chapter 8 - Nervous system Development Flashcards
which chromosome does the egg contribute
X
which chromosome does the sperm contribute
X or Y
- What age of mother does prenatal development issues increase?
- What issues can arise?
- What is a solution?
35+
- genetic errors
- birth defects
this is people use donor eggs
About a week afer conception, which hormone is released into the bloodstream and what does it do?
human Chorionic Gonadotropin
-released by the placenta
-prevents menstration
-stimulates proestrone production (stability)
How is sex determination different in reptiles compaired with mammals
mammals - **sex chromosomes **(XY)
reptiles -** tempurature dependent**
which chromosome is bigger? X or Y
X - 1600 genes
Y - 50 genes
what is the SRY gene
**Sex Determining region-Y
**
found on the Y chromosome and determines male gender
ABSENCE (mutation, deletion, XX) - leads to female reproductive parts
What are the primordial reproductive systems
Males - Wolfian (mullerian inhibiting substance regresses Mullerian)
female - Mullerian (absence of Testosterone regresses Wolfian)
What happens to the male fetus at 3 month?
more testoterones
more MIS (mullerian inhibiting substance)
What is “Masculization of the male Brain”
developing traits of the male brain caused by:
- perinatal testosterone exposure
- Aromatization: Aromatase (conversion of the test into estradiol)
The conversion of testosterone into estrogen is essential for making the male brain develop in a way that aligns with male characteristics, such as aggression, spatial skills, or sex drive.
What is Aromatization?
Gonadal Testosterone –> brain (aromatase) –> Estradiol
The conversion of testosterone into estrogen is essential for making the male brain develop in a way that aligns with male characteristics, such as aggression, spatial skills, or sex drive.
What is Estradiol?
A powerful form of estrogen
masulinizes the male brain
Female fetus: what prevents estradiol from masulinzing the female brain
Alpha-Feto-Protein keeps it out of the female BBB
Where is Aromatization most active?
Hypothalamus (hormone regulation)
Amygdala (emotion and behaviour)
How is spatial visualiztion differnt in males and females
males: object rotation (partietal Lobe)
females:** location memory** (Hippocampus)
different cognitive effects from different receptors in the brain being acted on
what is totipotent
ability of a cell to differentiate into all types of cells necessary to form a complete organism (CELLS IN FERTILIZED EGG)
- skin and bone cells
- neurons and glial cells
fertilized egg —-> zygot stage —–> embryo stage —-> fetal stage
Zygot stage
first stage after fertilization
cells divide and start multiplying
fertilized egg —-> zygot stage —–> embryo stage —-> fetal stage
Embryo stage
fertilized egg —-> zygot stage —–> embryo stage —-> fetal stage
Embryo stage: all vertebrates look the same in this stage
Neural plate
Formed during embryo stage
ectodermal structure that forms the CNS
Neural tube
formed by neural plate after it folds and closes
anterior end - brain
posterior end - spinal cord
Neural Crest
formed by cells from neural tube and ectoderm
becomes PNS
Ectoderm
Mesoderm
Endoderm
Ectoderm - skin, CNS
Mesoderm - bones, muscle, dermis (underskin)
Endoderm - internal organs linning
Development of the human nervous system: day 18 - 24
day 18: neural plate (primitive neural tissue)
day 21: neural plate —-> neural groove
day 22: nerual groove —> neural tube
day 23:
anterior neural tube –> folds into brain
posterior neural tube –> folds spinal cord
day 24: you have a developing forbrain and heart
what does the open regions in the center of the neuronal tube form into?
the ventricles of the heart
Spina Bifida
Neural tube defect…
posterior neuronal tube fails to close
Anecephaly
Neural tube defect…
anterior neuronal tube fails to close
what day does the heart start beating
day 35
why are stem cells so important
Totipotent - can become any cell or duplicate itsself
DAUGHTER CELLS are Multipotent - differentiates into a specific lineage
where are stem cells found
stem cell –> Progenitor Cell –> blast cell
subventricular zone
Progenitor Cell
stem cell –> Progenitor Cell –> blast cell
differentiates into neural cells or glial cells
blast Cells
stem cell –> Progenitor Cell –> blast cell
neuroblast or glioblast
Tangentail migration
cells leaving the neural tube tangential to hte subventricular zone
Radial Migration
cells leaving the neural tube in the direction of the radius of the subventricular zone
MAIN way of cell migration
NeoCortex
source of higher cognition
Radial Cell migration in the NeoCortex
reelin tells the cell exactly what layer to go to. They aggregate (clump/cluster) to make connections
during radial cell migration in the NeoCortex, does it fill top-bottom or bottom-top
bottom-top
deepest layers closer to the ventricular zone get filled first
migration -> aggregation -> differentiates -> matures
what grows faster, axon or dendrite
axon
Axonal Growth: growth cone & filopodia
growth cone: tip of axon that is growing
filopodia: the end of the cones that are reaching out looking for connections (Synaptogenesis)
Synaptogenesis
making new connections
-help from Neurotropic Factors (BDNF)
neurotropic factors (ex: BDNF)
proteins that aid in signaling and contribute to the browth and health of neurons
-help plasticity
brain development (slide 54) look at this
Cell death methods (2)
Necrosis - uncontrolled death (cut)
Apoptosis - programmed death
Why is cell death important? give an example
Example: SynDactyly
fingers welded together beacuse skin cells dont die
last stage of development
myelination
How does synaptic pruning work?
(occurs after 1st year alive and then into childhood)
happens because neurons compete for BDNF (NEURAL DARWANISM)
only the nessecary synapses stay
Whats an example of synapses rearranging/focusing/streamlining/pruning
2 months: baby reaches towards object
4 months: grabs with entire hand
10 months: pincer with thumb and index
experience and brain development: Critical period vs. Sensitive Period
Critical Period: Development is irreversibly impacted (vision)(amblyopia)
Sensitive Period: Development is optimal during the period, but it is possible to learn or adapt later (language)
what is Amblyopia? which period?
Vision doesnt develope properly (lazy eye) in Critical Period
Development disorders:
Autism Spectrum Disorder (ASD)
-bad social skills
-repetitive behaviours (extreme cases)
-too many synapses
Williams Syndrome
-genetic
-physical abnormalities (big eyes)
-good at music and speak alot
-bad social skills
-low IQ
Brain changes in Williams Syndrom
increased cortical volume in Broncus area (speach)(music)
decrease cortical volume in Frontal Lobe (spatial awarness)
