- [Narrator] The brain
is the most complex organ
in the human body.
As part of the nervous system,
the brain coordinates all
of the body's function.
In adult humans, the
brain is a three-pound
gelatinous mass of fat and protein.
It's comprised of four main regions:
the cerebrum, the
cerebellum, the brainstem,
and the diencephalon, and each
one controls specific tasks.
The largest section is the cerebrum,
and it makes up over 3/4
of the brain's volume.
It consists of neurons and nerve fibers
that transmit information from the neurons
throughout the brain and body.
The cerebrum controls higher functions
such as learning, reasoning, and speech,
plus senses like sight and hearing.
Under the cerebrum is the second largest
part of the brain: the cerebellum.
Much like the cerebrum,
the cerebellum has nerve
cells and nerve fibers.
It carries signals to the
other parts of the brain
and to the spinal cord.
The cerebellum is responsible
for coordinating muscle movements,
particularly those that help maintain
the body's balance and posture.
The third region, the brainstem,
lies in front of the cerebellum
and anchors the brain to the spinal cord.
The brainstem is a
collection of structures
that include the pons,
a mass of nerve fibers that
carry sensory information;
the midbrain, a region
of fibers and structures
that help control movement,
along with auditory and visual processing;
and the medulla oblongata,
which creates motor and sensory pathways
between the midbrain, the
pons, and the spinal cord.
Altogether, the parts of the brainstem
control vital bodily functions,
such as cardiac activity,
respiration, digesting, and sleep.
The fourth region is
located above the brainstem
and makes up the core of
the brain: the diencephalon.
About the size of a apricot,
the diencephalon is a grouping
of several structures.
The thalamus, which processes
and transmits information
from all senses except smell,
and the hypothalamus and pituitary gland,
which work together to produce
and regulate neurochemicals.
These structures help govern sensations,
weight regulation, energy,
and instinctual behaviors,
such as eating, drinking, and having sex.
The brain's four main components,
the diencephalon, brainstem,
cerebellum, and cerebrum,
work in-sync to ensure bodily functions
are fully operational.
The brain has even evolved
mechanisms to protect itself.
One such mechanism is
the blood-brain barrier,
a semipermeable cellular wall
that only allows specific chemicals
to enter from the body's
bloodstream into the brain.
Despite this protection,
tumors and other complications
can lead to life-threatening problems
and diseases in the
brain, such as dementia.
Thankfully, scientists have found ways
to improve brain health.
Staying physically active
and eating a balanced diet
may preserve cognitive function
and even reduce the risk
of developing Alzheimer's.
So, while the brain only makes up
a small percentage of the body,
it plays a crucial role
in the body's functions
and overall well-being.
