Activities for learning about neurobiology and behavior
Class 1: Sensing the world
Outline the diversity of stimuli that can be detected by human sensory receptors
Receptor
Function
Example
Mechanoreceptor
Chemoreceptor
Photoreceptor
Thermoreceptor
Rod cells and cone cells
There are two kinds of photosensitive cells in the retina: rod cells and cone cells. Rod cells function well in bright light and dim
light. Cone cells only function well in bright light. Rod cells provide black and white vision whereas cone cells detect colors.
Neuron fatigue
Stare at the small black square in the middle of the
colored patches for 30 seconds and then shift your gaze
to the small black square in the grey area and you will see
patches of color appear there. This happens because the
neurons that are sensitive to one color become fatigued
after use and become 'overridden' by their
complementary colors. You thus see what is not there:
clockwise from the upper left (red) you perceive green,
red, blue and yellow instead of the original red, green,
yellow and blue. This shows you that there is no such
thing as red. Rather, red is just your brain’s perception,
and your brain’s perception can change.
Color blindness
Not all people can see in color. In fact color blindness is
quite common, especially amongst males. Why do you
think color blindness would be more common in boys
than girls? To test for color blindness you can go online
and take some very simple tests. Try these websites.
http://colorvisiontesting.com/online%20test.htm
http://home.sc.rr.com/mikebennett/colorblind.html#Top
Evidence of your blind spot
First, close your right eye and stare at the blue square.
Then slowly move closer to the image. The red dot will
eventually disappear from your view when it is focused
on the 'blind spot' on your retina. This is the area where
the optic nerve passes through the retina. As a result
there are no photoreceptors to respond to sensory input
and whatever is in front of that spot cannot be seen.
However, we do not have a blind spot in our visual field
because the brain improvises 'information' from the
surrounding area and 'fills in' the 'blind spot'. We see a
complete image.
What is reality?
Human and animal senses
We think we see the world for what it really is. But the truth is we will never know reality. The best we can do is to make use of our
senses and let our brain create their own interpretations of the world. In fact, many animals experience the world very differently from
us because their senses are either far more powerful than ours or they have altogether different senses. A dog’s sense of smell is 200
times stronger than ours, for example, and a bear’s sense of smell is far better than a dog’s. Pit vipers have organs that allow them to
see heat, which means they can see you in the dark because you are warmer than the air. Crickets hear with their legs and vampire bats
see in the dark with their noses. Birds and bees can see ultraviolet light, which is invisible to you. Birds sense magnetic fields, which they
use for navigation. Some fish can ‘see’ electric fields and whales can ‘see’ sound.
Synesthesia
Can you imagine if you could see sound, or hear smell, or taste colors? Well,
some people can!!! Such people are said to have synesthesia. In one common
form of synesthesia, letters or numbers are perceived as colored. The boxes show a
test for synesthesia: for a regular person it takes a long time to locate the 2’s
amongst the 5’s; someone with synesthesia can do it in an instant.
Deep thought!!!
Some scientists believe that within 300 years we will have a complete
understanding of the human brain. And some even think that technology will
reach the point that we will be able to keep human brains alive in some sort of
high tech vat of jelly. It even might be possible to stimulate those brains with
the very brain chemicals that create thoughts, ideas, memories, emotions and
perceptions. In other words, it may be possible to raise conscious, thinking
and sentient human brains in the laboratory; brains that believe they are alive,
with a body and with an ordinary life just because the scientists are probing
them in just the right ways. And if that day ever does come true then how will
those brains know what they truly are: mere brains in vats of jelly? Well they
won’t of course,; not unless the scientists probe them to believe as such. No,
they will be just like you and me, believing they understand reality. And since
this is true, how do we know that the technology hasn’t already been
developed. How can we say for sure that we are nothing more than a brain in
some scientist’s lab; that our lives as we know them are illusionary?
Optical illusions
http://www.youtube.com/watch?v=bOP37A1EhEs
It is generally believed that visual and touch illusions are simply curiosities but by studying illusions it is possible to understand
how normal vision and brain functioning work.
What do you see?
The horizontal grey bar is
the same shade throughout
Square A is exactly the same
shade of grey as square B.
What do you see?
Which yellow line is bigger?
The circles seem to move if you move forward
and backward while looking at the black dot.
Shape, position and color-contrast
converge to produce the illusion
of grey blobs at the intersections.
What can you see that
does not exist?
What do you see?
Touch illusions

Push outwards with your hands against something for 90 seconds, and then stop. Record what you feel.

Pull your arms outward for 90 seconds by pulling on the sides of your pants, and then stop. Record what you feel.

Have your partner lie on his/her stomach with arms stretched in front, chin tucked in, and eyes closed. Lift up your partners arms
about 2 feet off of the ground and hold them there for approximately 90 seconds. Then slowly let your partner’s arms to the
ground. Record what she/he feels.

Immerse one hand in cold water and the other in hot water. Then place both hands in lukewarm water. Record what you feel.
Auditory illusions
http://littleshop.physics.colostate.edu/onlineexperiments/Auditory_Illusion.html
http://www.youtube.com/watch?v=e6JSTkwXg90
http://listverse.com/2007/09/16/20-amazing-optical-illusions/
http://listverse.com/2007/12/09/another-10-amazing-optical-illusions/
http://listverse.com/2008/02/29/top-10-incredible-sound-illusions/
Medical advances
Perception
http://www.youtube.com/watch?v=RJmP34WRFKU
http://www.youtube.com/watch?v=mf5otGNbkuc
http://www.youtube.com/watch?v=AqnEGu8VF8Y&feature=related
Class 2: Perception of Light
The human eye
http://www.youtube.com/watch?v=cFVbLnXWn6A
http://www.youtube.com/watch?v=JunCyiGfreo
http://www.youtube.com/watch?v=lmiQ-0Qw8Tk&feature=related
Label a diagram of the structure of the human eye and retina
Compare rod and cone cells
http://www.youtube.com/watch?v=f0JpsTgy6ck
http://www.youtube.com/watch?v=eWmc5pei7ow&feature=related
http://www.youtube.com/watch?v=nspVjwAnGb4&feature=related
Feature
Rod cells
Cone cells
Brightness sensitivity
Color sensitivity
Passage of impulses
How signal is sent to optic nerve
The Edge enhancement Theory
 Ganglion cells send impulses to the optic nerve when they are stimulated by
retinal cells.
 A ganglion cell pools the inputs of several photoreceptors.
 The group of photoreceptors is called the ganglion cell's "receptive field".
 In the center of the receptive field there are “on-center retina cells” that excite
the ganglion cell when they detect increased light intensity, and there are “offcenter ganglion cells” that inhibit the ganglion cell.
 Evidence for this is provided by the scintillating grid illusion, in which dark
dots seem to appear at the intersections. The intersection appears darker since
a point at an intersection is surrounded by high light intensity, which causes
high inhibition of the ganglion cell.
Contra-lateral processing

Contra-lateral processing of visual stimuli means that light
entering each eye from the right side of the person passes to
the left side of the brain, and vice versa.

The effect is illustrated by a form of partial blindness called
Homonymous hemianopsia, which is caused by an injury to
the brain in-between the optic chiasma and the visual cortex.
Paris as seen with left homonymous hemianopsia
Processing of visual stimuli
http://www.youtube.com/watch?v=wbVdlIc5DPE&feature=related
The retina has two halves: one half is on the inside (i.e., closer to the nose) and the other half is on the outside
(i.e., further from the nose). When
send impulses to
and
cells are stimulated by
, they
cells. The bipolar cells combine the impulses and forward them to
cells, which are the sensory neurons of the
right optic nerves intersect near the center of the brain - at a structure called the optic
nerve. The left and
and half
the sensory neurons cross over to the opposite optic nerve. The neurons that cross over are the ones carrying
impulses from the
half of the retina (i.e., closer to the nose). Thus, as each optic nerve
continues from the optic chiasma it carries impulses from both eyes. The optic nerves end at the
processes the information and forwards it to the
brain, which forms the final image.
, which
at the back of the
Class 3: Perception of Sound
Human ear: Structure and Function
http://www.youtube.com/watch?v=M99cKqU8tyg&feature=related
http://www.youtube.com/watch?v=0jyxhozq89g
http://nobelprize.org/educational_games/medicine/ear/game/index.html
Hearing test
http://www.youtube.com/watch?v=4G60hM1W_mk&NR=1&feature=fvwp
http://www.youtube.com/watch?v=D9m2LImsgmQ&feature=fvw
http://www.youtube.com/watch?v=Sxkj3o3SzO0&feature=related
Sesame Street: I can’t hear you Bert
http://www.youtube.com/watch?v=-_0_suZntks
Owl sonar
http://www.youtube.com/watch?v=yps7pgq1TAk
Cricket sounds
http://www.youtube.com/watch?v=vXupVqDfK34
Echolocation bats
http://www.youtube.com/watch?v=5mwoOyOleGc
http://www.youtube.com/watch?v=hUN0JkV3eCQ
Echolocation dolphins
http://www.youtube.com/watch?v=p0p4kDYY_tY&feature=related
http://www.youtube.com/watch?v=2CP8qdnmqHQ&feature=related
http://www.youtube.com/watch?v=rW1WUPF5ros&feature=related
Echolocation human
http://www.youtube.com/watch?v=YBv79LKfMt4
http://www.youtube.com/watch?v=zhtMXpNW1zc&feature=fvw
4D ultrasound
http://www.youtube.com/watch?v=de9LrgYBd68
Label a diagram of the ear
Explain how sound is perceived by the ear
The folds of cartilage surrounding the ear canal are called the
. The folds cause sound waves to
be reflected, and these changes of direction provide information to help the brain determine the direction from
which the sounds came.
The sound waves enter a simple tube called the
sounds.
that amplifies
At the far end of the ear canal is the
, which marks the beginning of the middle ear.
Sound waves from the eardrum travel across the air-filled middle ear cavity via a series of delicate bones called the:
1.
.
2.
.
3.
.
These bones convert the lower-pressure eardrum vibrations into higher-pressure vibrations at another, smaller
membrane called the
The round window is a membrane on the
with vibrations entering the
move, which in turn causes
bundle of 100-200 specialized
.
of the inner ear that pulsates in accordance
through the oval window. It allows fluid in the cochlea to
cells of the cochlea to be stimulated. Each
cell has a
at the top that act as mechanoreceptors for hearing.
Class 4: Stimulus and Response
Videos:
Stimulus and Response
http://www.youtube.com/watch?v=fRYvDbY-2E8 http://www.youtube.com/watch?v=p12ng38iis0&feature=related
http://www.youtube.com/watch?v=uGbvCsoV6lw&feature=related
Olfaction
http://www.youtube.com/watch?v=0uMIu7-ZvOs
http://www.youtube.com/watch?v=9qdor5V0SDk&feature=related
Touch receptors
http://www.youtube.com/watch?v=IC3YTJNu0Ec
http://www.youtube.com/watch?v=d-IJhAWrsm0&feature=related
Reflex arc
http://www.youtube.com/watch?v=eHgvMKT-20Q&feature=related
http://www.youtube.com/watch?v=LwuV5JbgCNk&feature=related
Define the terms
Stimulus:
Response:
Reflex:
Explain the role of receptors, sensory/relay/motor neurons/synapses/effectors
A behavior is an animal’s response to a
. For an animal to ‘behave’ it must be able to
perceive changes in its environment, which it does with
and
. Each type of sensory receptor functions as an energy transducer, which means the
energy of a stimulus is converted into the electrical energy of a
. Animals
respond to stimuli with a coordinated sequence of events involving sensory receptors, different kinds of neurons,
synapses and
.
List four types of sensory receptors:
1.
.
2.
.
3.
.
4.
.
Use numbers to show the correct sequence of events:
Annotate the diagram of a reflex arc
The pain withdrawal reflex is an
action in which the body reacts to pain by trying
to move itself away from the source of the pain. The response is so fast that if you step on a sharp object with your
right foot, the pain withdrawal reflex will cause you to lift your right leg before your brain
In the leg example, the
when they
pain.
muscles in your right leg are flexors, which bend the right leg
.
Class 5: Natural Selection of Behaviors
Natural Selection
http://www.youtube.com/watch?v=aEsotWAAUFw&p=62F12407AE3AAFF5&playnext=1&index=2
http://www.youtube.com/watch?v=1YQrLPW5DdY
http://www.youtube.com/watch?v=GPbWJPsBPdA&feature=related
http://www.youtube.com/watch?v=GAN8y9_tn1c
http://www.youtube.com/watch?v=6svAIgEnFvw
http://www.youtube.com/watch?v=mNXgh333ihQ&feature=related
http://www.youtube.com/watch?v=gKybAp--n7M&p=50A8BE972F50F5FC&playnext=1&index=58
Individual organisms can vary in many ways. When the variation between individuals is caused by genes we say that
the variation is
. Individuals with favorable heritable variations are more likely to pass on their
than individuals with unfavorable heritable variations, a process that we call
. Favorable variations increase the likelihood of reproductive success by increasing an
individual’s chances of: avoiding
or attracting
, avoiding
. Natural selection requires the
, obtaining
of offspring
so that there is a struggle for survival. Through natural selection, nature selects the ‘fittest’ individuals because they
survive long enough to
and pass on their
.
List three necessary conditions for a particular behavior to evolve:

There must be
for the behavior

The behavior must be

Some variations of the behavior must confer a greater
Online simulations
http://www.biologycorner.com/worksheets/pepperedmoth.html
http://www.biologyinmotion.com/evol/index.html
http://www.techapps.net/interactives/pepperMoths.swf
http://www.youtube.com/watch?v=5Xi2Nc1UicQ&feature=related
http://www.youtube.com/watch?v=zjR6L38yReE&feature=related
(caused by differences in alleles)
advantage than the others
Example 1: Sticklebacks
Working in pairs, perform a dramatization of the stickleback mating behavior.
http://www.youtube.com/watch?v=lopTMhAbXoI
http://www.youtube.com/watch?v=KtaoDr5kGSg&feature=related






Sticklebacks (Gasterosteus aculeatus) are small fish that perform an elaborate mating ritual, carried out the same way by all
members of the species.
First, the male stakes out a little area of sand on the bottom of the pond (or aquarium). This becomes his territory, defended
against all other males. Male sticklebacks turn red in color once they have staked a territory; females do not.
Second, the male stickleback digs a little hole, shoveling sand with his snout until the hole is about two inches deep and two
inches wide. He gathers stringy pieces of algae and piles the algae in the pit, forming a little mound. Finally, the male
stickleback wiggles through the mound, leaving a tunnel.
Third, the male turns a red color and at once begins to court females with a ‘zigzag’ dance that is always performed in the
same way. When the male sights a female, he darts toward her then veers toward the nest. The female, once attracted by the
dance, will follow the male to the nest. She will only enter the nest if the male pokes his head in the sand.
Fourth, once a female has entered a male’s nest, the male will prod the female near the base of her tail with his snout, and
this causes her to lay eggs in the nest. The male fertilizes the eggs, and then chases the female off.
Fifth, whilst the male is waiting for the eggs to hatch, he not only keeps an eye on predators, but also makes sure the water
around the eggs has sufficient oxygen. He does this by 'fanning' fresher water towards the eggs, using his fins.
Class 6: Innate Behavior
http://www.youtube.com/watch?v=TYEPC8lwv5I&p=653F963E191A1C10&playnext=1&index=4
Innate behavior
Innate behavior is:
.
Learned behavior is:
.
Innate behaviors are controlled by
, independent of learning. They ‘pre-program’ an individual for
‘success’ in its natural environment. In evolutionary terms, ‘success’ means surviving, reproducing and passing
on
to the next generation. Taxix and
are categories of innate behavior.
is the random movement of an animal in which the rate of movement is related to the intensity of a stimulus but not to its
direction. (e.g. the positive relationship between humidity and the rate of movement in sowbugs).
is the movement of an animal in response to the direction of a stimulus. Movement towards a stimulus is
movement away from a stimulus is
negative.
Analyse data on invertebrate behavior in the context of natural selection





Identify the humidity range at which sow bugs remain in one place.
Identify the humidity range at which sow bugs travel the furthest.
State the preferred humidity of pill bugs
Compare the relationship between humidy and turns with the relationship between humidity and speed.
Explain how natural selection could produce the observed innate behavior in pill bugs.
Design experiments to investigate taxis and kinesis

http://www.youtube.com/watch?v=9696M3VSePo
http://www.youtube.com/watch?v=4NtegAOQpSs&feature=related
http://www.youtube.com/watch?v=nga4Z_HRUsU&feature=related
http://www.youtube.com/watch?v=NWij3uO_5x8&feature=related
Quantitative evidence from carefully controlled experiments is necessary to make conclusions about the relative
influence of ‘learning’ and ‘heredity’ on animal behavior. Now go out to the science pond and collect some
invertebrates . Return them to the lab and design an experiment to investigate one factor affecting taxis or kinesis.
.
and
Example of taxis – the promethia moth
 Perform a skit with a friend to show how this works.

In order to pass on his genes, a male promethia moth must avoid being eaten by predators and he must find a fertile female
to copulate with. This isn’t an easy task because females spend most of their time hiding under branches, and they are
distributed very sparsely over large forest landscapes.

Through natural selection, male promethia moths have adapted two innate behaviors - menotaxis and chemotaxis - to help
them locate mates. Menotaxis refers to an animal in motion that maintains a constant angle to a stimulus. Chemotaxis is
movement in response to chemicals.

Male promethia moths fly at an angle (menotaxis) perpendicular to the direction of the wind (stimulus). Once a male
detects a female’s scent trail (stimulus), he turns upwind and follows the chemical gradient (chemotaxis) of the trail, which
leads to the female.

The menotaxis response increases the male’s chance of successful reproduction by: 1) reducing his searching time; 2) lowering
his energy costs; 3) decreasing his risk of being eaten by predators; and 4) increasing his chance of finding a female.
Example of kinesis – the sowbug
http://www.youtube.com/watch?v=1zRI7QK_5J8&feature=related
 Perform this behavior in the courtyard where grass=dry and non-grass= wet. Your teacher will explain.

Organisms that settle in more favorable areas enjoy a reproductive advantage over those settling in less favorable areas.
Therefore, natural selection favors animal behaviors that help individuals to move to, and remain in, ideal habitat.

Humidity is one factor that affects the reproductive success and survival of the sowbug. Sowbugs are land animals with
external gills that must remain moist. Therefore, sowbugs are restricted to humid areas and are commonly found under
damp logs, rocks, and fallen leaves.

To settle in a suitable habitat, a sowbug must perceive, and respond to, changes in humidity. When humidity is favorable, a
sowbug will remain (more or less) in the same place. When humidity is unfavorable, a sowbug will emigrate to a new
location.

Sowbugs respond to humidity with a form of kinesis called hygrokinesis. In hygrokinesis, sowbugs respond to changes in
humidity by altering the rate of locomotion and/or the rate of change in direction.

When conditions are ideal, sowbugs move slowly and change directions frequently, which has the effect of keeping them in
the ideal microhabitat? When conditions become dry, sowbugs increase their speed of travel and change direction less
frequently, which has the effect of taking them far away. Once a sowbug reaches a moister microhabitat it will move slower
and change directions more frequently.
Class 7: Learning

http://www.youtube.com/watch?v=uGbvCsoV6lw
Habituation is a type of learning in which a behavior is reduced when no reward or punishment follows. Deer become
habituated in Canada’s National Parks, for example. Deer are initially frightened by the sound of highway traffic and
therefore run from vehicles. Individuals that habituate, however, learn to feed near highways.
Therefore, habituated deer gain greater access to food and produce more offspring than un-habituated deer.
http://www.youtube.com/watch?v=Kfu0FAAu-10&feature=related


Perform a skit with a friend to show how habituation can improve the chance of survival
Conditioning is a type of learning in which an animal associates two separate stimuli and then modifies its behavior. An
example of conditioning in nature involves birds that prey on butterflies: birds that can distinguish between edible and toxic
butterflies have a survival advantage. For example, after eating a toxic Monarch butterfly, a flycatcher feels ill and experiences
an unpleasant taste. The flycatcher learns to avoid monarchs by remembering the butterfly’s appearance (a visual stimulus)
and associating it with the butterfly’s toxicity (a chemical stimulus).
http://www.youtube.com/watch?v=MWT51807cyM
http://www.youtube.com/watch?v=j3qgwMOOM0U&feature=related


Perform a skit with a friend to show how conditioning can improve the chance of survival
Imprinting is a type of learning that keeps goslings near their mother, which helps them avoid predators and learn how to
feed. In his famous experiment, Lorenz divided the eggs of a graylag goose into two groups: 1) eggs hatched by their mother
and 2) eggs hatched in an incubator. After hatching, the chicks that hatched with their mother began to follow her around.
The incubated chicks however, began instead to follow Lorenz. The sign stimulus for the goslings is any moving object the
size of a mother goose.
http://www.youtube.com/watch?v=eqZmW7uIPW4
http://www.youtube.com/watch?v=YPyJlH7Ac0o&feature=related

Perform a skit with a friend to show how imprinting can improve the chance of survival
Outline Pavlov’s experiments into conditioning of dogs

http://www.youtube.com/watch?v=hhqumfpxuzI&feature=related
Perform a skit with a friend to show Pavlov’s experiment.

Ivan Pavlov was the first researcher to use quantitative data to show how conditioning occurs. He observed that dogs
naturally salivate to food; and he called this correlation between food and salivation the unconditioned reflex. The food was
called the unconditioned stimulus, and the salivation was called the unconditioned response.

In one of his experiments, Pavlov fed his dogs several times over a period of several days; and on each occasion, he rang a bell
a few seconds prior to presenting the food. Before the experiment, the ringing bell was a neutral stimulus since it had no
effect on salivation. During the experiment, the ringing bell stopped being a neutral stimulus and became a conditioned
stimulus because the dogs learned to associate the bell with food.

As a result, Pavlov could make his dogs salivate just by ringing a bell; and he called this correlation between the ringing and
salivation the conditional reflex. The origins of the two reflexes are different: the unconditioned reflex has its origins in the
evolution of the species, whereas the conditioned reflex has its origins in the experience of the individual animal.

Pavlov repeated this experiment with other stimuli; a metronome and vanilla and achieved the same results.
Outline the role of inheritance and learning in the development of birdsong

http://www.youtube.com/watch?v=VjE0Kdfos4Y
http://www.youtube.com/watch?v=rL4Z9d9oObY
Perform a skit with a friend to show how this works.

Virtually all 9000 species of birds have the ability to vocalize. Birds vocalize for many purposes including: information about
danger, food, sex and group movements.

Vocalizations with extended melodies are termed, ‘song’. Singing birds have special vocal organs at the base of the trachea
that vibrate when air is forced over them. Muscles for left and right sound producing structures can act independently,
enabling many birds to sing harmonies with themselves.

Birdsongs can be compared by looking at sonograms. A sonogram is a plot of the intensity of pitch against time (time is on
the x-axis and pitch on the y-axis).

The three sonograms below compare the songs of three bird species.
Evidence for the role of inheritance in the development of birdsong in white-capped sparrows

Perform a skit with a friend to show how this works.

White-capped sparrows that are deafened are at birth can still develop a song with some of the normal elements. This
indicates the important role of inheritance in song development.

White-capped sparrows cannot learn to sing songs of non-sparrow species which indicates the presence of a song template in
the brain (which must be inherited).

White-crowned sparrows that are castrated early in development have low testosterone levels compared to their male
siblings, and they only acquire song to an intermediate stage. This finding provides evidence that song is to some extent
under genetic control because hormone levels in birds is under genetic control.

Males and female white-crowned sparrows sing different songs. The different songs of males and females correlate with
measurable differences in brain structures that control singing. Since the differences of brain structures exist in hatchlings –
before learning has occurred - singing must be, to a large extent, determined by the genes.
Evidence for the role of learning in the development of birdsong in white-capped sparrows

Perform a skit with a friend to show how this works.

In white-crowned sparrows, an established song pattern remains fixed, meaning that it goes unchanged each breeding season.
This shows that the role of learning is limited to a brief sensitive stage of development. A few bird species, like the canary, are
life-long learners; their songs can be practiced and modified throughout life.

White-crowned sparrows have local song dialects. When a male develops his song in a location where two sparrow
populations overlap it can become bilingual, meaning he can sing the two different songs. This shows that song development
requires learning the calls of a nearby tutor during an early, sensitive phase of life.
Class 8: Neurotransmitters and Synapses
http://www.youtube.com/watch?v=FZ3401XVYww&feature=related
http://www.youtube.com/watch?v=90cj4NX87Yk&feature=related
http://www.youtube.com/watch?v=DF04XPBj5uc&p=038EA316C28985D1&playnext=1&index=42
http://www.youtube.com/watch?v=LT3VKAr4roo
http://www.youtube.com/watch?v=HXx9qlJetSU
Synapses and neurotransmitters

Make a poster with a friend to show your understanding of how this works.

A nervous impulse is transmitted from one neuron to another across a narrow, fluid-filled space called a synapse. The signal
travels across the synapse in the form of special chemicals called neurotransmitters, of which there are many kinds.

Two neurotransmitters that control brain activity are glutamate (which increases brain activity) and GABA (which decreases
brain activity). Glutamate and GABA are strongly influenced by a class of neurotransmitters called monoamines, which
include dopamine, serotonin, acetylcholine and noradrenalin.
Excitatory neurons versus inhibitory neurons

Make a poster with a friend to show your understanding of how this works.
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Decisions result from excitatory & inhibitory pre-synaptic neurons
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When an excitatory neuron sends an impulse to the pre-synaptic membrane an excitatory neurotransmitter will be released
into the synapse. When excitatory neurotransmitters bind to receptors on the post-synaptic membrane, gated-sodiumchannels open, causing sodium ions to flow into the post-synaptic neuron. This depolarizes the post-synaptic neuron,
triggering an action potential.
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When an inhibitory neuron sends an impulse to the pre-synaptic membrane an inhibatory neurotransmitter will be released
into the synapse. When inhibitory neurotransmitters bind to receptors on the post-synaptic membrane, gated-chlorinechannels open, causing chlorine ions to flow into the post-synaptic neuron. This hyperpolarizes the post-synaptic neuron,
preventing it from forming an action potential.
The role of excitatory and inhibitory neurons in decision making
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Make a poster with a friend to show your understanding of how this works.
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Pre-synaptic neurons only release one kind of neurotransmitter. Therefore, a pre-synaptic membrane can either excite or
inhibit a post-synaptic neuron – it can’t do both.
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Some post-synaptic neurons synapse with large numbers of both excitatory and inhibitory pre-synaptic neurons. In this
situation, a post-synaptic neuron will form an action potential if it is receiving more excitatory neurotransmitters (from
excitatory pre-synaptic neurons) than inhibitory neurotransmitters (from inhibitory pre-synaptic neurons). This is the basis
of decision-making processes in the central nervous system.
Class 9: How psychoactive drugs affect the brain and personality
A
drug is a chemical that alters brain function, resulting in temporary changes in
perception, mood, consciousness, or behavior.
drugs are taken by some people: to
treat neurological illnesses; for ‘recreational drug use’; or for spiritual purposes.
substances
can be habit-forming, causing chemical dependency, often leading to substance abuse. Personality, behavior and
decision-making are the result of trillions of
in the brain ‘talking’ with one another;
‘talking’ by means of
at the synapses. Drugs affect brain activity by interrupting
the normal transmission of messages from pre-synaptic membranes to
Drugs can work by mimicking
membranes.
or influencing them in other ways.
drugs
increase post-synaptic transmission (e.g. cocaine). Cocaine works by preventing the normal re-uptake of a
neurotransmitter called
.
drugs decrease post-
synaptic transmission. (e.g. THC in marijuana). THC binds to
membrane thereby inhibiting the release of
in the pre-synaptic
neurotransmitters.
List 3 examples of excitatory and 3 examples of inhibitory psychoactive drugs
Excitatory psychoactive drugs
Inhibitory psychoactive drugs
Class 10: Cocaine and Marijuana Presentations
http://www.youtube.com/watch?v=VBIxA0CqNx4&feature=related
http://www.youtube.com/watch?v=_j_qhPSwmz4&feature=related
http://www.youtube.com/watch?v=SQEsPIS4oY4&feature=related
http://www.youtube.com/watch?v=hpV6licCOMw&feature=related
http://www.youtube.com/watch?v=J46pvxFWNTY
http://www.youtube.com/watch?v=Tqwo9dmIXAQ&NR=1
http://www.youtube.com/watch?v=7A4Qxx7j63Y&feature=related
http://www.youtube.com/watch?v=dTNrrtWA4_o&feature=related
http://www.youtube.com/watch?v=4mQndbmisvI&feature=fvw
http://www.youtube.com/watch?v=rEP-eRjePZU&feature=channel
http://www.youtube.com/watch?v=HR3Oo3azgkY&feature=channel
http://www.youtube.com/watch?v=de_b7k9kQp0&feature=related
http://www.youtube.com/watch?v=PA1gDo4OXp4&NR=1
Cocaine
 Make a video with a friend to show your understanding of the mode of action of cocaine and its effects on users
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Cocaine is a powerful but short-acting stimulant drug (the high lasts no more than 40 minutes).
Cocaine is a white powder made from the leaves of the coca shrub, which grows in the mountain regions of South
American. Most users sniff it into the nostrils where it is absorbed through the thin nasal lining.
Cocaine works by preventing the normal re-uptake of a neurotransmitter called dopamine. Dopamine stimulates
the pleasure center of the brain and thus functions to give us a sense of well-being and happiness.
When cocaine is in the blood, dopamine accumulates in synapses, resulting in repeated action potentials in the
post-synaptic neuron. This over-stimulates the pleasure center and the user feels euphoric.
While intoxicated, a cocaine user is likely to be talkative, alert, energetic and euphoric. Repeated use of cocaine
over extended periods of time causes the body to produce less dopamine than normal; the result being a
depressed person who feels unhappy unless high on coke.
Marijuana
 Make a video with a friend to show your understanding of the mode of action of THC and its effects on users
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Cannabis is a genus of flowering plant from northern India. It is smoked in the form of dried flowers (marijuana)
or resin (hashish). The high lasts 2-4 hours and the effects vary amongst individuals.
THC, the main drug in marijuana, works in this way: THC binds to receptors in the pre-synaptic membrane
thereby inhibiting the release of excitatory neurotransmitters.
Brain regions affected by THC include the cerebral hemispheres and the cerebellum.
Marijuana affects both mood and behavior. It makes some people talkative and silly with laughter, while others
become quiet and contemplative. A person intoxicated with marijuana is likely to feel relaxed and calm.
Marijuana users often have an increased appetite while intoxicated and some report a heightened sense of taste
and touch, making food and sex more stimulating than normal.
Repeated use of marijuana over extended periods of time can cause some people to feel calmer than they
normally would while other users may develop negative symptoms such as lethargy and depression.
Work in groups of three to produce a video or PowerPoint presentation on either cocaine or marijuana.
Drug addiction
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http://www.youtube.com/watch?v=hEHzUQGb31A
Make a video with a friend to show your understanding of addiction: you can present on one or more of the following
aspects: physical addiction, social implications of drug use, political issues, mode of action, or another aspect of interest.
Drug addiction is a mental disorder characterized by:
Preoccupation: constant cravings and a urge to obtain and use the drug
Binging: inability to control intake, using more of the substance than necessary to experience the intoxicating effects
Withdrawal affect: emergence of a negative emotional state when access to the drug is prevented; and reduced ability to
respond to a naturally rewarding stimuli
The biological basis of drug addiction
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The biological basis of drug addiction involves the neurotransmitter dopamine. The brain experiences pleasure through the
interaction of many brain parts, and dopamine is the major neurotransmitter in this ‘reward circuit’.
Recreational drug use causes the release and prolonged action of dopamine within the reward circuit. In other words,
addictive drugs produce a reward; the euphoric feeling resulting from sustained dopamine concentrations in the synaptic cleft
of neurons in the brain.
Operant conditioning is exhibited in drug addicts as well as laboratory mice, rats, and primates; they are able to associate an
action or behavior, in this case seeking out the drug, with a reward, which is the effect of the drug.
Evidence shows that drug-addictive behavior is likely a result of synaptic changes in the pre-frontal cortex – the decisionmaking part of the brain – which develops increased glutamate receptors in drug addicts.
Drugs known to cause addiction include illegal drugs (like cocaine) as well as prescription or over-the-counter drugs (like
nicotine, alcohol, and caffeine).
Genetic predisposition to drug addiction
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Genetic predisposition is the increased chance of developing an addiction based on the genes that a person has.
A person may have a genetic predisposition to engage in risk-taking behavior. Such a person would be more likely to
experiment with drugs.
A person may have a genetic predisposition based on a gene that affects brain chemistry. The DRD2 gene, for example, codes
for a dopamine receptor. Research shows that people with the A1 allele consume less alcohol on average than those with the
A2 allele.
Genetic predisposition explains why some people never try drugs, and why some people who do try drugs don't become
addicts.
Social factors in drug addiction
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Certain drugs are important to some cultures. In Korea and Japan, for example, alcohol is sometimes consumed to help
complete business deals. In France, wine is revered as an important aspect of French culture. Cultural traditions can lead to
increased rates of addiction.
Teenagers are especially vulnerable to peer pressure, which is a common motivator for the use of nicotine, alcohol and
marijuana. Therefore drug prevention programs in schools often deal with peer pressure.
Advertisers sometimes glamorize drugs like nicotine and alcohol. They make these drugs seem ‘safe’, ‘cool’, and ‘fun’ even
though they are potentially dangerous.
Unemployment, poverty and traumatic life experiences may also be contributing factors.
Neuroscience Crossword Puzzle