Prac: Histology of CNS Flashcards
Anterograde axonal transport - which protein, and direction?
Away from cell body
Kinesin
Retrograde axonal transport - direction and protein?
Towards cell body
Dyenein
Describe multipolar neuron
Have elaborate (multiple) dendrites which attach to the cell body. Only a single axon.
Example of multipolar neuron?
Purkinje cell of cerebellum
Internuerons
Motor Neurons
Describe unipolar cell - examples?
Single dendrite, single axon
General sensory neuron
Describe bipolar neuron - examples?
Single process extends from the cell body, which splits into a single axond, and a single dendrite
Sepcial sensory neurons - e.g. bipolar neurons of the retina
Proportion of glial cells to neurons
10x as many glial cells
What is a Nissl body?
Densely packed rhibosomes and RER. Nissl stain shows this
Magnification required to image motor neuron’s cell bodies well - e.g. to see nissl bodies, nucleus etc
40x
What is best stain to visualise how the nervous system is wired/connected?
Fluroescent stains
What are the largest and smallest neurons in the cerebellum?
Largest = Purkinje cells Smallest = granule cells of granular layer
What is retrograde fluorescent tracing useful for?
Determining the locations of neurons whose axons synapse with neurons in a particular nucleus - i.e. the fluorescent stain would be taken up from the terminal end of the axon, and would travel (be moved) in a retrograde motion, towards the cell body of the nucleus
What is anterograde fluorescent tracing useful for?
Used to trace neural connections from the cell body -> fluorescent stain taken up and moves in anterograde fashion -> to terminal end of axon/synapse
What are satellite cells?
Modified Schwann cells
What is the embryological origin of the DRG?
Neural Crest Cells
The DRG is considered grey matter (of the spinal cord), which becomes translocated to the periphery
What structural type of neuron is found in DRGs?
Bipolar (sensory) or Unipolar
Describe the distribution of the sympathetic chain ganglia
Located just ventral / lateral to the spinal cord:
3 ganglia in cervical region, 11 in thoracic region, 4 inlumbar region, 4-5 in sacral region
(~22-23 pairs in total)
What are the three connective tissue components of a peripheral nerve?
Epineurium (Type 1 collaged & Fibroblasts - covers entire nerve)
Perineurium (Segregates axons into fascicles. A basal lamina surrounds layers of fibroblasts which are tightly adhered, forming a blood-nerve barrier)
Endoneurium (surrounds individual axons and their associated Schwann cells) -> Type III collaged fibrils and a few fibroblasts make up this layer
What does osmium stain show?
Reacts with the lipid in the myelin sheath - black stain
Functional significance of nodes of ranvier
Unmyelinated gap along the axon which is capable of propagating an electrical impulse - areas of myelin ‘insulate’ the axon so that the signal moves faster, node-to-node
What is the structural and functional difference between myelinated and unmyelinated axons in the PNS and CNS?
Unmyelinated axons in CNS are essentially ‘naked’
Unmyelinated axons in PNS are still associated with schwann cells
Unmyelinated axons - generally slower conduction, more prone to injury, reduced capacity for repair
What are the dark spots in white matter?
Nuclei of glial cells
What are the different glial cells of the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependyma
FUnctions of Astrocytes
Functions:
Formation of the Glia Limitans - Thin membrane (tight junctions between foot processes) that contributes to the BBB underlying the pia mater.
Uptake of K ions (important for neuron polarisation/repolarisation process)
Undergo proliferation in resonse to neuronal injury
Recycling of neurotransmitters
Functions of oligodendrocytes
They are associated with which important pathology?
Primary myelinators in the CNS***
Multiple cytoplasmic processes myelinate multiple axons
(Associated with MS)
Functions of Microglia
Smallest of the glia
Resident immune cell - phagocytic functions, cytokine secretion, can be seen converging in a site of injury
Function of Ependymal glial cells
Movement of CSF
What are the glial cells of the PNS?
Schwann Cell Satellite cell (type of modified schwann cell)
Function of Schwann Cells
Myelination of PNS axons
Unlike oligodendrocytes of CNS, one schwann cell myelinates a single axon. Cytoplasm forms concentric rings around the axon
Describe the 2 types of Astrocytes and where they are found
Protoplasmic - grey matter - look like clouds with some spindy bits radiating outwards
Fibrous - Look fibrous with defined spindles radiating outwards
Major way to differentiate dendrite from axon?
Rhibosomes not present in axons or axon hillocks, but are present in dendrites - visualized as nissl bodies
What ATPases mediate axonal transport, and in which direction
Kinesin -> anterograde
Dynein -> Retrograde
What type of axonal transport is thought to be responsible for peripheral neuropathies involving degeneration of the terminal ends of axons
Defective anterograde transport -> i.e. cannot transport cytoskeletal or cytosolic proteins and enzymes etc.
= Wallerian Degeneration
What is the Neuropil?
What is the largest neuropil area in the body?
A synaptically dense area
With many dendrites, axons, and some glial cells
But relatively few neuron cell bodies
Brain = neuropil. Largest and highest concentration of synapses out of the whole body.
