Hierarchy of organisation
- Levels are connected.
- Any manipulation at any level can change the function at other and at all levels of the hierarchy.
* Whole brain
* Brain Circuits
* Brain Regions
* Cells (neurons and glia)
* Organelles (synapses/axons)
* Protein complexes
* Proteins
* Genes
The Building blocks of the brain
Neurodevelopment -> genetics
Neurophysiology
Neurotransmission + Neuromodulation, Molecular Aspects of L&M, Pain
Behaviour
Social Behaviour, Sleep & Circadian Rhythms, Typical + Atypical, Functioning
Facts about the brain
- Brain weight at birth weighs about 350g whereas, in adulthood it is about 1300g.
- There are about 85 billion neurons and trillions of synapses in the mature brain.
- At the peak of neurogenesis, 250,000 neurons are born per minute.
Germinal stage
First part after fertilisation
* The nuclei of the egg and the sperm fuse to form a zygote.
* Zygote starts to divide at 12h, by a process called cleavage, to form a cluster of homogeneous cells – morulla.
* The morulla continues to divide to form a blastocyst (200-300 cells)
Once implantation in the uterus takes place the embryonic stage begins.
Embryonic stage
- Gastrulation -> refers to the differentiation of different layers of cell formation.
- Initially – embryonic disc – it starts to develop in an uneven way.
Uneven rates of cell development from three distinct layers
- Ectoderm
- Mesoderm
- Endoderm
The Ectoderm will fold to form the neural tube which will eventually become the nervous system. Formation of the Nervous System:
Neural tube defects
Spina Bifida -> failure of the closure of the neural fold at the level of the spinal cord.
* 1 in 1000 live births
* small openings can often be surgically corrected.
* larger opening can lead to paralysis and limb deformities.
* Can be prevented by folic acid supplements.
Anencephaly -> brain fails to develop – generally results in stillborn.
Stages of brain development
Cell birth/ Proliferation (Neurogenesis and Gliogenesis)
2. Cell migration
3. Cell differentiation and maturation
4. Synaptogenesis and synaptic pruning
5. Cell death
6. Myelination (myelogenesis)
Impact of experience on synapse formation
Experience expectant (Greenough and Black, 1992)
* Development will not happen unless an experience happens during its critical period (the result of evolution and genes) and it is species-specific.
Experience dependent are not permitted but are generated in response to the environment.
* Vary between individuals i.e., rats in complex environments have more synapses and more neurons than the ones in standard conditions.
