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NE Exam 2 > Histology Of The CNS > Flashcards

Histology Of The CNS Flashcards

1
Q

Describe the dendrites of a neuron

A

Numerous dendrites extend from the perikaryon
Extensive branching/arborization
Numerous dendritic spines increase receptive area
Spines are plastic

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2
Q

What is a neutropil?

A

Dense network of nerve fibers and their branches and synapses, together with glial processes

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3
Q

What are Nissl bodies/substances?

A

A large granular body found in neurons

Site of protein synthesis

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4
Q

What is a multipolar neuron?

A

Numerous poles associated with the extensive amount of dendrites
An axon on the other side

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5
Q

What is a bipolar neuron?

A

Centrally located cell body
Two processes extending on each side (one with dendrites and the other axon)
Found in the retina

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6
Q

What are unipolar neurons?

A

Sensory neurons
One cell body
One process extending from the cell body which branches (peripheral and central process)

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7
Q

What is an anaxonic neurons?

A

Single cell body with multiple dendrites surrounding it but no clear axon

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8
Q

Describe synaptic communication

A

Nerve impulses are transmitted from one neuron to effector cells
Synaptic transmission is unidirectional
Converts an electrical signal (nerve impulse) from a presynaptic cell —> chemical signal that affects the postsynaptic cell
Most act by releasing NTs

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9
Q

What does the presynaptic terminal button contain?

A

Mitochondria and synaptic vesicles which release NTs via exocytosis

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10
Q

What separates pre and postsynaptic membranes?

A

Synaptic cleft

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11
Q

What does the postsynaptic cell membrane contain?

A

Receptors for the NT

Ion channels to initiate new impulse

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12
Q

What are the different types of synapses?

A

Axodendritic
Axosomatic
Axoaxonic

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13
Q

Describe an electrical synapse

A

Direct passive flow of electrical current between neurons via gap junctions
Link pre and postsynaptic membranes
Contain connexon proteins which link pre and postsynaptic membranes

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14
Q

Describe astrocytes

A

Large number of long branching processes

Proximal regions are reinforced with intermediate filaments made of glial fibrillary acid protein (GFAP)

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15
Q

What is the function of astrocytes?

A

Form a vast network of delicate terminals contacting synapses and other structures
Terminal processes of a single astrocyte typically associate 1M+ synaptic sites
Involved in the BBB
Structural and metabolic support of neurons especially at synapses
Repair processes

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16
Q

What are ependymal cells?

A

Columnar or cuboidal cells that line the brain ventricles and the central canal of the SC
Apical end may have cilia and long microvilli which facilitate movement of CSF and likely involved in absorption
Joined apical by apical junctional complexes
No basal lamina present

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17
Q

Describe the choroid plexus

A

Found in the roofs of the 3rd and 4th ventricles and parts of lateral ventricular walls
Thin elaborated folded layer of well vascularized pia mater covered by cuboidal ependymal cells

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18
Q

What is the function of choroid plexus?

A

Removes H2O from blood and release it as CSF
Contains Na+, K+, Cl-
Very little protein
Only cells include sparse lymphocytes

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19
Q

What contributes to the blood CSF barrier?

A

Tight junctions (zonula occludens) between epithelial cells

20
Q

Describe the villous structure observed when identifying the choroid plexus

A

Branching system of blood vessels which run in fronds composed of a fibrous core covered by cuboidal/columnar epithelium

21
Q

Describe microglia

A

Less numerous oligodendrocytes or Astrocytes
Migratory, will remove damaged or inactive synapses or other fibrous components
Major mechanism of immune defense in the CNS removing any microbial invaders
Originate from monocytes

22
Q

Describe oligodendrocytes

A

Extend processes that enwrap nearby axons in myelin
Enwrap axons from multiple neurons
A single axon may be entrapped by many oligodendrocytes
Usually appear as small cells with rounded condensed nuclei and sustained cytoplasm

23
Q

What are peripheral glia?

A 
Includes neurolemmocytes (Schwann cells) and satelittle cells 
Both NCC derived
24
Q

What is the function of neurolemmocytes (Schwann cells)?

A

Myelinate peripheral nerves and provide electrical insulation

25
Q

What is the function of satellite cells?

A

Provide structural and metabolic support for neuronal cell bodies

26
Q

What are the different central glial cells?

A

Astrocytes, ependymal cells, microglia and oligodendrocytes

27
Q

Describe the cerebral cortex

A

Biologically older parts of the cortex are arranged as archicortex (3 layered)
Most of the cortex is neocortex and consists of 6 layers

28
Q

What are the 6 layers of the cerebral cortex (neocortex)?

A
  1. Molecular layer (largely fibers and neuroglial cells)
  2. External granular layer
  3. External pyramidal layer
  4. Inner granular layer
  5. Ganglionic layer (extra large pyramidal cells - Betz cells - especially in motor areas)
  6. Multiform (polymorphic) layer contains cells with diverse heaped)
29
Q

Describe Alzheimer’s disease

A

Most common neurodegenerative disease
Sx: memory failure, progressing steadily to involve motor skills, speech and sensation
Striking thinning of gyri particularly those of the frontal and temporal bones

30
Q

What are the different structures seen in someone with Alzheimer’s?

A

Plaques, neurofibrillary tangles and neuronal loss are identified on sections
Amyloid beta plaques: amorphous, pink masses in cortex
Neurofibrillary tangles: flame shaped skeins formed by abnormal accumulation of tau protein

31
Q

Describe the substantia nigra

A

Large mass of grey matter containing multipolar neurons w/ dark pigment
Connections with the cortex, SC, corpus striatum and reticular formation
Important role in fine control of motor movement

32
Q

What type of granules do neurons of the substantia nigra contain?

A

Granules of neuromelanin pigment

Neuromelanin contains dopamine -> inhibitory effects in brain areas dedicated to movement

33
Q

Describe Parkinson’s disease

A

Clinical features of tremor, slow movement and rigidity resulting from degeneration of neurons in the substantia nigra -> loss of dopamine

34
Q

What distinctive inclusions are seen in the remaining neurons in someone with Parkinson’s?

A

Lewy bodies
Rounded pink staining inclusions with pale halo around them
Composed of aggregates of the protein alpha synuclein and other proteins

35
Q

What are the three layers of the cerebellar cortex?

A

Molecular layer
Purkinje layer
Granular layer
Organized into folia with the cerebellar medulla located deep

36
Q

What are characteristics of the molecular layer of the cerebellar cortex?

A

Has many neuropils and scattered neuronal cell bodies

37
Q

What are characteristics of the Purkinje layer of the cerebellar cortex?

A

Extend dendrites throughout the molecular layer as a branching basket of nerve fibers
Conspicuous in H&E stained sections

38
Q

What are characteristics of the granular layer of the cerebellar cortex?

A

Contains various very small densely packed neurons (i.e. granule cells) and little neuropil

39
Q

Describe the spinal cord

A

Central masses of gray matter has the shape of a butterfly, ventral, dorsal and lateral horns
Central canal lies in the central commissure of gray matter
White matter consists of ascending tracts of sensory fibers and descending motor tracts

40
Q

Describe peripheral nerves

A

Bundles of nerve fibers individually surrounded by neurolemmocytes and CT
Multiple layers of neurolemmocytes memrbane can unite as the myelin sheath

41
Q

Describe myelin sheath

A

Composed mainly of lipid bilayer and membrane proteins
Amount of myelin is dependent on axon diameter
Degraded by standard staining procedures

42
Q

What are nodes of Ranvier?

A

Intervening regions on an axon that lack myelin

43
Q

Describe the formation of the myelin sheath

A
  1. Schwann cell becomes aligned along the axon and extends a wide cytoplasmic process to encircle it
  2. Growing process completely encloses the axon but continues its spiral extension
  3. Spiral wrappings become compacted layers of cell membrane (myelin) as cytoplasm leaves the growing process
44
Q

Describe unmyelinated axons

A
  1. Schwann cell starts to envelop multiple axons

2. The unmyelinated axons are enveloped by the Schwann cell but there are no myelin sheath warps around each axon

45
Q

What is endoneurium?

A

Immediately around the neurolemmocytes

Consist of reticular fibers, fibroblasts and capillaries

46
Q

What is perineurium?

A

Enwrap fascicles of axons, neurolemmocytes and endoneurium

47
Q

What is epineurium?

A

Dense, irregular fibrous coat in between fascicles and surrounding the peripheral nerve (continuous with spinal meninges)

NE Exam 2 (19 decks)

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