Neurobiology and
Behavior
Option E
Introduction
• Stimuli  Bee Sting
• Response  pain
• Caused by chemical messages sent to our brain
•
•
•
•
Euglena: stimuli light
Insects: response  complex social patterns
Birds: response  complicated songs
Fish: response  mating rituals
E.1 STIMULUS AND RESPONSE
Stimulus and response
Assessment Statements
E.1.1
Define terms stimulus, response and reflex in the content of animal
behavior
E.1.2
Explain the role of receptors, sensory neurons, relay neurons, motor
neurons, synapses and effectors in the response of animals to stimuli
E.1.3
Draw and label a reflex arc for a pain withdrawal reflex, including the
spinal cord and its spinal nerves, relay neuron, motor neuron and
effector
E.1.4
Explain how animal responses can be affected by natural selection, using
two examples
Definition of Terms
• Stimulus: change in the environment (internal/external) that is
detected by a receptor and elicits a response
• Reflex: rapid, unconscious response
• Response: reaction to a stimulus
Pain Reflex Arc
Effects of Natural Selection
• Behavior  complicated series of responses to environment
• Change behavior as response to change in environment
• Change can be extreme  speciation
• Peppered Moths  light and dark depending on the tree they reside
on  genetic trait
• Variations in genetic traits, lead to variations in behavior, lead to
survival due to natural selection
European Blackcaps (Bird)
• Small warblers – migrate
between Spain and
Germany
• Breed in Germany
(spring/summer), spend
winter in Spain
• Change?
• Blackcaps migrating to UK
instead
• Return migration 10 days
earlier than Spain
Blackcaps
• Early return  more
territory choice  more
eggs
European Blackcaps
• Genetic basis?
• Eggs collected from UK
and Spain Blackcaps
• Young reared, migration
monitored (not guided
by parents)
• All birds tended to
migrate in same
direction as parents
• Supports hypothesis:
Blackcaps genetically
programmed to fly a
certain direction
• Environmental
Benefit?
• Warmer winters in UK 
more surviving birds
• Change in migration,
could lead to speciation
• Result from changes in
courtship due to earlier
arrival at breeding
grounds
Sockeye Salmon
• Introduced species into
Lake Washington
• Some migrated to
Cedar River (flows into
lake)
• River flows quickly,
lake deep and quiet
• Over 60 years, 13
generations produced
• DNA evidence = river
and lake salmon
stopped interbreeding
Sockeye Salmon
• Cause?
• Separate breeding methods
• Lake salmon = spawn on beaches
• Males heavy – perfect for deep waters, not flowing river
• River salmon = bury eggs on river bottom
• Males thinner for fast moving water
• Found fish hatched in river, little success at spawning on beach
• Creation of two distinct species
E.2 PERCEPTION OF STIMULI
Perception of stimuli
Assessment Statements
E.2.1 Outline the diversity of stimuli that can be detected by human sensory
receptors, including mechanoreceptors, chemoreceptors,
thermoreceptors and photoreceptors
E.2.2 Label a diagram of the structure of the human eye
E.2.3 Annotate a diagram of the retina to show the cell types and the direction
in which the light moves
E.2.4 Compare rod and cone cells
E.2.5 Explain the processing of visual stimuli, including edge enhancement and
contralateral processing
E.2.6 Label a diagram of the ear
E.2.7 Explain how sound is perceived by the ear, including the roles of the
eardrum, bones of the middle ear, oval and round windows, and the hair
cells of the cochlea
Sensory Receptors and Diversity of
Stimuli
• Sensory cells send messages to certain parts of brain 
control emotion and memory
• Link tastes, sights and sounds with emotions
• Taste and sound = provide protection
• Bad tastes, smelling smoke, moving away cars (sound of engine)
• Sense organs  windows to brain
• Keep brain aware of outside world
• Stimulation  sense organs send message to CNS  nerve
impulses arrives at brain sensation
• Actually see, smell, taste, feel with our brain
Sensory Receptors and Diversity of
Stimuli
• Mechanoreceptors
• Stimulation: mechanical force (pressure)
•
•
•
•
Sense of touch  pressure sensors on skin
Arteries  pressure receptors detect change in blood pressure
Lungs  stretch receptors respond to lung inflation
Position of legs/arms  proprioceptors (muscle fiber, tendons,
joints, ligaments)
• Help maintain posture and balance
• Ear: pressure receptors – information about equilibrium
Sensory Receptors and Diversity of
Stimuli
• Chemoreceptors
• Response to chemical substances
• Taste and Smell
• Provide information about internal body environment
• Blood vessels  monitor pH changes  which adjusts breathing
rates
• Pain receptors  respond to chemicals released by damaged tissue
Sensory Receptors and Diversity of
Stimuli
• Thermoreceptors
• Respond to change in temperature
• Photoreceptors
• Respond to light energy
• Found in eyes  sensitive to light  vision
• Rod cells: respond to dim light (black and white vision)
• Cone cells: respond to bright light (color vision)
Human Eye
Part
Function
Iris
Regulates size of pupil
Pupil
Admits light
Retina
Receptors for vision
Anterior
chamber
Transmit light rays,
supports eyeball
Posterior
chamber
Transmit light rays,
supports eyeball
Fovea
Area densely packed
cone cells, vision most
acute
Lens
Focuses light rays
Sclera
Protects, supports
eyeball
Cornea
Begins focusing
Choroid
Absorbs stray light
Conjunctiva
Covers sclera & cornea,
keeps eye moist
Optic nerve
Impulses to brain
The Retina
Vision:
1. Begins when light enters
the eye
2. Focused on
photoreceptor cells on
retina
1.
3.
4.
5.
Photoreceptor cells: rods
and cones
Rods and cones synapse
with own bipolar neurons
Bipolar neurons synapses
with a ganglion cell
Axons of ganglion cells
make up optic nerve 
carries message to brain
Rods and Cones
Rods
Cones
More sensitive to light (function well
in dim light)
Less sensitive to light (function well in
bright light)
Only 1 type found in retina: it can
absorb all wavelengths of visible light
3 types found in retina: 1 – sensitive to
red light, 1 – to blue, 1 – green
Impulses from group of rod cells pass
to single nerve fiber
Impulse from single cone cell passes to
single nerve fiber
Processing Visual Stimuli
1.
2.
3.
4.
5.
6.
Light rays pass through pupil
Focused by cornea, lens, humors
Image focused on retina: upside down and reversed (left to
right)
Photoreceptors stimulated  send impulses to bipolar
neurons and ganglion cells
Axons of ganglion cells travel to visual area of cerebral cortex
(brain)
Brain corrects position of image (right side up and unreversed)
• Coordinates images from left and right eye
Edge Enhancement
• Scientists studying vision
use optical illusions
• Grey spots?
• Are seen in peripheral
vision (fewer light sensitive
cells), not direct (fovea,
heaviest concentration of
cells)
• Special mechanism for
seeing edges
• Theory: light-sensitive
receptors switch off
neighboring receptors.
• Making edges more
distinct
Contralateral Processing
• Right half of visual field: nerves converge at optic chiasma,
pass to left side of brain
• Left half of visual field: nerves converge at optic chiasma, pass
to right side of brain
• Each visual area has half of the overall vision, must share
information to complete image
• Image is inverted and reversed
• Brain must correct image
• Impulses relating to other stimuli (color, form, motion),
parceled out to other areas of brain
• Cerebral cortex rebuilds all parts into a visual image
Contralateral Processing
• How Studied?
• Abnormal perceptions of patients with brain lesions
• Vision is information processing
Normal brain: sees a
bucket, no matter the
angle
Left side brain injury:
describe function of
bucket, but cannot
come up with name
Right side brain injury:
when looking at bucket
from top  no
recognition
Conclusion: need both
sides of brain to
recognize and
understand an object
Structure of Ear
Outer ear
Middle ear Inner ear
How Sound is Perceived
1.
Outer ear = catches sounds waves
• Successive vibrations of air molecules
2.
3.
4.
5.
6.
7.
8.
Travel down auditory canal, causing ear drum (tympanic
membrane) to move back and forth
Bones (malleus, incus, stapes) receive vibrations from
tympanic membrane, multiply 20x
Stapes strikes oval window, causing vibration
Vibration passed to fluid in cochlea
Fluid causes special cells (hair cells) to vibrate
Hair cells (receptors) release chemical message across
synapse to sensory neuron of auditory nerve, moves to brain
Wave in fluid dissipates as it reaches round window
How Sound is Perceived
• Loud noises cause fluid to vibrate at higher degree
• Hair cells bend more
• Interpreted by brain as higher volume
• Pitch: function of sound wave frequency
• Short, high frequency waves = high pitch sounds
• Long, low-frequency waves = low pitch sounds
• Sounds is sensed by brain is processed in auditory area of
cerebral cortex
INNATE AND LEARNED BEHAVIOR
Innate and Learned Behavior
Assessment Statements
E.3.1
Distinguish between innate and learned behavior
E.3.2
Design experiments to investigate innate behavior in invertebrates,
including either a taxis or a kinesis
E.3.3
Analyze data from invertebrate behavior experiments in terms of the
effect on chances of survival and reproduction
E.3.4
Discuss how the process of learning can improve the chance of survival
E.3.5
Outline Pavlov’s experiments into conditioning of dogs
E.3.6
Outline the role of inheritance and learning in the development of
birdsong in young birds
Innate Behavior
• Develops independently of environmental
• Spider spins a web correctly, first time
• No trail and error learning
• Controlled by genes and inherited by parents
• Genetically programmed behaviors – ensure survival of animal
• Types of behaviors
•
•
•
•
Wasps building nest
Termites build mounds
Birds song
Sucking in human infants
Innate Behavior
Some performed in certain order
Male
Female
appears
Zig zag dance
courts
Leads to nest
follows
Shows nest entrance
Enters nest
trembles
spawns
Fertilizes eggs
Learned Behavior
• Not genetically programmed
• New knowledge/skills formed or modifying existing knowledge
• Measured by performance
• Learning explained as change in performance
• Stored in nervous system as memory
• Behavior output is not always easily seen = measuring learning
difficult
Summary
Innate Behavior
Learned Behavior
Develops independently of the
environmental context
Dependent on the environmental
context of the animal for development
Controlled by genes
Not controlled by genes
Inherited from parents
Not inherited from parents
Developed by natural selection
Develops by response to an
environmental stimulus
Increases chance of survival and
reproduction
May or may not increase change of
survival and reproduction
Investigating Innate Behavior
• Study simple invertebrate – innate behavior measure as
response to environmental stimuli
• Taxis
• Directed response to stimulus
• Body toward stimulus – positive response
• Body away from stimulus – negative response
• Chemotaxis – response to chemicals
• pH, concentration of dissolved drugs, foods, pesticides
• Phototaxis – response to light
• Different wavelengths, light intensities, types of light bulbs
Investigating Innate Behavior
• Taxis
• Gravitaxis – response to gravity
• Upside down container, slow-spinning turntable
• Rheotaxis – response to water current
• Move with or against current
• Thigmotaxis – response to touch
• Does any organism have positive thigmotaxis
Investigating Innate Behavior
• Taxis
• Types of invertebrates
• Planaria – flatworm
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•
•
•
•
Quite active, move by contraction of muscle fibers
Simple nervous systems
Two eye spots – photoreceptors stimulated by light (negative phototaxic)
Chemoreceptors – response to certain chemicals (positive chemotaxic)
Studies: different wavelengths, food substances in water, temperature
gradient, concentrations of pesticides
• Euglena – single-celled protist
•
•
•
•
Flagellum for propulsion
Eyespot – stimulate by light
Photosynthetic – positive phototaxic
Study: different wavelengths of light
Investigating Innate Behavior
• Kinesis
• Movement in response to non-directional stimulus
• Humidity
• Does not move away from or toward stimulus, but erratically till
new spot found
• “comfort zone” – movement slows
• Orthokinesis
• Organism moves slowly/rapidly (changes speed) in response to
stimulus
• Klinokinesis
• Turns slowly/rapidly in response to stimulus
Investigating Innate Behavior
• Kinesis
• Isopods (terrestrial crustaceans)
• Live in damp places – have gills, not lungs
• Kinesis  humidity
• Moist, slow movement
• Dry, rapid movement
• Species for study: woodlice (Porcellio scaber, Armadillidium vulgare)
Experimental Design
1.
Observe organism of choice.
•
Write specific research question which allows collection of
measurable data
EX: What is the effect of humidity on the distribution of the
isopod Porcellio scaber?
•
2.
Describe a method for collection of relevant data
a)
b)
c)
d)
e)
Modify a pair of Petri dishes, for choice chamber (dry and
humid environments). One chamber has drying agent, other
wet towels. Measure humidity with Vernier Probe
Place 10 individuals in each chamber.
Count number of individuals in each chamber for 5 minutes
Repeat method, data for 40 organisms
As control, set up petri dishes which have no difference in
humidity. Repeat b, c, d.
Experimental Design
3.
Design a method for control of the variable
a)
b)
c)
d)
Measure light conditions with Vernier probes. Make sure light
conditions remain constant. Isopods may respond to light, so
amount of light needs to be controlled.
Measure temperature conditions with a Vernier probe. Make
sure temperature conditions remain constant
There must be an equal possibility for isopods to travel to
either chamber
Sizes of chambers must be equal
Experimental Design
4.
5.
Record raw data, including units (minutes) and uncertainties
(± 0.5 minutes). Make sure you title each data table. Do not
split a data table across two pages.
Process the raw data. Processing includes any mathematical
manipulation of the data or graphing of manipulated data
(graphing raw data is not considered processing)
a)
6.
Determine the means of numbers of isopods in humid and dry
conditions in two trials, compared with controls
Graph the mean values from the two trials.
Reasons for Experiments
• Survival and Reproduction of invertebrates based of behavior
• Need to use statistical analysis to determine significance in data
• Chi-square used because you have categories (dry and humid)
• Draw conclusions based on statistical analysis
• Behavior of isopods is to move randomly in dry conditions, until they
find humid conditions.
• Humidity is important for survival and ability to reproduce
• Supporting conclusion with research
• Outer covering of isopods (exoskeleton) lacks waterproof cuticle so
animal is highly subjected to desiccation (drying out)
• Quick, random movements enables isopod to find humidity.
• Natural selection favors isopods with this response
Learning Improves Survival
• Learning = new knowledge/skill
• Occurs best when tied to survival
• Types of learning
• Imprinting
• Young animals attached to mother within first day
• Young ducklings will follow mother
• Assures young stay close to mother for protection and food
• Food hoarding
• Store food when plentiful, return to food when shortage
• Squirrels nuts, moles paralyze worms
• Assures nourishment in times of food shortages
Learning Improves Survival
• Types of learning
• Birdsong
• Two functions: attracts mate, deters rival males
• Best song, promotes reproduction of those genes
• Bears learning to catch slippery salmon
• Learned from mother
• Chimpanzees learning to stick branch into termite nest, pull it
out, dinner
• Learned through trial and error
• Mimicry – uses false learning to trick predators
Obtaining
food in
difficult
places
Pavlov and Conditioning
• Classical conditioning used to modify reflex response
• Subjects responds in new way
• Blinking (reflex response)
• Unconditioned stimulus (UCS): waving a hand in subjects face 
Unconditioned response (UCR) unconditionally stimulates eyeblink response
• Train eye to elicit reflex response with new, neutral stimulus (NS)
• NS (musical notes) introduced, subject does not blink
• Period of training: musical note sounded immediately before wave of
hand
• Subject learns to eye-blink to musical note – conditioned stimulus
(CS), conditioned response (CR)
Pavlov and Conditioning
• Ivan Pavlov designed classical training response
• Subjects: dogs
• UCS: food in mouth  UCR: salivation
• NS: ringing of bell
• Rang bell just before dog tasted food
• CS: ring bell  CR: salivate
• Dog learned to salivate to NS alone
Learning of Birdsong
• Well studied example of animal behavior
• Species-specific songs in birds – inherited
• Birds can learn to improve song  inherited and learned
behaviors
• Syrinx – vocal organ in birds
• Bony structure at bottom of trachea
• Force air past membrane in syrinx  vibrates  sound
• Control:
• Pitch – altering tension in membranes
• Volume – altering air flow
Learning of Birdsong
• Males sing because:
• Attracts mate
• Deters male rivals
• Birds hatch with ‘crude template – species specific
• Shown in experimental data
• Measured with acoustical spectroscope
• Conclusion: template is inherited
Learning of Birdsong
Memorization
phase
Duration 100 days: if hear no
song in time, does not move to
motor phase  sensitive
period
Motor phase
Crude template
Template matched to song
heard by adults
Exact template
Song output
Hears own song
Song matched to template
Sings more or less accurate copy
of song heard
E.4 NEUROTRANSMITTERS AND
SYNAPSE
Neurotransmitters and
Synapses
Assessment Statements
E.4.1 State that some presynaptic neurons excite postsynaptic transmission
and others inhibit postsynaptic transmission
E.4.2 Explain how decision making in the CNS can result from the interaction
between the activities of excitatory and inhibitory presynaptic neurons at
synapses
E.4.3 Explain how psychoactive drugs affect the brain and personality by either
increasing or decreasing postsynaptic transmission
E.4.4 List three examples of excitatory and three examples of inhibitory
psychoactive drugs
E.4.5 Explain the effects of THC and cocaine in terms of their action at the
synapses in the brain
E.4.6 Discuss the causes of addiction, including genetic predisposition, social
factors and dopamine secretion
Synaptic Transmission
• Synapse – space
between neurons, where
chemical message is sent
• Excitatory
neurotransmitters =
stimulate transmission in
next neuron
• Increase permeability to
positive ions (transmitters)
• Inhibitory = cause
positive ions move out
postsynaptic cell
• Chemically depresses
neuron
Decision Making in CNS
• Impulse moves down presynaptic neuron  action potential
• Reaches axon bulb  Ca+2 rush into end of neuron
• Vesicles containing neurotransmitters fuse with presynaptic
membrane
• Release neurotransmitters into synaptic cleft
• Neurotransmitter binds to specific receptors on postsynaptic
membrane
• Ions enter or leave when neurotransmitter binds to receptor
1. Many axons synapse
with each cell body
2. After action potential
arrives, synaptic vesicles
fuse
3. Neurotransmitter
molecules released,
bind to receptors
Excitatory Neurotransmitters
• Example – acetylcholine
• Generates an action potential
• Increase permeability of postsynaptic membrane to positive
ions
• Na+, located in synaptic cleft, diffuse into postsynaptic neuron
(PSN)
• PSN depolarized locally by influx of Na+
• PSN develops net positive charge compared to outside cell
• Depolarization is how impulse is carried
• Na+ continue to diffuse further depolarizing neuron from one
area to the next (like a wave)
• Action potential formed as membrane depolarization is raised
above threshold
• Impulse in being carried along nerve
Inhibitory Neurotransmitters
• Example – GABA
• Inhibits action potential
• Causes hyperpolarization of neuron  more difficult
for generation of action potential
• Inside of neuron becomes more negative
• Binds to specific receptor
• Causes Cl- to move across postsynaptic membrane
into cell, or
• Causes K+ to move out of PSN
Cause
hyperpolarization
Putting it together
•
•
•
•
•
Neuron receiving end of excitatory and inhibitory stimuli
Neuron sums up signals
If, sum is inhibitory  axon does not fire
If, sum is excitatory  axon fires
Summation of messages  way that decisions are made in
CNS
Psychoactive Drugs
Cholinergic Synapses
• Acetylcholine  release by all motor neurons – activates skeletal
muscle
•
•
•
•
Travels across synapses, depolarizes PSN
If it remained in synapse, PSN would go on firing indefinitely
Prevention – acetyl cholinesterase breaks down acetylcholine in synapse
Involved in parasympathetic nervous system – causes relaxation rather
than flight
• Nicotine stimulates these transmission – why calming effect on body
and personality
• Adrenergic Synapses
• Noradrenaline  depolarizes PSN
• Involved in sympathetic nervous system – causes ‘fight or flight’
• Cocaine and Amphetamines – cause increased alertness, energy,
euphoria
Psychoactive Drugs
Cholinergic
Adrenergic
Neurotransmitter
Acetylcholine (Ach)
Noradrenaline
System
Parasympathetic
Sympathetic
Effect on mood
Calming
Increased energy,
alertness, euphoria
Drug increase
transmission at synapse
Nicotine
Cocaine and
amphetamines
Psychoactive Drugs
• Effects of Drugs on Brain
• Alter mood or emotional state
• Excitatory drugs (nicotine, cocaine, amphetamines) – increase nerve
transmission
• Inhibitory drugs (benzodiazepines, alcohol, tetrahydrocannabinol
(THC)) – decrease nerve transmission
• Use different mechanisms at synapses of brain
• Block receptor for neurotransmitter (similar structure as normal
neurotransmitter)
• Block release of neurotransmitter for presynaptic membrane
• Enhance release of neurotransmitter
• Enhance neurotransmission by mimicking neurotransmitter
• Drugs have same chemical structure, same effect, not broken down easily,
effect is stronger
• Block removal of neurotransmitter from synapse, prolong effect of
neurotransmitter
Excitatory drugs
• Nicotine
• Mimics acetylcholine (Ach)
• Acts on cholinergic synapses  cause calming effect
• Ach, once received, broken down by acetyl cholinesterase
• Enzyme cannot break down nicotine
• Excites the postsynaptic neuron  begins to fire  releasing
dopamine
• Gives you feeling of pleasure  ‘reward pathway’ of brain
Excitatory Drugs
• Cocaine
• Stimulates transmission
at adrenergic synapses
• Causes euphoria,
alertness
• Dopamine released
blocks removal
dopamine  build up
• Causes overstimulation
 ‘reward pathway’ 
euphoria
Excitatory Drugs
• Amphetamine
• Stimulates transmission at adrenergic synapses
• Increased energy, alertness
• Acts by passing directly into nerve cells (carry dopamine,
noradrenaline)
• Moves directly into vesicles  released at synaptic cleft
• NT normally broken down by enzymes, amphetamines interfere
• Synapse  high concentrations dopamine (euphoria),
noradrenaline (alertness)  high energy effect (amphetamines)
Inhibitory Drugs
• Benzodiazepine
• Reduces anxiety, used
against epileptic seizures
• Modulate activity of GABA
 main inhibitory
neurotransmitter
• GABA binds to
postsynaptic membrane 
Cl- enter neuron
• Cl- causes neuron to
become hyperpolarized 
resists firing
• Increases binding of GABA
to receptor  postsynaptic
neuron more
hyperpolarized
Inhibitory Drugs
• Alcohol
• Increases the binding of
GABA  causes
hyperpolarization
• Explains sedative effect of
alcohol
• Decreases activity of
glutamate (excitatory NT)
• Helps increase release of
dopamine (process not well
understood)
• Appears to stop enzyme
break down of dopamine at
synaptic cleft
• Dopamine works ‘reward
pathway’
• Tetrahydrocannabinol
(THC)
• Main psychoactive chemical
in marijuana
• Mimics NT – anandamide
• Binds to same receptors
• Causes postsynaptic neuron
to by hyperpolarized
• Role of anandamide not
completely understood 
may play role in memory
functions
• May eliminate unneeded
information from memory
• Marijuana disrupts shortterm memory
Effect of THC and Cocaine
• THC
• Feelings
• relaxed, mellow, panic, paranoia
• May dilate pupils causing color perception to be more intense
• Acts on cannabinoid receptors, affect:
• Learning, coordination, problem solving, short-term memory
• Inhibits same neurons as anandamide  no enzyme to break
down THC  synapse lasts longer
• High concentrations of cannabinoid found in:
• Hippocampus – short-term memory
• Cerebellum and basal ganglia – controls coordination
Effect of THC and Cocaine
• Cocaine
• Feelings:
• Euphoria, talkativeness, increased mental awareness
• Temporary decrease in need for food or sleep
• Large quantities – erratic, violent behavior
• Synaptic effect
• Ability to sustain level of dopamine  longer it stays  better you
feel
Causes of Addiction
• Drugs:
• Alcohol, tobacco, psychoactive drugs, pharmaceuticals
• Reason for drugs:
• Alleviate symptoms to mental illness
• Pleasure
• Response:
• Body develops tolerance  need more and more for same result
• Addiction: chemical dependency on drugs
• Drugs ‘rewired’ brain  drug has become essential biochemical
Causes of Addiction
• Smoking
• Not just a bad habit
• Nicotine ‘rewired’ brain  due to mimicking acetylcholine 
releases dopamine
• Crave dopamine spikes
• Role of common abused drugs  stimulates ‘reward pathway’
• Withdrawal symptoms opposite of euphoria
• Anxiety, depression, cravings
• Alcohol – cause seizures, delirium tremens (severe shaking)
• Inhaled drugs  lung damage
• Needles  HIV, Hepatitis B/C, kidney disease
Causes of Addiction
• Genetically predisposition
• Research
• Twin studies
• One twin suffers addiction, rate of addiction in second twin is 50% greater in
identical vs. fraternal twins
• Genetic deficiency of dopamine receptors predisposes people to
addiction
• Used predisposed rats and ‘normal rats’
• Social Factors
• Determine child’s vulnerability to substance abuse
• Family addiction, parenting skills, mental health problems
• Behavior
• Peer pressure very influential
• Culture
• Introducing drug into a society that wasn’t present  cause social
problems and abuse
Causes of Addiction
• Dopamine Secretion
• Drug addiction – dopamine receptors constantly stimulated
• Overstimulation decreases number of receptors, remaining
receptors less sensitive desensitization/tolerance
• Causes less response
• More and more drug is needed  neuroadaptive change
• Glutamate – may be more important than dopamine
• ‘oversee’ learning and memories which lead to cocaine-seeking
E.5 THE HUMAN BRAIN (HL ONLY)
The Human Brain (HL)
Assessment Statements
E.5.1 Label, on a diagram of the human brain, the medulla oblongata,
cerebellum, hypothalamus, pituitary gland and cerebral hemispheres
E.5.2 Outline the functions of each of the parts of the brain listed above
E.5.3 Explain how animal experiments, lesion and fMRI (functional magnetic
resonance imaging) scanning can be used in the identification of the
brain part involved in specific functions
E.5.4 Explain sympathetic and parasympathetic control of the heart rate,
movements of the iris and flow of the blood to the gut
E.5.5 Explain the pupil reflex
E.5.6 Discuss the concept of brain death and the use of the pupil reflex in
testing for this
E.5.7 Outline how pain is perceived and how endorphins can act as painkillers
Structure and Function of
Brain
• Most complex organ in body
•
•
•
•
•
•
•
Weighs 1.4kg
Produces: thoughts, feelings, actions, memories
Contains: 100 billion neurons, thousands of synapses
Connections: store memories, learning, personality traits
No two brains same, changes throughout lifetime
Regulates and monitors: blood pressure, heart rate, breathing
Controls: balance, muscle coordination, most voluntary
movement, speech, emotions, problem solving
Neuroscience
•
•
•
•
•
New technology  insights into function
Animal experimentation  causes our drives
Brain injuries  what occurs when parts of brain are damaged
Brain scans  effects of addictive drugs
Studies show
• How pain is perceived
• How endorphins act as painkillers
Cerebral Hemisphere:
Integrating center for high
complex functions –
learning, memory, emotions
Pituitary gland:
Posterior lobe –
stores, releases
hormones regulating
body functions
Hypothalamus:
Maintains homeostasis,
coordinates
nervous/endocrine systems,
secretes hormones
Cerebellum:
Two hemispheres,
highly folded
surface, coordinates
unconscious
functions (balance
and movement)
Medulla:
Controls automatic and hemostatic
activities – swallowing, digestion, vomiting,
breathing, heart activity
Functions to Brain
• Brain Lesions
• Indirectly tells about functions to parts of brain
• Right and Left Hemispheres
• Connected by thick band of axons (corpus callosum)
• Left Hemisphere:
• Important for communication
• Stroke (broken or blocked blood vessels) can cause damage
• Difficulty: speaking, doing complicated movements with hands/arms
• Right Hemisphere:
• Helps understand words
• Specializes in receiving and analyzing information
• Lesions – problems identifying faces, locating objects in space (spacial
awareness)
Functions to Brain
• Brain Lesions
• Conclusions:
• 1850’s research Left side injury – speech, language problems
• Broca’s area – interferes with vocalizing words
• Wernicke’s area – affects ability of creating sentences
• 1960’s research
• Studied severed corpus callosum  used to relieve symptoms of epilepsy
• Card with dot in middle – spoon may appear on left or right of dot
• Right side  left hemisphere identifies as spoon
• Left side  right hemisphere sees nothing (no language ability) – but knows
what to do with it
Functions to Brain
• Brain Lesions
• Use of chimerical
pictures
• Patients focus on dot
• Woman goes to right
side, man goes to left
• If patients then look
complete normal
picture  point to face
just seen  woman
• If asked to say whether
is man or woman 
man
Functional Magnetic
Resonance Imaging (fMRI)
• Use Radio waves and strong magnetic field
• See blood flow in brain as it is occurring
• Scientists make movies of brain as subjects perform tasks
• Can produce new image every second
• Determine regions of active brain and how long stay active
• Activity occurs in same regions or various parts?
• Used to determine:
•
•
•
•
•
Plan for surgery
Treatment for stroke
Placements of radiation therapy for brain tumor
Effects of degenerative brain disease
Diagnosing how diseased or injured brain works
Animal experiments
• Expose animals to addictive substances in controlled situations
• Findings
•
•
•
•
•
Want more substance
Spends lots of time and energy getting it
Keep taking it despite adverse conditions
Have withdrawal symptoms
Go back when stressed
• Can shed light on ways drugs promote abuse and addiction
• Limitations
• Never replicate complete picture of human interactions
• Social factors are not considered
Animal experiments
• To test if chemical is addictive
• Design a self-administration
experiment  response is
recorded
• Animal is trained to press lever
to get reward
• Animal is given injection of
addictive substance as pushes
lever
• Two levers available: one gives
substance, one does not
• If substance is ‘reinforcing’ –
animal will seek to repeat
experience by pushing lever
more  supports hypothesis
Sympathetic and
Parasympathetic Control
• Central nervous system (CNS)
• Brain
• Spinal core
• Peripheral nervous system (PNS)
• Somatic System (voluntary)
• Information is received by senses, messages sent to skeletal muscles
• Pain reflex arc
• Autonomic system (involuntary
• Controls cardiac muscle (heart), smooth muscle glands
• Antagonistic systems:
• Sympathetic
• parasympathetic
Sympathetic and
Parasympathetic Control
Sympathetic System
Parasympathetic System
Important in emergency
Important in returning to normal
Response is ‘fight or flight’
Response is to relax
NT is noradrenaline
NT is acetylcholine
Excitatory
inhibitory
Sympathetic and
Parasympathetic Control
• Sympathetic
•
•
•
•
•
Facing emergency  need quick supply of glucose and oxygen
Increase in heart rate and stroke volume of heart
Dilates bronchi to get more oxygen
Dilates pupil making radial muscles contract
Blood flow to gut is restricted by contraction of smooth muscle in
blood vessels  digestion not necessary
• Parasympathetic
•
•
•
•
•
Relaxed state
Returns system to normal
Pupil constricts  protects retina
Heart rate slows, stroke volume reduced
Blood flow returns to digestive system
Pupil Reflex
• When close eyes and open quickly  pupil close in response
to sudden exposure to light
• Reflex (just like pain reflex)
• Cranial reflex (not tied to spinal cord)
Pupil Reflex
• Optic nerve receives message from retina tin back of eye
• Remember how retina works
• Optic nerve connects with pretectal nucleus of brain stem
(rectangle)
• From the pretectal nucleus, a message is sent to the EdingerWestphal nucleus (triangle), whose axons run along the
oculomotor nerves back to the eye
• Oculomotor nerves synapse on the ciliary ganglion (small
circle)
• Axons of ciliary ganglion stimulate the circular muscle of the
iris  contraction
Brain Death
• Brain controls:
• Heart rate, breathing rate, blood flow to digestive system
• Body temperature, blood pressure, fluid retention
• Definition of brain death:
• Time when a physician(s) has determined that the brain and brain
stem have irreversibly lost all neurological function
• Coma:
• Neurological signs that can be measured
• Based on responses to external stimuli
Brain Death
• Examination includes:
• Movement of extremities: arms and legs are raised, let fall – must
be no other movement or hesitation in fall
• Eye movement: eyes must remain fixed showing lack of brain-tomotor-nerve reflex
• As head is turned no rolling motion of eyes
• Corneal reflex: must be absent
• When cotton swab is dragged over cornea, eye does not blink
• Pupil reflex: must be absent
• Do not constrict in response to very bright light
• Gag reflex: must be absent
• Insertion of small tube into throat
• Respiration (breathing) response: must be absent
• Removal from ventilator, no response
Brain Death
• Brain dead person can still have spinal reflexes
• Knee jerk can be functional
• Do not involve the brain
• Further tests:
• Electroencephalogram (EEG)
• Measures brain activity in microvolts
• Very sensitive test
• Brain dead – electrocerebral silence
• Cerebral blood flow (CBF) study
• Radioactive isotope is injected into bloodstream
• Radioactive counter place over the head
• No activity detected – brain death
Perception of Pain
• Pain signals carried by peripheral nerve fibers to spinal cord 
relayed to sensory area of brain
• Peripheral fibers connect with pain receptors – nocioreceptors
• Sense excess heat, pressure, or chemicals from injured tissues
• Located in: skin, muscle, bone, joints, membranes
• Nerve impulses of pain travel to spinal cord
• Ascending tracts in spinal cord send message to brain
• Travels to cerebral cortex  receives message of pain 
directs body to respond
• Muscles to stop action which is causing pain
• Alter autonomic nervous system (change heart rate or breathing)
• Direct other brain cells to release pain-suppressing endorphins
Endorphins
• Endorphins are CNS NT with pain-relieving properties
• Small peptides which bind to opiate receptors
• Block transmission of impulses at synapses
• Opiates, morphine, heroin bind to same receptors – mimic
endorphins
E.6 FURTHER STUDIES OF BEHAVIOR
(HL)
Further Studies of Behavior
(HL)
Assessment Statements
E.6.1 Describe the social organization of honey bee colonies and one other
non-human example
E.6.2 Outline how natural selection may act at the level of the colony in the
case of social organisms
E.6.3 Discuss the evolution of altruistic behavior using two non-human
examples
E.6.4 Outline two examples of how foraging behavior optimizes food intake,
including bluegill fish foraging for Daphnia
E.6.5 Explain how mate selection can lead to exaggerated tails
E.6.6 State that animals show rhythmical variations in activity
E.6.7 Outline two examples illustrating the adaptive value of rhythmical
behavior patterns
Social Organization
• Social behavior
• Two or more animals interacting with each other
• Social organization of Honey Bee colonies
• Very complex
• No member of the hive can survive without the others
• Nest above ground
• Make wax combs with individual compartments (cells) – store honey or
rearing young
• Queen (fertile female) – lay eggs
• Live 2 years
• Workers
• Female – but sterile
• Jobs: household duties, search for nectar/pollen, make wax and honey,
feed and protect young
• Live 6 weeks
• Males (drones) develop from unfertilized eggs (mating is only function)
Social Organization
• Social organization of Honey Bee colonies
• Influenced by diet
• Queen lays eggs in cells of honeycomb
• If eggs unfertilized – develop into males, no matter diet
• If fertilized and female – type of food fed to as larva determines
worker or queen status
• Worker diet: fed grandular secretions (royal jelly) first days, switched to
honey and pollen
• Queen diet: fed royal jelly during whole larval development
• Queen controls hive with secretions – pheromones
• Inhibits ovarian development in workers
• Workers lick pheromones from queen’s body, passes to others during
food exchange
• Swarming
• Hive is too big – queen leaves with large number of workers
• New queen stay behind
Social Organization
• Social organization of Honey Bee colonies
• Use signals to communicate
• Chemical secreted from top of abdomen of one bee – used to
identify source of nectar/water
• Scouts do a waggle dance to indicate direction and distance to
source
• Chemical released from mouth when danger is near
• Table summarizes roles of bees
Queen
Fertile
female
Lays eggs
Produces pheromones – calm colony, sterilizes other females
Worker
Sterile
female
Feeds larva
Produces wax and honey
Searches for nectar and pollen
Protects hive
Drone
Fertile male
Mates with queen
Social Organization
• Social Organization in Chimpanzees
• Community – highest order in society
• 40-60 members
• Party – smaller group within community
• Up to 5 members
• Male, a family unit, nursery unit, combination of individuals
• Make up depends on food supply
• Hierarchy
• Highest ranked male – age 20-26
• Dominance determined – physical fitness, fighting ability
• Males dominate over females
• Hierarchy in females linked with age
Social Organization
• Social Organization in Chimpanzees
• strong social bonds between males
• Stay in same community in which born, females migrate
• Male bonding important:
• Keep intruders out, hunt, share food
• Parenting – mother
• Critical for survival of infants
• Receive food, warmth, protection, learned skills
• Communication
• Facial expressions
• vocalizations
Natural Selection
• Acts on the colony as a whole
• Genes are selected to promote social organization
• Genes for:
• Pheromones selected to control workers
• Finding nectar and making wax
• Taking care of young
• Evolution of Altruistic Behavior
• Worker bees are altruistic
• Help queen produce offspring, in place of reproducing themselves
• Evolved?
• ‘kin selection’ – behavior results in a decrease in fitness of altruist,
increase in fitness of close relative
Natural Selection
• Belding’s Ground Squirrel
• Predator approaches  one squirrel sounds alarm (high pitched
call)  alerts rest of population
• Alarm squirrel more likely to be killed  gives away its position
• Calls predominantly performed by females
• Live close to relatives
• Males live at far distance
• Alarm squirrel does not increase own fitness, but increases
relatives fitness
• Sacrificing to save relative to reproduce
• If relatives are dead, no alarm call given
Natural Selection
• Naked Mole Rats
• Live underground, burrows are excavated and extended by
workers
• make nesting chambers
• Forage for plant roots
• Bite off tuber and brings it to queen
• Larger workers stay near queen and young
• Queen suppresses sexual behavior of other females and males
(except with ovulating)
• Snakes main predator
• Workers attack snake – sacrificed for queen and young
• Almost genetically similar to each other
• Another example of ‘kin selection’
• Believe essential for survival based on living conditions – dry soil,
little food
Foraging Behavior
• Measure feeding behaviors/ foraging activities
• Food essential to survival and reproduction
• Study based of cost-benefit analysis of foraging
• Cost of foraging – energy used to locate, catch, eat food
• Benefit – calories of energy gained
• Conclusion – change in behavior to keep high ratio energy intake
to energy expended
• Small Mouth Bass
• Forage minnows or crayfish
• Minnows – more energy per unit weight
• Easier to digest
• Crayfish – easier to catch
• Not picky eaters, eat whichever does not extend to much energy
Foraging Behavior
• Bluegill Sunfish
• Eat Daphnia
• Small crustaceans – varying sizes
• Forage larger Daphnia – supply more energy
• Will select smaller Daphnia if larger ones to far away
• Predictions:
• Density low – bluegill will not be selective
• Density high – will be more selective, eat only larger Daphnia
• Conclusion:
• High density – larger Daphnia eaten 57% of the time
• Young bluegill did not distinguish between sizes like adults – less
efficient feeding methods
Mate Selection
• Exaggerated Traits
• Theory of natural selection – sexual selection evolves because
females prefer more highly decorated males
• Peahens choose their mates by the size and shape of peacocks
tails
• Largest tail – healthiest birds
• Correlation between number of mates and size of tail
• Not cause – eliminate possibility large tail is not superior in some
other way
• Offspring of males with larger tails – larger at birth and survive
better in wild
• Disadvantage – over time, tails become too large and colorful 
attract predators
Rhythmic Variations
• Reproductive Rhythm
• Seen in all reef-building species of coral
• Coral release millions of gametes
• Releasing all at the same time increases chances of fertilization
• Predators overwhelmed with more food than can eat
• After fertilization, larva develop
• Animals repeat patterns of behavior daily, monthly, yearly
• Adaptations to niche
• Daily Rhythms
• Regulated by strong endogenous (internal) component
• Exogenous cues (light) important to synchronizing internal clock
• North
Rhythmic Variations
• Daily Rhythms
• Regulated by strong endogenous (internal) component
• Exogenous cues (light) important to synchronizing internal clock
• North American Flying Squirrel
• Placed in constant darkness
• Rhythmic activity continued on 24-hr cycle without light
• Squirrel continued pattern controlled by internal block
• 8 hrs activity, 16 hrs inactivity
• Normally, synchronized with light/dark cycles of habitat
• But without stimulation of nature, synchronization altered
• Biological clocks keep animals in sync with environment
• External cues regulate the internal clock to keep with changing
environment