Exam 2 Flashcards
fertilization
- occurs when sperm enters egg and they fuse together
- series of steps that leads to a zygote
zygote
- a set of multiple cells that double during each round of division
- zygotic period (few days long) is the early stage of the embryonic period
- zygote is an embryo
- zygote cells can become any cell
gastrula
- multiple divisions of zygote lead to gastrula
- hollow cup-shaped structure with 3 layers of cells (ectoderm, endoderm, mesoderm)
3 layers of gastrula
- ectoderm
- endoderm
- mesoderm
ectoderm
becomes nervous system and brain
mesoderm
- includes notochord
- includes somites (nerves that come out of spinal cord)
notochord
sends signals to the ectoderm to transform into nervous system
steps from ectoderm to nervous system/brain
- ectoderm has neural plate
- notochord sends neurotrophins to initiate neural folding
- neural plate folds creating neural groove
- neural crest cells fuse together creating the neural tube from the neural groove
- neural tube stretches and zippers up at posterior and anterior ends
- the neural tube elongates to create the spinal cord and the brain
forebrain
- prosencephalon
- made up of cortex, basal ganglia, limbic system
midbrain
mesencephalon
hindbrain
- rhombencephalon
- made up of cerebellum, pons, medulla
neurogenesis
- creation of new neurons that fill cortical layers that cause the cortex to undergo rapid growth
- occurs in ventricular zone (lining of ventricles)
cortex
- contains 6 layers
- neurons radiate from ventricular zone outwards to fill out cortical layers by riding on radial glial cells
- radial glial cells must be made and extend to the top of the cortex; neurons that are created use the radial glial cells as a scaffold to climb up and integrate themselves into cortical layers
- cortex layers lower down are thicker
process outgrowth
growth of axons and dendrites
synaptogenesis
formation of synapse extensions emerge from growth cones at the tips of axons and dendrites
synaptic pruning
- synapses are lost and myelination occurs, increasing efficiency of neuronal communication
- leads to reduction of cortical thickness over time (loss of dendrites and cell death)
growth cone
- extension of a developing neuron
- growth cone connects to target forming a synapse and if enough stimulation a larger synapse will occur
filopodia
- tips of growth cone
- make synapses onto dendritic spines
- after growth cone meets target, filopodia makes direct contact
- can retract into lamopodia and extend in different directions
chemoattractants
chemicals that attract lamopodia/filopodia and tell them to grow in their direction
chemorepellants
chemicals that repel growth cones/filopodia and tell them not to grow in their direction
neuronal migration
- filopodia extend and find targets to synapse with
- chemoattractants and chemorepellants direct filopodia
- this process occurs during initial development of NS as seen in neural tube and spinal cord development
- this continues to occur throughout development as shown by cortical development
neurotrophins
- can increase/decrease synaptic pruning
- neurons compete for neurotrophins that the target cells make, and without enough neurotrophins, the neurons die
- help maintain synapses
brain derived neurotrophic factor (BDNF)
- neurotrophin
- supports neuronal survival
- can increase synaptogenesis
- shown to be important in preventing depression
- necessary for inhibiting anxiety
- loss of BDNF can result in shrinking of hippocampus
nerve growth factor (NGF)
- neurotrophin
- affects growth of neurons
schizophrenia
- abnormal prefrontal cortical development
- impairs working memory
- during early adulthood brain goes through synaptic pruning/myelination increase, which can cause onset of schizophrenia
working memory
- the ability to hold information in mind, it’s like concentrating
- working memory deficits in schizophrenics is likely due to the abnormal function of the prefrontal cortex
DISC1
- gene associated with schizophrenia
- DISC1 is important in neuronal migration during early cortical development and plays a crucial role in neuronal communication
- the mutation causes neurons to fill cortical layers incorrectly
evolution
- occurs when there is a change of gene frequency within a population over time
- the change in genes occurs when the next generation inherits genes from their parents