Semester A
Reviewed
Explain the basic structure and general function of ‘the neuron’
structure
1. dendritic spines
increase surface area of post synaptic membranes to hold receptors =
receive input in isolated chemical reactions
2. dendrites (neurites)
similar to axons except may have polyribosomes, usually <2nm and taper
crossing microfilaments, plasticity
3. cell body (aka soma, perikaryon)
20um diam
nucleus (central, 5-10um, double envelope, post mitotic so diffuse
chromatin and don’t divide, stained with nissl)
prominent nucleolus (transcriptionally active)
mitochondrion
neurofilaments - coiled coil 10nm diam = structure
microfilaments - 5nm diam actin dimers, run longitudinally = structure,
movement, shape
nissl bodies - DNA (nucleus) and RNA stained with basic dye (RER clusters
and free ribosomes, large amount RER in comparison to other cells allows
protein production that gives neurones function, distinguish from glia)
all other organelles
4. axon (neurite)
hillock (most Na channels), axolemma membrane, axoplasm inner
Semester A 1
, can be >1m, constant diameter
no RER and few ribosomes (no protein synthesis), different protein
composition of membrane to soma
microtubules = a/b tubulin dimers (globular) polymerise into 20nm diam
tube, regulated by MAPs eg. tau - transport
myelinated = inc conduction velocity, dec in MS
5. telodendria > synaptic terminals (no microtubules, many vesicles, many
proteins covering inner synaptic membrane, many mitochondria) >
synapses
inner transport
anterograde (-→+ synapse) = kinesins (head on tubule, coiled coil and tail
with light chain) = 100-400nm/day for mitochondria and neurotransmitters
anterograde visualisation = soma injection with radioactive AA,
autoradiography
retrograde (synapse +→- ie backwards) = dyneins (head on tubule, light
and intermediate chain base) = 50-250nm/day for aging mitochondria,
endocytic vesicles
retrograde visualisation = enzyme (WGA)HRP selectively uptaken by
terminals and stained OR viruses eg. oral herpes, rabies jump across
synapses and replicate (strong signal amplification)
Be able to identify the different subtypes of neurons and neuroglia and
describe their roles in the nervous system
structure classes (polarity - number of processes/neurites from cell body)
multipolar = ≥3 (dendrites straight off soma), most, eg. lower motor
neurone in spinal cord
unipolar = 1, rare, eg. invertebrates
bipolar = 2, rare, eg. retina
pseudo unipolar = 1 then splits like bipolar, eg. primary somatosensory
DRG
Semester A 2
, dendritic structure = stellate (star) or pyrimidal (long thin)
fibre classes
type I/projection = long axons, extend between brain areas eg. pyrimidal
cells
type II/local circuit = short axons, stay near soma eg. stellate cells
sensory afferents (largest/fastest/myelinated >
smallest/slowest/unmyelinated) letters skin numbers muscle
Ia eg. muscle spindle proprioceptors/Ib eg. golgi tendon organ/Aa eg.
motor neurones in spinal cord
13-20um diameter, 80-120m/s, myelinated, ~7mv/2ms, glutamatergic,
no thermal threshold, Runx3+ and Pvalb+
II eg. secondary spindle afferents/Ab eg. skin mechanoreceptors
(discriminative touch, pressure)
6-12um diameter, 35-75m/s, myelinated, 7mv/2ms, glutamatergic,
Atoh1 Cck and Krt14
Ag eg. g motor neurones (EFFERENT feedback)
Semester A 3
, medium diam and conduction (smaller/slower than a), myelinated
III/Ad eg. touch, fast pain, temp
1-5um diam, 5-30m/s, 1mv/5ms, glutamatergic, myelinated, Ntrk2/TrkB
IV/C eg. slow pain, innocuous temp, olfaction, itch, social touch?
0.2-1.5um diameter, 0.5-2m/s, 0.2mV/40ms, unmyelinated (but still
have schwann cells), peptidergic (CGRP, substance P) or non-
peptidergic (glutamate ), Slc17a8 (VGLUT3)/Th
CNS glia
oligodendrocytes = one myelinates multiple, inhibit axon regen,
regenerated from precursors in ventral ventricular zone spinal cord (target
for MS treatment), identified by expression of Olig2, PDGFR1, ganglioside,
NG2 CSPG
microglia = blood derived (foetal macrophages), pro-inflammatory,
immune, debris removal via phagocytosis (ramified surveillance then
activated by purines from dead cell to retract processes and become
ameboid), neuronal circuit shaping (removing spines/changing synapses)
(stain with Iba1)
ependymal = line ventricles and spinal canal, cuboidal/columnar
epithelium, ependymocytes (cilia/microvilli to circulate CSF), choroid
plexus (specialised cuboidal epi in ventricles, secrete 500ml CSF/day) and
tanycytes (3rd vent/hypothalamus sense gluocse etc, antennae and
neurogenic stem - rarely differentiate but release signals)
astrocytes = fibrous (white, long thin, support axons) or protoplasmic
(grey, branched (stars in dark), homeostasis)
structure/support
extracellular electrolyte homeostasis
energy storage and transport (glucose, glycogen, lactate shuttle,
cholesterol via apoE)
affect endothelial and angiogenic factors to regulate BBB (not form)
glia limitans
Semester A 4
Reviewed
Explain the basic structure and general function of ‘the neuron’
structure
1. dendritic spines
increase surface area of post synaptic membranes to hold receptors =
receive input in isolated chemical reactions
2. dendrites (neurites)
similar to axons except may have polyribosomes, usually <2nm and taper
crossing microfilaments, plasticity
3. cell body (aka soma, perikaryon)
20um diam
nucleus (central, 5-10um, double envelope, post mitotic so diffuse
chromatin and don’t divide, stained with nissl)
prominent nucleolus (transcriptionally active)
mitochondrion
neurofilaments - coiled coil 10nm diam = structure
microfilaments - 5nm diam actin dimers, run longitudinally = structure,
movement, shape
nissl bodies - DNA (nucleus) and RNA stained with basic dye (RER clusters
and free ribosomes, large amount RER in comparison to other cells allows
protein production that gives neurones function, distinguish from glia)
all other organelles
4. axon (neurite)
hillock (most Na channels), axolemma membrane, axoplasm inner
Semester A 1
, can be >1m, constant diameter
no RER and few ribosomes (no protein synthesis), different protein
composition of membrane to soma
microtubules = a/b tubulin dimers (globular) polymerise into 20nm diam
tube, regulated by MAPs eg. tau - transport
myelinated = inc conduction velocity, dec in MS
5. telodendria > synaptic terminals (no microtubules, many vesicles, many
proteins covering inner synaptic membrane, many mitochondria) >
synapses
inner transport
anterograde (-→+ synapse) = kinesins (head on tubule, coiled coil and tail
with light chain) = 100-400nm/day for mitochondria and neurotransmitters
anterograde visualisation = soma injection with radioactive AA,
autoradiography
retrograde (synapse +→- ie backwards) = dyneins (head on tubule, light
and intermediate chain base) = 50-250nm/day for aging mitochondria,
endocytic vesicles
retrograde visualisation = enzyme (WGA)HRP selectively uptaken by
terminals and stained OR viruses eg. oral herpes, rabies jump across
synapses and replicate (strong signal amplification)
Be able to identify the different subtypes of neurons and neuroglia and
describe their roles in the nervous system
structure classes (polarity - number of processes/neurites from cell body)
multipolar = ≥3 (dendrites straight off soma), most, eg. lower motor
neurone in spinal cord
unipolar = 1, rare, eg. invertebrates
bipolar = 2, rare, eg. retina
pseudo unipolar = 1 then splits like bipolar, eg. primary somatosensory
DRG
Semester A 2
, dendritic structure = stellate (star) or pyrimidal (long thin)
fibre classes
type I/projection = long axons, extend between brain areas eg. pyrimidal
cells
type II/local circuit = short axons, stay near soma eg. stellate cells
sensory afferents (largest/fastest/myelinated >
smallest/slowest/unmyelinated) letters skin numbers muscle
Ia eg. muscle spindle proprioceptors/Ib eg. golgi tendon organ/Aa eg.
motor neurones in spinal cord
13-20um diameter, 80-120m/s, myelinated, ~7mv/2ms, glutamatergic,
no thermal threshold, Runx3+ and Pvalb+
II eg. secondary spindle afferents/Ab eg. skin mechanoreceptors
(discriminative touch, pressure)
6-12um diameter, 35-75m/s, myelinated, 7mv/2ms, glutamatergic,
Atoh1 Cck and Krt14
Ag eg. g motor neurones (EFFERENT feedback)
Semester A 3
, medium diam and conduction (smaller/slower than a), myelinated
III/Ad eg. touch, fast pain, temp
1-5um diam, 5-30m/s, 1mv/5ms, glutamatergic, myelinated, Ntrk2/TrkB
IV/C eg. slow pain, innocuous temp, olfaction, itch, social touch?
0.2-1.5um diameter, 0.5-2m/s, 0.2mV/40ms, unmyelinated (but still
have schwann cells), peptidergic (CGRP, substance P) or non-
peptidergic (glutamate ), Slc17a8 (VGLUT3)/Th
CNS glia
oligodendrocytes = one myelinates multiple, inhibit axon regen,
regenerated from precursors in ventral ventricular zone spinal cord (target
for MS treatment), identified by expression of Olig2, PDGFR1, ganglioside,
NG2 CSPG
microglia = blood derived (foetal macrophages), pro-inflammatory,
immune, debris removal via phagocytosis (ramified surveillance then
activated by purines from dead cell to retract processes and become
ameboid), neuronal circuit shaping (removing spines/changing synapses)
(stain with Iba1)
ependymal = line ventricles and spinal canal, cuboidal/columnar
epithelium, ependymocytes (cilia/microvilli to circulate CSF), choroid
plexus (specialised cuboidal epi in ventricles, secrete 500ml CSF/day) and
tanycytes (3rd vent/hypothalamus sense gluocse etc, antennae and
neurogenic stem - rarely differentiate but release signals)
astrocytes = fibrous (white, long thin, support axons) or protoplasmic
(grey, branched (stars in dark), homeostasis)
structure/support
extracellular electrolyte homeostasis
energy storage and transport (glucose, glycogen, lactate shuttle,
cholesterol via apoE)
affect endothelial and angiogenic factors to regulate BBB (not form)
glia limitans
Semester A 4
