Brain Awareness Week 2012

Welcome to Brain Development

width=320px|height=260px|controller=false|autoplay=true</qt>

In today's demonstration we will be looking at how the brain develops from a simple tube into the complex folded structure that you will be seeing (and using) today. This animation shows a real human adult brain being "sliced", the cortex (grey matter) is on the outside. This page has been prepared as a simplified introduction to human neural development.

Here is Human Development

This graph shows how we divide human development into different times. Key events occur in the first trimester (embryonic), though the neural system continues to develop through the second and third trimester (fetal) and even after birth (postnatal). This is why it one reason why it is so susceptible to damage.

Here is how the human nervous system grows

Week 3	Week 4 to 5	Week 5	Week 6	Week 8	Week 13 to 21	Adult Human
Neural Plate	Neural Tube	Simple Tube	Folded Tube	Central Nervous	Fetal Brain	Brain Slices

Here is a developing mouse nervous system

width=336px|height=415px|controller=true|autoplay=false</qt>

This movie shows a 11.5 days old mouse brain. (Mouse development takes 21 days and is a model used in research) Red - brain Blue - heart Brown - liver

Mouse E11.5

It begins as a Plate

width=316px|height=520px|controller=true|autoplay=false</qt> Quicktime

This embryo is the whole human embryo at just 3 weeks after fertilisation. the entire nervous system will form from the flat region shown in blue. this is called the NEURAL PLATE. the broad blue region at the top will form the brain. the narrow blue region at the bottom will form the spinal cord.

This human embryo in week 3 is about 1-1.5 mm long and is viewed from the back, head end to the top. Almost all you see is the neural plate.

That folds to a Tube

width=480px|height=500px|controller=true|autoplay=false</qt>

The human embryo is now 4 weeks old and sits on top of a big yolk sac. the neural plate is shown on the embryo back. the plate now folds to form a hollow NEURAL TUBE

The same view at week 4, the embryo is now 2 - 3.5 mm long. The neural plate can be seen folding down the middle of the back, beginning to form the neural tube.

The tube then Closes at each End

These images show the neural tube closing leaving an opening (neuropore) at each end.

Why are these important?

The brain end of the tube forms 3 Vesicles

width=516px|height=540px|controller=true|loop=true|autoplay=true</qt>

Week 6 - the brain and spinal cord of the human embryo. Also visible are the heart (bright white) and placental cord containing placental blood vessels. Week 6 Carnegie stage 17

Brain

At the brain end - the tube expands to form three vesicle (sac or bubble) regions. These will form different parts of the brain and brain stem.

Week 8 wall of the neural tube at the brain end, the smaller images (top right) show the section level from the embryo. The thin layer outer called cortical plate will eventually form the adult brain cortex. The other underlying layers are part of the development process and will continue to supply cells to the cortex through fetal period, these layers will eventually be mainly lost. The ventricle is the fluid-filled space within the brain.

Spinal Cord

At the spinal cord end - the tube stays narrow. This region begins to put out motor nerves to innervate muscle and sensory nerves grow towards the developing spinal cord.

Week 8 wall of the neural tube at the spinal cord end, lying behind the vertebral body. The dark central region is where the neurons (cell bodies, grey matter) are located, the pale outer region is where nerve fibres run (axons, white matter). The dorsal root ganglia lie outside the spinal cord and contain the cell bodies of the sensory neurons.

Fetal brain Grows

This shows the growth of the brain and the fluid-filled space within the brain (the red bar is 1 cm).

• The brain goes from having a smooth surface to begin to fold or "wrinkle" as the surface area grows.
• The fluid space is filled with cerebrospinal fluid or CSF.

Newborn brain Grows

The brain has not finished growing at birth.

Much of the growth in size after birth is due to "white matter" development, the support cells of the brain, spinal cord and nerves.