anatomy of a neuron Flashcards
what are the main cellular components of the prototypical neuron?
dendritic tree- receive incoming signals
soma- metabolic centre, gene expression and protein synthesis
axon hillock- initation of AP
myelin
node of ranvier
axon- propagation of AP
axonal arbour- contains presynaptic bouton for transmission
cerebellar purkinje cell structure
- cell body- large and tree like, spherical
- dendritic tree- elaborate, fan-shaped dendritic tree that extends into the molecular layer, creates very large surface area
3, axon- projects to deep cerebellar nuclei
function of cerebellar purkinje cell
intergration station- lots of info coming from different places
principal output neurons of the cerebellar cortex and play a key role in regulating motor movements and maintaining fine motor skills
found in middle layer of cerebellum
axons vs dendrites in dissociated hippocampal neuron
- dendrites tend to be thicker than axons in an individual neuron
dendrites have spines, though not always (aspiny neurons are
inhibitory; spiny neuron can be exitatory or inhibitory) - molecular makeup is different, they express different cytosketetal proteins
- both are electrically active
how can we split neurons into classes?
- excitatory or inhibitory
- number of neurite extensions
- stellate and non-stellate multipolar cells
- communication distance
example of excitatory neurons
glutamatergic
example of inhibitory neurons
GABAergic
are all pyramidal cells inhibitory or excitatory?
excitatory
how can we class neurons by extensions?
multipolar
bipolar
pseduo-unipolar
structure of stellate cells
star-like form that have multiple dendrites that emerge randomly from the soma
examples of stellate cells
thalamic nuclei
inferior olivary nucleus neuron
large reticular formation
is the thalamic nuclei a relay or intergration centre?
intergration, short dendrites and axons close together, a lot of them
where do you find the cell bodies/apical dendrites of cortical pyramidal cells?
layer 5 and 3
why do cortical pyramidal cells have long apical dendrites?
axons are coming from other pyramidal cells
TF different parts of apical dendrites can pick up connections from different parts of the brain
TF synaptic integration
what are the parts of a pyramidal cell?
tuft
apical
soma
basal
connections in the hippocampus
dentate gyrus connects to CA3 connects to CA1 that connects to the subiculum
function of inhibitory interneurons (stellate)
regulate function and excitatibility of pyramidal cell excitatory neurons
cut off information by synapsing at certain points of apical dendrites
roles on network modulation
how can information in the pyramidal cell be blocked?
information from tuft can be blocked by inhibitory interneurons as they are above
soma cannot be blocked as it is underneath
what are local circuit neurons?
neurons with short axons that do not extend beyond the vicinity of the cell body (e.g stellate cells in the cortex and sub-cortical regions)
what are projection neurons?
neurons with long axons that extend from one part of the brain to another (principally pyramidal cells in the cortex; other cell types in the sub-cortical grey matter)
retrograde neuronal tracing steps
1.inject dye at axonal arbour
2. dye is transported in retrograde direction (backwards)
3. soma is stained
example of retrograde neuronal tracing
injecting dye into somatosensory cortex causes visible dye in the thalamus (cell bodies of 3rd order neurons)
CTB (cholera toxin B labelled with GFP) injection
evidence for interhemispheric communication
stains in contralateral cortex via corpus callosum
using HSV (herpes simplex virus) as a retrograde tracer
see all the cells projected from the injected area not the area itself
e.g if you inject the auditory cortex there is dye in the secondary and contralateral cortex and medial geniculate body
what are multipolar neurons?
one axon and multiple dendrites
found in CNS
typically motor neurons (e.g somatic motor neurons)
what are bipolar neurons?
one axon and one dendrite
found in sensory systems like retina of eye and olfactory system
what are pseudo-unipolar neurons?
single axons that divides into 2 branches
have one peripheral terminal and one CNS terminal
found in PNS (particularly dorsal root ganglion)
sensory functions like temperature, touch and pain
difference between pyramidal and stellate cells
both interneurons
pyramidal= long apical dendrite and several basal dendrites
stellate= star shaped
pryamidal= layer 3 and 5 of cortex (motor, prefrontal & hippocampus)
stellate= layer 4 (visual and sensory)
pyramdial= excitatory
stellate= inhibitory
what is retograde neuronal tracing?
maps the pathways of afferent (incoming) neural connections to a specific neuron or group of neurons
this method allows researchers to study the origin of inputs that synapse onto a particular target neuron
