Histology Flashcards
Role neurons
Process, transmit info
Electrically excitable
2 types nerve cells
Neurons
Neuroglia (glial cells)
Role of glial cells
Nourish, support protect neurons
Definition of a nerve
A bundle of 1 or more neurons
Neurons consist of
Cell body Dendrites Axon Myelin sheath Terminal endings
Neurons possess electrical excitability what does this mean
The ability to make action potential
Nerve stimulus definition
Anything able to trigger generation of action potential in a neuron
Can be internal/external
Neurons: cell bodies are known collectively as
Grey matter of NS
Collections of cell bodies are referred to as
Nuclei/centres in the CNS
ganglia in the PNS
Axons determine nerve length, vary from
<1mm CNS to 1m sciatic nerve
Function axon
Carries nerve impulses to another neuron away from body
Axon covered by a membrane called
The axolemma
The ends of axons are called
Axon terminals
Axon bundles are called
Tracts in CNS
Nerves in PNS
What makes up white matter of NS
Axons and dendrites
What are dendrites
‘Little trees’
Receiving end of neuron
What is myelin sheath
Multi layered lipid & protein covering around the axons
Myelin sheath formed by what in embryo
Neuroglia/ glial cells
Myelin atom continues through childhood and peaks in
Adolescence
Covered axons are termed
Myelinated
3 functions myelin sheath
Insulates axon (covers axolemma)
Regeneration of axons in peripheral NS
Increases speed of nerve impulse conduction (by forming gaps)
Neuroglia also known as
Glia
Glial cells
Can neuroglia multiply & divide
Yes
Unlike neurons
Situation of neuroglia
Surround and bind neurons
Size/no neuroglia compared to neurons
Far smaller
3-50 times as many
What will glia do after trauma
Fill spaces left by damaged neurons
- malignant growth of tumours
4 functions of Glia
Surround neurons and hold them in place
Supply nutrients/oxygen to neurons
Insulate one neuron from another
Destroy pathogens, remove dead neurons
4 functions neuroglia
Surround Neurons, hold in place
Supply nutrients/oxygen to Neurons
Insulate one Neurons from another
Destroy pathogens and remove dead Neurons
Where are Schwann cells
PNS
Where are oligodendrocytes
CNS
4 types neuroglia in CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
2 types neuroglia PNS
Neurolemmocytes (Schwann cells)
Satellite cells
Describe Astrocytes
Star shaped with breaching processes
In CNS
2 functions Astrocytes
Hold Neurons to their blood supply
Contribute to blood brain barrier
Describe oligodendrocytes
Smaller than Astrocytes
In CNS
Role of oligodendrocytes
Form, maintain myelin in CNS
Similar role to Schwann cells in PNS
Microglia derived from what
Monocytes migrate before birth
Where are microglia found
Near blood vessels in CNS
Also mobile in the brain
What do microglia do when brain is damaged
Multiply
What else do microglia do
Phagocytic - clean up
Describe ependymal cells
Where are they found
Endothelial and epithelial cells which line walls of
4 ventricles of the cerebrum
Central canal of spinal cord
CNS
What do ependymal cells make
How is it circulated
Cerebrospinal fluid CSF
Beat their cilia to circulate it
What do Schwann cells produce
Myelin sheaths around neurons in the PNS - specifically the Axons
Describe myeline sheath
Multi-layered lipid and protein covering
Role of myelin sheath
Insulates axon
Increased speed of nerve impulse conduction
Covered axons are termed
Myelinated
Dendrite connections and most myelination is finished by what age
3
Malnutrition in infancy causes irreversible damage
Gap between Schwann cells along a neuron called
Node of ranvier
Function of nodes of ranvier
Increase speed of nerve transmission
