_____ bring a cell to threshold while _____ bring a cell further from threshold -
️️EPSPs; IPSPs
Describe the mechanism of fusimotor drive - ️️muscle spindles are parallel to
extrafusal fibres; the extrafusal fibres shorten when they contract, and the gamamotorneuron causes the intrafusa...
OCCTH 585 Neuro
_____ bring a cell to threshold while _____ bring a cell further from threshold -
✔️✔️EPSPs; IPSPs
Describe the mechanism of fusimotor drive - ✔️✔️muscle spindles are parallel to
extrafusal fibres; the extrafusal fibres shorten when they contract, and the gama-
motorneuron causes the intrafusal fibres to contract in order to maintain tension in the
centre of the muscle spindle so it is still able to detect muscle stretch thoughout the
entire ROM
What things determine the type of cell that stem cells differentiate into? (2) - ✔️✔️-
level of hormones (estrogen increases, glucocorticoids decrease)
- environmental factors (in CNS, most often are astrocytes; neurons survive longer in
enriched environment)
Do neurons have to be close to the "free real estate" in order to make new collaterals?
Do they need to already be involved with it? - ✔️✔️no, the closest ones will usually get
there first, but the axons can grow out 1-2cm to form a connection (any further = stuff in
the way, would take too long and die); no
What is dendritic pruning? - ✔️✔️when dendrites with no active synapses are retracted
to reduce the amount of resources wasted to keep those useless dendrites alive;
changes cellular properties (size and shape) and creates as 'loss of real estate',
decreases energy expenditure
What 3 main things is neuroplasticity capable of? - ✔️✔️- changing the properties of
neurotransmission
- changes in cell properties
- structural/ anatomical changes of cells
How does neuroplasticity change the properties of neurotransmission? (2) - ✔️✔️-
change in transmitter size
- change in PSP size or shape
How does neuroplasticity change the properties of cells? (3) - ✔️✔️- size and shape
- electrical properties (resistance)
- "leakiness" of membrane
Information flows through neurons from ____ to ____ in the neuron - ✔️✔️dendrite;
axon
,What is unmasking? - ✔️✔️when an injury, event, or illness eliminates the inputs that a
neuron most commonly responds to (i.e. blue --> blue region of brain), the neuron will
become more responsive to the other inputs on the neuron (i.e. yellow --> yellow region
of brain) and that new representation will increase; is immediate, involves exposure of
pre-existing synapses, and creates functional changes in the cell
What is collateral sprouting? - ✔️✔️when neurons sprout new synapses on bare
dendrites (either after pruning of dead synapses or less used working ones) leading the
cell to become more responsive to those new inputs
What can lead to collateral sprouting? - ✔️✔️more stimulation; higher representation is
driven by high rates of APs
What are the 6 mechanisms of collateral sprouting? - ✔️✔️- growth of new bits
- requires time
- fill vacancy OR push less used synapses out of the way
- activity dependent
- produces functional changes
What signals to other neurons that there is space to form new collaterals and guides
them to it? - ✔️✔️neurotrophin (released by dendritic spines through APs)
What are chemoattractants? - ✔️✔️neurotrophins and other chemical signals that
signal to a neuron to grow their collaterals in that direction
What are chemorepellants? - ✔️✔️chemical signals that signal to a neuron to grow
their collaterals away from that direction
What structures release chemoattractants and chemorepellants? - ✔️✔️guide cells
What is a growth cone? - ✔️✔️a specialized structure at the end of the axon that has
filopodia that branch out in multiple directions to look for chemoattractive and
chemorepellant signals
Are neurons always responsive to guidance molecules? - ✔️✔️no, they are time-locked
based on the developmental clock of the embryo; some guidance molecules can be
both a chemoattractant and a chemorepellant depending on the embryo's current stage
of development
A large chemorepellant signal can lead to ____ ____ ____; exposure can also signal
____________________ - ✔️✔️growth cone collapse; growth of filipodia off growth of
different spots of the neuron
, Where are new neurons produced? (3) - ✔️✔️- subventricular zone (olfactory)
- dentrate gyrus of hippocampus (memory)
- Cerebral cortex
What are neurons and neurogenesis' roles in learning and memory? (3) - ✔️✔️-
undergo synaptic plasticity to retain memory
- can become "locked" for longterm memory
- can be replaced to allow new learning
___-___% of neurons in the hippocampus are replaced _____ - ✔️✔️20-25%; monthly
What types of cells can stem cells turn into? - ✔️✔️- oligodendrocyte
- astrocyte
- neuron
What barriers do we face in attempting to direct stem cells to produce neurons needed
to repair injuries? (6) - ✔️✔️- nervous system laid out first in embryos; difficult to build
around everything else in adults
- difficult to replicate static environment needed for neurons to be generated
- difficult to get cells to go to the repair location (no guide cells)
- migration and differentiation occur simultaneously
- don't integrate well and will eventually die
- if stem cells are poorly activated, a tumor can be created
What is different about mature neurons vs embryonic neurons? - ✔️✔️- many cues no
longer produced
- cells, especially neurons, are no longer responsive
- guide cells no longer exist
What 7 things occur in the nervous system following an injury? - ✔️✔️- terminal
degeneration
- Wallerian degeneration
- myelin debris
- macrophage infiltration
- chromatolysis
- retraction of synaptic terminals
- degeneration
ALL HAPPENS SIMULTANEOUSLY
What is Wallerian degeneration? - ✔️✔️axon distal to injury degenerates because it is
cut off from the cell body
Why is myelin debris created? - ✔️✔️the part of the axon it is on degenerated, so it is
no longer needed
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