|Do cells have brains?
|Question Date: 2007-09-11|
Brains are complex assemblies of cells arranged
to form processing centers in animals. When we
get to smaller and simpler animals, such as worms,
the number of cells in the brain is proportionally
smaller.While human brains have many billions of
cells, a worm may have millions, and the simplest
multcelled life, such as the nearly microscopic
worms C. elegens, have only dozens of brain cells.
But even then, the brain is a group of
specialized cells, such as neurons.
individual cell, there is no brain. But single
cells must still"make decisions". They must react
to the changing environment around them; engage in
growth and cell division, and many of processes.
On the cellular scale, these processes are mostly
mediated by feedback loops-- that is, chains of
chemical events that either reinforce that chain
of events happening again, or that die off when a
critical threshold is released.
if a lake water bacteria has a protein on its
surface that detects food (sugar), then it might
set of a range of chemical reactions in the cell
that cause the cell to move in the direction of
the food. Once it reaches the food, that sensor
protein won't sense food in that direction
anymore, and will stop the chain of chemical
reactions, so the cell will stop and can eat the
food it found. That reaction is very simple, but
as you add up the thousands of proteins and chains
of signaling events within a cell, quite complex
behavior can start to appear. This is a
phenomenon called "emergent behavior", and is also
seen in the patterns that emerge in traffic, or
the complexities that can emerge from a simple set
of rules (like all the billions of possible games
of chess, even though the rules are very
Within each cell this complex set
of interacting chains of simple chemical reactions
controls cell behavior. When we form
multicellular creatures, like humans, the cells
send signals between each other and some cells
specialize in signaling, becoming nerve cells.
This makes the map of chemical interactions
incredibly more complex and intricate, and allows
the formation of higher-order emergent behavior,
such as brain activity and thought.
First we have to define the words cell and
brain. Scientists consider a cell to be the most
basic structure of all living organisms. All
living organisms are composed of one or more
cells, and cells are capable of sustaining
themselves: cells can take in nutrients, convert
nutrients to energy and reproduce themselves. Some
organisms, such as bacteria, are composed of only
one cell, while other organisms, such as humans,
are composed of millions of cells.
Scientists define a brain as the organ of
the body that is enclosed within the skull and
contains all the higher nervous centers. The brain
receives information from other parts of the body
and tells those parts how to operate. So
technically, cells do not have brains because a
brain is defined by scientists as an organ
composed of many cells. Plus, brains are enclosed
within skulls, and only vertebrate animals have
skulls. Individual cells, such as bacteria, do not
have skulls or brains.
cells may seem to have brains because they can
perform complicated activities on their own. Like
brains, they can receive information and respond
The short answer is that cells do not have
brains. Brains are made of many nerve cells
Here's the longer, more
interesting, answer. Some living things are made
of only one cell. We call some of them "protozoa"
(Pro-toe-zoh-uh). Protozoa can have behaviors.
They can go toward or away from light, go around
obstacles, and go toward food. So they don't have
brains, but have simple systems that work like
very basic brains. They can't think,"I'll go over
there," but they can have chemical reactions that
make them move toward the side of a dish that has
Even some animals, the
sponges, don't have nerve cells, but the different
parts of the animal communicate with chemicals.
Sponge adults don't move much but their young are
a lot like protozoa and they swim without any
Some plants actually move their
flowers to face the light. Is this a behavior?
Is it different than a fish swimming toward the
What a great question!We don't generally think
of a cell in our body as having a brain in the way
we think of the human brain. I bet you have heard
about or studied organisms that don't have true
brains but rather "nerve networks" that regulate
and coordinate all the processes of the organism's
body. It seems that our definition of"brain" is
what determines the answer to a question such as
yours. So if we define "brain" as the ability to
receive information, process it and then respond,
then you know what? Cells DO have that ability and
I guess we can say they have "brains." Each cell
has the ability to detect signals from other cells
or the environment and respond to those signals.
That's true for a single celled organism such as
an amoeba or paramecium as well as for an
individual cell living in your body right now.
No - cells (eukaryotic cells, anyway, which
include animals and plants) have organization
centers that function similarly to brains,
however. A cell's information that allows it to
make proteins that do the things that the cell
does is contained in the nucleus. These proteins
are then organized and released in a cluster of
membrane-bound vesicles called the Golgi
apparatus. Individual other organelles within the
cell, such as eye spots and flagella, can
communicate directly, just as our muscles can
communicate with our spinal cord and don't need
direct input from the brain. So, if you will, the
nucleus is like the outer cerebrum (where at least
some memory is stored), and the Golgi apparatus is
like the cerebellum (which coordinates muscle
No, but our brains are made of many
There is a part of the cell called
the nucleus, and it contains the instructions
(genes) that the cell needs to do its job. But
this is not like a brain. It's more like a recipe
or a building plan.
Cells do have something like a brain; it is
called the nucleus. The nucleus is the part of
the cell that holds the entire DNA. I don't know
how much you've learned about DNA, but it is like
a set of blueprints or instructions for the cell.
The DNA has the information the cell needs to
make all of the proteins that it uses to do its
job in the body. Your body can also use
chemicals called hormones to send instructions to
the nucleus of a cell. When a hormone reaches the
nucleus, it gives the nucleus a signal to have the
cell use different parts of the DNA to make
different proteins, which can change the function
of the cell in the body.
There is one
major way that the nucleus is not like a brain,
though. A cell's nucleus can't think for itself -
it just follows the instructions in the DNA. It
can get signals from your body or the outside
environment that tell it to follow those
instructions in a slightly different way. But a
cell cannot plan for the future or make decisions
the same way you can with your brain.
hope this helps answer your question.
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