neurons and glia Flashcards
what are neurons?
excitable cells of the nervous system
sense changes, communicate this information and bring about responses in other cells
what are glia?
no electrically excitable
4 main types
supporting, nourishing, immune defence and blood brain barrier
how do we stain neurons?
nissl staining and golgi staining
what is nissl staining?
nissl staining highlights the rough endoplasmic reiticulum and ribosome rich regions
uses basic dyes like cresyl violet and thionin that are attracted to rRNA and nucleic acids
predominantly highlight neuronal cell bodies (soma) as they have lots of RER
good for distinguishing neurons from glia (more RER in neurons)
what is golgi staining?
uses silver nitrate based stain
provides a detailed image of individual neurons including dendrites, axons branches and synaptic terminals
it does not stain all neurons in a tissue
difference between nissl and golgi staining?
nissl identifies neuro density however golgi identifies neuron structure
neuron structure
cell body (soma)
nucleus
mitochondria, ER etc
cytoskeleton- microtubules, microfilaments and nanofilamemts (provide structure and determine shape of neuron, also transport molecules)
dendrites- synaptic input from other regions
axon hillock (initial segment)- specialied region at start of axon that initiates action potential
axon- conducts action potential
myeline sheath- made by oligodendrocytes/schwann cells
nodes of ranvier- gaps between sheath
axon terminal (bouton)- site of communication to next cell
unipolar neurons
only have one axonal branch/process (pseduo-unipolar in humans)
sensory neurons in PNS
bipolar neurons
two processes: one axon and one dendrite
only in olfactory epithelium and bipolar retinal cells
involved in sensory transmission of special senses
multi-polar neurons
most common type
single axon and multiple dendrites extending from the cell body
found throughout the CNS
sensory and motor functions
what are the 4 types of glial cells?
astrocyte
oligodendrocytes
microglia
ependymal
what are astrocytes?
star shape in CNS
many processes (not axons or dendrites)
formation and maintenance of the blood brain barrier
closely associated with neuronal cell bodies, dendites and synapses
maintain chemical balance of extracellular fluids
how do astrocytes maintain chemical balance in the brain?
astrocytes buffer the release of potassium in the extracellular space using processes warpped arounf the neurons
processes have proteins permeable to potassium
how do astrocytes clear neurotransmitters?
specialised proteins restrict the amount of time the neurotransmitter is active
gliotransmission
astrocytes detect neurotransmitter from syanpses via receptors
evokes change of intracellular calcium concentration
release of gliotransmitters from glia that effect neurons- modulates synaptic transmission
what do gliotransmitters include?
glutamate, d-serine, ATP and taurine
what are oligodendrocytes?
in the CNS
single cell can wrap around several axons in different places
what are schwann cells?
in the PNS
only in one place on a single axon
what do oligodendrocytes and schwann cells do?
produce myelin sheath
myelin aids the propogation of neural signals along myelinated axons
gaps between myelin segments enables the neuron to conserve resources by having ion channels and pumps concentrated in the myelin gap
what are microglial cells?
closely related to macrophages (WBC)
ingest pathogens and dead cells- found near sites of inflammation and trauma
also involved in the elimination of parts of neurons- move around and detect what needs removing
what are ependymal cells?
ependymal- tightly linked- filter plasma and make CSF
found in choroid plexus at ventricles and have cilia to move CSF
