Brain Function
Copyright 2010:PEER.tamu.edu
We Will Discuss:
• How the brain operates.
• What nerve cells (neurons)
are and what they do.
• What the different parts of
the brain do.
• How the brain creates “three
minds”.
• Healthy Brain
How The Brain Operates
Brains are designed as a control
system for the body. As with any
control system, it has to have sensors
to know what is going on and has to
have ways of evaluating information
making decisions and then issuing
commands.
Class Discussion:
What are some things you
think your brain tells you to
do?
The Brain is an Information
Processor:
(subconscious processing)
Internal vs. External
Stimulus
What Is a Stimulus???
1.
3.
2.
6.
4.
5.
Neuron Function
Nerve Cells are Called Neurons
When neurons are active, as they almost
always are even when you sleep, they do
two things:
– generate electrical pulses
– release chemical secretions
dendrites
(input)
cell body and
nucleus
Direction of impulse and
information flow
axon
dendrites
(terminal)
How NEURONS Take in Information and
Process it!
Neuron Signaling is the term used to
describe the process of neurons passing
information back and forth to one
another.
Neurons have the ability
to pass intracellular
information (within the
cell) and intercellular
information (from one
cell to another cell).
Speedy Processing
Continued:
• Neurons pass information from cell to cell
(intercellular) at synapses through
neurotransmission.
– communication between neurons is accomplished
by the movement of chemicals or electrical signals
across a synapse.
– A synapse occurs where a axon of one neuron
passes information to an dendrite of another
neuron.
How Neurons Have Evolved for
Speedy Processing:
• Neurons communicate within the
cell (intracellular) through
conduction.
– Conduction is when an electrical
signal generated near the cell body
of a neuron moves along the axon
to the axon terminals.
– Ions are the electrically charged
particles moving within the neuron.
Electrical signals are used to
represent, distribute and process
information.
Chemical Signals:
Above: This picture shows 3
different neurons all transmitting
information. Yellow axon to blue
dendrite, blue axon to pink dendrite
is one way to look at it.
An axon to
dendrite
passage of
information
represents
the passing
of chemical
signals.
Chemical signals
help form
memories.
Neurons Excrete Chemicals
• Some neurons excrete chemicals called
hormones into the blood stream
• Most neurons secrete chemicals
directly on each other or on muscle
cell targets.
– The chemicals acts as messengers
(neurotransmitters) to convey information
from one neuron to others.
• Chemicals released vary with different
parts of the brain.
• Over 100 chemical secretions have
been found in nerve tissue
Brain Chemicals
• Neurotransmitters
– excite
– inhibit
– modulate (create a bias for being excited or inhibited)
• Hormones
– Excite neurons (make them fire impulses)
– Inhibit neurons (reduce impulse firing)
– Change the sensitivity of neurons (make them more or
less responsive to other chemicals or electrical input)
Neurochemical Transmission
Packets of
chemicals are
released at
the axon
terminal.
Drugs that
affect the
brain
typically
act on one
or more of
these
processes.
Neurochemical Transmission
Receptors
Nervous System vs. Electricity
How It is Different
• Current carried by ions, not electrons.
• Current flows as pulses, not continuous.
• Current is continuous in the junctions between
neurons.
• Can travel in many different directions at once.
• Chemical and electrical transmitters specifies
different kinds of information being passed.
• Not rigid like solid electrical curcuits.
Lets Discuss:
Can you think of some
advantages of a processing
and communicating system
(the brain) operating this
way?
How does the brain differ from how
computers work? That is, how is the
transfer of communication different
between elements in a computer and
neurons in the brain?
Brains Operate on the Nerveimpulse Representation of the
World, Not the World Itself
Think about that!
Function of Different
Parts of the Brain
Spinal Cord
There is a central "H" zone containing
millions of neurons
• It is surrounded by white
substance, which is many nerve
fibers (axons).
• Some fiber bundles go to the
brain, while others are bringing
information to the spinal cord
from the brain.
Spinal Cord
• Two Way Wiring: Like electrical wiring in your car or your house,
neurons in the spinal cord communicate with the brain by insulated
cables.
• Example: pain information excites neurons to activate muscles that
flex the hip and knee of the leg on the same side as the stimulus.
Pain information is carried in fiber
bundles in the lateral part of the
cord. The pathway has relays in
the brainstem and thalamus
before reaching the cortex.
Common pain killer drugs act at
different levels of the pathway.
Brainstem
Note that human
brainstem is about
the diameter of a
pencil.
deep in the brain – leads to the
spinal cord
Functions:
Breathing,
Heart Rate, Swallowing,
Reflexes to seeing and
hearing (startle response),
Controls sweating, blood
pressure, digestion,
temperature (autonomic
nervous system),
Affects level of alertness
Ability to sleep,
Sense of balance (vestibular
function).
Cerebrum
The biggest part of the brain is the
cerebrum.
The cerebrum makes up 85% of the
brain's weight, and it's easy to see why.
The cerebrum is the thinking part of the
brain and it controls your voluntary
muscles — the ones that move when
you want them to.
So you can't dance — or kick a soccer
ball — without your cerebrum.
Your memory lives in the cerebrum —
both short-term memory (what you
ate for dinner last night) and longterm memory (the name of that
roller-coaster you rode on two
summers ago).
When you're
thinking hard,
you're using your
cerebrum.
You need it to solve
math problems,
figure out a video
game, and draw a
picture.
Cerebrum Continued:
The cerebrum also helps you
reason, like when you figure out
that you'd better do your
homework now because your
mom is taking you to a movie
later.
The left half is said to be more
analytical, helping you with
The cerebrum has
math, logic, and speech.
two halves, with
one on either side
Scientists do know for sure that
of the head.
the right half of the cerebrum
controls the left side of your
Some scientists think that
body, and the left half controls
the right half helps you
the right side
think about abstract things
like music, colors, and
shapes.
Frontal Lobe:
Most anterior, right
under the forehead
Functions:
How we know what we are
doing within our
environment
(consciousness)
How we initiate activity in
response to our
environment
Judgments we make about
what occurs in our daily
activities
Controls our emotional
response
Controls our speaking
language
Memory for habits and
motor activities
Parietal Lobe:
Functions:
Location for visual attention
and touch perception.
Goal-directed, voluntary
movements.
Manipulation of objects.
Integration of different
senses that allows for
understanding a single
concept.
Near the back
and top of the
head
Occipital Lobe:
Most posterior, at
the back of the
head
Functions:
Vision
Temporal Lobe:
Side of head
above ears
Functions:
Hearing ability
Memory acquisition
Some visual
perceptions
Categorization of
objects
Cerebellum
Gold colored area located at the base of the skull.
Functions:
Coordination of voluntary movement
Balance and equilibrium
Some memory for reflex motor acts
The Brain Makes Us
Aware
• Humans have detector cells for:
–
–
–
–
–
–
Light waves (eyes)
Sound waves (ears)
Chemicals that we smell (sensors in the nose)
Chemicals that we taste (tongue sensors)
Physical forces (touch, pressure, cold, heat) (skin sensors)
Muscle tone and limb position (sensors in muscles)
Humans can be consciously aware of many of these
stimuli. We not only know this information, we are
aware that we are aware of it.
The “Reptilian” Brain
“Reptilian” Brain
Functions
• Mostly controlled by brainstem structures
found in all animals (even fish)
• Interaction with spinal reflexes
• Control over neurohormone systems (pituitary
gland)
• Control over automated movements
• Activation of the rest of brain in response to
stimulation
The Brain Makes Us Feel Emotions
• Some of the same
structures used in
emotions are also
involved in memory
formation.
The Limbic System
• Controls emotions
• Controls formation of certain kinds of long-term
memories
• The limbic system is a complex set of structures that lies
on both sides of the thalamus, just under the cerebrum. It
includes the hypothalamus, the hippocampus, the
amygdala, and several other nearby areas.
In primitive mammal brain, most of the brain
is the limbic system.
OB = olfactory bulb, HIP = hippocampus, AC
= anterior commissure (fiber tract connecting
olfactory structures), V – ventricles (cavity),
NC = neocortex, but most of this is really
limbic cortex.
Memory
• Memories are stored widely in the brain.
• The medial temporal lobe and nearby structures,
are responsible for converting temporary
memories into more permanent form.
Ventral view of brain.
Temporal lobe is outlined in
white. * indicates the visible
part of hippocampus.
Hippocampus Consolidates Memory
• Located in area beneath
the ears (medial
temporal lobe)
• Consolidation:
temporary memories
into more permanent
form.
Memory “Consolidation”
• This conversion has certain requirements:
– The brain needs to pay attention so that the
information actually registers in the first place
– Motivation to remember helps
– Time must elapse (seconds to minutes)
– Distractions and other stimuli should be kept to a
minimum, because they will otherwise interfere
with the conversion process
Class Discussion: how do these
ideas apply to learning effectively in
school?
Cool Link Break!
The following link is helpful and useful for kids to
see and hear about the brain:
http://kidshealth.org/misc/movie/bodybasics/bod
ybasics_brain.html
What Sets Us Apart?
The cerebral cortex or neocortex is
what makes us human.
The cerebral cortex is the layer of the brain
often referred to as gray matter.
The cortex (thin layer of tissue) is gray
because nerves in this area lack the
insulation that makes most other parts of
the brain appear to be white.
The cortex covers the outer portion the
cerebrum and cerebellum.
The human cerebral cortex is 2–
4 mm (0.08–0.16 inches) thick.
It is this outer layer
that gives us the
ability to think, to
make choices, and
to reflect on our
emotions rather
than unthinkingly
act on them.
“Wiring Diagram
of Cerebral Cortex
This is what makes us different
• Six layers of cells
surrounding the rest of
brain.
– Other mammals have such
cells, but not as many layers
and not so many.
– Cells organized vertically,
as columns
Area A and B, outer layer 6: mostly all
fibers. Circles labeled L are cell bodies in
different layers. “Thal” and “Sub” refer
the cells in the thalamus and subthalamus
that send inputs to the columns.
Circuit diagram of one column…
connects with adjacent columns.
Humans Are Unique
• What motivates you?
– The desire for pleasurable sensations and
experiences
– The desire to avoid unpleasant sensations and
experiences
• Laughter is one clear difference humans have from
animals
• Likewise, emotion-based crying seems unique to
humans.
The Brain Is the Organ of Personality
• Teenage brains are rapidly changing,
sculpted by experience
• Social environment and thoughts will
affect that sculpting.
• The most profound changes occur in
the front of the brain, the part that is
crucial for advanced functions such as
critical thinking, self-control, and
judgment.
• The frontal cortex does not mature
until about age 25.
Importance of Technology:
The Oscilloscope
The electricity in a nerve involves such a small amount of current that it
has to be made bigger and displayed by a TV-like instrument called
an oscilloscope.
Voltage changes deflect the beam
moving across the screen
Brain Waves
• Currents in the part of the brain nearest to the scalp are large
enough to be detected with electrodes
• This electrical activity is small (on the order of 10 to 50
millionths of a volt).
Brain Creates Mind
Actually Three Minds
• Unconscious: spinal and brainstem
reflexes, hormone controls
• Subconscious: emotions, wellestablished memories
• Conscious: newly forming
memories, self awareness
Your brain has a mind of its own
Brain affects mind. Mind affects brain.
Brain affects behavior and hormone release.
Where Does Consciousness Come
From?
It comes from the interaction between:
– the cerebral cortex (outer part of the brain)
– a cluster of cells in the core of the brainstem
• Lower animals have many fewer
cells in their cortex than us.
• Therefore, they cannot operate at
the same high level of
consciousness as we do.
Improving Your Mind
• You can train your brain to have
certain attitudes, beliefs, capabilities.
• You can abuse your brain by feeding it
bad ideas, unhealthy ideas, or drugs
that affect the mind.
• Feeding junk ideas, information, and
feelings to your brain can affect your
brain and behavior permanently.
Improving Your Mind, cont.
• Brains affect behavior.
• But behavior (and thoughts that control
behavior) affect the brain.
Let’s Discuss:
Can we blame our bad brains for our bad
behavior and thoughts?
Or is that just an excuse for our failure to
make better behavior choices?
Be Good to Your Brain
What can you do for your brain?
• Eat healthy foods.
– They contain potassium and calcium, two
minerals that are important for the nervous
system.
• Get a lot of playtime (exercise).
• Wear a helmet when you ride your bike or play
other sports that require head protection.
• Don't drink alcohol, take drugs, or use tobacco.
• Use your brain by doing challenging activities\
– such as puzzles, reading, playing music,
making art, or anything else that gives your
brain a workout
Do you want
your brain to
look like
this?
or
This?
Brain Function: Conclusion
• Remember, mistreating your brain can
permanently alter the way you learn, feel
rewarded, and store memories.
• Keep your brain healthy through proper
nutrition to support neuron development and
by training yourself to have positive attitudes,
beliefs, capabilities!
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Brain Development and Behavior