Neuronal degeneration and reg

Question 1

Damage at the Dendrite or synapses usually causes?

Answer 1

Loss of dendrites or synapses can usually be resorted by regrowth/plasticity

Question 2

Damage at the cell body usually causes?

Answer 2

Cell death and due to the fact that mature neurons are post-mitotic it is no replaced

Question 3

Damage to an Axon or target innervation causes?

Answer 3

In the CNS axon regrowth is inhibited/limited by the environment; in the PNS axonal regrowth is possible but it needs support/guidance cues

Question 4

How does Axonal injury elicit a regenerative response I the neuron soma?

Answer 4

Loss of normal retrograde neurotropic signals; Retrograde axonal transport of positive (growth) signals from nerve stump

Question 5

in Wallerian degeneration what is the distal and proximal end? What happens to the distal end? What happens to the proximal end?

Answer 5

the distal end is the end that has been severed from the cell body it degrades all the way to the site of innervation; the proximal end is the side with the cell body and it degrades to the next node of ranvea

Question 6

in Wallerian degeneration what three things happen to re-establish normal neuronal function?

Answer 6

Regeneration of the proximal axon involves; Axon guidance path and molecular cues; re-myelination by the glial cells; re-innervation of target tissue

Question 7

In axonal transport what supports the movement? Synthesis and assembly of molecules occurs in the? What molecules are responsible for the movement and in what direction?

Answer 7

Microtubules; Synthesis and assembly take place in the soma of the neuron; Anterograde (toward the nerve terminal) is accomplished by Kinesins; Retrograde transport (toward the nerve cell body) is accomplished by dynein

Question 8

in general what is transported anterograde?

Answer 8

Transmitters and Structural proteins

Question 9

in general what is transported retrograde?

Answer 9

Debris viruses; and growth factors

Question 10

in Axonal guidance what it the first area called; what does it do?

Answer 10

The growth cone; establishes a pathway and detects physical cues to continue to grow or degrade

Question 11

in terms of guidance signals; what are three broad types and some examples of each?

Answer 11

Adhesive substrate-bound cues (the roadway) CAMs and ECM; Repellent substrate-bound cues (the roadways guard rails) Slits and ephrins Chondroitin sulphate proteoglycans; Diffusible chemotropic cues (Road signs) class guidance molecules (netrins and semphorins) neurotransmitters growth factors

Question 12

A nerve is usually made up from a variety of fascicles what are the layers around these fascicles?

Answer 12

Epineurium (surrounds the many fascicles that make up the anatomical nerve); perineurium (surrounding individual fascicles); endoneurium (surrounds the nerve fibbers them selves)

Question 13

even if an axon is damaged the conduit made up of What and what will often survive and provide a pathway for regrowing axons?

Answer 13

even if an axon is damaged the conduit made up of Perineurium and epineurium will often survive and provide a pathway for regrowing axons?

Question 14

what can trigger wallerian degeneration in the PNS?

Answer 14

Triggered by severe nerve injury (trauma; transection; toxins; inflammation and demyelination; neurodegeneration) or blockade of axonal transport

Question 15

in Wallerian degeneration describe what happens in the neuron soma and proximal axon.

Answer 15

there is an aggregation of protein in the soma; trophic factors prevent proximal axon loss; macrophages invade injury and secrete cytokines and secretion of extracellular proteins by Schwann cells cause a proximal axon to sprout within around 96 hours

Question 16

in wallerian degeneration describe what happens in the distal axon.

Answer 16

Degeneration over a 1-2 weeks; Glial cells push synaptic terminals away from the muscle; the myelin sheath degrades; Schwann cells begin to remove debris; but the Schwann cells and endoneural tube persists as support/guides for 1-2 months

Question 17

what is the main tool in determining peripheral nerve damage/demyelination

Answer 17

Electrophysiology

Question 18

what is the prognosis of a injury that leaves the axon and nerve structure intact but creates a nerve conduction block in the PNS?

Answer 18

Prognosis is very good; 3-4 month recovery

Question 19

what is the prognosis of a injury that leaves axonal damage but the nerve structure is intact in the PNS?

Answer 19

prognosis is good; axon regrowth at ~1 mm/day from injury to tissue target

Question 20

what is the prognosis of an injury that has axonal and nerve structure damage in the PNS?

Answer 20

variable; needs surgical nerve reconnection followed by axonal regrowth; up to 18 mths

Question 21

what does surgical approximation of a peripheral nerve aim to do?

Answer 21

Realign the nerve fascicles for axon guidance

Question 22

what are four aids to peripheral nerve repair?

Answer 22

Fibrin tissue glue; nerve conduits; electrical stimulation; nerve graft

Question 23

how does fibrin tissue glue help with peripheral nerve repair

Answer 23

provides extracellular matrix around the nerve approximation; prevents invasion of scar tissue

Question 24

what are the two types of nerve graft

Answer 24

isograft uses sensory nerves from the same patient; allograft uses processed nerve from donor

Question 25

how do nerve conduits help peripheral nerve repair?

Answer 25

They provide a guidance path for axonal growth; prevent scar tissue invasion and axon escape; creates a nerve growth factor rich local environment;

Question 26

CNS axons have the capacity to regenerate but?

Answer 26

the environment inhibits this

Question 27

what are two factors that inhibit axon growth in the CNS?

Answer 27

glial cells secrete inhibitory factors; formation of glial scar block axonal growth;

Question 28

what are three stem cell sources?

Answer 28

Pluripotent stem cells from embryonic tissue; induced transformation of tissue stem cells; the adult brain has a small number of stem cells

Question 29

where are pluripotent stem cells derived from?

Answer 29

blastocyst or embryonic tissue

Question 30

where do induced pluripotent stem cells come from?

Answer 30

Genetic reprogramming of adult cells (skin)

Question 31

what are some benefits to induced pluripotent stem cells?

Answer 31

Avoids rejection problems; less ethical concerns

Question 32

what are some issue with using adult neural stem cells?

Answer 32

there are few present; identification and harvesting is very difficult; they may have some significant DNA errors

Question 33

describe neural interface systems

Answer 33

Brain activity can be used to directly control muscle; computers or other assistive or prosthetic devices