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examBoard: AQA
examType: GCSE
lessonTitle: Neural Structures in the Womb
The human brain begins as a simple tube of cells and develops into the most complex organ in our body - all before we're even born! This amazing journey happens during pregnancy, when billions of neurons (brain cells) form, organise themselves and create connections that will shape who we become.
Key Definitions:
Brain development follows a specific timeline during pregnancy. Let's explore what happens at each stage:
Weeks 3-4: The neural tube forms. This is the very beginning of the brain and spinal cord.
Weeks 5-6: The neural tube closes and begins to divide into three main sections that will become the forebrain, midbrain and hindbrain.
Weeks 7-12: Neurons begin to form at an astonishing rate - about 250,000 neurons per minute! The cerebral hemispheres start to develop.
Weeks 13-24: The cerebral cortex develops its six layers. Neurons migrate to their final positions. The cerebellum begins to form.
Weeks 25-28: The brain begins to fold, creating its characteristic wrinkled appearance to fit more surface area inside the skull.
Weeks 29-40: Rapid synaptogenesis (connection-making) occurs. Myelination begins. The brain grows dramatically in size.
Different parts of the brain develop at different times and rates. Understanding this helps us see how the brain's architecture is built from the ground up.
One of the first structures to develop. Controls basic life functions like breathing and heart rate. Nearly complete by the end of the second trimester.
Develops throughout pregnancy. Responsible for coordination and movement. Continues rapid growth after birth.
Develops mainly in the second half of pregnancy. Responsible for thinking, memory, language and consciousness. The most complex part of the brain.
Brain development isn't just about growth - it's about creating a precisely organised network. This happens through several key processes:
Neurogenesis is the birth of neurons, which begins around week 5 of pregnancy. By the time a baby is born, they have almost all the neurons they'll ever have - about 100 billion! Most neurons are produced in special zones near the centre of the developing brain, then they travel outward to their final destinations.
Once neurons are born, they need to travel to the right location. This migration is guided by special cells called glial cells, which act like scaffolding for the neurons to climb along. If neurons don't reach the right place, it can lead to developmental problems.
After neurons reach their destinations, they start to connect with each other by forming synapses. These connections allow neurons to communicate. By the time a baby is born, they have about 50 trillion synapses! After birth, the brain continues to form new connections based on experiences and learning.
Interestingly, brain development isn't just about growing - it's also about cutting back. The brain creates more connections than it needs, then "prunes" the ones that aren't used. This process continues throughout childhood and adolescence, helping the brain become more efficient.
In the 1980s and 1990s, thousands of children in Romania were raised in severely deprived orphanages. Studies of these children showed that early brain development can be significantly affected by environment. Children who spent their early years in these institutions often had smaller brains and reduced activity in certain brain regions compared to children raised in families. This research highlighted how crucial the early environment is for proper brain development, even after birth. When some orphans were later adopted into supportive families, they showed some recovery, but certain effects remained, suggesting critical periods for brain development.
Several factors can influence how the brain develops before birth:
As the brain develops, it begins to function even before birth. By the third trimester, the fetus can:
These early functions show that the brain is already working and preparing for life outside the womb. For example, a fetus that regularly hears a particular song or story may show recognition of it after birth!
The way the brain develops before birth sets the foundation for all future development. The basic architecture of the brain is established during this time, creating the framework for learning, behaviour and health throughout life.
Scientists now understand that many conditions that appear later in life may have roots in prenatal brain development. This is why protecting brain development during pregnancy is so important - it's much easier to build a healthy brain from the start than to try to fix problems later.
Brain development in the womb is an incredible journey from a simple tube to a complex organ with billions of connected neurons. This development follows a specific timeline and involves processes like neurogenesis, migration and synaptogenesis. Many factors can influence brain development, including nutrition, stress and exposure to toxins. The brain begins functioning before birth, showing early signs of learning and sensory processing. This early development sets the stage for all future brain function and development throughout life.
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