Cells Of The Nervous System 2 - Reier

Front 1

Damage to a single nerve or nerve group that leads to loss of function or sensation of that nerve

Back 1

Mononeuropathy

Front 2

Symmetric dysfunction of multiple nerves simultaneously, with effects usually greater distally

Back 2

Polyneuropathy

Front 3

Loss of nerve function caused by damage to nerve roots (i.e. from herniated spinal disc), usually painful, and often in dermatomal distribution

Back 3

Radiculopathy

Front 4

Group of symptoms related to damage of one or more peripheral nerves in random distribution, usually from vessel or connective tissue disease (i.e. DM)

Back 4

Mononeuritis multiplex

Front 5

What happens to the distal segment of an axon after axonal transsection (i.e. cut in the axon)?

Back 5

Anterograde (Wallerian) degeneration

-axon and myelin break down, removal of debris by macrophages

Front 6

What two things can happen to the cell body after the axon has been cut or damaged?

Back 6

-Cell body shrinkage (neuronal atrophy)
-Retrograde cell body death

Front 7

After injury, what changes occur with regards to protein synthesis organelles?

Back 7

-Chromatolysis - loss of RER and Nissl substance

-also change of nuclear positioning
-swelling of cell body

Front 8

Rough ER/Nissl substance are lost but what structures are present instead?

Back 8

Polyribosomes - present during cell growth

Front 9

In order to regenerate, neurons need what intrinsic property?

Back 9

Metabolic ability to regrow

Front 10

In order to regenerate, what extrinsic 4 extrinsic criteria need to be met?

Back 10

-"permissive" extracellular environment
-cellular terrain provides cues
-axon can respond to these cues
-ability to compensate for neuronal loss

Front 11

During development, this structure is sent out to "taste" the environment and extend the axon in the right direction. It also forms and begins the regeneration process at the proximal site of the injured axon.

Back 11

Growth cone

Front 12

What cells are crucial to encouraging the extension of the growth cone/making sure it encounters a "friendly" environment in the PNS

Back 12

Schwann cells

-produce adhesion molecules growth cone can "stick" to

Front 13

Regrowing axons are initially myelinated or unmyelinated?

Back 13

Unmyelinated

Front 14

T/F Axons will be present in the microenvironment distal to the site of axotomy in a peripheral nerve.

Back 14

FALSE - NO AXONS

SCs, fibroblasts, collagen, axonal debris, macrophages, degenerating myelin, vascular elements will be present

Front 15

The rate of regeneration of the axon is similar to that of what kind of transport?

Back 15

Slow anterograde axonal transport

-makes sense because transporting cytoskeletal elements

Front 16

Which has a better chance of regeneration - an axon damaged by a crush injury or an axon damaged by a transection injury?

Back 16

Crush - some of axon still there and can regenerate better than if severed completely

Front 17

T/F Distance of the gap between the axon proximal stump and the microenvironment plays a role in regeneration

Back 17

True - greater distance, worse outcome

Front 18

Besides gap distance, what other factor is important to whether or not regeneration is successful?

Back 18

Nerve internal geometry

Front 19

Lack of innervation can lead to what happening to muscle?

Back 19

-Muscle atrophy ("denervation atrophy")

-from lack of trophic factors and lack of activity

Front 20

For peripheral nerves, _______________ is more important for regeneration than vigor (ability to regrow).

Back 20

Accuracy (A function of proximity - so the closer the better)

Front 21

What is secondary demyelination?

Back 21

Loss of myelin as a result of loss of the axon (Wallerian degeneration)

Front 22

What is primary demyelination?

Back 22

Loss of myelin from an intact neuron

-Occurs in MS, Guillan-Barre syndrome

Front 23

What is the "onion bulb change" depicted above?

Back 23

Results from repeated cycles of demyelination and remyelination

Front 24

How does new/regenerated myelin compare to old myelin?

Back 24

It is thinner and shorter than original segments

Front 25

What are the two major problems in CNS pathology? What are the two basic forms of neuronal loss?

Back 25

-Neuronal loss, axonal damage

-Necrosis and apoptosis

Front 26

What is secondary tissue damage or collateral damage?

Back 26

A site of necrosis from trauma (i.e. stroke) triggers apoptosis in surrounding areas

Front 27

What are the two major mechanisms of secondary tissue damage?

Back 27

-excitotoxicity
-free radical formation

Front 28

What is excitotoxicity? What two neurotransmitters are involved?

Back 28

-unregulated release of glutamate and aspartate (excitatory AAs/neurotransmitters) causing cell death by overactivation of neurotransmitter receptors

Front 29

What can break down free radicals for neuroprotection?

Back 29

Antioxidants - Vit E, C, and beta carotene

Front 30

What component of the cell is affected by free radicals and excitatory AAs?

Back 30

cell membrane - breaks down and becomes more permeable to Ca2+ causing cell death

Front 31

What is transneuronal degeneration?

Back 31

-Damage to axons or demyelination can disrupt axonal pathways/neuron networks and cause damage to other neurons in the network

Front 32

T/F As a rule, there is limited cellular regeneration in the CNS.

Back 32

True

Front 33

Why is regrowth limited in the CNS?

Back 33

-Environment is not permissive (upside - CNS protects itself, downside - limited regrowth)
-cell have metabolic capability but bad environment (no SCs, removal of cellular debris is slow)