Astounding Facts About the Amazing Human Brain!
- The brain is one of the first organs to develop in a human embryo, and it continues to change and mature for a person’s entire life!
- All 100 billion nerve cells present in an adult’s brain have been made by the time a fetus is six months old!
- A newborn’s brain weighs 25 percent of its adult weight at birth. By two years of age, a toddler’s brain has reached 75 percent of its adult weight!
- Sixty percent of the human genome (a person’s genetic makeup) — or 60 thousand genes — is dedicated to brain development!
While the brain’s different parts develop on different timelines for different individuals, the stages of development are the same for all of us. Below are some developmental milestones of the human brain, beginning with its formation in utero.
Four weeks after conception, a thin layer of cells forms along the back side of the embryo. The cells continue dividing, and the layer, now the neural plate, thickens, eventually folding in on itself and forming a tube whose ends later fuse. The upper end will become the brain structure, and the lower end will form the spinal cord. The neural tube is the beginning of the embryo’s central nervous system.
One month after conception, cells in the neural tube begin multiplying extremely fast — at times, as many as 250 thousand nerve cells, or neurons, are created per minute!
Neurons conduct electrical impulses, or signals, from the brain to the rest of the body, and from the body to the brain. All organs and body parts continuously send the brain status reports through tiny electric signals that are passed along a neuron’s body, or axon, and out to the connecting points between neurons, or synapses. Neurons, then, support the brain’s ongoing regulation and maintenance of the body’s basic homeostatic processes, as well as the brain’s processing of input from all five senses.
At birth, most of the brain’s 100 billion neurons are not yet interconnected. Some neurons have been assigned to specific autonomic, life-sustaining functions (e.g., heart beat and breathing); but most have not yet been given a task and are inactive. These neurons now wait for the newborn to begin having sensory experiences — seeing, smelling, hearing, tasting, feeling — which will stimulate the neurons to form trillions of synapses, as well as establish neural communication pathways.
The first three years of life are a period of fast growth in the human brain. A three-year-old’s brain is twice as active as an adult’s! Ways to enrich a toddler’s brain and stimulate synaptic connections include: having back-and-forth, loving conversations; singing; reading to her; playing. Interactions with other humans, of any age, are a better method of stimulating a child’s brain than watching television!
Educators rely on the young brain’s plasticity — its ability to be molded by experiences — to teach school-age children. Repeating learned information, such as the spelling of words or multiplication tables, will form synaptic connections that will preserve those memories for life. Synaptogenesis, the formation of connections between synapses that started in the womb, continues throughout childhood and into adulthood.
From around age ten on, most brain changes serve to improve function of the more sophisticated and versatile frontal lobes, which are involved in motor function, problem-solving, memory, language and impulse control.
Two brain growth spurts occur as the child enters the teenage years: between ages 13 and 15, brain size and function increase, especially in motor and spatial perception areas of the frontal cortex. At around this time, the pea-sized pituitary gland, located at the base of the brain, starts secreting different hormones into the bloodstream that will cause other organs to secrete hormones of their own — giving way to sexual maturation and reproductive capability.
The second growth spurt happens at about age 17, when the frontal lobes increase in size again, as do their synaptic connections to the rest of the brain. Final adult brain weight of 1300 – 1400g (3 lbs.) is reached in the late teens.
By age 18, through periodic “pruning” — the brain’s shedding of weak connections between neurons — the number of synapses in an 18-year-old’s brain has been reduced from 1,000 trillion to 500 trillion — the same number that an 8-month-old baby has!
The ongoing debate about the influence of nature, or genes, vs. nurture, or environment, in shaping a young person’s brain — and by extension, their personality — seems to be reaching a peaceful compromise, with most health and medical experts now agreeing that both nature and nurture can be, and are, important. Many of the genes or genetic predispositions in a person’s genome can be swayed in this or the opposite direction, based on the experiences to which we’re exposed from birth — or even before birth.
And in our age of increased vigilance over such factors as pollutants and maintaining healthy lifestyles, it’s worthy of mention that avoiding toxins, eating healthy natural diets, and getting plenty of sleep and exercise will optimize the brain’s potential, helping to keep it — and the rest of our body — healthy and happy.
By Marc Courtiol