Development and Regeneration

Question 1

what germ layer is the neural plate, crest, and placode made from?

Answer 1

ectoderm

Question 2

what is neurulation?

Answer 2

the neural plate folds dorsally until the borders touch to form a hollow tube (neural tube)

Question 3

where do neural crest cells migrate?

Answer 3

laterally and ventrally

Question 4

what do neural crest cells form?

Answer 4

most of the peripheral nervous system including sensory and autonomic ganglia

Question 5

what part of the peripheral nervous system is not formed from the neural crest cells?

Answer 5

neurogenic placodes

Question 6

what are neurogenic placodes associated with?

Answer 6

cranial sensory systems

Question 7

what cranial sensory systems are associated with neurogenic placodes?

Answer 7

trigeminal, otic, geniculate, petrosal, nodose

Question 8

what are the openings of the neural tube?

Answer 8

cranial and caudal neuropore

Question 9

what does the neural tube form?

Answer 9

the CNS

Question 10

what are the 3 initial vesicles of the CNS

Answer 10

prosencephalon, mesenchephalon, rhombencephalon

Question 11

what are the 5 initial vesicles of the CNS

Answer 11

telencephalon, diencephalon, mesencephalon, metenchephalon, myelencephalon

Question 12

what is anencephaly

Answer 12

defect that occurs when cranial neuropore does not close

Question 13

what is spina bifida

Answer 13

defect that occurs when caudal neuropore does not close

Question 14

what reduces defects of the neuropores?

Answer 14

folic acid

Question 15

during the 4th week, what does the neural tube differentiate into?

Answer 15

dorsal and ventral portions

Question 16

what is the dorsal portion of the neural tube?

Answer 16

alar plates, sensory

Question 17

what are the alar plates crucial for?

Answer 17

reflexes

Question 18

what is the ventral portion of the neural tube?

Answer 18

basal plate, motor

Question 19

what is the dorsal root ganglion from?

Answer 19

neural crest cells

Question 20

what is holoprosencephaly?

Answer 20

failure of the forebrain to separate into distinct hemispheres

Question 21

where do holoprosencephaly facial deformities affect?

Answer 21

the eyes, nose, and upper lip

Question 22

what are causes of holoprosencephaly?

Answer 22

teratogens and/or genetics
trisomy 13

Question 23

where can cell bodies migrate?

Answer 23

radially or tangentially

Question 24

what direction is radial migration?

Answer 24

from ventricles toward pial surface (built from the inside to out)

Question 25

what direction is tangential migration?

Answer 25

parallel with ventricular system

Question 26

when is radial migration not toward the pial surface?

Answer 26

in the cerebellum (pia to ventricle)

Question 27

what is lissencephaly?

Answer 27

failure of neuronal migration, appears as a smooth brain
often accompanied by microcephaly

Question 28

what are causes of lissencephaly?

Answer 28

viral infections or genetic mutations

Question 29

what are the three Seddon classifications of injury?

Answer 29

neurapraxia, axonotmesis, neurotmesis

Question 30

neurapraxia

Answer 30

transient loss of function with minimal myelin damage

Question 31

axonotmesis

Answer 31

longer term loss of function with damage to axons while the epineurium remains intact

Question 32

neurotmesis

Answer 32

complete disruption of a nerve as well as coverings

Question 33

what is Sunderland’s 1st degree of injury?

Answer 33

neurapraxia
heals in minutes to weeks

Question 34

what is Sunderland’s 2nd degree of injury?

Answer 34

damage of axon with intact CT
heals 1mm/day by following existing CT

Question 35

what is Sunderland’s 3rd degree of injury?

Answer 35

damage of axon and endoneurium
possible surgery, usually incomplete healing

Question 36

what is Sunderland’s 4th degree of injury?

Answer 36

damage of axon, endoneurium, and perineurium
surgery needed, poor recovery

Question 37

what is Sunderland’s 5th degree of injury?

Answer 37

damage of all layers
recovery is unlikely

Question 38

what do growth cones do in axons?

Answer 38

send guidance cues as to where they should grow

Question 39

adhesive cues

Answer 39

found on surfaces or extracellular matrix

Question 40

tropic cues

Answer 40

attractants or repellants that cause intracellular changes in cytoskeleton growth

Question 41

modulatory cues

Answer 41

change the sensitivity of the growth cones

Question 42

can the CNS regenerate?

Answer 42

mostly no

Question 43

olfactory epithelium regeneration

Answer 43

allows for regrowth of neurons which attach to CNS

Question 44

subventricular zone regeneration

Answer 44

regenerates new cells that migrate to the olfactory bulb

Question 45

subgranular zone of the hippocampus regeneration

Answer 45

contains stem cells that regenerate into part of the hippocampal circuitry

Question 46

anterograde nerve degeneration

Answer 46

affects the axon away from the cell body

Question 47

retrograde nerve degeneration

Answer 47

affects the axon toward the cell body

Question 48

what happens when the nerve is damaged

Answer 48

axonal skeleton disintegrates, membrane breaks, macrophages infiltrate myelin sheath to clear the debris

Question 49

how does PNS regeneration occur?

Answer 49

Schwann cells accompany macrophages and create a tube that produces growth factor

Question 50

proximal portion of PNS regeneration

Answer 50

develops a growth cone and will regrow about 1mm/day