neurons: cellular and network properties-chp 8 Flashcards
pseudo unipolar neurons
they have a single process called the axon. During development the dendrites fuse with the axon
bipolar neuron
bipolar neurons have two relatively equal fibers extending off the central cell body.
Anaxonic
CNS interneurons that have no apparent axon
look like a star :)
multipolar
these CNS interneurons are highly branched but lack long extensions
slow axonal transport
moves material by axoplasmic (cytoplasmic) flow at 0.2-2.5 mm/day
fast axonal transport
moves organelles at rates up to 400 mm/day
forwards and backward transport
forward (or anterograde) transport:
from cell body to axonal terminal
backward (or retrograde) transport:
from axon terminal to cell body
where are peptides in neurons synthesized and packaged?
they are synthesized on rough ER and are packages by the golgi apparatus
explain the steps of fast axonal transport
1-peptides are synthesized on rough ER and packages by the golgi apparatus
2-fast axonal transport walks vesicles and mitochondria along microtubule network
3-vesicle contents are released by exocytosis
4-synaptic vesicle recycling
5-retrograde fast axonal transport
6- old membrane components digested in lysosome.
where do neurons receive input?
the spines/dendrites
____% or cells in the brain are neurons and _____% of them are Glial Cells
10% neuron
90% glial cells
Which Glial Cells are found in the PNS?
schwann cells
satellite cells
schwann cells
form myelin sheaths and secrete neurotropic factors
satellite cells
support cell bodies
which glial cells are found in the CNS?
ependymal cells
astrocytes
microglia
oligodendrocytes
oligodendrocytes
form myelin sheaths in the CNS
Microglia
modified immune cells-monocytes
act as scavengers
astrocytes
are a source of neural stem cells take up water , K+, neurotransmitters secrete neurotrophic factors help form blood brain barrier provide substrates for ATP production
membrane potential is influenced by:
concentration gradient of ions
membrane permeability to those ions
which channels control ion permeability?
gated channels
mechanically, chemically and voltage
action potentials change resting membrane potential to send signal so they use….
voltage-gated channels
depolarization is a response to membrane potential being more____
positive
How does a cell depolarize?
by opening Na+ gated channels
how does a cell repolarize?
by opening + gated channels but this also causes the cell to hyperpolarize
What causes graded potentials to lose strength as they move through the cell?
current leak and cytoplasmic resistance
the goals of graded potentials is to….
stimulate/open Na+ voltage gated channels to send the signal.
when do voltage gated Na channels open?
at -55 mV
when do voltage gated K+ channels open?
+30mV
why do K+ gated Na channels open?
to repolarize the cell
why does it go to -80 when it is hyperpolarized?
because the reversal potential for K+ is -90 so it can technically go to -90 but it stops at -80
Why cant you get another AP during the absolute refractory period?
because the inactivation gate is closed and incapable of opening until you repolarize to -55 and open the inactivation gate and close the Na+ voltage gated channel. plus you are hyperpolarized so you would need a lot of Na
if you wanted to block pain, how would you do it?
by blocking voltage gated Na channels because they are the initiator
what happens if too much K+ builds up outside our cells?
Constant firing because the blood K+ would be closer to threshold so a stimulus that would have probably been subthreshold would trigger an action potential .
true or false: the more action potentials (higher frequency) the more pain.
true
What influences speed of an action potential?
diameter (the bigger the faster)
resistance of axon membrane to ion leakage out of the cell (myelinated axons are faster)
____ cells in the peripheral nervous system guide the regeneration of cut axons.
Schwann
Schwann cells for a _________ that the axon grows back through
regeneration tube
which cells inhibit regeneration of cut axons in the central nervous system?
oligodendrocytes
which mediate faster responses? ionotropic or metabotropic recepors
ionotropic
Divergent Pathway
one presynaptic neuron branches to affect a larger number of postsynaptic neurons
convergent pathway
many presynaptic neurons provide input to influence a smaller number of postsynaptic neurons.
what is an example of a divergent pathway?
reflex
what is an example of convergent pathways?
reticular activating
what ion(s) can make a synapse excitatory?
Ca2+
an excitatory synapse mainly signals the ____of ____ ions into the postsynaptic neuron
influx of Na+ ions
in inhibitory synapse signals the _____ of____ ions from the postsynaptic neuron or ______
outflow of K+ ions or the influx of chloride ions.
