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The Biological Basis for
Behavior
The Human Brain
I. Neurons
• A. Three types of
Neurons
– 1. Sensory neuron =
neurons that carry
incoming
information from
the sense receptors
to the Central
Nervous
System(CNS) also
known as
AFFERENT
NEURONS.
Sensory Neuron
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
• 2. Motor neurons = the
neurons that carry outgoing
messages from the CNS to
the muscles and glands. Also
known as EFFERENT
NEURONS.
• 3. Inter-neurons = CNS
neurons that internally
communicate and intervene
between the sensory inputs
and motor outputs
Diagram of a Neuron
• B. The structure of the Neuron
– 1. Dendrites = the bushy, branching extensions
of a neuron that receive messages and conduct
impulses forward toward the cell body. Get its
name from the Greek word for tree.
– 2. Axon = the extension of a neuron, ending in
branching terminal fibers, through which
messages are sent to other neurons or to
muscles or glands
– 3. The Soma = aka the Cell body – its function
is to support the cell. At the center is the
nucleus
– 4. The myelin sheath is a layer of fatty
segmented tissue that encases the fibers of
many neurons
• a. Enables vastly greater transmission speed
of neural impulses as the impulse hops from
one node to the next
• b. The Nodes of Ranvier = the nodes along
the myelin sheath
– 5. The Synapse = the junction between the
axon tip of the sending neuron and the dendrite
or cell body of the receiving neuron – also
called the synaptic gap or cleft
– 6. Neurotransmitters = chemical messengers
that transverse the synaptic gaps between
neurons. They create or inhibit the receiving
neuron form generating a neural impulse
The Synapse
II. The Nervous System
• A. The Central Nervous System
– 1. Also known as the CNS
– 2. It consist of the brain and the spinal cord
– 3. Cerebrospinal Fluid (CSF) is a liquid similar
to blood serum found in the ventricles of the
brain and in the central canal of the spinal cord
• B. The Peripheral Nervous System PNS
– 1. The sensory and motor neurons that connect
the CNS to the rest of the body
– 2. It sends sensory input to the brain and relays
commands from the brain to muscles
– 3. Nerves = neural cables containing many
axons which connect the CNS with muscles,
glands, and sense organs
– 4. The PNS consists of
• a. The Somatic System = the division of the
PNS that controls the body’s skeletal
muscles; AKA the skeletal nervous system
• b. Autonomic System = the part of the PNS
that controls the glands and the muscles of
the internal organs such as the heart.
– Parasympathetic Nervous System = the
division of the ANS that calms the body,
conserving its energy
– Sympathetic Nervous System = the
division of the ANS that arouses the
body, mobilizing its energy in stressful
situations
The Nervous System
III. The Brain
• A. Tools of Discovery
– 1. Lesions and Accidents=
• a. Tissue destruction. A brain lesion is a naturally or
experimentally caused destruction of brain tissue
• b. Used to determine the impact on the brain functioning
• 2. EEG
– a. Electroencephalogram
– b. An amplified recording of
the waves of electrical activity
that sweep across the brain’s
surface. These waves are
measured by electrodes placed
on the scalp
– c. Evoked potentials – the
amplified tracings of the
change in voltage when the
subject is presented with a
stimuli
• Advantage = non invasive and
useful to identify sleep patterns
and some brain damage
• Disadvantage = not precise
• 3. CT/CAT SCAN
– a. Aka Computed Tomography
– b. A series of x-ray photos
taken from different angles and
combined by a computer into a
composite representation of a
slice through the brain or body
• Advantages non invasive and good
for seeing damage on the brain,
also more cost effective than an
MRI or PET scan
• Disadvantage – not as clear as an
MRI and doesn’t show the brain at
work
• 5. PET SCAN
– a. Short for Positron Emission
Tomography
– b. A visual display of brain activity
that detects where a radioactive form
of glucose goes while the brain
performs a given task
• Advantage is that it shows areas of the
brain in use by the person
• Disadvantages include that it doesn’t
clearly how structures and it is very
expensive
6. MRI
a. Short for Magnetic Resonance
Imaging
b. A technique that uses
magnetic fields and radio waves
to produce computer-generated
images that distinguish between
different types of soft tissue
c. Allows us to see structures
within the brain
• Advantages include that
is provides the most
complete picture of the
structures of the brain
• Disadvantages include
that it doesn’t show the
brain at work and it is
very expensive
– 7. FMRI
• a. Short for
functional MRI
• b. Similar to the
MRI but pictures are
taken less than a
second apart
• c. These pictures
reveal when things
happen, how the
brain changes with
experience and how
different areas of the
brain work together
– 8. Pros and cons of scans in general
• a. Advantages = detailed knowledge, clear pictures
of brain structures, some allow to see the brain at
work, very precise
• b. Disadvantages = can be invasive, or involve use
of potentially damaging x-rays or radioactive
substances. Also very expensive
• B. The Central Core
– 1. The brain stem
• a. brainstem = the oldest part and central core of the brain
• b. Begins where the spinal cord swells as it enters the
skull
• c. The brainstem is responsible for automatic survival
functions
• d. The hindbrain is the most posterior part of the brain it
includes the medulla, Pons and cerebellum
– 2. Medulla oblongata
• a. Medulla = the base of the brainstem;
• b. Controls heartbeat and breathing
• c. It lies directly on top of the spinal cord
– 3. Pons
• lies directly above the Medulla
• acts as a bridge between the Medulla and the rest of
the brain, as well as between the cerebral cortex and
the cerebellum
– 4. . Reticular formation = a nerve network in
the brainstem that plays an important role in
controlling arousal
– 5. The Midbrain – located between the
hindbrain and forebrain, it controls and
coordinates some basic sensory and muscle
movements.
– 6. The Thalamus
• a. The thalamus = the brain’s sensory switchboard
• b. Located on top of the brainstem; located in both
hemispheres resembling twin avocados
• c. It directs messages to the sensory receiving areas
of the cortex and transmits replies to the cerebellum
and medulla
– 7. Cerebellum
• a. The “little brain” attached to the rear of the brain
stem, to the side of the pons and medulla
• b. It helps to coordinate voluntary movement and
balance
• D. The Limbic System
– 1. Sometimes referred to as
the forebrain
– 2. The limbic system =
• a. a doughnut shaped system
of neural structures at the
border of the brainstem and
the cerebra hemispheres
• b. Associated with emotions
such as fear and aggression
and drives such as those for
food and sex
• c. Includes the hippocampus,
the amygdala, and the
hypothalamus
– 2. The amygdale = Two almond shaped neural
clusters that are components of the limbic
system and are linked to emotion
– 3. The Hippocampus =
• a. From the Latin word meaning seahorse
• b. Lies between the thalamus and the cerebral
cortex
• .c Is linked with forming new memories
– 4. The Hypothalamus
• a. A neural structure lying below (hypo) the
thalamus.
• b. It directs several maintenance activities (eating,
drinking and body temp), it helps govern the
endocrine system via the pituitary gland and it is
linked to emotion
IV. The Cerebral Cortex
• A. General Description
– 1. The convoluted portion of our brain where
thinking, memories and our personality are
located.
– 2. Physical description
• a. Convolutions increase the surface area of the
brain
• b. Gyri = rolls that form the folding out portion of
the cerebral cortex
VII. The Cerebral Cortex
• c. Sulci = valleys that form from the folding in
portions of the cerebral cortex.
• d. Fissures are deeper than valleys
• B. The four lobes
– 1. Frontal lobes
• a. The portion of the cerebral cortex lying just
behind the forehead;
• b. Involved in speaking and muscle movements and
in making plans and judgments
• c. prefrontal cortex receives sensory information
from all senses
– 2. Occipital lobes
– The portion of the cerebral cortex lying at the back of the
head;
– Includes the visual areas, (V1 & V2) which receive visual
information from the opposite visual field
– cortical blindness is a specific type of blindness due to
brain damage
– 3. Parietal lobes
• a. The portion of the cerebral cortex lying at the top
of the head and toward the rear;
• b. Includes the sensory cortex which specializes in
processing body information such as touch and body
location
– 4. Temporal lobes
• a. The portion of the cerebral cortex lying roughly
above the ears;
• b. Includes the auditory areas, each of which
receives auditory information primarily from the
opposite ear.
• c. One of the key areas of speech known as
Wernicke’s Area is located in this lobe
• C. The motor cortex = an area at the rear
of the frontal lobes that controls voluntary
movement
• D. The sensory cortex = the area at the
front of the parietal lobes that registers and
processes body sensations
Motor and Sensory Areas
• E. Association areas = areas of the cerebral
cortex that are not involved in primary motor
or sensory functions. They are involved in
higher mental functions such as learning
remembering, thinking and speaking.
V. Sleep and Dreams
• A. Biological Rhythms
– 1. Biological Rhythms = patterns associated with our
biological clock. These patterns can span days, hours
or even minutes.
– 2. Circadian Rhythms = Biological cycles that occur
about every 24 hours. For example or sleep, blood
pressure, body temperature and urine production
• B. How is our sleep cycle controlled
– 1. The suprachiasmatic nucleus (SCN)lies in
the hypothalamus and is the body’s main
biological clock.
– 2. When light hits the retina it sends a signal to
the SCN which then relays a message to the
pineal glands which in turn secrete melatonin
which is a hormone that plays a key role in
regulating sleep
• 3. Brain structures associated with sleep
– a. The superchiasmatic nucleus – influences the entire sleep cycle.
In rats with damage to this structure they will still sleep the same
number of hours but the length and frequency of the their sleep
episodes will be disrupted. It uses specialized optic receptors to
pick up light. This is why it is important to turn off all lights
including the tv, computer and phone in your room.
– b. The pineal gland also plays an important role in that it controls
production of melatonin an important sleep hormone. The pineal
gland is stimulated to produce melatonin in the dark and stimulated
to cease production when in the light
• 4. Sleep studies
– a. The Siffre Cave Study - -French cave explorer
Michael Siffre spent 6 months in a cave without
any external cues to set his biological clock.
Sleep patterns were erratic at first but settled into
a 25 hour cycle.
– b. Sleep research on teens indicates that pineal
gland does not turn on production of melatonin
until later in the day for teens. Thus teens tend to
stay up later and have trouble waking early.
– c. Teens NEED at least 8 ½ hours to 9 hours or
more of sleep a day. How many do you get?
• 4. Brain waves
accompanying sleep and
wake cycles.
– a. Every 90 minutes are so we
cycle through all the sleep
stages
– b. Alpha waves = awake and
resting
– c. Beta waves = awake and
working
– d. Theta waves = drowsy
– e. Delta waves = two different
types, one accompanying
dreaming the other deep sleep
without dreams
– 5. Sleep Stages
• a. Stage 1 – last about 5 minutes maybe
accompanied by hallucinations which are false
sensory experiences, and sudden jerks of the body
often referred to as a hypnogogic state
• b. Stage 2 – Last about 20 minutes characterized by
sleep spindles also known as K-Complex activity–
brain waves that show sharp increases in brain
activity. Sometimes accompanied by sleep-talking
• c. Stage 3 is a transitional stage where your brain
waves begin to slow into what is known as Delta
Waves.
• d. Stage 4 is the deepest stage of sleep last about 30
minutes and is often the period of sleepwalking or
somnambulism, and bed wetting. During this stage
we can actually be aware of certain stimuli such as
the sound of our baby crying.
• e. Finally you move back through stage 3 and stage
2 into a state known as REM Sleep
– 6. REM Sleep
• a. This is your “dream time” lasting about 10
minutes at a stretch.
• b. Characterized by increased heart rate and
complete muscle relaxation.
• c. For this reason REM sleep is often called
paradoxical sleep.
d. During this stage both the male and the female
genitalia become aroused even if the nature of the
dream is not sexual.
e. As the night progress you spend more and more
time in dream sleep (about 100 minutes) a night
C. Why do we sleep?
1. Studies on Sleep Deprivation
a. In various animal studies including those on both
cats and rats, long term sleep deprivation resulted in
death.
• b. Studies on humans show many effects such as
difficulty concentrating, more accidents and even a
weakened immune system. Periods of sleep
deprivation in humans are often followed by REM
Rebound where the participant spends more time in
REM sleep.
– 2. Theories on why we sleep
• a. Restoration Theory – to restore the body’s energy
systems, repair muscles and cells as well as to allow
for growth.
– Evidence for – Longer sleep usually occurs after large
amounts of physical exercise and growth hormones are
released during sleep.
 Evidence against – Sleep duration is not reduced with lack of
exercise and sleep deprivation does not produce significantly
adverse effects in humans.
b. Memory Consolidation Theory = Sleep, especially
REM sleep allows for memories to be consolidated.
 Evidence for suggest that subjects given information prior to sleep
who are deprived of REM sleep remember less than those who go
through normal sleep cycles.
 There is little evidence against this theory, however memory
consolidation can occur without sleep
• D. Dreams
– 1. Dreams are a sequence of images, emotions
and thoughts passing through the sleeping
person’s mind.
– 2. Dreams are notable for their hallucinatory
imagery, discontinuities and incongruities and
the dreamer’s delusional acceptance of the
content and later difficulties in remembering it.
 3. Freudian Theory of
Dreams(Wish Fulfillment)
 a. Freud believed the dreams
reflected unconscious wishes
that were too harmful to our
psyche to be dealt with by the
conscious self.
 b. Manifest Content =
according to Freud the
remembered story line of a
dream
 c. Latent Content = according
to Freud the underlying
meaning of a dream
– 4. Activation-synthesis model
• a. Proposed by Hobson and McCarley in 1977 it is
a biological theory of dreams
• b. It hypothesizes that dreams are random firings of
the brain that your brain tries to make sense of by
creating a story – essential dreams are just random
misfiring of the brain
• c. This theory has some biological support as it
explains how the content of dreams could be
influenced by particular areas of brain activation,
such as when external stimuli get worked into your
dreams.
VI. Theories of Emotion
A. Emotion = A response of the whole
organism, involving (1) physiological
arousal, (2) expressive behaviors, and (3)
conscious experience
B. The James-Lange and Cannon-Bard theories
1. James-Lange theory states that our experience of
emotion is our awareness of our physiological
responses to emotion-arousing stimuli
2. Study done by Hohmanna. Interviewed 25 soldiers who suffered injuries to the
spinal cord
b. Those who suffered injuries that left them
paralyzed from the neck down responded that their
emotions were much less intense
c. Seemingly supports the James-Lange Theory
3. Cannon-Bard Theory = the theory that an
emotion arousing stimulus simultaneously
triggers (1) physiological responses and (2) the
subjective experiences of emotion
• C. Cognition and Emotion
– 1. Schacter’s Two-Factor Theory of Emotion
• a. Two factor theory = the theory that to experience
emotion one must (1) be physically aroused and (2)
cognitively label the arousal
VII. Expressing Emotion
 A. Nonverbal Communication
 1. In a study by Rosenthal and Hall they showed film
clips of an emotionally expressive women. They found
that some people are better at reading emotions in
others. They found introverts tend read others better
while extroverts are easier to read.
 2. Gender and Nonverbal Behavior
 a. Surveys reveal that women are much more empathetic than
males, however when monitored electronically the gap between
men and women is much smaller.
• b. Coats and Feldman demonstrated that women are also
more expressive of their emotions.
• B. Detecting and Computing Emotion
– 1. Ekman and O’Sullivan on detecting lies
• a. Some students watched nature films while others
watched a gruesome film
Detecting Emotion Test 1
• b. All of the students were asked to talk about the
movie as if they were watching a nature film (in
other words they were to lie.)
• c. They found that people are not very good lie
detectors. They tried, students, psychiatrist, judges
and police officers. They all performed at the level
of chance. Only Secret Service Agents performed
better.
2. In a follow-up study Ekman found that
Government Agents (CIA), trained
psychologist and special trained street smart
interrogators from LA were able to detect liars.
 C. Culture and Emotional Expression
 1. The Ekman and Friesen study on Emotional
Expression studied people from around the world and
their ability to identify emotions through facial
expressions across cultures. They found that this ability
seemed to transcend culture.
 2. One other study on blind and deaf children showed
they made the same facial expressions as we all do.
This shows the universality of emotional expression
because it would have been impossible for them to have
learned to express emotions in this way.
 3. Charles Darwin points to the adaptive purpose of reading
emotions. It was probably important to our survival to read
the emotions of others. We would want to stay away from
angry people and move closer to people who are attracted to
us.
 4. Display Rules = learned ways of controlling displays of
emotion in social settings.
 D. The Effects of Facial Expressions
 1. The study done by Laird found that when people are
forced to smile they feel happy, when they scowl they feel
angry and when (facial feedback hypothesis)
V. The Sense of Smell
• A. Smell or OLFACTION
– 1. Like taste smell is a
chemical sense
– 2. We have over 350 types
of olfactory receptor cells
each of which picks up a
different chemical
compositions which equates
to the over 10,000 various
odors we can detect.
 3. 1% of our genes are used to develop the many
different smell receptors in our nose
 4. Path of odor
 Enters the nose and is picked up by receptor cells located
on the surface of the nasal passage on the olfactory
membrane

Olfactory receptors send electric signals to the
OLFACTORY BULB
 The olfactory bulb then relays the information to the
OLFACTORY NERVE which in turn sends the
information to the brain.