Extra Yaffas Notes

Question 1

where do the neural crest arise from

Answer 1

the dorsal neural tube along the entire length of the spinal cord and hindbrain

Question 2

what gene to neural crest cells express

Answer 2

Hox genes that are limited to various spinal cord and hindbrain domains

Question 3

what do all neural crest cells begin as

Answer 3

neuroepithelial cells and thus have all the cellular junctions and adhesive interaction that jeep epithelial cells inlace

Question 4

what do neural crest cells have to do to move

Answer 4

must down regulate expression of these adhesive genes and undergo an epithelial-to-mesenchymal transition

Question 5

what transcription factors to neural crest cells express

Answer 5

bHLH family members Snail1 and Snail 2 which repress expression of intercellular junctional proteins and epithelial adhesion molecules

Question 6

when the neural crest cells reach their final destination what happens

Answer 6

they cease to express Snail1/Snail2 and other transcription factors that favour the mesenchymal migratory state

Question 7

what do a minatory of nerve and glial cells in the CNS use as migratory guides

Answer 7

existing axon pathways

Question 8

how do neuroblasts reach their final destination

Answer 8

use the long process of radial glia as scaffolds, travelling along the radial glial fibres in order to reach their final destinations

Question 9

what is the nervous system patterned along

Answer 9

both the DV and AP axes

Question 10

what is the DV axis set up by

Answer 10

by the TGF-beta family and Shh

Question 11

what is the AP axis set up by

Answer 11

retinoic acid, FGF, and homeotic genes

Question 12

what is dysraphism

Answer 12

incomplete fusion - where there is continuity between the posterior neuroextoderm and the cutaneous ectoderm

Question 13

when is the abnormal increase in maternal serum alpha fetoprotein detected

Answer 13

16-18 weeks

Question 14

what does maternal serum screening not detect

Answer 14

closed defects and is less sensitive in women taking sodium valproate

Question 15

when can anencephaly be detected

Answer 15

12th weel

Question 16

when can SB be detected

Answer 16

16-20weels

Question 17

what is the banana sign

Answer 17

refers to the shape of the cerebellum, owing to caudal tail displacement

Question 18

when does the lemon sign disappear

Answer 18

24 weeks

Question 19

what is the treatment for adults with type 1 oe 2 chairi malformations

Answer 19

posterior fossa decompression surgery to create more space for the cerebella, and to relieve pressure on the spinal cord

Question 20

what is the absent brain replaced by in anencephaly

Answer 20

malformed cystic tissue

Question 21

what is a cephalocele

Answer 21

herniation of cranial contents through a skull defect

Question 22

what are the several subtypes of cephaloceles

Answer 22

1. cranial meningocele: contains ony meninges
2. encephalocele: contains brain tissue
3. ventriculocele: contains part of the ventricle within the herniated portion of the brain

Question 23

what are cephaloceles also associated with

Answer 23

other brain abnormalities such as agenesis pf the corpus callosum or abnormal gyration

Question 24

what is holoprosencephaly

Answer 24

occurs when the embryonic prosencephalon does not undergo segmentation and cleavage - into telencephalon and diencephalon

Question 25

what is abnormal in holoprosencephaly

Answer 25

the anterior midline brain, cranium and face are abnormal

Question 26

what is the holoprosencephaly caused by

Answer 26

defects of the sonic hedgehog gene

Question 27

what can hydrocephalus result from

Answer 27

1. excess CSF production 2. decrease in reabsorption via the arachnoid granulations 3. obstruction of flow at any point in the ventricles or subarachnoid space

Question 28

what is hydrocephalus catagorised into in clinical practice

Answer 28

1. communicating hydrocephalus: this is caused by impaired CSF reabsorption in the arachnoid granulations, obstruction of flow in the subarachnoid space, or excess CSF production 2. obstructive (non communicating) hydrocephalus: caused by obstruction of flow within the ventricular system

Question 29

which nerve may be affected in hydrocephalus

Answer 29

the sixth cranial nerve - affects eyes

Question 30

what is bipolar type 1

Answer 30

this is defined as one of more manic or mixed (signs of mania and depression) episodes - severe bipolar

Question 31

what is bipolar 2

Answer 31

this is defined as a depressive episode with at least one episode of hypomania - milder form of bipolar

Question 32

what is the average onset age of bipolar

Answer 32

21

Question 33

sodium valporate (Depakote) mode of action

Answer 33

1) maybe increasing gamma levels in the brain 2) altering the properties of voltage dependent sodium channels

Question 34

mechanism of valproate in more detail

Answer 34

Valproic Acid dissociates to the valproate ion in the GI tract and then binds to and inhibits GABA transaminase. The drug's anticonvulsant activity may be related to increased brain concentrations of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the CNS, by inhibiting enzymes that catabolize (break down) GABA or block the reuptake of GABA into glia and nerve endings. Valproic Acid may also work by suppressing repetitive neuronal firing through inhibition of voltage-sensitive sodium channels.

Question 35

what are glia

Answer 35

connective tissue of the nervous system, consisting of several different types of cell associated with neurones

Question 36

by what ratio do glia outnumber neurones

Answer 36

3 to 1

Question 37

what roles do glial cells play in the nervous system

Answer 37

- maintaining the ionic Millieu of nerve cells - modulating the rate of nerve signal propagation - modulating synaptic action by controlling the uptake of neurotransmitters at or near the synaptic cleft - aiding in recovery from neural injury

Question 38

what are the three types of glial cells in the CNS

Answer 38

1. astrocytes 2. oligodendrocytes 3. microglial cells

Question 39

what are astrocytes

Answer 39

these are restricted to the brain and spinal cord. have elaborate local processes that give these cells a star like appearance. the main function of astrocytes is to maintain, an appropriate chemical environment for neuronal signalling and maintain the blood brain barrier

Question 40

what are oligodendrocytes

Answer 40

these are restricted to the brain and spinal cord, lay down a laminated, lipid rich wrapping called myelin around some axons. in the PNSs, the cells that elaborate myelin are called Schwann cells

Question 41

what are microglial ells

Answer 41

primary scavenger cells that remove cellular debris from sites of injury or normal cell turnover. in addition, microglia, like their macrophage counterparts, secrete signalling molecules - particularly a wide range of cytokines that are also produced by immune system cells that can modulate local inflammation and influence cell survival or death

Question 42

what happens to the number of microglia following brain damage

Answer 42

the number of microglia increases at site of injury drastically. some of these cell proliferate from microglia resident in the brain, while others come from macrophages that migrate to the injured area and enter the brain via local disruptions to the blood brain barrier