6. Nerve structure Flashcards
Where do neurones receive impulses
dendrites and cell body (perikaryon)
what is a perikaryon
cell body surrounded by cytoplasm
where do neurones send impulses through
axons
specialised contact sites between nerve cells
synapse
terminal boutons of axons are in close contact to target cell
how do neurones adapt
strengthening or weakening synpases
altering branching
allows us to learn and memorise
what is between the terminal bouton of an axon and target cell
synaptic cleft
what is stored in terminal boutons
vesicles containing NTs
what happens at the post synaptic side
they have ion channels that open when NTs are bound to binding site
creates a mini current
synaptic transmission is
unidirectional and highly specific
synaptic junction in EM
electron dense layer on postsynaptic side
mitochondria provide ATP for vesicle recycling and NT synth
afferent
neurone impulses along dendrite towards cell body
efferent
neurones convey impulses away from cell body
shapes of neurones
multipolar
bipolar
pseudo- unipolar (simple reflex- max speed)
very large SA:V
Nissl bodies
dark dots in cytoplasm
aggregation of RER towards dendrite
- maintain large membrane area
Why is the nucleus in nerve much larger than nuclei of surrounding nuclei but contain same amount of DNA?
a lot more space required for RNA processing
transport system of neurones
rails: microtubuli and neurofilaments
vehicles: kinesis and dynein
axoplasmic flow
oligodendrites
make myelin (40-50 sheaths) (myelin have saltatory conduction)
myelin sheath
are eletrical insulators
formed by oligodendrites or schwann cells in PNS
Glial cells
astrocytes
cover all surfaces of neurone that are not occupied by synapses or myelin
touch other glial cells, capillaries and neurones
take up nutrients from capillaries and provide to neurones
form BBB and seal on CNS surface
capable of mitosis: brain tumours usually glial origin
no cytoplasm
function of glial cells
support neuronal architecture
aid in repair
support in functioning/ metabolism
defence
Microglia cells
immune system of CNS
release cytokines if they detect infectious agents or dead cells
phagocytose and act as local APC
maintain and remodel CNS (eliminate under used synpases)
PNS peripheral nerve
nerve fibre bundles: small nerves, one fasicle Epineurium: dense collagenous tissue holds large nerves together- several fascicles
CNS: efferent neurones
perikarya in CNS, axons in PNS
CNS: afferent neurones
cell bodies and dendrites in PNS
axons in CNS
gangla
clusters of PNS perikarya
clusters of CNS cell bodies
nuclei
grey matter
clusters of neurones (perikarya and some glial)
white matter
nerve connections (axons and dendrites), mostly myelinised
PNS:Perineurium:
sheath with flat cells of epithelial character with collagen fibres between them. bundles axons into fasicles
PNS: endoneurium
loose connective tissue between axon/ dendrite within a fasicle
satellite (glial) cells
support cells for PNS ganglia
PNS: anatomical nerves
bundles of nerve extensions (axons, dendrites), held together by epineurium, perineurium and endoneurium
PNS: Functional nerve cells in vertebrates
are always fully covered by contacts to other neurons or glial cells. They cannot exist without them.
schwann cells PNS
create one myelin sheath per cell
or wraps itself around unmyelinated nerve extensions
