Lecture 1 Flashcards
Brain weighs how much at birth
About 350g
Brain weighs how much in adulthood
About 1300g
Brain development and maturation is not
Linear
Whens the germinal stage
1-2 weeks
Whens the embryonic stage
3-8 weeks
Whens the fetal stage
9-38 weeks
The nuclei of the egg and sperm fuse to form
A zygote
Zygotes divide by a process called
Cleavage, to form morula
What’s morula
A cluster of homogeneous cells
The morula continues to divide to form
A blastocyst
What stage begins when implantation takes place
Embryonic
In gastrulation, uneven rate of cell development forms what three layers
- Ectoderm
- Mesoderm
- Endoderm
In gastrulation, the ectoderm folds in on itself to form
- The neural tube
- Will eventually become the nervous system
Stages of brain development
- Cell birth (Neurogenesis)
- Cell migration
- Cell differentiation
- Synaptogenesis and synaptic pruning
- Cell death
- Myelination
Cell birth process
- 250,000 neurons are born per minute
- Involves stem cells found in the inner surface of the neural tube
- Stem cells form progenitor cells
- Once formed, new cells migrate out the ventricular zone
Migration process occurs with the help of
- Chemical signals
- Physical support provided by the radial glia
Differentiation and maturation process
- Primitive neurons begin to express genes that cause them to specialise
- Start to form axons and dendrites
- Immature cells get the traits of the region if implanted early
- Once they mature they lose that property
Synaptogenesis and synaptic pruning
- Growth cone is the growing end of axon
- Filopodia is growth cone extensions
- Growth comes attracted to chemicals released from target sites
Cell death process
- Non active synapses will be eliminated
- Apoptosis is programmed cell death
- To avoid apoptosis neurons need neurotrophins and active communication with other neurons
Myelination process
- Glia form fatty sheath on neurons
- Occurs first in the spinal cord, then hindbrain, midbrain and forebrain
- Slow process
- Correlation between Myelination and ability to grasp
Nottebohm found that songbirds
Had a steady replacement of neurons in the singing area
Stem cells in the nose remain
Immature and periodically divide
Hippocampus experiences
Neurogenesis, facilitates learning
Are new neurons formed in our cerebral cortex
No
Where is recovery better than in the brain
The periphery
Can destroyed cell bodies be replaced
No
Can damaged axons grow back
Yes
Recovery in the axons involves
Collateral sprouting, cells secrete neurotrophins that allow sprouting to occur
People blind since infancy have
Enhanced tactile and auditory ability
Burton et al 2002- blindness study
- Sighted and blind people were asked to feel Braille letters and state wether they were the same
- Blind performed better
- Blind had substantial activity in the occipital cortex
What is a critical period
A period during which the brain is most sensitive to a specific experience
When is the brain most vulnerable
Immature brain
What is spina bifida
Failure of the closure of the neural fold at the level of the spinal cord
What is anencephaly
Brain fails to develop, results in stillborn
What things during early development can cause disorders
- Activation of the mother’s immune system
- Prenatal malnutrition
- Substance abuse
- Complications during pregnancy
Which stage of life is more impulsive
Adolescents
Adolescents are 3-4 times more likely to
Die than younger children past infancy
