cells and signaling in nervous system Flashcards
what is the neuron doctrine
Brain composed of neurons connected by functional space (synapses) that communicate with neurochemical signals
what are the two main parts of neurons
perikaryon and neurites
what are perikaryon
cell bodies (soma) that are metabolic centers
what are neurites
cellular fibers that extend off the soma and conduct electrical signals to the body
how many neurites can a neuron have
1 or many
what are dendrites
branches off the cell body that are the “receptive area”
what are dendritic spines and what do they do
mushroom shaped branches off the dendrite that increase SA and are where other cells contact the cell
what are axons
single neurite that goes from the cell body and conduct electrical signal
what covers axons
mutelin sheath
what are myelin sheath made of and what do they do
fat and protein that cover the axons and insulates the electrical signal
what produce myelin sheath
schwann cells in PNS and oligodendrocytes in CNS
what are presynaptic terminals
bulbs at ends of axons that contain synaptic vesicles to store and release neurochemical signals
what does neuron types depend on
number of neurites originating from the soma
where does the electrical signal travel
dendrite –> cell body –> axon –> presynaptic terminal
what do neurotransmitter receptors do
when they receive neurotransmitters they open up channels for K+ and Na+ to excite or inhibit postsynaptic neuron through electrical charge
differences between neurotransmitters and neuropeptides
both are released from synaptic vesicles
transmitters: small molecules where receptor determines effect
peptides: product of genes (5-30 AA long)
where can neurons receive input
any place along length of terminal
axodendritic synapse
synapse onto dendrite (inc dendritic spine)a
axosomatic synapase
onto cell body
axo-axonal synapse
onto axon (at nodes of ranvier not myelin)
axo synaptic synapse
synapse onto other synapse
nuclei vs ganglia
both clusters of neurons but nuclei in CNS while ganglia outside of CNS
types of neuroglia
macro and microglia
what don’t neuroglia form
synapses
types of macroglia
oligodendrocytes, schwann cells, astrocytes
relationship of oligodendrocyte to axons and why this relationship
1 olig: N axons
1 axon: N olig
CNS has less space than PNS so CNS evolved to have less myelination cells in cranial vault
differences between oligodendroytes and schwann cells
both myelinate
olig - cNS
schwann - PNS
relationship of schwann cells to axons
1 schwann: 1 axon
1 axon: N schwann
differences between myelin sheaths in cns and pns
Sheaths longer and thicker in PNS
types of astrocytes
protoplasmic and fibrous
functions of astrocytes
Provide structural support
Act as glial guides during dev
Maintain ion balance
Recycle neurotransmitters
Blood brain barrier
differences between protoplasmic and fibrous astrocytes
proto –> buchy and branches, grey matter
fibrous –> more fibrous, spindly, robust, white matter, long processes in all directions
what is a subtype of protoplasmic astrocytes and what do they do
reactive astrocytes –> repair damaged neurons by migrating to site of injury and proliferating. act like scar tissue if too much damage
what is glial scarring made of and what can it cause
strong collagen matrix that can cause behavioral changes if too many issues
what do microglia do
immune surveillance of CNS by being mobile cells that activate and invade injured zones to fight infection and neural damage
where do mobile cells exist
Some exist in CNS and are looking around for damage but some are from the blood and differentiate into microglial when they make their way into CNS
where does wallerian degeneration happen
mostly CNS but some PNS
what is wallerian degeneration
axon is cut so distal end of axons degenerates so the neuron dies
how long does wallerian degeneration take
almost 2 days
where does neuron regeneration happen and how does it work
PNS
When axon damaged, schwann cell forms guidance tube to guide the regenerating end of axon to target end so damage is temporary.
differences between schwann and olig relating to regenerating
schwann produce nerve growth factor
olig produce no go factor which inhibits repair factor
where does collateral sprouting happening and what does it do
CNS and PNS
Neighboring neurons form new collaterals that try to reinnervate end organ to fill vacant synapses when neuron dies to retain function
