Ch. 4: Neuroplasticity

Question 1

What is “Plasticity” in the brain?

Answer 1

• Brain can change to be better or worse
  
  • Ex: change in # or strength of connections

Question 2

What is Habituation?

Answer 2

• Short-lived “turning down”strength of synaptic connections following benign stimulation
  
  • Ex: initial nausea on roller coaster → ride again and again and it goes away
  • Maybe due to dec release of excitatoty neurotransmitters

Question 3

What is Adaptation?

Answer 3

• Longer term phenomenon of Habituation
  
  • Long term stimulation leading to structural changes (dec # of synaptic connections between neurons
• Ex: tactile defensiveness → prolonged touch cant reduce defensiveness
• Ex: vestibular therapy → find thing that makes them dizzy and repeat until it goes away

Question 4

What is Experience-Dependent Plasticity?

Answer 4

• Associated with learning and memory
• “Turning up” strangth of synaptic connections
• Making a pathway more active!

Question 5

What is “Long Term Potentiation” (LTP)?

Answer 5

• Formaton of long-term declaritive memories
• “Repetition with intent and results”

Question 6

What are the mechanisms of Long Term Potentiation (LTP)?

Answer 6

• Conversion of silent synapses to active synapes
• Change in morphology or pre-and post-synaptic membranes (creating increased number of concentrated “synapse” points)
• Possible role of astrocytes

Question 7

What is Long-Term Depression (LTD)?

Answer 7

• Reverse when no reception in that pathway
  
  • Ex: Not maintaining learning

Question 8

What are the initial responses to axonal injury?

Answer 8

• Retraction of proximal segment
• “Wallerian” degeneration (photo below)
  
  • degeneration of distal segment
• Chromatolysis in cell body of damaged cell
  
  • cell becomes sick
• Possible atrophy of postsynaptic cell membrance

Question 9

What is Sprouting?

What are the two types that occur?

Answer 9

• Regrowth of damaged axons
  
  • 1. Regenerative
  • 2. Collateral

Question 10

What is Regenerative Sprouting?

Answer 10

Damaged axon regenerates itself

Question 11

What is Collateral Sprouting?

Answer 11

Cell body damage. Other survivng cell bodies branch out to innervate tissue that lost nerve supply.

Question 12

What mechanisms of axonal injury in the CNS can be reversed? Which cannot?

Answer 12

• Mechanical (tearing and shearing) → irreversible
• Chemical (ischemia and excitotoxicity) → reversible

Question 13

What is Recovery of Synaptic Effectiveness?

Answer 13

Asleep neurons, due to edema, wake back up after edema removal

Question 14

After mechanical damage, what is Denervation Hypersensitivity?

Answer 14

Postsynaptic receptor develops at remaining terminals after destruction of presynaptic terminal.

Question 15

After mechanical damage, what is Synaptic Hypereffectiveness?

Answer 15

Axon branches are taken out → extra neurotransmitters in surviving axon → release more than normal to try to send signal

Question 16

After mechanical damage, what is the Unmasking of Silent Synapses?

Answer 16

Activat silent synapse to make it functional

Question 17

How can we functional reorganize the cerebral cortex?

Answer 17

When something no longer works, lots of repetions remap things in the brain and can bring it back

(ex: monkey and banana pellets - tied good arm behind back and had him use nonfunctioning arm over and over - regained full use of arm)

Question 18

What is Excitotoxicity?

How does it work?

Answer 18

• Large amoutns of glutamate can excite cell to death.
• Glutamate binds to NMDA receptors - opening Ca++ channels
• Ca++ floods into cell

Question 19

What are the metabolic effects of brain injury?

Answer 19

• Large amts of glutamate released from dead neurons
  
  • Can exctie cells to death!