Neurobiology and BehaviorOption 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 responseAssessment 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 stimuliAssessment 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)

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

Human Eye

The RetinaVision:1. Begins when light enters

the eye2. Focused on photoreceptor

cells on retina1. Photoreceptor cells: rods

and cones

3. Rods and cones synapse with own bipolar neurons

4. Bipolar neurons synapses with a ganglion cell

5. 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. Light rays pass through pupil2. Focused by cornea, lens, humors 3. Image focused on retina: upside down and reversed (left to

right)4. Photoreceptors stimulated send impulses to bipolar

neurons and ganglion cells5. Axons of ganglion cells travel to visual area of cerebral cortex

(brain)6. Brain corrects position of image (right side up and un-

reversed) • 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

Right side brain injury: when looking at bucket from top no recognition

Left side brain injury: describe function of bucket, but cannot come up with name

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. Travel down auditory canal, causing ear drum (tympanic membrane) to move back and forth

3. Bones (malleus, incus, stapes) receive vibrations from tympanic membrane, multiply 20x

4. Stapes strikes oval window, causing vibration5. Vibration passed to fluid in cochlea6. Fluid causes special cells (hair cells) to vibrate7. Hair cells (receptors) release chemical message across

synapse to sensory neuron of auditory nerve, moves to brain8. 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 BehaviorAssessment 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 BehaviorSome performed in certain order

FemaleMale

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

SummaryInnate 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• 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) 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

b) Place 10 individuals in each chamber.c) Count number of individuals in each chamber for 5 minutesd) Repeat method, data for 40 organismse) 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 variablea) 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.

b) Measure temperature conditions with a Vernier probe. Make sure temperature conditions remain constant

c) There must be an equal possibility for isopods to travel to either chamber

d) Sizes of chambers must be equal

Experimental Design

4. 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.

5. 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) Determine the means of numbers of isopods in humid and dry conditions in two trials, compared with controls

6. 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 eye-blink 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 BirdsongCrude 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

Memorization phase

Motor phase

Duration 100 days: if hear no song in time, does not move to motor phase sensitive period

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 DrugsCholinergic 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 short-term 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 Edinger-Westphal 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-to-

motor-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 eggsProduces pheromones – calm colony, sterilizes other females

Worker Sterile female

Feeds larvaProduces wax and honeySearches for nectar and pollenProtects 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