
  • Neuropathies caused by drugs and industrial poisoning (pesticides, acrylamide, organic phosphates, and industrial solvents)
  • Thought to be caused by pathology of the neuronal body resulting in its inability to keep up with the metabolic demands of the axon
56
Q

Segmental Demyelination

A
  • Originally described in experimental lead poisoning
  • Characterized by breakdown and loss of myelin over a few segments
  • Axon remains intact and there is no change in neuronal body
  • Loss of saltatory conduction leads to decrease of conduction velocity
  • Deficits develop rapidly but are reversible because schwann cells make new myelin
    Causes: inflammatory response
57
Q

Amytrophic Lateral Sclerosis (ALS) (or Lou Gehrig’s disease)

A
  • Results from loss of motor neurons, most often in the anterior horn cells of spinal cord with loss of lower motor neurons
  • Marked initially by muscle fasciculation - involuntary contractions
  • Astrocytosis is seen in response to the loss of motor neurons: abnormal increase in the # of astrocytes
58
Q

Amytrophic lateral sclerosis

A

Definition: progressive neurodegenerative disorder characterized by degeneration of upper/lower motor neurons resulting in progressive skeletal muscle wasting and weakness leading to respiratory failure and death
Essential features:
- spinal cord and anterior spinal root atrophy
- upper motor neuron loss with associated loss of myelinated axons
- Neuronal inclusions: skein-like inclusions, Hyaline (lewy-like) inclusions, Bunina bodies

59
Q

Bunina Bodies

A

Protein accumulation: cystatin C, transferrin, and peripherin

60
Q

Bacterial Meningitis

A

Clinical Findings:
- fever, severe headache, and stiff neck
- inflamed spinal structures - sensitive to stretch (pain)
- bending the leg with an outstretched knee (Kernig sign)
- Bending the neck (Brudzinski sign)
- later stages: confusion, coma, and seizures
Diagnosis and pathology:
- Cornerstone in the diagnosis of bacterial meningitis is CSF examination
- CSF: hundreds-thousands of neutrophils and many organisms
- CSF: protein is elevated and glucose is low (consumed by inflammatory cells)

61
Q

Histopathology of meningitis

A
  • Inflammatory exudate in the subarachnoid space
  • Layered-neutrophils on top
  • fibrin in the deeper layer
  • a vein with phlebitis (inflammation) and a clot is also present

Pneumococcal meningitis: meningeal inflammatory infiltrates consisting of neutrophilic granulocytes

Histopathology (13 decks)

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