Neuromorphology

Question 1

at how many days does neurulation occur?

Answer 1

begins at 18 days

Question 2

describe neurulation

Answer 2

thickeming of ectoderm that results in tall columnar cells in the neural plate on the dorsal midline of embyro

occurs immediately dorsal to notochord and results in the neural groove

neural groove becomes deeper d/t increased cell growth. eventually the dorsal neural crests meet and form a tube. this process occurs first in cervical region and progresses up and done

Question 3

neural crest cells

Answer 3

neural crest cells are derived from the crests of the neural groove and the floorplate of the groove

become the sensory ganglia (such as dorsal root ganglia)

Question 4

where does the ventricle system of the brain come from

Answer 4

the middle of the neural tube

Question 5

how many cell layers thick is the wall of the neural tube?

Answer 5

1 cell

Question 6

how does the neural tube close

Answer 6

closes both caudally and rostrally, leading down to anterior and posterior neuropore

Question 7

what are the last parts of the neural tube to close?

Answer 7

anterior and posterior neuropore

Question 8

anterior neuropore fails to close

Answer 8

anencephaly- death

Question 9

posterior neuropore fails to close

Answer 9

spina bifida

spina bifida occulta- minor defect where lamina of vertebrae don’t fully fuse

meningocele- meninges bulge out of palce

meningomyelocele- spinal cord and meneinges are bulging out of canal. associated w/ damage to lower spinal cord and nerve roots

Question 10

how cap spina bifida be prevented?

Answer 10

folic acid supplementation before pregnancy

Question 11

cevical and cephalic flexure

Answer 11

after anterior neural pore closes, tube elongates faster than embyro can keep up. this causes a bends in the neural tube, called the cervical and cephalic flexures

Question 12

how do the vesicles form?

Answer 12

after the anterior neural pore closes, the tube elongates faster than embryo can keep up. creates bulges in the transverse plans that become vessicles

Question 13

rhombencephalic vesicle

Answer 13

at level of brain stem

Question 14

mesencephalic vesicle

Answer 14

at level of midbrain

Question 15

prosencephalic vesicle

Answer 15

most rostral vesicle. eventually differentiates into diencephalic vesicle and two telencephalic vesicles on either side of it

Question 16

pontine flexure

Answer 16

an anterior flexure that forms in the rhombencephalic vesicle, which separates it into the mylenephalon caudally and metencephalon rostrally

Question 17

lateral ventricles develop from?

Answer 17

telecephalic vesicles

Question 18

third ventricle develops from?

Answer 18

diecephalic vesicle

Question 19

what forms the cerebral aqueduct

Answer 19

mesencephalic vesicle

Question 20

fourth ventricle develops from what?

Answer 20

metencephalic and myelencephalic vesicles

Question 21

neural crest cells become what

Answer 21

dorsal root ganglia and all sensory nerves
ganglia of cranial nerves
autonomic ganglia- gut
adrenal medulla
schwann cells
leptomeninges
bone and connective tissues of face and skull

Question 22

what is important for initiation of the neural tube

Answer 22

bone morphogenetic protein (BMP) is secreted by ectoderm and must be inhibited by noggin and chordin, which bind to BMP and inhibt it

Question 23

where do noggin and chordin come from/

Answer 23

notochord

Question 24

what does sonic hedgehog do?

Answer 24

secreted from notochord, (and eventually floorplate) causes ventral differentiation

Question 25

what do TGF betas do?

Answer 25

secreted by neural crest cells secrete TGF beta like BMP to cause dorsal spinal differentiation. they are no longer inhibited by noggin and chordin b/c the neural tube is much bigger and thus the concentration are much smaller

Question 26

why is cholesterol important for SHH?

Answer 26

SHH is released inactive SHH is autoproteolytic, and cholesterol binds to N-terminus which is required for proper diffusion and activity statins inhibit this and cannot be taken during pregnancy

Question 27

basal/alar plate

Answer 27

basal- contains motor neurons alar plate- becomes dorsal horn involved in sensory processing in the brainstem, motor neurons are medial and sensory are lateral

Question 28

why is retonic acid important

Answer 28

important for determining to rostral and caudal. diffuses from brainstem and activates Hox genes, close to retnoic acid = caudal certain acne drugs have retonic acid analogues, but cannot be taken during pregnancy

Question 29

what do the cells in the wall of the neural tube become?

Answer 29

macroglia- cells of the CNS

Question 30

what are notch 1 and numb

Answer 30

cell surface molecules- notch 1 occurs closer to pia and numb occurs basally notch 1 signals cells to stop dividing, migrate away into mantle zone and mature

Question 31

notch v delta

Answer 31

notch and delta are both cell membrane proteins that interact w/ each other. when one cell upregulates notch, it down regulates notch on adjacent cells and upregulates delta. delta does the reverse. this creates a good ratio of glia and neurons. glia are high notch cells

Question 32

radial glial cells

Answer 32

they radiate from ventricle surface outward in waves, using surface markers on the glia

Question 33

cajal retzius cells

Answer 33

found in layer 1, secrete reelin which is important for normal migration

Question 34

what factors influence the differentiation of the neural crest cells

Answer 34

leukocyte inhibiting factor- sensory neuron FGF2- sympathetic cell stem cell factor- melanocyte glucocorticoids- chromaffin cell