Brain and Behaviour (1): Neurodevelopment 1

What is the weight of the brain at birth and adulthood?

• Birth: 350g

• Adult: 1300g

How many neurons are in the brain, and how many synapses are there?

85 Billion Neurons, Trillions of synapses

How many neurons are born per minute during peak neurogenesis?

250,000 neurons per minute

What are the Prenatal Development Stages?

• Germinal Stage (1-2 weeks)

• Embryonic Stage (3-8 Weeks)

• Foetal Stage (9-38 weeks)

What happens during the germinal stage of development?

• Nuclei of egg and sperm fuse to form a zygote.

• Zygote cleaves at 12 hours to form the morula.

• Morula divides to form the blastocyst (200-300 cells)

  After this, implantation occurs.

What happens during gastrulation in the embryonic stage?

1. Formation of the embryonic disc.

2. Cell development forms 3 layers:

   • Ectoderm

   • Mesoderm

   • Endoderm

3. Endoderm folds in on itself to form the neural tube, which becomes the nervous system.

What are types of 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 be surgically corrected; larger openings may lead to paralysis and limb deformities.

• Anencephaly: Brain fails to develop, leading to stillbirth.

What are the stages of brain development?

• Cell Birth

• Cell Migration

• Cell Differentiation and Maturation

• Synaptogenesis and Synaptic Pruning

• Cell Death

• Myelination

What is the difference between Experience-Expectant and Experience-Dependent synapse formation?

• Experience-Expectant: Development depends on an experience occurring during a critical period.

• Experience-Dependent: Development is NOT predetermined and happens in response to the environment.