Plasticity and regeneration in the Nervous system

Question 1

Axotomy

Answer 1

is the cutting or otherwise severing of an axon

Question 2

Wallerian or anterograde degeneration

Answer 2

-the degeneration of the distal end an axon of the PNS and its myelin sheath when it undergoes axotomy

Question 3

What cells will clear the degenerating axons and myelin sheath of a nerve who underwent anterograde degeneration

Answer 3

tissue macrophages

Question 4

Schwann cells stay in the damaged area undergo mitosis and proliferation
promoted by

Answer 4

macrophages

Question 5

Schwann cells recruited and influenced by macrophages will do what to a PNS neuron that underwent an axotomy

Answer 5

The Schwann cells will form a column that connects the cut end of
the axon with the original target. This column will be important for guiding a regenerating
axon back to its appropriate target.

Question 6

The proximal end of the axon will also die back by ___degeneration,

Answer 6

retrograde

Question 7

In early stages of regeneration, the cell will exhibit chromatolysis. Define chromatolysis

Answer 7

disruption of Nissl bodies

Question 8

Nissl bodies

Answer 8

These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis. It was named after Franz Nissl, a German neuropathologist who invented the Nissl staining method.

Question 9

In early stages of regeneration, the cell will exhibit ___ and ___

Answer 9

chromatolysis and eccentric relocation of the nucleus.

Question 10

bouton shedding

Answer 10

presynaptic inputs to axotomzed neurons disconnect and withdrawal

• shedding of inputs
• helped by glia; they insert themselves and peel of synapses

Question 11

Transneuronal degeneration

Answer 11

anterograde (innervated neuron dies) or retrograde direction (innervating neuron dies).

Question 12

if regenerated axons are able to reach their target, are they remyelinated?

Answer 12

yes

-Determination of the extent of myelination is made by the characteristics of the axon and not the Schwann cell

Question 13

Collateral and paraterminal sprouts originate from ____ or _____, respectively, and are stimulated by factors released from the ____

Answer 13

• nodes of Ranvier (collateral) or axon terminals (paraterminal)
• stimulated by factors released from denervated tissue

Question 14

What findings suggest that axotomy removes a retrogradely transported neutropic signal derived from the target?

Answer 14

-Collateral sprouting can be induced in motor neurons simply by inactivating the target muscle
-Conversely, sprouting following damage in adjacent axons can be blocked by electrically
stimulating the target muscle.

Question 15

After axotomy, local application of NGF to the soma

can ___ chromatolysis and bouton shedding.

Answer 15

-prevent

Question 16

Administration of the microtubule poison colchicine

can also ____chromatolysis and bouton shedding.

Answer 16

induce

Question 17

colchicine

Answer 17

-microtubule poison that can induce chromatolysis and bouton shedding

Question 18

The best known of these myelin-associated growth inhibitors is ___

Answer 18

-Nogo-A.

Question 19

laminin and fibronectin

Answer 19

-growth factors that are found in the PNS and CNS extracellular matrix during development, but only in the PNS in adulthood

Question 20

oligodendrocytes in the CNS synthesize glycoproteins that ____

Answer 20

-suppress axon outgrowth

Question 21

what did Aguayo et al. show about regeneration of the optic nerve?

Answer 21

-the optic nerve was transected near the eye and they
demonstrated that the axons of retinal ganglion cells would not grow through a resected
optic nerve
-However, they would regenerate through a Schwann cell column from a peripheral nerve graft
-Regenerated retinal ganglion cell axons grew through the graft and innervated the superior colliculus, a normal target.

Question 22

failure to show regeneration in the CNS is a property of the____

Answer 22

• supporting cells and not the neurons

Question 23

what cells were injected in an area of axotomy that actually improved recovery and even facilitated walking in a paraplegic patient

Answer 23

olfactory ensheathing cells

Question 24

what are some areas where adult neurogenesis has been observed?

Answer 24

• olfactory epithelium/ bulb
• hippocampus- (especially -dentate gyrus)
• caudate nucleus

Question 25

what would be the consequences of no neurogenesis

Answer 25

-the DG either has to encode new information at the expense of old
information or face saturation.

Question 26

Occasional spontaneous cell loss is often
followed by _____and
reactive _____ from surviving
local axons.

Answer 26

collateral sprouting and synaptogenesis

Question 27

Jon Kaas showed that somatotopic maps are

Answer 27

Somatotopic maps are

modifiable by experience

Question 28

Synapse strengthening

Answer 28

probablyaccounts for earlyreorganization, implying that weak connections
exist that are not readily apparent in physiological recordings. These weaker connections can be
revealed when the dominant pathways are inactivated (or lost).

Question 29

phantom limb sensations

Answer 29

-patients who have lost a hand experience cortical expansion of the
intact afferent pathways that normally terminate in areas surrounding the hand representation
(face, shoulder, and upper torso).

Question 30

remapping of referred sensations.

Answer 30

cortical expansion of the

intact afferent pathways that normally terminate in areas surrounding the lost limb