Extra Yaffas Notes Flashcards
where do the neural crest arise from
the dorsal neural tube along the entire length of the spinal cord and hindbrain
what gene to neural crest cells express
Hox genes that are limited to various spinal cord and hindbrain domains
what do all neural crest cells begin as
neuroepithelial cells and thus have all the cellular junctions and adhesive interaction that jeep epithelial cells inlace
what do neural crest cells have to do to move
must down regulate expression of these adhesive genes and undergo an epithelial-to-mesenchymal transition
what transcription factors to neural crest cells express
bHLH family members Snail1 and Snail 2 which repress expression of intercellular junctional proteins and epithelial adhesion molecules
when the neural crest cells reach their final destination what happens
they cease to express Snail1/Snail2 and other transcription factors that favour the mesenchymal migratory state
what do a minatory of nerve and glial cells in the CNS use as migratory guides
existing axon pathways
how do neuroblasts reach their final destination
use the long process of radial glia as scaffolds, travelling along the radial glial fibres in order to reach their final destinations
what is the nervous system patterned along
both the DV and AP axes
what is the DV axis set up by
by the TGF-beta family and Shh
what is the AP axis set up by
retinoic acid, FGF, and homeotic genes
what is dysraphism
incomplete fusion - where there is continuity between the posterior neuroextoderm and the cutaneous ectoderm
when is the abnormal increase in maternal serum alpha fetoprotein detected
16-18 weeks
what does maternal serum screening not detect
closed defects and is less sensitive in women taking sodium valproate
when can anencephaly be detected
12th weel
when can SB be detected
16-20weels
what is the banana sign
refers to the shape of the cerebellum, owing to caudal tail displacement
when does the lemon sign disappear
24 weeks
what is the treatment for adults with type 1 oe 2 chairi malformations
posterior fossa decompression surgery to create more space for the cerebella, and to relieve pressure on the spinal cord
what is the absent brain replaced by in anencephaly
malformed cystic tissue
what is a cephalocele
herniation of cranial contents through a skull defect
what are the several subtypes of cephaloceles
- cranial meningocele: contains ony meninges
- encephalocele: contains brain tissue
- ventriculocele: contains part of the ventricle within the herniated portion of the brain
what are cephaloceles also associated with
other brain abnormalities such as agenesis pf the corpus callosum or abnormal gyration
what is holoprosencephaly
occurs when the embryonic prosencephalon does not undergo segmentation and cleavage - into telencephalon and diencephalon
what is abnormal in holoprosencephaly
the anterior midline brain, cranium and face are abnormal
what is the holoprosencephaly caused by
defects of the sonic hedgehog gene
what can hydrocephalus result from
- excess CSF production
- decrease in reabsorption via the arachnoid granulations
- obstruction of flow at any point in the ventricles or subarachnoid space
what is hydrocephalus catagorised into in clinical practice
- communicating hydrocephalus: this is caused by impaired CSF reabsorption in the arachnoid granulations, obstruction of flow in the subarachnoid space, or excess CSF production
- obstructive (non communicating) hydrocephalus: caused by obstruction of flow within the ventricular system
which nerve may be affected in hydrocephalus
the sixth cranial nerve - affects eyes
what is bipolar type 1
this is defined as one of more manic or mixed (signs of mania and depression) episodes - severe bipolar
what is bipolar 2
this is defined as a depressive episode with at least one episode of hypomania - milder form of bipolar
what is the average onset age of bipolar
21
sodium valporate (Depakote) mode of action
1) maybe increasing gamma levels in the brain
2) altering the properties of voltage dependent sodium channels
mechanism of valproate in more detail
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.
what are glia
connective tissue of the nervous system, consisting of several different types of cell associated with neurones
by what ratio do glia outnumber neurones
3 to 1
what roles do glial cells play in the nervous system
- 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
what are the three types of glial cells in the CNS
- astrocytes
- oligodendrocytes
- microglial cells
what are astrocytes
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
what are oligodendrocytes
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
what are microglial ells
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
what happens to the number of microglia following brain damage
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
