Biological Bases
of Behavior
Neural Anatomy
Searching for the self by studying the body
Phrenology
Phrenology
(developed by Franz Gall in
the early 1800’s):
the study of bumps on the
skull and their relationship
to mental abilities and
character traits
 Phrenology yielded one big idea-that the brain might have
different areas that do different
things (localization of function).
Today’s search for the biology of the self: biological
psychology
 Biological psychology
includes neuroscience,
behavior genetics,
neuropsychology, and
evolutionary psychology.
 All of these
subspecialties explore
different aspects of:
how the nature of mind
and behavior is rooted in
our biological heritage.
 Our study of the biology
of the mind begins with
the “atoms” of the mind:
neurons.
Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
Action potential:
a neural impulse that travels down an
axon like a wave
Just as “the wave” can flow to the right in a stadium even
though the people only move up and down, a wave moves
down an axon although it is only made up of ion exchanges
moving in and out.
The Synapse
The synapse is a
junction between the
axon tip of the
sending neuron and
the dendrite or cell
body of the receiving
neuron.
The synapse is
also known as the
“synaptic
junction” or
“synaptic gap.”
Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
Neural Transmission
Neural Transmission
 Movement
of ions causes polarization, which
potentiates the impulse along the axon.
 The INSIDE of the neuron (axon) contains more
K+ than the OUTSIDE.

Keep in mind, this is NOT a case of one side
being positive and the other being negative.
 Bozeman
 TED-Ed
Ted-Ed Review
Refractory
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission
Neural Transmission Interrupted
Neural Transmission Interrupted
The Synapse
The synapse is a
junction between the
axon tip of the
sending neuron and
the dendrite or cell
body of the receiving
neuron.
The synapse is
also known as the
“synaptic
junction” or
“synaptic gap.”
Neurotransmitters
Neurotransmitters are
chemicals used to
send a signal across
the synaptic gap.
Reuptake:
Recycling Neurotransmitters [NTs]
Reuptake:
After the neurotransmitters
stimulate the receptors on
the receiving neuron, the
chemicals are taken back up
into the sending neuron to
be used again.
Neural Communication:
Seeing all the Steps Together
Neurotransmitters
Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
Keys that almost fit:
Agonist and Antagonist Molecules
An agonist molecule fills
the receptor site and
activates it, acting like the
neurotransmitter.
An antagonist molecule fills the
lock so that the
neurotransmitter cannot get in
and activate the receptor site.
Roles of Different Neurotransmitters
Some Neurotransmitters and Their Functions
Neurotransmitter Function
Problems Caused by Imbalances
Serotonin
Affects mood, hunger,
sleep, and arousal
Undersupply linked to depression;
some antidepressant drugs raise
serotonin levels
Dopamine
Influences movement,
learning, attention, and
emotion
Oversupply linked to schizophrenia;
undersupply linked to tremors and
decreased mobility in Parkinson’s
disease and ADHD
Acetylcholine
(ACh)
Enables muscle action,
learning, and memory
ACh-producing neurons deteriorate as
Alzheimer’s disease progresses
Norepinephrine
Helps control alertness
and arousal
Undersupply can depress mood and
cause ADHD-like attention problems
GABA (gammaaminobutyric acid
A major inhibitory
neurotransmitter
Undersupply linked to seizures,
tremors, and insomnia
Glutamate
A major excitatory
neurotransmitter;
involved in memory
Oversupply can overstimulate the brain,
producing migraines or seizures; this is
why some people avoid MSG
(monosodium glutamate) in food
Serotonin
pathways
Networks of neurons that
communicate with serotonin
help regulate mood.
Dopamine
pathways
Networks of neurons that
communicate with dopamine are
involved in focusing attention
and controlling movement.
Nervous System
The Inner and Outer Parts of the
Nervous System
The central
nervous
system
[CNS]
consists of
the brain
and spinal
cord.
The CNS
makes
decisions
for the
body.
The
peripheral
nervous
system [PNS]
consists of
‘the rest’ of
the nervous
system.
The PNS
gathers and
sends
information
to and from
the rest of
the body.
Types of Neurons
Sensory
neurons
carry
messages IN
from the
body’s tissues
and sensory
receptors to
the CNS for
processing.
Motor
neurons
carry
instructions
OUT from
the CNS out
to the
body’s
tissues.
Interneurons
(in the brain
and spinal
cord) process
information
between the
sensory input
and motor
output.
The “Nerves”
are not the same as neurons.
Nerves consist of
neural “cables”
containing many
axons.
Nerves are part of
the peripheral
nervous system and
connect muscles,
glands, and sense
organs to the
central nervous
system.
More Parts of the Nervous System
The Peripheral Nervous System
The
Autonomic
Nervous
System:
The sympathetic
NS arouses
(fight-or-flight)
The
parasympathetic
NS calms
(rest and digest)
The Central Nervous System
 The brain is a web of
neural networks.
 The spinal cord is full of
interneurons that
sometimes have a “mind
of their own.”
Neural Networks
These complex webs of interconnected
neurons form with experience.
Remember:
“Neurons that fire together, wire together.”
Interneurons in the Spine
Your spine’s
interneurons trigger
your hand to pull
away from a fire
before you can say
OUCH!
This is an example
of a reflex action.
The Brain
Plasticity: The Brain is Flexible
If the brain is damaged,
especially in the general
association areas of the
cortex:
 the brain does not
repair damaged
neurons, BUT it can
restore some functions
 it can form new
connections, reassign
existing networks, and
insert new neurons,
some grown from stem
cells
This 6-year-old had a
hemispherectomy to end lifethreatening seizures; her
remaining hemisphere
compensated for the damage.
Our Two
Hemispheres
Lateralization (“going to one side”)
The two hemispheres serve some different functions.
How do we know about these differences?
 Brain damage studies revealed many functions of
the left hemisphere.
 Brain scans and split brain studies show more about
the functions of the two hemispheres, and how they
coordinate with each other.
The intact but lateralized brain
Right-Left Hemisphere Differences
Left Hemisphere
Thoughts and logic
Details such as “trees”
Language: words and
definitions
Linear and literal
Calculation
Pieces and details
Right Hemisphere
Feelings and intuition
Big picture such as “forest”
Language: tone, inflection,
context
Inferences and associations
Perception
Wholes, including the self
Separating the Hemispheres:
Factors to Keep in Mind
 Each hemisphere controls the opposite side of
the body AND is aware of the visual field on
that opposite side.
 Without the corpus callosum, the halves of
the body and the halves of the visual field do
not work together.
 Only the left half of the brain has enough
verbal ability to express its thoughts out loud.
Split visual field
Each hemisphere does
not perceive what each
EYE sees. Instead, it
perceives the half of the
view in front of you that
goes with the half of the
body that is controlled
by that hemisphere.
Split Brain Research
Split Brain Research
Split Brain Research
Areas of the brain and their functions
The brainstem
and cerebellum:
The limbic
(border) system:
The cortex (the
outer covering):
• coordinates
the body
• manages
emotions, and
connects
thought to
body
• integrates
information
The Brain:
Less Complex Brain Structures
Our tour of the brain begins with parts of the
human brain found also in simpler animals;
these parts generally deal with less complex
functions:
Brainstem (Pons and Medulla)
Thalamus
Reticular Formation
Cerebellum
Limbic System
The Brainstem:
Pons and Medulla
The Base of the
Brainstem:
The Medulla
 The medulla controls the most basic functions
such as heartbeat and breathing.
 Someone with total brain damage above the
medulla could still breathe independently, but
someone with damage in this area could not.
The Brainstem:
The Pons
The pons helps
coordinate automatic
and unconscious
movements.
The Thalamus (“Inner Chamber”)
 The thalamus is the “sensory
switchboard” or “router.”
 All sensory messages, except
smell, are routed through the
thalamus on the way to the
cortex (higher, outer brain).
 The thalamus also sends
messages from the cortex to
the medulla and cerebellum.
Reticular (“Netlike”) Formation
 The reticular formation is a nerve
network in the brainstem.
 It enables alertness, (arousal) from
coma to wide awake (as demonstrated
in the cat experiments).
 It also filters incoming sensory
information.
Cerebellum (“little brain”)
The cerebellum
helps coordinate
voluntary
movement such as
playing a sport.
The cerebellum has many other
functions, including enabling
nonverbal learning and memory.
The Limbic (“Border”) System
The limbic system coordinates:
 emotions such as fear and
aggression.
 basic drives such as hunger
and sex.
 the formation of episodic
memories.
The hippocampus
(“seahorse”)
 processes conscious,
episodic memories.
 works with the amygdala
to form emotionally
charged memories.
The Amygdala (“almond”)
 consists of two lima beansized neural clusters.
 helps process emotions,
especially fear and
aggression.
The Amygdala
 Electrical
stimulation of a
cat’s amygdala
provokes aggressive
reactions.
 If you move the
electrode very
slightly and cage
the cat with a
mouse, the cat will
cower in terror.
The Hypothalamus:
 lies below (“hypo”) the thalamus.
 regulates body temperature and
ensures adequate food and water
intake (homeostasis), and is
involved in sex drive.
 directs the endocrine system via
messages to the pituitary gland.
Thalamus
The Hypothalamus as a Reward Center Riddle: Why did the rat
cross the grid?
Why did the rat want to
get to the other side?
Pushing the pedal that
stimulated the electrode
placed in the
hypothalamus was much
more rewarding than food
pellets.
Endocrine System
The Endocrine System
The endocrine system
refers to a set of glands that
produce chemical
messengers called
hormones.
The Body’s “Slow but Sure”
Endocrine Message System
 The endocrine
system sends
molecules as
messages, just like
the nervous system,
but it sends them
through the
bloodstream instead
of across synapses.
 These molecules,
called hormones,
are produced in
various glands
around the body.
 The messages go to
the brain and other
tissues.
Adrenal Glands
produce hormones such as
adrenaline/epinephrine,
noradrenaline/norepinephrine, and
cortisol.
Adrenal Glands
Pancreas
1. The sympathetic
“fight or flight”
nervous system
responds to stress
by sending a
message to
adrenal glands to
release the
hormones listed
above.
2. Effect: increased
heart rate, blood
pressure, and
blood sugar. These
provide ENERGY
for the fight or
flight!
The Pituitary Gland
 The pituitary gland is the
“master gland” of the
endocrine system.
 It is controlled through
the nervous system by the
nearby brain area--the
hypothalamus.
 The pituitary gland
produces hormones that
regulate other glands
such as the thyroid.
 It also produces growth
hormone (especially
during sleep) and
oxytocin, the “bonding”
hormone.
Pituitary gland
Scanning Technology
Intentional brain damage:
Lesions (surgical
destruction of brain
tissue)
 performed on animals
 has yielded some insights,
especially about less
complex brain structures
 no longer necessary, as
we now can chemically or
magnetically deactivate
brain areas to get similar
information
67
Split-Brain Patients
 “Split” = surgery in
which the connection
between the brain
hemispheres is cut in
order to end severe
full-brain seizures
 Study of split-brain
patients has yielded
insights discussed at
the end of the chapter
Monitoring activity in the brain
Tools to read electrical, metabolic, and
magnetic activity in the brain:
EEG:
electroencephalogram
PET: positron emission
tomography
MRI: magnetic
resonance imaging
fMRI: functional MRI
EEG:
electroencephalogram
An EEG (electroencephalogram)
is a recording of the electrical
waves sweeping across the
brain’s surface.
An EEG is useful in studying
seizures and sleep.
70
PET: positron emission
tomography
The PET scan allows us to see what
part of the brain is active by
tracing where a radioactive form
of glucose goes while the brain
performs a given task.
MRI: magnetic
resonance imaging
MRI (magnetic resonance
imaging) makes images from
signals produced by brain tissue
after magnets align the spin of
atoms.
The arrows below show
ventricular enlargement in a
schizophrenic patient (right).
fMRI: functional MRI
Functional MRI reveals
brain activity and
function rather than
structures.
Functional MRI
compares successive
MRI images taken a
split second apart, and
shows changes in the
level of oxygen in
bloodflow in the brain.
72
Twin Studies
Basic Biology Review
 Genes
are located in our DNA, which is
wrapped tightly in chromosomes.
 Humans have 46 chromosomes each

23 from each parent
 Meiosis
- How we create sex cells.
More Biology Review
 Humans

have 46 chromosomes each
The 23rd pair determine sex.
 Sex
≠ Gender ≠ Sexuality
More Biology Review
Sex is biological.
 Humans have 46 chromosomes
It can be changedeach
surgically.
 The 23rd pair determine
sex.
 Sex
≠ Gender ≠ Sexuality
Gender is social.
It can be changed with
behaviors and dress.
Sexuality is almost
entirely different.
It describes who you
are attracted to,
if at all.
Twinning!
Twinning!
Monozygotic
(Identical)
Dizygotic
(Fraternal)
Twinning!
Monozygotic
(Identical)
 Same
DNA
 If
traits are the
same, we assume
it’s because of
twinning.

So what if they were
raised in different
environments?
Dizygotic
(Fraternal)
 Different
 No
DNA
more related
than any other pair
of siblings. They just
so happen to be
born at the same
time.
Twin Studies
Monozygotic Twins
(Identical)
Same Genes
Dizygotic Twins
(Fraternal)
Different Genes
Same Environment
Same genes,
same environment.
If intelligence is
nurture
same, ________.
If intelligence is
nature
different, ________.
Different Environment
If intelligence is
same, ________.
nature
If intelligence is
different, ________.
nurture
Different genes,
different
environment.
Nature AND Nurture
Nature’s Influence
 Genetics


influence personality.
Ex: Bouchard (2009) – 74 pairs of identical twins
Preferences, physical attributes, attitudes,
interests, patterns of thinking and feeling, etc.
 Temperament,
in part regulated by genes
for neurotransmitters, is hereditary.

Note: Heritability refers to differences among people –
probability and likelihood. NOT how much of your
personal traits are nature vs. nurture.
Nurture’s Influence




Environment accounts for less than 10% of differences.
Parents and family influence attitudes, values, manners,
faith, and politics.
 Adoptive families are screened, so adoptive homes
tend to have less neglect, abuse, and divorce.
 Adopted children tend to score higher than
biological parents and tend to be more stable as
adults.
Peers and culture affect preferences and habits.
Individualistic vs. Collectivistic cultures

Ex: American vs. Asian or Latino cultures
Howard Gardner (1998)
“Parents are more important when it comes to
education, discipline, responsibility, orderliness,
charitableness, and ways of interacting with authority
figures. Peers are more important for learning
cooperation, for finding the road to popularity, for
inventing styles of interaction among people of the
same age. Youngsters may find their peers more
interesting, but they will look to their parents when
contemplating their own futures. Moreover, parents
[often] choose the neighborhoods and schools that
supply the peers.”
In retrospect….
 “This


makes sense, doesn’t it? Think about it….
Things that are biological or come naturally are
influenced by genetics, and
things that are social come from environment.”
hindsight bias.
is an example of __________
 It’s also a criticism for evolutionary psychology:
it’s making explanations from examples in
history (__________),
induction not prediction.
 This
Evolution and
Mating Preferences




Males think about sex, are more easily aroused, and
masturbate more often than females.
Males are more comfortable with casual sex and less
interested in monogamy.
Females are more interested in long-term
relationships, security and affection.
 Even in homosexual populations, trends hold true.
From an evolutionary argument, this makes sense:
Men spread their seed while women have to select a
desirable mate, because making offspring is costly.
 In spanish, we say “Los hombres propone, y
las mujeres dispone.”
Nature AND Nurture
 Nature


Hardware; does the work.
It’s like a line drawing.
 Nurture



gives us experience.
Epigenetics
Software; tells nature what to do.
It’s like coloring in the lines.
 Ex:

sets the boundaries.
rats and their environments.
Rats in rich environments had thicker brains.
Some brain cells get potentiated, while
others get pruned.
Culture confounds
correlations. Wat.
 Culture
(nurture) can produce trends that we
misinterpret as coming from nature.
 Ex: Black men tend to have higher blood
pressure than White men.


Salty, fatty foods correlate with blood pressure.
Black people in general consume more salty, fatty
foods than White people because of their cultural
foods.