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Synapses, Neuroplasticity
Day 3
129
Anatomy
Graduate
01/21/2015

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Term
Neurons interact with one another at specialized sites called what
Definition
synapses
Term
most synapses in the CNS are what type of synapses
Definition
chemical
Term
what happens at excitatory synapses upon binding of the transmitter substance
Definition
local depolarization of the postsynaptic membrane
Term
what occurs at inhibitory synpases upon binding of the transmitter substance
Definition
hyperpoarlization of the post synaptic membrane
Term
the overall excitatory or inhibitory effect of the postsynaptic neuron depends on what
Definition
summation of postsynaptic responses at its many synapses
Term
how are synapses named
Definition
according to their locations
Term
synapses made by one axon made by one neuron onto the synapse of another neuron
Definition
axoaxonic synapse
Term
synapses that are made onto the soma or cell body of a neuron
Definition
axosomatic synapse
Term
synapses that one neuron makes onto the dendrites of another axon
Definition
axodendritic synapse
Term
the potential across the membrane of an excitatory cell at rest
Definition
resting membrane potential (RMP)
Term
RMP is typically what range, depending on the cell
Definition
-40 mV to -90 mV
Term
If the post synaptic cell is excited what happesn
Definition
an action potential is generated
Term
If the postsynaptic cell is inhibited, what occurs to the action potential?
Definition
none developed
Term
inhibition is what type of process
Definition
active
Term
some neurons fire regularly, the rate of spontaneous firing can be altered by what
Definition
inhibition
Term
Inhibition does not simply result in an ______ of activity
Definition
absence
Term
EPSP
Definition
excitatory postsynaptic potential
Term
EPSP is what type of event
Definition
depolarizing event
Term
EPSP & IPSP have a graded potential meaning what
Definition
they are capable of having an additive effect
Term
action potential may result from _______/________ summation of many ESPSs
Definition
spatial/temporal
Term
cumulative effect from the firing of synapses
Definition
summation
Term
The net effect of many ESPSs may result in what
Definition
production of an action potential
Term
cumulative effect from the firing of many synapses at approximately the same time
Definition
spatial summation
Term
cumulative effect from the rapid repeated firing of a single synapse
Definition
temporal summation
Term
IPSP
Definition
inhibitory postsynaptic potential
Term
IPSPs are what type of event
Definition
hyperpolarizing
Term
bringing the membrane closer to threshold but not necessarily producing an action potential
Definition
Facilitation
Term
Facilitation results from what
Definition
EPSPs
Term
results from volleys of ISPSs, sometimes called depression, may be pre-/postsynaptic
Definition
inhibition
Term
removal of facilitation
Definition
disfacilitation
Term
disfacilitation causes what
Definition
relative hyperpolarization
Term
disfacilitation causes relative hyperpolarization resulting in what
Definition
net inhibition
Term
removal of inhibitory pulses
Definition
disinhibition
Term
removal of inhibitory impulses moves closer to firing threshold, resulting in net ______
Definition
facilitation
Term
Describe recurrent inhibition in terms of axons
Definition
a collateral axon excites an inhibitory interneuron, that in turn inhibits the same and/or neighboring neurons
Term
found throughout the CNS as a means of feedback inhibition to control transmission or inhibit competing impulses
Definition
recurrent inhibition
Term
inhibitory interneuron is excited inhibiting homonymous/synergistic neurons. What type of inhibition?
Definition
autogenous inhibition
Term
what is the feedback system for (golgi) tendon organs
Definition
autogenous inhibition
Term
impulses activating agonist muscles send collaterals to inhibitory interneurons to inhibit antagonists. what type of inhibition
Definition
reciprocal inhibition
Term
reciprocal inhibition is limited to action of what types of neurons
Definition
alpha motor neurons
Term
in reciprocal inhibition, antagonists go flaccid. True or false
Definition
false, antagonists relax
Term
Type of inhibition: Inactivation of calcium channels by another synapse, resulting in less calcium entering, meaning less neurotransmitter is released, meaning a reduced effect on the postsynaptic membrane
Definition
presynaptic inhibition
Term
volitional and reflexive behavior is due to what
Definition
activity of neurons communicating with each other via synapses
Term
within discrete populations of neurons, certain ones will fire as a result of incoming excitatory impulses, and are described as what
Definition
being in the discharge zone
Term
firing of a neuron is related to: 1 of 5
Definition
membrane properties
Term
firing of a neuron is related to: 2 of 5
Definition
size of neuron, the larger it is the more difficult to excite/inhibit
Term
firing of a neuron is related to: 3 of 5
Definition
location of synapse
Term
how is the location of the synpase related the firing of a neuron
Definition
the closer it is to the initial segment, the more effective
Term
firing of a neuron is related to: 4 of 5
Definition
number of competing EPSPs and IPSPs
Term
firing of a neuron is related to: 5 of 5
Definition
relative excitability of the membrane
Term
neurons that are subjected to teh same EPSPs as the neurons in the discharge zone, but do not fire are considered to be in what
Definition
the subliminal fringe
Term
inhibition is often referred to as an increase in what
Definition
subliminal fringe
Term
describe post-tetanic potentiation
Definition
prolonged period of facilitation of synaptic transmission, following repetitive tetanic stimulation of the presynaptic neuron
Term
this effect is related to an increased release of transmitter rather than a change in the postsynaptic excitability
Definition
post-tetanic potentiation
Term
a reduction in response to maintained stimulation
Definition
accomodation
Term
what is it called when the membrane acts as if it is beocming accustomed to the stimulus
Definition
accommodation
Term
accommodation allows the neuron to be more responsive to what
Definition
change in stimulation
Term
describe convergence
Definition
inputs from several interneurons may converge onto one neuron to increase its chances of firing or to provide it with information from different neural systems
Term
input from one area may spread to a larger area (neuron integration)
Definition
divergence
Term
when an impulse excites a neuron, thereby initiating a discharge, setting up a positive feed back loop which continues the discharge long after the original stimulus has occured
Definition
reverberating circuits
Term
what is the difference between an infant's CNS and an adult's CNS.
Definition
functional capacity
Term
Postnatal Maturation of the Spinal Cord-proliferation of ______ root collaterals
Definition
dorsal
Term
proliferation of dorsal root collaterals increases the strength of what
Definition
spinal level reflexes
Term
proliferation of dorsal root collaterals results in ties between what
Definition
afferents, efferents overlying a particular muscle and its synergists
Term
Postnatal Maturation of the Spinal Cord - what undergoes remodeling
Definition
synapses, dendrites
Term
what happens during synaptic and dendritic remodeling, simply?
Definition
morphology and numbers of synapses change
Term
if neurons add dendrites during synaptic and dendritic remodeling, what happens
Definition
increased number of synapses
Term
if neurons lose dendrites during synaptic and dendritic remodeling, what happens
Definition
decreased number of synapses
Term
Postnatal Maturation of the Spinal Cord - continued ________ of the CNS
Definition
myelination
Term
during continued myelination within the CNS, what neuroglia will synthesize several times their own weight of myelin
Definition
oligodendrocytes
Term
during continued myelination within the CNS, what role do Oligodendrocytes play
Definition
synthesize several times their own weight of myelin each day during infancy
Term
During continued myelination within the CNS< any one oligodendrocyte may send out processes to invest segments of how many axons
Definition
15-50
Term
using a part of a body more frequently causes what in terms of cortical representation
Definition
that part is given greater cortical representation
Term
neuroplasticity may include: activation of ______ ____
Definition
silent synapses
Term
what are silent synapses
Definition
neurons previously not active
Term
neuroplasticity may include: increased ______ efficacy
Definition
synaptic
Term
given the same input, a greater number of postsynaptic cells become active after injury, which indicates what
Definition
increased synaptic efficiency
Term
neuroplasticity may include: ______ reorganization
Definition
anatomical
Term
what happens during anatomical reorganization due to neuroplasticity
Definition
collateral sprouts to undamaged synaptic sites, rengeneration or growth of injured axons
Term
Response of Peripheral Nerves to Axotomy: What happens proximal to the lesion in terms of the cut end?
Definition
the cut end is sealed off
Term
Response of Peripheral Nerves to Axotomy: what happens to the distal most part of the axon stump
Definition
rapid degeneration of the distal most part of the axon stump
Term
Response of Peripheral Nerves to Axotomy: What happens if the lesion close to the cell body
Definition
entire neuron may die
Term
Response of Peripheral Nerves to Axotomy: dispersion of rough ER in readiness for protein production
Definition
chromatolysis
Term
Response of Peripheral Nerves to Axotomy: displacement of what to the edge of the soma
Definition
nucleus
Term
Response of Peripheral Nerves to Axotomy: number and diameter of dendrites decreases
Definition
dedifferentiation
Term
Response of Peripheral Nerves to Axotomy: what happens at the cut end of the axon
Definition
sprouting
Term
Response of Peripheral Nerves to Axotomy: what is formed?
Definition
growth cones
Term
terminal degeneration resulting in teh axon distal to the lesion degenerates and is removed
Definition
wallerian degeneration
Term
Schwann cells phagocytose the presynaptic element of the neuromuscular junction is an example of what
Definition
wallerian degeneration
Term
fine connective tissue sleeves that surround each axon
Definition
endoneurium
Term
what purpose do the endoneurial tubes serve
Definition
can serve as guides for regenerating axons
Term
what happens to the endoneurium and basement membrane of axolemma during wallerian degeneration
Definition
show little change
Term
regeneration of peripheral nerves begins with what
Definition
degenerative changes
Term
regeneration of peripheral nerves: degenerative changes represent an early preparation for what
Definition
regrowth of the peripheral elements of the nerve
Term
what are the two factors that influence peripheral nerve recovery
Definition
site of injury, extent of trauma
Term
How does site of injury influence the regeneration of peripheral nerves?
Definition
proximal injuries often result in neuronal death
Term
What are the terms used to describe the severity of a peripheral nerve injury
Definition
neurapraxia, axonotmesis, neurotmesis
Term
a transient nerve block, usually caused by pressure. Loss of function is probably related to ischemia, full functional recovery is expected
Definition
neurapraxia
Term
axons are severed, but the connective tissue ensheathing them remain intact. Type of lesion occurs in crush and traction injuries.
Definition
axonotmesis
Term
Good recovery of function may be expected because the nerve fibers maintain their normal anatomical relationships as they regenerate
Definition
axonotmesis
Term
Regenerating axons may grow how much per day
Definition
1-2 mm
Term
a complete sectioning of the gross peripheral nerve. Functional recovery is dependent upon accurate surgical re-approximation of the cut ends of the nerve trunk
Definition
neurotmesis
Term
What can happen to denervated muscle fibers, when some motor fibers are lost
Definition
may be adopted by regenerating nerve fibers
Term
when regenerating nerve fibers adopt denervated nerve fibers what happens
Definition
some motor units may increase in size
Term
What happens when a motor unit increases in size
Definition
may contribute to the decrease in the fine coordination of affected muscles
Term
a normal reduction in the input to a neuron alters its morphology, leading to what happening to the dendritic tree
Definition
atrophy
Term
with minor loss of input leads to what kind of changes occur to the dendrites
Definition
minor changes to the dendrites
Term
dendrite shrinkage is specific to what
Definition
region denervated
Term
With severe loss of a large part of the neuron's afferents, what happens to the denervated neurons
Definition
total degeneration, no part of it survives
Term
the morphology of a neuron is plastically matched to what
Definition
its input
Term
the morphology of a neuron is plastically matched to its input, meaning what
Definition
if there is little significant input, the neuron dies
Term
process whereby an uninjured cell dies in consequence of injury to its afferent neurons
Definition
transneuronal degeneration
Term
a transneuronally degenerated cell will in turn deprive its target neuron(s) of what
Definition
its/their input
Term
What happens to a cell with a damaged axon?
Definition
depends on the damage, loss of a small part of the axonal tree has no great effect on the cell
Term
if the damaged part of the axon is considerable, the cell lacks some vital signal from its target and it shuts down
Definition
retrograde degeneration
Term
if the degenerated cell was part of a closed circuit so that its afferents have no other target neurons what will happen
Definition
suffer from deprivation of vital signal from their target and die
Term
retrograde degeneration in a closed circuit can result in what
Definition
transneuronal degeneration of successively earlier cells in the pathway
Term
transneuronal degeneration as a result of retrograde degeneration may present with what clinical symptoms
Definition
result of loss of these secondarily damaged cells than of the original lesion
Term
if part of the total input to a nucleus is lost what happens
Definition
surviving fibers replace them
Term
if part of teh total input to a nucleus is lost, surviving fibers replace them, if teh fibers are from the neighbors from the lost input, what is this called?
Definition
reactive synaptogenesis
Term
if part of the total input to a total nucelus is lost, surviving fibers replace them, and fibers come from outside the immediate region of damage, what is this caleld
Definition
axonal sprouting
Term
In topographically precise circuits, where the position of a fiber in a tract is part of the information conveyed by that fiber, replaced synapses may what
Definition
blur the acuity of the system, perhaps increasing the handicap
Term
In circuits where topographical relations are uninformative, replacement of a lost fiber by its neighbors may what
Definition
successfully restore function
Term
key points of plasticity of the CNS: 1 of 3: developmental changes
Definition
postnatal changes
Term
key points of plasticity of the CNS: 2 of 3. ______-induced plasticity of the brain
Definition
function-induced plasticity of the brain
Term
key points of plasticity of the CNS: 3 of 3. plasticity and the Physical therapist
Definition
clinical implications of neural plasticity
Term
key points of plasticity of the PNS: 1 of 4. response of peripheral nerves to ______
Definition
axotomy
Term
key points of plasticity of the PNS: 2&3 of 4. changes due to damage to a cells _________ or ________
Definition
afferents, output
Term
key points of plasticity of the PNS: 4 of 4. on the topic of neighbors
Definition
changes due to damage in neighboring cells
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