Development of the Nervous System

Question 1

how long does the preembryonic stage last?

Answer 1

conception to week 2

Question 2

how long does the embryonic stage last?

Answer 2

week 2 to week 8

Question 3

how long does the fetal stage last?

Answer 3

week 8 to birth

Question 4

what occurs during the preembryonic stage?

Answer 4

ovum becomes fertilized
cell division begins
solid sphere formed (blastocyst)

zygote-> divisions-> blastocyst-> binds to uterus

Question 5

what do the layers of the blastocyte form?

Answer 5

outer layer: becomes placenta

inn cell mass: becomes embryo

Question 6

what does the blastocytes inner cell mass develop into?

Answer 6

embryonic disk

1. ectoderm: becomes sensory organs, epidermis, NS
2. endoderm: becomes digestive tract, glands, respiratory system

Question 7

what does the blastocyte develop into during the embryonic stage?

Answer 7

1. mesoderm: develops muscles, skeletal bones, NS

2. notochord: within mesoderm, becomes spinal vertebrae

Question 8

What occurs on day 18 of the embryonic stage?

Answer 8

neural plate forms into neural grooves

Question 9

what occurs on day 21 of the embryonic stage?

Answer 9

the neural groove folds in on itself and forms a neural tube (rostrally->caudally like zipper)

Question 10

when does the neural tube close?

Answer 10

superior neuropore closes by day 27

inferior neuropore closes by day 30

Question 11

what are the layers of the neural tube and what do they form eventually?

Answer 11

1. marginal layer (outer): contain cell bodies-> become white matter-> becomes myelinated axons for cell bodies
2. mantle layer (inner): contain cell bodies that become gray matter for brain + spinal cord

Question 12

what occurs during the embryonic stage?

Answer 12

development of major organs, digits, brain

Question 13

what stage of development occurs at 30 days?

Answer 13

three vesicle stage

forebrain, midbrain, hindbrain division

Question 14

what stage of development occurs at 40 days?

Answer 14

five vesicle stage

telencephalon, diencephalon, mesencephalon, pons, medulla division

Question 15

what are the layers of neural tube that becomes the spinal cord?

Answer 15

1. germinal zone: interior, becomes lining to ventricular layer aka spinal fluid area
2. mantle zone: where cell bodies are
3. marginal layer: where white matter will be

Question 16

what happens to the mantle layer during week 5?

Answer 16

the gray matter is split by the sulcus limitans into motor (ventral) and sensory (dorsal) areas

Question 17

what happens after 10 weeks of development to the spinal cord?

Answer 17

dorsal root projects itself into dorsal gray matter (sensory neuron bodies)
ventral root projects itself out of ventral gray horn (motor neuron bodies)

Question 18

how does the spinal cord grow?

Answer 18

spinal column grows faster than cord

adult spina lcord ends at L1-L2

Question 19

what occurs at the end of the vertbrae?

Answer 19

spinal nerves have large amnt of cell bodies twd end

Conus medulliaris attaches to cauda equina (all the spinal nerves from the spinal cord coming together)

Question 20

what % of infant deaths are caused by defects?

when do they occur most?

Answer 20

20%

1st trimester