neurons and glia

Question 1

what are neurons?

Answer 1

excitable cells of the nervous system
sense changes, communicate this information and bring about responses in other cells

Question 2

what are glia?

Answer 2

no electrically excitable
4 main types
supporting, nourishing, immune defence and blood brain barrier

Question 3

how do we stain neurons?

Answer 3

nissl staining and golgi staining

Question 4

what is nissl staining?

Answer 4

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)

Question 5

what is golgi staining?

Answer 5

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

Question 6

difference between nissl and golgi staining?

Answer 6

nissl identifies neuro density however golgi identifies neuron structure

Question 7

neuron structure

Answer 7

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

Question 8

unipolar neurons

Answer 8

only have one axonal branch/process (pseduo-unipolar in humans)
sensory neurons in PNS

Question 9

bipolar neurons

Answer 9

two processes: one axon and one dendrite
only in olfactory epithelium and bipolar retinal cells
involved in sensory transmission of special senses

Question 10

multi-polar neurons

Answer 10

most common type
single axon and multiple dendrites extending from the cell body
found throughout the CNS
sensory and motor functions

Question 11

what are the 4 types of glial cells?

Answer 11

astrocyte
oligodendrocytes
microglia
ependymal

Question 12

what are astrocytes?

Answer 12

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

Question 13

how do astrocytes maintain chemical balance in the brain?

Answer 13

astrocytes buffer the release of potassium in the extracellular space using processes warpped arounf the neurons
processes have proteins permeable to potassium

Question 14

how do astrocytes clear neurotransmitters?

Answer 14

specialised proteins restrict the amount of time the neurotransmitter is active

Question 15

gliotransmission

Answer 15

astrocytes detect neurotransmitter from syanpses via receptors
evokes change of intracellular calcium concentration
release of gliotransmitters from glia that effect neurons- modulates synaptic transmission

Question 16

what do gliotransmitters include?

Answer 16

glutamate, d-serine, ATP and taurine

Question 17

what are oligodendrocytes?

Answer 17

in the CNS
single cell can wrap around several axons in different places

Question 18

what are schwann cells?

Answer 18

in the PNS
only in one place on a single axon

Question 19

what do oligodendrocytes and schwann cells do?

Answer 19

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

Question 20

what are microglial cells?

Answer 20

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

Question 21

what are ependymal cells?

Answer 21

ependymal- tightly linked- filter plasma and make CSF
found in choroid plexus at ventricles and have cilia to move CSF