Lesson 17: Neuroplasticity and Recovery Flashcards Preview

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Flashcards in Lesson 17: Neuroplasticity and Recovery Deck (22)
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1
Q

What is learned disuse?

A

Possible to learn disuse by a very natural process of ignoring the involved limb, impaired speech function, or reduced skill. The brain, like all tissues, adapts to the level of demand put on it

2
Q

Which system regrows, the CNS or PNS?

A

PNS

3
Q

What is the difference in the potential for actual recovery of neurons in the PNS vs. the CNS?

A

Types of neurotropic factors (substances that enhance nerve growth) and the cell types supporting myelination. Oligodendrocytes are not as effective in this role, although they do better outside the milieu of the CNS, showing that they have potential to support recovery when removed from the inhibiting environment of the brain
Thought to be some factors in the CNS that inhibit regeneration that are not present in the PNS and the myelinating cells have a role in this difference

4
Q

What is sparing? It is neuroplasticity?

A
  • Areas responsible for brain functions, which appear initially to have been lost, may have only been compressed and, with time, the neurons not actually “killed” will recover and resume function
  • ## It is not neuroplasticity
5
Q

In sparing, what is the area around a focus of injury, in which the neurons have not been irreversibly damaged?

A

“penumbra” and is the site of this type of “recovery”

6
Q

What is compensation?

A
  • For example with a loss of sensory input, the brain often makes extensive use of vision in place of the lost function
  • It is a common target of rehab to find methods of compensation for otherwise irretrievable functions
7
Q

What is rerouting?

A
  • It can be rerouting of signals along an intact pathway, a neural rerouting
  • There is also a potential shunting or rerouting of circulation to the area of injury to supply cells that have experienced a loss of circulation
8
Q

What are the typical ways of recovering circulation?

A

Reduction in swelling; rerouting of the circulation through anastomosis such as the circle of Willis and improvement in metabolic status

9
Q

What structures are involved as a source of renewal of circulation?
What do they require?

A

Areas of overlap between the cortical blood vessels

These require angiogenesis (new blood vessel growth) and therefore may take time

10
Q

What is transneuronal degeneration?

A
  • When neurons distant to the site of injury lose input, they in turn degenerate, or make connections with other neurons. It may cause an apparent “new” problem.
11
Q

What is an example of transneuronal degeneration and rerouting?

A
  • For example, damage to the cerebellum has been followed by symptoms of problems in the thalamus, one of its major targets. These were due to transneuronal degeneration. However, it is possible to turn this into a good thing using “rerouting”. This takes advantage of the plasticity of neurons to develop new connections and in some cases cause changes in the density of dendrites when new connections form.
12
Q

What is sprouting?

A

This takes advantage of the plastic nature of neurons as they grow new processes, especially additional ends on the axon terminus

13
Q

What is an example of sprouting?

A

PNS: Polio. The anterior horn cell is attacked by the polio virus and dies. Those alpha motor neurons that escape the virus will respond to substances released from the denervated muscle and be induced to sprout at their axon terminus to expand their motor unit size to include the denervated muscle fibres.

14
Q

What is neuroplasticity?

A

A means of recovery in the CNS following brain trauma that could include sprouting, transneuronal degeneration, rerouting possible with some growth, and actual regeneration of new neurons

15
Q

What is Hebb’s Hypothesis?

A

If neuron A releases NT to neuron B at the same time and sufficient membrane depolarization occurs to result in firing of neuron B, then “the neurons that fire together, wire together” meaning that this linked firing results in reinforcement of the neuron A to B synapse and neuroplasticity occurs

16
Q

How does age affect the outcome after injury?

A
  • Usually the younger the individual experiencing the trauma, the more likely their neurons are to recover. It cells are so “young” that they have not differentiated
  • During development, some functions are completed and cannot be revisited. Others may have “windows of opportunity
17
Q

How does time affect the outcome after injury?

A

When trauma is imposed rapidly, the brain has little time to accommodate, whether it is new circulation, accommodation to pressure, or rerouting of the pathways.
If an insult is delivered slowly there is a much better change for the cells to survive and be able to recover their function

18
Q

How does availability of collateral circulation affect the outcome after injury?

A

Some areas of the brain have considerable redundancy of circulation, while others do not.

19
Q

How does the site of injury affect the outcome after injury?

A

Some vital areas are simply vulnerable and when lost, there is no recovery. Others may have redundancy of functions built in to the system.

20
Q

How does use affect the outcome after injury?

A

Use it or Lose it – Transneuronal Degeneration: If the functional level of input is not maintained, neurons earlier in the pathway may be included in the “injury” through disuse

21
Q

How does the potential of the area for forming new junctions affect the outcome after injury?

A

Synaptic strength and dendritic density are terms used to describe this process, which is part of neuroplasticity.
There is an increased use of neurotropic factors as early mediations as a preventative treatment if the damage is addressed early enough

22
Q

What are the important principles about neuroplasticity?

A
  1. Simply repeating an activity is not enough to stimulate neuroplasticity; it needs to be a “shaping” of novel activity that is new to the NS
  2. It is necessary to find the critical time points, the essential conditions and factors involved in stimulating neuroplasticity
  3. There are combinations of effects that need to be worked out. Studying these things one factor at a time may rule out factors that are only effective in combination.