BMS11004 WEEK 1 - WEDNESDAY, THURSDAY Flashcards
neurons structural components and function, methods of visualising neurons, neuronal classification, glial cells, myelins
outline main role of neurons
excitable cells conducting impulses, to integrate and relay info within neural circuit
outline main role of glial cells
supporting cells, surround neurons, glue, maintain homeostasis, protection, assist neural function
explain what neural circuits are
join together to form neural systems
made up of neurons and glial cells
what does nissel staining show
distinguish between neurons and glia, stains cell nucleuolus. darker circles are glial cell nucleolus, dark circles with surrounding purple are neurons
bind to negative charge (so bind to RNA) so only stain soma
neuron has nissl bodies allowing visualisation of variation in size, density and distribution
name the 4 main compartments of a neuron
- soma/perikaryon
- dendrites
- axon
- presynaptic terminal
what does golgi (camillo) stain do
small % silver chromate to show soma, processes
doesn’t show all neurons - unknown why
Cajal used this to map out parts of brains and neurons
name 3 components of cytoskeleton
microtubules, microfilaments, neurofilaments
what are microtubules
longitudinally down neurites, hollow tube composed of polymers of tubulin
what is axon hillock
thick lump bit at top of axon
what is role of axons initial segment
important specialised area in generation of AP
what are axon collaterals
branches off main bit of axon (often at right angle), targets other neurons
what do axons with “many levels” have
high levels of divergence of signals - wider spread of signals, instead of just relay between 2
do axons have ribosomes
no rough ER (no ribosomes, no RNA so wont show on nissel stain)
give the length and diameter of axons
length: <1mm to >1m
diameter: 1um-25um
what is immunohistochemistry relating to axons
using antibodies (proteins specific to proteins) which may recognise sodium channel, then secondary antibody specific to primary antibody, with fluroescent secondary antibodies “tags”
very high v/gated Na+ channel density in axon initial segment as needed to activate AP
give key features of presynaptic terminals
no microtubules, vesicles, many mitochondria, specialised receptor proteins on membrane, often branching to allow signal amplifications
outline boutons en passent
“buttons in passing”, terminals placed along an axon
what is axoplasmic transport
movement of material down axon, as cytoplasm of axon doesn’t have ribosomes so axon proteins need to be synthesised in soma and shipped down axon
what is fast axoplasmic transport for and how far do they move
radioactive amino acids, 1000mm per day
what is anterograde axoplasmic transport
move from soma to terminal
vesicles have proteins, eg: kinesin bound to them and use ATP to help them ‘walk’ microtubule down to temrinals
what is retrograde axoplasmic transport
move from terminal to soma, eg: by dyenin
can be manipulated to study brain connection
inject tracer into muscle, taken up by presyn terminals and move back via dyein to soma. take samples and see where tracers are to find soma
outline dendritic arbour
dendritic trees made from dendritic branches, allowing signal convergence (gathering signals from different axons and integrating to send to soma)
give roles of dendritic spines, what happens with abnormalities or if not being used
isolate chemical reactions, plasticity, abnormalities can cause cognitive impairment, if less activity coming from synaptic terminal then dendritic spine lost
name a nissl stain, and what it stains
cresyl violet
neurons, glia and cytoarchitecture
what can electron microscopes study
synapses and organelles
name 4 methods of structural neuronal classification
number of neurites
dendritic geometry
connection/projection
axon length
give 2 methods of classifying neurons by gene expression
underlying structural differences
defines NT expression: inhibitory/excitatory
neuronal classification: name 3 categories by neurites number
unipolar, bipolar, multipolar
neuronal classification: explain unipolar
peripheral process is part axon too, small area for receiving inputs, reliable info relays
includes pseudounipolar
neuronal classification: what is pseudounipolar
eg: dorsal root ganglion, 1 neurite out of some that splits and has peripherally projecting and central projections. when sensing stimuli, peripheral sends info straight from peripheral to central
neuronal classification: outline bipolar
one dendrite come off one side, axon off other. only has small dendritic area at end so less area for receiving synaptic input (but highly specialised function), reliable relay of info eg: retinal bipolar cells
neuronal classification: outline multipolar
still only one axon
can branch or have collaterals, but has dendrites coming off all sides of soma, with dendritic arbour
receives around 150,000 contacts
high level of convergence
most of brains neurons
eg: cerebellar purkinje cell
dendritic geometry classifications- explain stellate cell
star shaped dendritic arbours
dendritic geometry classifications- explain pyramidal cells
distinct atypical (long process coming off soma, splitting into tree) and basal (coming off around soma) dendritic trees
pyramidial shaped soma
allow integration of info
explain what classification by neuron projections mean
classify neurons depending on whereabouts they project (sensory, motor, interneurons)
neuronal projections classification- explain sensory
SNS- afferent carry sensory signal to CNS, efferent carry motor from CNS to skeletal muscle
ANS- afferent carry sensory signal from internal organ to CNS, efferent carry motor from CNS to internal organ
outline what sympathetic efferent nerves are, where do they project from/to
autonomic motor nerves, project from CNS in lumar and thoracic spinal cord region
outline what parasympathetic efferent nerves are/do
autonomic motor nerve, project from brain and sacral region of spinal cord
explain afferent+efferent
afferent = toward CNS
efferent = away from CNS
outline what interneurons are
largest class, dont leave CNS, integrate neural activity in brain structure, stay in structure alongside soma
IN COMPARISON, to: relay/projection neurons connect brain regions, axons leaving soma area to go somewhere else in the nervous system
explain knock-out gene-expression
manipulating neurons to genetically fluoress specific colour based on their gene expression
use genetics for mapping projections
eg: using GFP
name 3 cell body shape classifications
ovoid
fusiform
triangular
what are golgi type 1/2
golgi type 1 = long axon
golgi type 2 = short axon
what are glia
fills in space around neurons, can proliferate during life
name glial cells involved in homeostasis, for CNS, PNS and ENS
CNS = astrocytes
PNS = satellite cells
ENS = enteric cells
what is ENS
enteric nervous system, around gut
what glial cells are myelinating cells in CNS and PNS
CNS = oligodendrocytes
PNS = schwann cells
what glial cells are phagocytic in CNS and PNS
CNS = microglia
PNS = schwann cells and macrophages
outline role of astrocytes
regulate chemical content of extracellular space (maintain ion level, pick up excess NT, actively remove NT via specialised proteins in membranes)
buffer extracellular potassium
forms BBB
neurovascular coupling to change blood supply to neuron
fence in neurons, cuff around NoR, ensheathe synapse and dendrite
outline structure of astrocytes
tripartite synapse
NT receptors which trigger electrical/biochem events within cell
spatial domains
unique GFAP markers for immunohisochemistry (allowing neurons to be identified, green tag)
what is role of astrocytes in glycogen/glucose involvement
when not enough glucose an astrocyte act as glycogen store, breakdown glycogen to ATP for 5-10min supply
needed for fuelling ion movement, walking kinesin along microtubule
metabolise glycogen and supply lactate
have processes surrounding blood vessels to take up glucose and convert to glycogen if needed
explain role of microglia
macrophages of CNS, phagocytosis, tissue survelliance, when in inactive form can sense apoptois and become activated, then phagocytic
allows BBB- immunologically privileged site
outline structure of microglia
small rod shaped soma, with many extending symmetrical processes to search for infection
what is a current research focus on microglia
potential harmful role for neurodegenerative disease, roles in cell death regulations
outline function of oligodendrocytes
form CNS axon myelin sheath
outline structure of oligodendrocytes
single sheet of ODC membranes wraps around 40-50 axon
can have 15-30 priocesses extending from soma
outline role of schwann cells
form PNS myelin sheath via oligo cytoplasms wrap multiple time around axon and cytoplasm being squeezed out of layers via compaction
maintains contact with glial cells for nourishment
guide axonal regeneration post damage (why only occur in PNS)
