Development of the NS

Question 1

pre embryonic stage

Answer 1

conception to day 14

zygote begins cells division

7-10 days: embryonic disk (ectoderm, mesoderm, and endoderm)

day 2: 4 cells in a clump
day 4: solid sphere of cells
day 5: 3 cell masses and egg attaches to uterus

Question 2

embryonic stage

Answer 2

day 15 to week 8

formation of organs

germ layer derivatives

ectoderm: NS, sensory organs, and epidermis

mesoderm: muscle, skeleton, circulatory system, and dermis

endoderm: endocrine glands, lungs, digestive tract, and liver

Question 3

fetal stage

Answer 3

week 9 to birth

NS continues to develop

myelination begins in the PNS at around week 11
- PNS myelination begins in the motor neurons then sensory

CNS myelination begins around 2 months b4 brith in the sensory neurons then motor

Question 4

which occurs first: neural tube formation or brain formation?

Answer 4

neural tube formation

Question 5

neural tube formation (neurulation)

Answer 5

day 18-26 (embryonic)

3rd gestational week: neural plate and neural tube
- 3 visible primary germ layers
- neural plate in middle with depression-neural groove
- neural crest on edge of neural plate
- notochordal plate (from mesoderm) creates the midline and defines where the groove and tube is going to be
–> hallmark sign of immature NS

4th gestational week: neural tube closure
- begins in cervical region then zips up and down with superior neural pore closing first
- day 24-superior neural pore closure and 3 vesicles (prosencephalon, mesencephalon, and rhombencephalon)
- day 26: inferior neural pore closure

Question 6

what happens when the superior neural pore doesn’t close?

Answer 6

anencephaly

Question 7

what happens when the inferior neural pore doesn’t close?

Answer 7

spina bifida

Question 8

is the inner layer of the neural tube gray or white matter?

Answer 8

gray

Question 9

association plate (AP)

Answer 9

dorsal half

develops into dorsal horn of SC

interneurons

input from sensory neurons

Question 10

basal (motor) plate

Answer 10

motor neurons

becomes ventral horn

neurons innervate myotome

Question 11

what is the sulcus limitans?

Answer 11

divides the AP and BP

Question 12

what develops into the peripheral sensory neurons?

Answer 12

neural crest

Question 13

what neurons innervate the dermatome?

Answer 13

neurons from the neural crest
- DRG
- pseudounipolar
- somas outside SC/neural tube
- projection onto dorsal horn and dermatome

Question 14

ectoderm neurons

Answer 14

sensory, motor, an d interneurons

Question 15

what are the 3 vesicles and what do they become?

Answer 15

prosencephalon: forebrain
- telencephalon–> cerebral hemispheres, cerebral cortex, basal ganglia, and lateral ventricle
- diencephalon–> thalamus, hypothalamus, and 3rd ventricle

mesencephalon: midbrain
- stays same
- becomes midbrain
- has cephalic flexure

rhombencephalon: hindbrain
- metencephalon–> pons, cerebellum, and cerebral aqueduct
–> has pontine flexure
- myelencephalon–> medulla and 4th ventricle
- has cervical flexure separating rhombencephalon and SC

Question 16

what is the pontine flexure? where is it? why is it important?

Answer 16

in the metencephalon

bends posteriorly while the other bend anteriorly

makes the AP move lateral of the BP and creates the 4th ventricle

Question 17

when do the gyri and sulcus form?

Answer 17

6-9 months

Question 18

what is differentiation in the developing NS?

Answer 18

neuroepithelial cells are undifferentiated cells in the NS that become neurons and glial cells

Question 19

what is neural migration?

Answer 19

neuroepithelial cells find the right target

axon guidance from growth cone projections out of the axon

filopodia at the ends of growth cones test the environment for targets:
- post molecules-guide growth in that direction (anterograde transport)
- neg molecules-retracted (retrograde transport)

Question 20

what is synaptogenesis?

Answer 20

creation of new synapes decided by the filopodia

dendritic spines-site for synapse formation and determine the number of synapses that can form

Question 21

determination of muscle fiber types

Answer 21

size principle: smalll recruited first

innervated by large neuron-type 2B

innervated by medium neruon-type 2A

innervated by small neuron-type 1

Question 22

what is synaptic pruning?

Answer 22

axon retraction or neuronal apoptosis

Question 23

what is neuronal apoptosis?

Answer 23

programmed death of neurons

Question 24

what is polyneuronal innervation?

Answer 24

muscles fibers innervate 2 neurons

hallmark of immature NS

Question 25

what are the roles of glial activities during development?

Answer 25

in synaptic pruning, astrocytes and microglia (CNS) and satellite and Schwann cells (PNS) guide axons

myelination

Question 26

where does myelination occur first?

Answer 26

In PNS-motor, then sensory
then CNS-sensory then motor

Question 27

what is growing into the deficit?

Answer 27

can’t discover a deficit until the system is expected to fully mature

Question 28

does myelination proceed postnatally?

Answer 28

yes

Question 29

what are critical periods?

Answer 29

period of time when skills are learned best

language-up to 8 years old
seeing and hearing-up to about 5-6 y/o
speech production-1-10 months
high cognitive function-2-4 y/o and 16-21 y/o

specific window to maximize skills acquisition

Question 30

what is experience expectant plasticity?

Answer 30

to have normal development, you need to have experiences

very limited sites for synapses to be formed and maintained

Question 31

If something happens during a critical period, would there be more or less deficits than if it happened after the critical periods for that skill?

Answer 31

more deficits

Question 32

what is anencephaly?

Answer 32

when the superior neural pore doesn’t close, so there is a rudamentary BS w/forebrain and no skull

Question 33

what is spina bifida?

Answer 33

when the inferior neural pore doesn’t close