neurons and their structures Flashcards
what are the three main functions of neurons
receive information
conduct information
transmit information
what are the two features of output on neurons
synaptic boutons and terminal branches
what are two differences with other cell types
large number of proteins are required to be made, hence rER is enteive ‘NIssl substance’
neurons are secretory cells therfore lot of transcription hence larger nucleus
what are dendrites
an extension of the cell body
what can be found at the base of dendrites
rER and sER
also mitochondria, free ribosomes , microtubules and microfilaments
what are dendritic spines
protrusion on dendritic shaft
synapses form here
what does number of spines represent
influencedby disease and input
what do spines not contain
mitochondria, microtubules, neurofilaments
what are axons
single specialised process but branches at the end generally thinner and longer than dendrites
what are the four parts of axons
initial segment- axon hillock
axon processes
synaptic boutons
growth cones
describe 3 features of initial segment
lacks ribosomes
contains bundles of microtubules and neurofilaments
voltage gated Na channels and other transmembrane proteins
where is initial segment located
ends at start of myelination and is beginning of action potential
describe 3 features of axon processes
has normal organelles but no ribosomes
diameter varies
can be myelinated
what do synaptic boutons contain
neurotransmitter in secretory vesicles, mitochondria but no microtubulues
what does the connecting membrane on synaptic bouton contain
large amount of protein
the post synaptic density- PSD
what are growth cones have the ability for
the ability to be very motile
capacity to detect environmental cues
what happens to growth cone cues
turned into signals that determine rate and direction
what are growth cones important for
development of the nervous system
describe the structure of growth cones (6)
lamellipodia filopodia p-domain t-domain c-domain cones can vary in shape and sizes in these domains
what is lamellipoda
flattened at the tip into a thin fan shaped sheet
what is filipodia
with many very thin spikes radiating forward
what is the p domain
peripheral
lamellipodia and filopodia
what is the t- domain
transition
interface of the p and c domain
what is the c domain
thicker region containing organelles, vesicles
what is present in growth cones
filipodia and lamellipodia
what do filipodia and lamellipodia contain
actin filaments, actin devoid in c domain
describe neurofilaments in growth cones
extend as far as the axon, do not penetrate into lamellae
describe microtubules in growth cones
extend further into the lamellae
what are the three processes of axon growth
protrusion
engorgment
consolidation
what is portrusion
rapid extensions of filipodia / thin lamallae containing aactin
what is engrogment
microtubules invade protrusions brining vesicles and organelles
what is consolidation
actin depolymerises in the neck of the growth cone, membrane shrinks forming cylindrical shaft
what are two problems about having really long neurons
transport reterograde but also local synthesis (i.e. if cut, growth cone still grows)
what are two cues growth cones can respond to
attracted or repelled
what is fasciculation and which neurons undergo it
axons that undergo bundling
guidepost cells
pioneer axons
follower axons
what can chemical signals affect
growth factors secreted by cells
substrates
other cells using adhesion receptors
what are three physical signals
tactile
electric
photonic
what are 5 ways to classify neurons
number of neurites- axons or dendrites number of dendrites type of connections axinal length neurotransmitter released
what are ligand gated ion channels and g protein linked receptors
ionotropic and metabotropic
what is the structure of neuromuscular junction in pns
junctional folds found on the postsynaptic side of the NMJ increase the number of Ach receptors that are exposed to release of neurotransmitter resulting in very efficient transmission
what does removal of neurotransmitter from post synaptic cleft do
prevetns desensitisation of receptor and interference with new incoming signals
what are two mechanisms of neurotransmitter removal from post synaptic cleft
enzymatic degredation
acetylocholinesterase
what is myasthenia gravia
autoimmune disorder
decrease in number of functional Ach receptors in neuromuscular junctions
progressive muscular weakness
