OPTION E:
NEUROBIOLOGY AND
BEHAVIOR
Madeleine Kresin
Stimulus and Response E.1
Definitions E.1.1
Stimulus: change in the environment (either
internal or external) that is detected by a
receptor and elicits a response
Reflex: rapid, unconscious response
Response: reaction to a stimulus
Stimulus and Response E.1.2
Response of Animals to Pain Stimuli: The Pain
Reflex Arc
• pain receptors receive the stimulus of excessive heat,
pressure or chemicals produced by injured tissues
 receptors generate nerve impulse in sensory neurons
 sensory neurons carry the impulse toward the spinal cord
 the sensory neuron's axon enters the spinal cord in the dorsal root


and send a chemical message across the synapse to a relay neuron
in the gray matter of the spinal cord
the relay neuron then synapses with a motor neuron in the grey
matter in the ventral root of the spinal cord, and carries the
impulse to an effector - organ that performs the response
in addition, the animal exhibits physical changes (growling etc.),
because the spinal cord nerves carry impulses to the brain, and as
the brain becomes aware of what is happening, it coordinates
physical manifestations (growling)
Reflex Arc Diagram E.1.3
Effects of Natural Selection E.1.4
•
Moth Population Variation in Behavior
o
in environment with dark tree bark, the moth
population is primarily darker colored - light moths
are more easily spotted by birds; in environment
with lighter tree bark (i.e. with large lichen
population), the population is primarily lighter
colored
Effect of Natural Selection E.1.4
•
European Blackcaps Variation in Behavior
o
traditionally breed in Germany in spring and summer and winter in Spain; 50
years ago it was observed that UK blackcaps left 10 days earlier in winter to
return to Germany than the Spanish blackcaps and the earlier the birds arrived
in Germany, they had more choice of territory and laid more eggs; warm UK
winters increase bird survival rate; change in migration patterns may
eventually result in a new species - especially likely if small changes in
courtship behavior occur
o
Experiment: UK eggs and Spanish eggs collected; all were reared but had no
parents to teach young which direction to fly, but UK eggs and Spanish eggs
still flew respectively -they are genetically programmed to fly in a certain
direction
Effects of Natural Selection E.1.4
• Sockeye Salmon Variation in Behavior
o
o
o
introduced into Lake Washington and over 60 years there have been 13 generations;
some migrated to Cedar River (flows into lake), and some stayed in the lake, which is
deep and quiet; DNA evidence shows that lake and river salmon have stopped
interbreeding
lake salmon spawn on beaches - females lay eggs in sand, and males have heavy
bodies for hiding in the deep lake waters, but are thus less efficient at navigating fast
currents
river salmon females bury eggs deep in sandy river bottom, males are thinner and
narrower for better maneuverability in the current, but can't spawn on the beach
Perception of Stimuli E.2
Sensory Receptors and Diversity of Stimuli: E.2.1
•
•
•
•
Mechanoreceptors: stimulated by mechanical force or pressure; sense of
touch due to pressure receptors, arterial pressure receptors detect change
in blood pressure; lung stretch receptors respond to degree of lung
inflation; proprioceptors in muscle fiber, tendons, joints and ligaments
maintain posture and balance; inner ear pressure receptors are sensitive to
waves of fluid moving over them - equilibrium
Chemoreceptors: stimulated by chemical substances - taste and smell;
arterial chemoreceptors monitor pH changes, which signal the body to
adjust breathing rate; pain receptors respond to chemicals released by
damaged tissues, which protects us from danger - pain reflex
Thermoreceptors: stimulated by change in temperature; warmth receptors
respond when temperature rises, cold receptors respond when
temperature drops
Photoreceptors: stimulated by light energy; in eyes - sensitive to light; rod
cells respond to dim light resulting in black and white vision, while cone
cells respond to bright light and give color vision
Structure and Function of Human Eye E.2.2
Part
Function
Iris
regulates pupil size
Pupil
admits light
Retina
contains receptors for vision
Aqueous Humor
transmits light rays and supports eyeball
Vitreous Humor
transmits light rays and supports eyeball
Rod
allows black and white vision in dim light
Cone
allows color vision in bright light
Fovea
area of densely packed cones - most acute
vision
Lens
focuses light rays
Sclera
protects and supports eyeball
Cornea
begins focusing
Choroid
absorbs stray light
Conjunctiva
covers sclera and cornea; keeps eye moist
Optic Nerve
transmits impulses to brain
Eye Lid
protects eye
The Retina E.2.3
•
vision begins when light enters eye and is focuses on retina photoreceptors cells rods and the cones; rods and cones synapse with their own bipolar neurons, each of
which synapses with a ganglion cell - axons of ganglions make up optic nerve
o
Rod Cells: photoreceptor cells which are very sensitive to light; receive stimulus
of light and synapse with bipolar neuron
o
Cone Cells: photoreceptor cells activated by bright light; receive stimulus and
synapse with bipolar neuron
o
Bipolar Neurons: retina cells which carry impulses from rod or cone to
ganglion cell of optic nerve; each have two processes extending from cell body
o
Ganglion Cells: cell bodies of optic nerve - synapse with bipolar neurons and
send impulses to brain
Rod Cells v. Cone Cells E.2.4
Rods
Cones
cells are more sensitive to light and
function well in dim light
cells are less sensitive to light and function
well in bright light
only one type of rod in retina - absorbs all
wavelengths of visible light
three types of cones in retina: sensitive to
red light, sensitive to blue light and
sensitive to green light
impulses from group of rod cells pass to
single nerve fiber in optic nerve
impulse from single cone cell passes to
single nerve fiber in optic nerve
Processing Visual Stimuli E.2.5
•
light rays pass through pupil and are focused by cornea,
lens, and humors; image focused on retina is upsidedown and reversed left to right; once retina
photoreceptors are stimulated, they send impulses to
bipolar neurons and ganglion cells - ganglion cell axons
travel to visual area of cerebral cortex, where the
position of image is corrected and is coordinated for
images coming from left and right eye
Processing Visual Stimuli E.2.5
Edge Enhancement
•
•
perception of grey blobs in white area between black squares vanishes when looked
at directly because areas where perceived gray are in peripheral vision where there
are fewer light-sensitive cells than in fovea - some cells present may even be 'turnedoff', sending the message of gray rather than white, but when the gray blobs are
looked at directly, the fovea, with a high concentration of light-sensitive cells, is
being used, so that even if some are 'turned-off', it is still perceived white
figure 'fools' the eye because of extreme contrast between black and white edges demonstrates that there is a special mechanism for seeing edges; light-sensitive
receptors in eye switch off neighboring receptors, making edges look more distinct
because of extreme contrast between dark and light
Processing Visual Stimuli E.2.5
Contralateral Processing
•
nerve fibers bringing information from right half of each visual field converge at
optic chiasma and pass to left side of the brain; nerve fibers bringing information
from left half of each visual field converge at optic chiasma and pass to right half of
brain; information eventually ends up in visual cortex, and since each visual area
only gets half the information from each field, the areas must share information to
form a complete visual image - image received by cortex is both inverted and
reversed, and so brain must correct image; impulses relating to the other stimuli color, form and motion are parcelled out to other visual association areas of brain,
and eventually the cerebral cortex rebuilds all parts into a cohesive whole
Structure of the Human Ear E.2.6
Perception of Sound By Human Ear E.2.7
•
•
•
Outer ear catches sound waves - successive vibrations of air molecules,
which, when travelling down auditory canal, cause eardrum (tympanic
membrane) to move back and forth slowly
Malleus, incus and stapes all receive vibrations from tympanic membrane
and multiply them 20X; stapes strikes oval window, causing it to vibrate,
which passes to the fluid in the cochlea, causing special cells - hair cells - to
vibrate; hair cells release chemical message across a synapse to the sensory
neuron of the auditory nerve, stimulating the sensory neuron, which is
then carried by sensory neuron in auditory nerve to brain; wave in fluid of
cochlea dissipates as it reaches round window
Loud noises cause fluid to vibrate to a higher degree and hair cells bend
more - interpreted by brain as higher volume; pitch is a function of sound
wave frequency - short, high-frequency waves produce high-pitched
sounds while long, low-frequency waves produce produce low-pitched
sounds; sound which is sensed by brain is processed in auditory area of
cerebral cortex
Innate and Learned Behavior E.3
Innate v. Learned Behavior E.3.1
•
Innate
Behavior:
develops
independently
of
environmental context; no trial-error learning;
controlled by genes and inherited from parents;
genetically programmed behaviors which ensure animal
survival; some are performed in a certain order (i.e.
mating behavior); example: male 3-spined stickleback
does a zigzag dance when he sees the female, attracting
her attention; she follows male as he leads her to the
nest constructed in the bed of the river, where he backs
out of the nest and she enters; he vibrates his body at
nest entrance and female releases her eggs; she leaves
nest and male enters; he releases sperm cells that
fertilize eggs
Innate v. Learned Behavior E.3.1
•
Learned Behavior: not genetically programmed; results
in new knowledge not previously existent or new skill
not originally possessed; process of gaining new
knowledge or skills or modifying existing knowledge or
skills; learning measured by performance - rat that
learns by pressing a pedal, food is released, rate
originally pressed pedal by accident during exploration
of cage, and after pellet of food was released over and
over again, rat learned to associate food with pedal, and
later pushing pedal to get food becomes deliberate act
Innate v. Learned Behavior E.3.1
Innate Behavior
Learned Behavior
develops independently of environmental
context
dependent on environmental context of
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 environmental
stimulus
increases chance of survival and
reproduction
may or may not increase chance of survival
and reproduction
Innate Behavior in Invertebrates E.3.2
•
Taxis: directed response to stimulus; positive response: animal's body is moved
toward the stimulus; negative response: animal moves away from stimulus
o
Chemotaxis: response to chemicals in environment; organisms in water can
move toward or away from food / other chemicals which are dissolved in their
aquatic medium
o
Phototaxis: response to light - different wavelengths and intensities of light
o
Gravitaxis: response to gravity
o
Rheotaxis: response to water current
o
Thigmotaxis: response to touch

Planaria: flatworm in lakes; move by contraction of muscle fibers, simple
nervous system at have 2 eyespots at anterior end which have
photoreceptors and chemoreceptors; negatively phototaxic and positively
chemotaxic - could be tested for response to temperature gradient

Euglena: protoctist; flagellum propels it through water, anterior eyespot;
positively phototaxic (needs light for photosynthesis) - could be tested for
wavelengths of light
•
Innate Behavior in
Invertebrates; Kinesis E.3.2
movement in response to non-directional stimulus; rate of animal
movement depends on intensity, not direction, of stimulus; does not move
toward or away from stimulus, if in an uncomfortable environment, it
moves rapidly and randomly until in a more comfortable 'zone'
o Orthokinesis: organism changes speed in response to stimulus but
doesn't move toward stimulus
o Klinokinesis: organism turns slowly or rapidly in response to stimulus
but doesn't move toward stimulus
 Isopods: live on land but breathe with gills, so live in damp
places; when placed in damp environment, they move slowly, in
dry environment, move rapidly; their exoskeleton lacks a
waterproof waxy cuticle, so it is highly subject to desiccation quick random movements enable isopod to find itself in a humid
environment, ensuring survival and enhancing ability to
reproduce; favored by natural selection
Learning Improves Chance
of Survival E.3.4
• Imprinting: process by which young animals
become attached to their mother within first
day after birth - assures that young stay close
to their mother for protection and food
source
o
o
o
food hoarding
birdsong for reproduction and territorial claims
false learning through mimicry of prey (butterflies
and snakes)
•
Pavlov and Conditioning
E.3.5
Classical conditioning: can be used to modify reflex response;
subject responds to stimulus in a new way
o blinking - waved hang experiment is the UCS because it
unconditionally stimulates eye-blink response; possible
to then elicit reflex response with neutral stimulus
(musical note); eventually subject responds with eyeblink to musical note and note is the conditioned
stimulus and the eye-blink is the conditioned response
o Pavlov: UCS of food elicits UCR of salivation; Pavlov
employed ringing of a bell as his neutral stimulus, and so
that he could eventually ring the bell - the conditioned
stimulus, and the dog would salivate - the conditioned
response; dog learns to salivate to neutral stimulus alone
•
Birdsong in Young Birds
E.3.6
birds sing through syrinx - bony structure at bottom of trachea; air
forces past membrane in syrinx causes syrinx to vibrate and results
in sound - pitch controlled by altering tension in syrinx membrane;
volume controlled by altering air flow
o singing important for male - reproduction and warning
o birds hatch with a crude template: template inherited, and all
next steps of development are learned:
 memorization phase: bird is silent but listens to adult
songs of his species (modifying inherited template); over at
about 100 days of age - the sensitive period
 motor phase: bird practices singing, hears his own singing
and begins to shape song to match what he has heard from
his father - bird must hear his own song in order to sing
accurate adult song; as he becomes sexually mature, his
song will become perfected and he will begin to search for a
mate
Synaptic Transmission E.4.1
• excitatory neurotransmitters stimulate next
•
neuron by increasing permeability of
postsynaptic membrane to positive ions
inhibitory transmitters cause positive ions to
move out of postsynaptic cell; movement of
positive ions back into cleft chemically
depresses postsynaptic cell and makes it
harder to excite the postsynaptic cell
•
Decision Making in the
Central Nervous System
E.4.2
as action potential reaches terminal, calcium ions rush in, causing
vesicles containing neurotransmitters to fuse with presynaptic
membrane and exocytose into the synaptic cleft, where they then
bind to specific receptors on postsynaptic membrane
o Excitatory Neurotransmitters: e.g. acetylcholine; increase
permeability of postsynaptic membrane to sodium ions in the
cleft to diffuse into the postsynaptic neuron, locally
depolarizing it by the influx of sodium, so that there is a net
positive interior charge compared to the outside;
depolarization continues along the axon; threshold must be
met to continue
o Inhibitory
Neurotransmitters:
e.g.
Gaba;
causes
hyperpolarization of neuron - making inside more negative, so
that it is more difficult to generate an action potential
•
Psychoactive Drugs Affect
Brain and Personality E.4.3
Acetylcholine, if left in synapse, would fire indefinitely; this is prevented by
acetylcholinesterase - breaks down acetylcholine in synapse
o Cholinergic Synapses: use acetylcholine; i.e. nicotine stimulating
transmission in cholinergic synapses calms body and personality;
parasympathetic
o Adrenergic: use noradrenaline - depolarizes postsynaptic neuron; e.g.
cocaine and amphetamines - increased alertness, energy and
euphoria; sympathetic
Cholinergic
Adrenergic
Neurotransmitter
Acetylcholine
Noradrenaline
System
Parasympathetic
Sympathetic
Effect on Mood
Calming
Increased energy, alertness
and euphoria
Drugs Increasing
Transmission at Synapse
Nicotine
Cocaine and Amphetamines
•
Psychoactive Drugs Affect
Brain and Personality E.4.3
excitatory drugs (nicotine, cocaine, amphetamine), increase nerve
transmission while inhibitory drugs (benzodiazepines, alcohol,
THC) decrease likelihood of nerve transmission
o block receptor for neurotransmitter (drug has similar structure
to neurotransmitter)
o block release of neurotransmitter from presynaptic membrane
o enhance release of neurotransmitter
o enhance neurotransmission by mimicking neurotransmitter
(when
drugs
have
same
chemical
structure
as
neurotransmitter, have same effect but aren't broken down as
easily so effect is stronger because they stay longer in synapse)
o block removal of neurotransmitter from synapse and prolong
effect of neurotransmitter
Excitatory v. Inhibitory
Drug Action E.4.4
•
•
•
EXCITATORY
Nicotine: mimics Ach; acts on cholinergic synapses of body and brain to cause
calming effect; after Ach is received by receptors, it is broken down by
acetylcholinesterase but it can't break down the nicotine molecules (because they
bind to same receptors), exciting postsynaptic neuron, which begins to fire,
releasing dopamine - molecule of reward pathway; addiction
Cocaine: stimulates transmission at adrenergic synapses, causing alertness,
euphoria, and dopamine release; blocks dopamine removal from synapse leading
to buildup of dopamine, leading to over-stimulation of postsynaptic neuron
(since its the reward pathway, it leads to euphoria); addiction
Amphetamine: stimulates transmission at adrenergic synapses and gives
increased energy and alertness; passes directly into nerve cells which carry
dopamine and noradrenaline, directly into vesicles of presynaptic neuron and
causes their release into the synaptic cleft; normally these neurotransmitters
would be broken down in the synapse, but the amphetamines interfere with
breakdown, so there's high concentrations of dopamine in the synapse, causing
euphoria, and high noradrenaline concentrations may be responsible for
alertness and high energy
Excitatory v. Inhibitory
Drug Action E.4.4
•
•
•
INHIBITORY
Benzodiazepine: reduces anxiety and can be used against epileptic seizures;
modulates GABA activity; when GABA binds to postsynaptic membrane,
Benzodiazepine increases binding of GABA to receptor, causing postsynaptic
neuron to become more hyperpolarized (release of chloride ions into neuron,
resisting firing)
Alcohol: increases GABA binding to postsynaptic membrane to cause neuron to
become hyperpolarized - sedative effect of alcohol; decreases glutamate
(excitatory neurotransmitter) activity and increases dopamine release and
stops enzyme activity of breaking down dopamine in synaptic cleft (more
reward pathway)
Tetrahydrocannabinol: main psychoactive chemical in marijuana; mimics
anandamide by binding to same receptor (cannabinoid receptor); THC is an
inhibitory neurotransmitter and causes postsynaptic neuron to be
hyperpolarized; disrupts short-term memory
•
•
Effects of THC and Cocaine
on Synaptic Action E.4.5
THC: dilates pupils, causing color perception to be more intense,
sense enhancement (panic / paranoia); cannabinoid receptors
affect learning, coordination, problem solving, and short-term
memory; since it mimics anandamide, it inhibits neurons that
anandamide inhibits but it has a much greater effect because
there's no enzyme breaking down THC in the synapse; when THC
binds to cannabinoid receptors in hippocampus, it interferes with
short-term memory; when THC binds to cannabinoid receptors in
cerebellum and basal ganglia, it affects coordination - motor
impairment
Cocaine: euphoria, talkativeness, increase in mental alertness;
temporary decrease in need for food and sleep, later erratic and
violent behavior; synaptic effect of cocaine is from its ability to
sustain dopamine level in synapse - the reward pathway
Causes of Addiction E.4.6
•
•
•
Genetic Predisposition: found in twin studies (when one twin
suffers alcohol / drug addiction, the other twin's rate of
addiction is 50% greater among identical twins than fraternal
twins)
Social Factors: family addiction, family parenting skills and
mental health problems of family / child; peer pressure;
cultural introductions
Dopamine Secretion: in drug addiction, dopamine receptors
are constantly stimulated, and over-stimulation decreases
receptor numbers and remaining receptors become less
sensitive to dopamine (desensitization), so that exposure to
drug causes less response so more and more is required;
glutamate may 'oversee' learning and memories which lead to
cocaine seeking
Structure and Function of
Human Brain E.5.1 and E.5.2
Structure and Function of
Human Brain E.5.1 and E.5.2
•
•
•
•
•
Cerebral Hemispheres: act as integrating center for high complex
functions (learning, memory, emotions), and are associated with
intelligence, personality, sensory impulses, motor function,
organization and problem solving
Hypothalamus: maintains homeostasis, coordinating nervous and
endocrine systems, secreting hormones of posterior pituitary and
releasing factors regulating the anterior pituitary
Cerebellum: has two hemispheres and highly folded surface;
coordinates unconscious functions (movement and balance)
Medulla oblongata: controls automatic and homeostatic activities
(swallowing, digestion, vomiting, breathing and heart activity)
Pituitary Gland: posterior lobe stores and releases hormones
produced by hypothalamus and anterior lobe, produces and
secretes hormones regulating body functions
Identification of Brain Parts
Involved in Specific Functions E.5.3
•
•
•
Brain Lesions: lesions in identifiable areas of brain tell indirectly about function of those areas; some lesions
which have been studied occur in either right or left half and give information about difference between halves
Right and Left Hemispheres: connected by thick band of axons - corpus callosum; Left: contains areas important
for communication; LH damage may result from stroke, and after damage there's difficulty in speaking or using
complicated hand / arm movement; Right: specializes in receiving and analyzing information coming from
senses; people with lesions in RH have problems identifying faces and locating an object correctly in space
Experiments:
o
mid 1800s - people with injuries on left side had speech and language problems; on right side no language
problems; injury to Broca's area interferes with ability to vocalize words, injury to Wernicke's area affects
ability to put words into sentences
o
1960s - study of group with severed corpus callosums to relieve epilepsy; already knew that input from
right visual field is received by LH and vise versa; projected picture of spoon onto right side of card with
dot in middle; split-brain looking at dot and spoon picture is flashed up, visual information about spoon
crosses optic chiasma and ends up on LH - can identify and say 'spoon'; if projected on left side of dot,
information goes to RH - no language ability, so the person will say that nothing is seen, when asked to
pick up spoon with left hand, they correctly pick it up and information travelled to RH understands what a
'spoon' is even if they can't verbalize it
o
use chimerical picture to test split brain patients - when focusing on dot, information about woman's face
will travel to R cerebral H and the information about man's face will go to LcH; if asked to look at pictures
of complete, normal faces and point to face they have just seen, they will choose picture of woman
(information of 'woman' went to RH), but if asked whether it was a man or woman, they say it's a man
(side of brain that dominates will depend on what patient is asked to do - facial recognition does not
require speech, and so RcH dominates
Identification of Brain Parts
Involved in Specific Functions E.5.3
•
•
fMRI: uses radio waves and strong magnetic field to enable scientists to see
blood flow in brain as it's occurring; can produce new image every second and
can determine with some precision when regions of brain become active and
how long they remain active - possible to determine if brain activity occurs in
same region or different regions all at same time as patient responds to
experimental conditions; PET scanner is slower but can identify areas of brain
activated by neurotransmitters and drugs; fMRI can determine: plan for
surgery, treatment for stroke, placement of radiation therapy for brain tumor,
effects of degenerative brain disease (i.e. Alzheimer's), diagnosing how a
diseased or injured brain is working
Animal Experiments:
o animal trained to press lever to get reward
o animal is given injection of addictive substance as it pushes lever (selfadministration required)
o two levers must be available - one which gives substance and one which
doesn't
o if substance is reinforcing, animal will seek to repeat experience by
pushing lever more frequently - supports hypothesis that substance is
Sympathetic v. Parasympathetic
Control E.5.4
•
•
Central Nervous System: brain and spinal
cord
Peripheral Nervous System: somatic system
(takes sensory information from sensory
receptors to CNS and then sends back motor
commands from CNS to muscles - pain
reflex
arc)
and
autonomic
system
(involuntary and regulates gland, smooth
muscle and heart activity) divided into
sympathetic and parasympathetic systems
Sympathetic System
Parasympathetic System
important in emergency
important in returning to normal
response is 'fight or flight'
response is 'rest and digest'
neurotransmitter is noradrenaline
neurotransmitter is acetylcholine
excitatory
inhibitory
dilates pupil
constricts pupil
inhibits salivary production
stimulates salivary production
dilates bronchi
constricts bronchi
speeds up heart
slows heart
stimulates adrenaline and noradrenaline
secretion
stimulates stomach, pancreas and
intestines
stimulates glucose release
stimulates large intestine
inhibits intestinal activity
stimulates urination
inhibits urination
causes erection
promotes ejaculation
The Pupil Reflex E.5.5
•
•
•
after closing and suddenly re-opening eyes, the pupil closes in response to
sudden input of light as eyes open - cranial reflex (sensory and motor neurons
connect in brain rather than spinal cord)
in eye, iris surrounds pupil (opening over lens); iris has two sets of smooth
muscle that open and close pupil; pupil closes by parasympathetic response
caused by acetylcholine; atropine stops acetylcholine action; constriction of
pupil due to motor neuron causing circular muscle to contract and radial
muscle relaxes
Pupil Reflex:
o optic nerve receives messages from retina in back of eye (retina contains
photoreceptors which receive light stimulus; synapse with bipolar neurons
and then with ganglion cells - nerve fibers of ganglion cells become optic
nerve)
o optic nerve connects with pretectal nucleus of brain stem
o from pretectal nucleus, message is send to Edinger-Westphal nucleus,
whose axons run along oculomotor nerves back to eye
o oculomotor nerves synapse on ciliary ganglion
o axons of ciliary ganglion stimulate circular muscle of iris so it contracts
Brain Death E.5.6
•
•
•
"That time when a physician has determined that the brain and brainstem have
irreversibly lost all neurological function" - artificial maintenance of body without
impulses which normally come from brain
Examination for Brain Death: movement of extremities: if arms / legs are raised and
let fall, there must be no other movement or hesitation in fall; eye movement: eyes
must remain fixed showing lack of brain-to-motor-nerve reflex; corneal reflex: must
be absent - when cotton swab is dragged over cornea, eye doesn't blink; pupil reflex:
must be absent - pupils don't constrict in response to very bright light shone into
both eyes; gag reflex: must be absent - insertion of small tube into throat of
comatose patient causes gag reflex; respiration response: must be absent - if patient
is removed from ventilator, brain gives no response; EEG - measures brain activity
in microvolts - lack of electrical activity is the electrocerebral silence; CBF:
radioactive isotope is injected into bloodstream, radioactive counter is then placed
over head for 30 minutes - if no activity is detected, conclusive evidence of brain
death
in brain dead person, there can still be spinal reflexes - knee jerk response, short
reflex motion can still be exhibited if hand / foot is touched in certain manner
•
•
Perception of Pain and
Effect of Endorphins E.5.7
pain signals are carried by peripheral nerve fibers from all around
body to spinal cord and relayed to brain sensory area, which
connect with nocioreceptors - sense excess heat, pressure or
chemicals from injured tissues, nerve impulses of pain travel to
spinal cord - ascending tracts in spinal cord send messages up
brain; message of pain travels to cerebral cortex - receives message
of pain from spinal nerves and directs body to respond by: telling
muscles to stop action which is causing pain stimulus, alert
autonomic nervous system if pain requires change in heart rate /
breathing, can direct other brain cells to release pain-suppressing
endorphins
Endorphins are CNS neurotransmitters with pain-relieving
properties; small peptides which bind to opiate receptors and block
transmission of impulses at synapses involved in pain perception
Social Organization of
Honey Bee Colonies E.6.1
•
•
•
•
nest above ground inside hollow tree, make wax combs with individual
compartments for storing honey and rearing young; each hive has queen who lays
eggs, female workers are sterile and search for nectar / pollen, make wax / honey,
and feed / protect the young; workers live for 6 weeks, queens live for 2 years, male
drones develop from unfertilized eggs, and mating with the queen is their only
function
queen lays eggs in cells of honeycomb; if eggs are unfertilized they develop into
males no matter what they are fed, but if fertilized and female, type of food they are
fed as larvae determines whether they will become a worker or a queen - eggs
develop into larvae and are fed royal jelly (glandular secretions) for the first few
days, workers then switch larvae destined to be workers to less nutritious diet of
honey and pollen, but if queen is needed, larvae destined to be queen are fed royal
jelly their whole development
queens control hive with pheromone secretion - inhibit ovarian development in
workers (workers lick pheromone from queen's body and pass it onto other workers
during food exchange)
chemical secreted from abdomen tip of one bee is used to identify source of nectar /
water for others; some bees scout out source of nectar and waggle to indicate
direction and distance of source, another chemical is released from mouth area
when colony is in danger and signal is spread to others
Social Organization of
Honey Bee Colonies E.6.1
•
•
•
•
Social Organization in
Chimpanzees E.6.1
highest order of society is the community - typically made up of 40-60
members; smaller group within community is the party - up to 5 members,
party may be all male, family unit, or nursery unit (makeup of parties
depends on food supply - the more food there is, the larger the groups
which travel together)
highest ranking male is 20-26; dominance determined by physical fitness
and fighting ability; dominance hierarchy in females linked with age (older
females dominant over younger females); strong social bonds exist
between males because they are related to each other - males stay in same
community where they were born, while females may migrate to other
communities
male bonding leads to cooperative behavior needed to keep out intruders,
hunt together and share food; parental care is responsibility of mother and
is crucial to infant survival; young chimpanzees receive food, warmth,
protection and learn skills from their mothers
communication includes facial expressions and vocalizations
Social Organization in
Chimpanzees E.6.1
Natural Selection at the
Level of the Colony E.6.2
• natural selection in the case of social organisms
is acting on colony as a whole; genes which are
selected are those who promote social
organization, for pheromones which control
worker behavior, for behavior of finding nectar
and making wax, for taking care of young all are
selected; all females have these genes and it is
just a matter of chance which female is fed the
royal jelly to become the queen; workers, even
though sterile, are ensuring survival of their
own genes
Evolution of Altruistic
Behavior E.6.3
•
•
Belding's Ground Squirrel: when predator approaches, one of ground squirrels gives
high-pitched call which alerts the rest of the population to nearby danger; alarm
squirrel is more likely to be killed than the other squirrels in the population because
the alarm call gives away the location of the caller to the predator; alarm calls are
predominantly performed by females, which live closer (than the males) to their
relatives - females sacrifice themselves so that their close relatives can reproduce; if
all female's close relatives are dead, she doesn't sound alarm calls; altruistic
behavior increasing representation of its genes in the next generation since it shares
genes with its relatives
Naked Mole Rats: workers excavate and extend their burrows, and make nesting
chambers and forage for food; worker bites off part of tuber and brings it to queen,
larger workers stay near queen and her young, and queen suppresses sexual
behavior of other females and of males except when she is ovulating; when snake
attacks burrow, queen sends out workers to attack snake - workers are sacrificed so
that queen and her young can live; developed this lifestyle because the soil is hard
and dry and food is scarce - pair of naked mole rats couldn't survive on their own,
but colony with altruistic behavior survives well; naked mole rats are almost
genetically identical
Evolution of Altruistic
Behavior E.6.3
Foraging Behavior
Optimizes Food Intake E.6.4
•
•
Smallmouth Bass: can forage for either minnows (more energy per unit) or
crayfish (easier to catch); minnows are easier to digest than crayfish exoskeleton; smallmouth bass switch from minnows to crayfish and back
again in order to keep energy that they take in higher than the energy they
expend; since no preference is shown for either minnows or crayfish, each
may be optimal under different conditions
Bluegill Sunfish: eats Daphnia - small crustaceans which are found in
varying sizes; bluegills forage for larger Daphnia - the most energy, but
will select smaller Daphnia if larger ones are too far away; when density of
Daphnia is low, bluegill won't be selective as to size when foraging, but
when there's high density, they become more selective and choose larger
Daphnia; young bluegill sunfish don't feed as efficiently as older sunfish,
not clear it that's due to lack of ability to see size of Daphnia correctly or if
it's due to learning that takes place as they mature
Mate Selection Leads to
Exaggerated Traits E.6.5
• when females choose males with an exaggerated
trait (i.e. peacock tail), males will father more
offspring than other males and trait will become
exaggerated in species; originally, tail size and
number of eyespots might have had real
advantage but is now just sign of best male, so
females are choosy and prefer males with
longest tales; this could become more extreme
until peacock tails become too big / colorful,
eventually becoming a disadvantage - attracting
new predator
Mate Selection Leads to
Exaggerated Traits E.6.5
Animals Show Rhythmical Variations
in Activity E.6.6 and E.6.7
•
•
Reef-building Coral: release millions of gametes once a year in
synchronized mass spawning ritual - releasing all at same time
increases chances of fertilization; predators are overwhelmed with
more food than they can possibly eat; may occur in response to
water temperature, lunar cycles or hours of daylight
North American Flying Squirrel: flies at night; gets most food and
least competition; upon experimentation in constant darkness, it
was discovered that the pattern continues without the
environmental cue (light), but it doesn't match up with actual light
and dark cycle of habitat - biological clocks are internal
mechanisms which keep animal in sync with its environment, but
external cues regulate biological clock so that it fits a changing
environment
Animals Show Rhythmical Variations
in Activity E.6.6 and E.6.7