cells of the nervous system Flashcards
what is the neuron
basic and main structural and functional unit of the nervous system
information processing unit
release chemicals at a synapse - communicate with other neurons
supported by microglia
describe the structure of neurons
more complex than other cells
cellular structure similar between neurons
diversity achieved by where it si found and what it is connected to, arrangement, morphology - some are complex and well ordered, function and how hard they work
vulnerability of neurones
it is the diversity in size, anatomical location, function and how hard they work make vulnerable to degeneration caused by genetics, environment and infection in MS, Alzheimers, parkinsons, ALS
cellular components of neurons and their functions
many mitochondria - high metabolic activity
highly organised cytoskeleton - they’re large and have many processes abundant RER - larger than most cells, processes extend large distances, cells need more proteins
well developed Golgi - protein partly glycosylated, packaged in vesicles and trafficked to distant sites
what type of cells are secretory cells and how does this affect their function
secretory cells
machinery reflects this
describe dendrites
input signals from sensory receptors
spread from soma - branch frequently
large SA - receive more inputs from different places
tree reflects where the inputs are coming from
spines - receive all synapses and connectivity
structure of a pyramidal cell
in cerebral cortex
3 primary dendrites - thick, they branch to secondary and primary dendrites
one axon after axon hillock
what are dendritic spines
one of most plastic areas off nervous system
they withdraw and are made - can see this with a genetic label
they can be destroyed by alcohol and Alzheimer’s
full of mitochondria - supply energy
each large pyramidal neuron has 30-40000spines
spines can have 10 sites of input each
Purkinje neurons
cerebellum
inhibitory neurons
trees are 2D
>80 000 spines - lots of inputs
involved in fine movements eg piano and memory
human cerebellum 15million Purkinje cells
dendritic trees make forest of processes that aaxons link onto
describe axons
conduct impulses away from cell body only 1 per cell emerge at axon hillock - swelling may branch just after leaving the cell body they can link to near cells small compared to dendrites
features of axons
stay the same diameter
intermediate filaments - maintain tensile strength, 5-10um diameter, travel down spinal chord so must be tough
microtubules - transport mitochondria/vesicles to synapse from cell body
myelinated/unmyelinated
myelinated only exposed at node of Ranvier - electrical signal boosted, where Na channels are then have end loop of myelin firmly attached to the axon then K channels
have cable properties - mean there is the same speed of conduction from soma to synapse
describe axon terminals
bouton - endo of axon form swelling
varicosities - axon has multiple points of swelling - pass onto different cells and purkinje dendrites
axons branch extensively close to target - terminal arbor
describe the synaptic structure
vesicles - some translucent, packaged in Golgi - shipped by fast anterograde transport
mitochondria - 45% total energy consumption required for ion pumping and synaptic transmission - sensitive to oxygen deprivation
synaptic density - increased number of proteins responsible for the machinery releasing vesicles and neurotransmitter, and ion channels and pumps in this region
mechanisms to target membrane and dock vesicles with membrane and release contents
describe synaptic organisation
neuron receive many input signals at different strengths - analogue
electrical potential is interpreted
output signal is digital
use inhibitory and excitatory neurotransmitters
competing inputs are integrated in post-synaptic neuron - neuronal integration
most volume of cerebellum is synapse
type of synapse
axo-dendritic - main ones, excitatory
axo-somatic - inhibitory
axo-axonic - modulate signal already travelling down axon
