Cellular organisation of the nervous system Flashcards
What did Golgi invent, and what did this allow?
a silver stain that allowed the staining of entire neurons (before this point only the cell bodies had been visualised under a microscope). It therefore allowed visualisation of neurites (processes)
What was the name of Golgi’s theory?
reticular theory
what was reticular theory?
that neurites (dendrites and axons) were fused together
Is reticular theory correct?
no (we now know that it is false)
Who used Golgi’s stian to make big discoveries?
Cajal
What was the name of Cajal’s theory?
the neurone doctrine
what did the neurone doctrine state?
that neurones are distinct cells (not fused together) which communicate by contact
Has well as the neurone doctrine, what else did Cajal find? (2)
neurons have a preferred direction in which they transmit information and that they don’t make connections at random (they only contact certain other neurones at particular points)
In more recent times, what 3 new technologies have allowed better understanding of the cellular structure of the nervous system?
- electron microscope
- fluorescence labelling techniques
- confocal microscopes
what did the development of the electron microscope allow?
the visualisation of cell ultrastructure (confirmed the existence of synapses)
What’s the disadvantage of Electron microscopes?
cells have to be dead to use this technique
What’s the principle of fluorescence labelling techniques?
- a selective antibody/ drug is tagged with a fluorescent label
- add tissue and allow to bind strongly to target protein
- wash off any free, labeled antibody/drug
- imaging to show fluorescence- distribution of binding
What’s the disadvantage of fluorescence labelling techniques?
it’s limited by the range of antibodies available
What is a confocal microscope?
uses lasers, high sensitivity cameras and imagine software to examine live cells/ physiology
what’s the disadvantage of a confocal microscope?
its resolution isn’t very high
What are the 2 major cell types of the nervous system?
Glia and Neurones
are there more glia or neurones in the brain?
it varies- they outnumber eachother at different regions
what’s the primary role of the glia?
to support neurons
what’s a major difference betwen glia and neurons?
glia can divide- neurons can’t
What are the 5 types of glia?
Astrocytes Oligodendriocytes Schwann cells Microglia Ependymal cells
What type of glia are the majority of glia?
astrocytes
What shape are astrocytes?
star
spatially what do astrocytes do?
fill space between neurons
what’s the role of astrocytes?
regulation composition of Extracellular fluid (may also have an important role in directing the proliferation and differentiation of neural stem cells)
Generally, what do oligodendrocytes and schwann cells do?
myelinate axons of neurons
Which part of the nervous system are oligodendrocytes found?
CNS
Do oligodendrocytes have 1 or many axons?
many
which part of the nervous system are schwann cells found?
PNS
do schwann cells have 1 or many axons?
one
What do microglia do?
They act as ‘brain scavengers’
have a phagocytic/ immune function
can microglia migrate?
Yes
what do ependymal cells do?
line ventricles and direct cell migration during development of brain
what do ependymal cells look like?
epithelial cells
What makes neurones highly polarised, generally?
large differences between the axons and dendrites (att either end)
generally, what do axons do?
propagate info.
generally, what do dendrites do?
receive info
what important organelles do axons contain? (1)
synaptic vesicles
What important organelles do dendrites contain (3)?
ER, Golgi and ribosomes
describe axon branches
long, untapered
describe dendrite branches
short, tapered
are axons myelinated?
yes
are dendrites myelinated?
no
do axons have nodes of ranvier?
yes
do dendrites have nodes of ranvier?
no
what can neurons trigger?
APs (action potentials)
do dendrites have Ca2+ channels?
yes
do axons have Ca2+ channels?
no
Do dendrites have ligand gated ion channels?
yes
do axons have ligand gated ion channels?
no
do dendrites have Na+ and K+ channels?
no
do axons have Na+ and K+ channels?
yes
do dendrites have GPCRs?
yes
do axons have GPCRs?
yes
what’s the purpose of the neuronal cytoskeleton?(3)
gives structural support, transports cargo from axons to dendrites, tethers components at membrane surface
what are microtubules made up of?
neurofilaments
what are neurofilaments made up of?
microfilaments
describe microtubules (structure/role etc.) (5)
- run longitudinally down axons and dendrites
- big + wide
- made of tubulin polymers
- role: structure/ support
- contain kinesin and dynein
Describe neurofilaments (structure/role etc.) (4)
- 10nm wide
- filamentous
- made of protein threads
- role: mechanistic strength
Describe microfilaments (structure/role etc.)
- 5nm wide
- tethered to membrane
- made of actin polymers
- role: mediate shape change
What are the 3 main structural classifications of neurons?
- unipolar
- bipolar
- multipolar
what are the 3 functional classificatiosn of neurons?
- sensory
- motor
- interneurons
what are interneurons?
neurons that join sensory and motor neurons (between them)
What does proximal dendrite malformation correlate well with?
severity of mental retardation
what is believed to cause proximal dendrite malformation?
impoverished environment during ‘critical period of brain development’
what nervous system problems are related to Alzheimers?
dead and dying neurons (neurofibrils) which form plaques
