NEURO Neurocognitive Disorders Flashcards
(10 cards)
What is neuroplasticity?
Changes in brain structure, connectivity and function over time, response to changing environment (internal or external).
Akin to evolution, in sense what already exists is modified to better suit requirements.
What are the three key principles of neuroplasticity?
Neurodegeneration, Neural Regeneration, Neural Reorganisation.
What is neurodegeneration?
Up to 100 billion neurons in adult brain. Remains stable throughout time but number of connections change dramatically.
1 quadrillion synapses at 3yrs of age. Reduces by 50-90%= 100-500 trillion at adulthood.
Neurons don’t normally die, their connections do (good cause optimises network).
Cell body volume decline due to reduction in connections + number of other support cells. (e.g. glial cells, which represent about 50% all cells in brain).
White matter volume up as connections get more insulated with myelin- connections to/from frontal cortex amongst last to become fully myelinated.
Experiments reveal effect of damage to individual neurons + neighbours (e.g. anterograde, retrograde, and trans-neuronal degeneration).
What causes most neurodegeneration?
most damage cause of neurodegeneration from disruption to homeostatic environment in and surrounding neuron or injury.
=disruption of normal neurotransmitter function ( loss of input).
=loss of fuel supply (oxygen, glucose).
=attack from infections, toxic or own immune system.
=fault genetic signallling.
=physical injury.
What are the two types of neuronal deaths?
Necrosis: death due to cellular ill health (unmanaged).
Apoptosis: cellular self-destruct option (adaptive).
What is neural regeneration?
Clear capacity for regrowth/ regeneration in peripheral nervous system, more complex/ difficult in central nervous system.
CNS= within the skull + spine.
PNS= outside the skull and spine.
Somatic Nervous system: part interacting with external environment.
Automatic Nervous System: regulates the body’s internal environment.
Regeneration or no regeneration depends on tissue environment- cause of degeneration been removed -> disease, injury, hypoxia.
What 3 things are critical in neural regeneration?
Axonal Neurotransmission
Schwann cells in PNS
Oligodendrocytes in CNS
How are Schwann cells involved in regeneration of PNS neurons?
Presence and distance is critical for effective regeneration.
Regrowth not always helpful- wiring gets messed up if remaining Schwann cells not able to guide it properly.
When nerve injured in first 24hrs the schwann cells line up either side of the injury, then they recruite macrophage. Then regeneration occurs.
How is the spinal cord affected by regeneration?
Spine part of CNS (myelin from oligodendrogytes). ‘Target’ of spinal cord axons usually distant., means regeneration potential reduced. Peripheral nerve targets e.g. muscles stand better chance.
-needs rigid nervous system + to be stable + fixed to how it was, expensive to learn new habits. CNS needs to be stable and PNS needs to be more adaptive.
Treatment strategies focus on guiding regrowth and enhancing tissue in environment.
What is Neural reorganisation?
Brain full of maps, damage needs ‘reconfiguring’.
Representations complex and overlapping (good for neural reorganisation following damage).
Few motor commands require isolated activation of a single muscle or small group of muscles.
Damage to limb can lead to phantom limb pain. Cause neural system loses input, but cell structure is still intact and connected to rest of nervous system.
Responses to loss of peripheral input, reorganisation involves intact/ connected areas expanding to take over tissue that receives no input.
Recovery based on changes in connectivity, strengthening of previous partially overlapping connections, some new connections. Continuous competition for space amongst neural circuits + maps- suggests real pressure for adequate space inside skull.
