Making sense of the brain's mind-boggling complexity isn't easy. What we do know is that it's the organ that makes us h...
Making sense of the brain's mind-boggling complexity isn't easy. What
we do know is that it's the organ that makes us human, giving people
the capacity for art, language, moral judgments, and rational thought.
It's also responsible for each individual's personality, memories,
movements, and how we sense the world.
All this comes from a
jellylike mass of fat and protein weighing about 3 pounds (1.4
kilograms). It is, nevertheless, one of the body's biggest organs,
consisting of some 100 billion nerve cells that not only put together
thoughts and highly coordinated physical actions but regulate our
unconscious body processes, such as digestion and breathing.
The brain's nerve cells are known as neurons,
which make up the organ's so-called "gray matter." The neurons transmit
and gather electrochemical signals that are communicated via a network
of millions of nerve fibers called dendrites and axons. These are the brain's "white matter."
The cerebrum
is the largest part of the brain, accounting for 85 percent of the
organ's weight. The distinctive, deeply wrinkled outer surface is the cerebral cortex,
which consists of gray matter. Beneath this lies the white matter. It's
the cerebrum that makes the human brain—and therefore humans—so
formidable. Whereas animals such as elephants, dolphins, and whales have
larger brains, humans have the most developed cerebrum. It's packed to
capacity inside our skulls, enveloping the rest of the brain, with the
deep folds cleverly maximizing the cortex area.
The cerebrum has two halves, or hemispheres. It is further divided into four regions, or lobes, in each hemisphere. The frontal lobes, located behind the forehead, are involved with speech, thought, learning, emotion, and movement. Behind them are the parietal lobes, which process sensory information such as touch, temperature, and pain. At the rear of the brain are the occipital lobes, dealing with vision. Lastly, there are the temporal lobes, near the temples, which are involved with hearing and memory.
Movement and Balance
The second largest part of the brain is the cerebellum,
which sits beneath the back of the cerebrum. It is responsible for
coordinating muscle movement and controlling our balance. Consisting of
both grey and white matter, the cerebellum transmits information to the
spinal cord and other parts of the brain.
The diencephalon is located in the core of the brain. A complex of structures roughly the size of an apricot, the two major sections are the thalamus and hypothalamus.
The thalamus acts as a relay station for incoming nerve impulses from
around the body that are then forwarded to the appropriate brain region
for processing. The hypothalamus controls hormone secretions from the
nearby pituitary gland. These hormones govern growth
and instinctual behavior such as eating, drinking, sex, anger, and
reproduction. The hypothalamus, for instance, controls when a new mother
starts to lactate.
The brain stem, at the
organ's base, controls reflexes and crucial, basic life functions such
as heart rate, breathing, and blood pressure. It also regulates when you
feel sleepy or awake.
The brain is extremely sensitive and
delicate, and so requires maximum protection. This is provided by the
surrounding skull and three tough membranes called meninges. The spaces
between these membranes are filled with fluid that cushions the brain
and keeps it from being damaged by contact with the inside of the skull.
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