N E U R O B I O LO GY
A
A . 1
B E H AV I O U R
N E U R A L
D EV E L O P M E N T
Y  knw:
✔
the
neural
formed
tube
by
elongation
✔
neurons
in
✔
the
✔
an
axon
the
to
axons
reach
other
a
✔
synapses
of
chordates
ectoderm
is
followed
✔
describe
neurulation.
✔
annotate
diagrams
Xenopus,
used
by
produced
by
differentiation
migrate
from
each
chemical
extend
parts
developing
neural
as
an
embryonic
animal
tissues
model,
in
during
neurulation
tube.
are
the
not
a
nal
immature
✔
explain
✔
state
neural
pruning
pruning.
location.
neuron
in
that
cultural
acquisition
stimuli.
beyond
of
neuron
that
to
of
a
experiences,
language,
including
results
in
the
neural
pruning.
the
neural
tube
to
✔
describe
✔
outline
the
plasticity
of
the
nervous
system.
body
.
forms
multiple
used
not
do
synapses.
persist.
✔
how
involves
the
loss
of
events
such
promote
reorganization
describe
how
embryonic
✔
of
tube.
neurons
some
✔
embryonic
initially
grows
response
✔
of
are
immature
of
Y  e ae t:
infolding
neural
AND
as
of
incomplete
neural
tube
strokes
brain
closure
can
may
function.
cause
of
the
spina
bida.
unused
neurons.
✔
the
plasticity
change
The
with
of
the
nervous
system
allows
it
to
experience.
modification
of
neurons
starts
in
the
earliest
stages
of
In Topic 6.5 you studied neurons
embryogenesis
and
continues
to
the
final
years
of
life.
The
neural
tube
and synapses.
of
by
embryonic
elongation
chordates
of
the
is
formed
by
infolding
of
ectoderm
followed
tube.
Xenopus is a genus of African frogs that are commonly known as the
African clawed frogs. Their worldwide use in research is due to the fact
that it is easy to obtain large amounts of their eggs inexpensively, which are
easily manipulated. The embryonic tissues of Xenopus are a good model for
human disease because most essential cellular and molecular mechanisms
are the same as in humans. Nematode worms (Caenorhabditis elegans), fruit
• Neatn is the development
of the dorsal nerve cord by the
infolding of the neural plate.
• Nea pnng is the elimination
of unused neurons or synapses.
flies (Drosophila melanogaster), zebrafish (Danio rerio), chickens (Gallus
• Nea patty is the ability of
gallus) and mice (Mus musculus) have also been used to discover the
molecular mechanisms fundamental to life, thereby providing a shor tcut to
understanding human biology.
the brain to change in time by gain
or loss of neurons, par ts of neurons
or synapses.
157
A
N E U R O BI O LO G Y
AND
BE H AV IO U R
Exape A .1.1.
The
diagram
(Xenopus
shows
the
stages
of
neurulation
during
the
first
two
weeks
in
the
African
clawed
frog
laevis).
A
B
dorsal surface
X
C
endoderm
gut cavity
a)
Label
A to
b)
Annotate
c)
Suggest
C.
the
diagram
to
explain
what
what
happens
in
humans
if
is
occurring
neurulation
at
X.
does
not
occur
properly
.
Solution
a)
and
b)
lateral edges of neural plate
neural plate
join together forming a tube
neural groove
dorsal surface
neural tube
endoderm
gut cavity
c)
Incomplete
closure
of
the
embryonic
neural
tube
Modification
and
by
the
location. An
chemical
other
parts
in
the
the
connections
between
there
Neural
pruning
interference
acquisition
Neurons
is
and
accessed
system
a
is
tube.
Immature
extend
the
that
these
plasticity
.
of
brain
of
unused
Cultural
result
are
in
used
a
lot
This
such
so
not
as
are
used
to
a
response
tube
multiple
there
are
in
neural
to
reach
synapses.
more
do
not
stimuli.
neurons,
experiences,
neural
neurons.
Events
that
between
the
produced
migrate
neuron
forms
synapses,
embryogenesis
initially
neurons
beyond
neuron
of
are
immature
Synapses
loss
stimuli.
language,
via
multiple
stages
Neurons
each
interference
synapses
reorganization
earliest
life.
from
neurons.
less
involves
faster
neural
the
of
axons
form
between
of
neural
Some
neurons
so
in
years
grows
bifida.
body
. A developing
Developing
persist,
spina
starts
final
axon
stimuli.
of
cause
neurons
to
differentiation
final
to
of
continues
can
again
reducing
including
the
pruning.
are
reinforced
process
strokes
gives
may
so
the
information
nervous
promote
function.
SAMPLE STUDENT ANSWER
The synaptic density is the number of synapses per unit volume. The
graph shows the synaptic density for a human from bir th to 4 years old.
7
01 / ytisned
8
citpanys
mm
3–
6
5
4
3
2
1
0
0
2
4
6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52
age / months
a) Determine the age when the synaptic density is highest.
This
answer
Remember to write the units,
8
otherwise no mark is given.
158
months.
could
have
achieved
1/1
marks:
[1]
A .2
ThE
humAN
brAiN
) Explain how the synaptic density decreases after the age determined
in (a).
This
[3]
answer
During
neural
neurons
T
here
are
is
could
achieved
pruning,
through
also
also
have
loss
of
to
the
A . 2
brain
by
T H E
are
which
dendrites
T
his
marks:
they
apoptosis,
eliminated.
damage
if
3/3
can
not
is
used,
programmed
and
axon
also
happen
strokes
or
there
by
branches.
due
to
chemical
H U M A N
the
anterior
form
the
✔
different
✔
the
part
of
cell
of
of
death.
age,
abuse.
B R A I N
Y  e ae t:
the
neural
tube
expands
✔
to
identify
brain.
parts
loss
Synapses
old
Y  knw:
✔
is
the
brain
have
specic
parts
nervous
system
located
processes
mainly
in
the
in
the
brain
medulla
oblongata,
the
body
using
cerebral
the
brain
cortex
forms
and
more
is
a
than
in
other
gland
outline
the
in
brain
a
photograph,
including
cerebellum,
the
hypothalamus,
and
cerebral
hemispheres.
functions
Broca’s
area
of
the
visual
cortex,
and
nucleus
with
specic
accumbens
as
areas
stem.
larger
highly
the
brain
functions.
proportion
developed
describe
swallowing,
breathing
and
heart
rate
in
as
humans
brain
the
centres
✔
of
of
controls
of
✔
scan
roles.
✔
involuntary
the
or
pituitary
autonomic
of
diagram
examples
of
activities
coordinated
by
the
animals.
medulla.
✔
the
human
cerebral
cortex
has
become
enlarged
✔
principally
by
an
increase
in
total
area,
analyse
brain
extensive
folding
to
accommodate
it
correlations
within
size
✔
describe
cerebral
hemispheres
are
responsible
different
Angelman
inherited
the
in
condition
order
size
and
syndrome
that
is
as
a
genetically
diagnosed
from
for
characteristically
higher
body
animals.
the
cranium.
✔
between
with
abnormal
patterns
on
an
reex
evaluate
functions.
electroencephalogram.
✔
the
left
cerebral
hemisphere
receives
sensory
✔
input
from
sensory
receptors
in
the
right
explain
brain
of
the
eld
body
in
and
both
the
eyes,
right
and
side
vice
of
the
versa
for
the
✔
right
explain
the
lesions
and
brain
the
left
cerebral
contraction
vice
versa
in
for
hemisphere
the
the
right
right
side
controls
of
the
use
of
the
pupil
of
animal
to
damage.
visual
hemisphere.
✔
the
side
use
fMRI
to
experiments,
identify
the
role
of
autopsy
,
different
parts.
muscle
body
✔
and
discuss
how
depending
hemisphere.
the
on
denition
local
and
of
living
national
varies
laws
and
culture.
✔
brain
The
metabolism
brain
and
spinal
requires
large
cord
mainly
are
energy
inputs.
formed
of
neurons.
These
In Topic A.1 you studied the
neurons
communicate
with
other
neurons
through
synapses.
Synaptic
formation of the neural tube.
communication
functional
The
cerebral
The
outer
In
the
body
neurons
circuits
hemispheres
part
of
posterior
brainstem
between
neural
and
through
the
part
the
the
that
form
cerebral
of
the
the
to
the
cerebral
The
establishment
sensory
largest
part
hemispheres
cerebellum.
spinal
leads
mediate
is
and
of
is
the
called
hemispheres
brain
motor
human
the
we
brain.
cerebral
can
connected
of
processing.
to
find
the
cortex.
the
rest
of
the
cord.
159
A
N E U R O BI O LO G Y
AND
BE H AV IO U R
Exape A .2.1.
The
diagram
shows
a
human
brain.
The par t labelled as A could
A
be cerebral cor tex or cerebral
a)
Label A to
C
shown
in
the
function
of
the
diagram.
hemisphere. If in doubt, it is better
to be as precise as possible.
b) Outline
the
Broca’s
You could have answered:
area
and
nucleus
accumbens.
cerebral cor tex of the cerebral
hemispheres.
c)
On
the
diagram
label
the
visual
B
C
cortex.
Solution
a)
A:
cerebral
b) The
Broca’s
brain
• The ea ngata controls
cortex,
with
area
B:
is
a
medulla
region
functions
breathing and reexes such as
processing.
swallowing, coughing, sneezing and
human
vomiting.
involved
The
brain
in
in
linked
nucleus
associated
laughter,
oblongata
the
to
frontal
speech
accumbens
with
fear,
and
lobe
cerebellum.
of
the
production
is
a
pleasure
aggression
C:
group
and
and
of
human
and
language
cells
reward.
It
in
is
the
also
addiction.
• The eee controls of
c)
Area
of
the
brain
above
the
cerebellum
shown
and
labelled.
equilibrium and posture.
• The yptaa regulates
metabolic processes and
The
autonomic
body
using
nervous
centres
system
located
controls
mainly
in
involuntary
the
brain
processes
stem.
The
in
the
autonomic
hormones.
system
• The pttay gan secretes
many
hormones.
the
• The eea epee are
involved in learning and memory.
is
divided
opposing
“fright
situations,
“rest
and
heart
and
flight”
while
the
digest”.
rate
into
while
parasympathetic
functions.
system,
and
sympathetic
as
it
example,
sympathetic,
system
prepares
parasympathetic
For
the
The
the
the
system
system
body
for
it
have
dangerous
the
system
slows
which
considered
prepares
sympathetic
parasympathetic
is
body
to
accelerates
the
down.
• The a  tex processes the
light images perceived in the eyes.
• ba’ aea controls speech.
The
cerebral
forms
a
humans
cortex
larger
than
is
the
outer
proportion
in
other
of
layer
the
animals.
of
brain
The
the
and
cerebral
is
more
hemispheres;
highly
human
cerebral
in
area,
it
developed
cortex
has
in
become
• The ne aen is the
enlarged
principally
by
an
increase
total
with
extensive
folding
pleasure reward centre.
to
accommodate
it
within
the
cranium.
Exape A .2.2.
The
The neuroscientist Wilder
graph
mass
Penfield experimented on
in
shows
some
the
relationship
between
body
mass
and
brain
mammals.
6
human brains, trying to identify
5
the areas responsible for epilepsy.
brain cor tex using a small electric
current and asked his patients
what they felt. With all the
information gathered, he mapped
gk gol / ssam niarb
He stimulated the surface of the
4
3
2
the areas of the cor tex that control
different par ts of the body.
1
Penfield developed a homunculus,
0
a car toon drawing of a human
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
body, sized propor tionally to the
body mass / log kg
amount of brain space devoted to
processing motor functions, or
a)
Describe
the
relationship
between
body
mass
and
brain
mass.
sensory functions, for different
b) Discuss
whether
the
data
provides
par ts of the body.
are
160
more
intellectually
developed.
evidence
that
larger
animals
A .3
PEr cEPTioN
of
s T im u li
Exape A .2.3.
Solution
a)
There
is
mass:
the
a
positive
correlation
between
body
mass
and
brain
Explain
larger
the
animal,
the
larger
the
contralateral
brain.
processing
b)
This
graph
does
not
provide
any
information
of
images.
about
Solution
development.
The
positive
correlation
between
body
mass
The
and
brain
mass
developed,
not
as
as
does
many
developed
as
not
mean
large
that
animals
smaller
the
that
organism
have
organisms
that
a
is
large
have
a
is
cortex,
increases
determined
the
by
the
brain
infolding
surface
of
brain
small
the
sensory
receptors
resonance
of
the
some
imaging
brain
functions
is
part
can
itself
by
energy
,
the
help
other
of
Glucose
ATP
to
meet
process
the
vessels
of
up
called
by
these
extra
is
many
large
back
or
neurons,
The
which
P E R C E P T I O N
receptors
the
right
the
of
the
eyes,
visual
right
and
the
optic
right
field
visual
even
processing
brain
field
versa
hemisphere.
chiasma,
information
that
vice
is
due
where
processes
from
and
the
vice
left
versa.
it
brain
more
which
lactate
use
the
for
the
energy
.
generates
that
this
aerobically
O F
in
detect
S T I M U L I
Y  e ae t:
changes
in
the
environment.
✔
explain
the
rods
the
the
can
require
supply
Y  knw:
✔
the
cycle.
A . 3
✔
shows
glucose
they
glycolysis
requirements.
to
with
means
to
to
specific
brain
Although
astrocytes
in
and
stroke.
neurons
cells
undergoes
a
the
side
both
Contralateral
identification
imagery
that
as
inputs.
the
these
cells
cells
energy
sent
brain
such
the
body
ratio.
magnetic
Although
and
energy
of
in
areas
supply
rate
used
areas,
disturbance
glial
glial
be
functional
the
cerebral
area:volume
functions.
certain
that
metabolic
generates
Krebs
a
requires
cells
to
and
can
specific
over
following
high
taken
in
spread
blood
lesions
scanning
attributed
are
metabolism
served
(fMRI)
involved
be
activities
reorganize
Brain
experiments,
from
brain.
for
animal
input
are
in
Nowadays,
hemisphere
sensory
right
which
cerebral
receives
side
Development
left
more
and
cones
are
photoreceptors
located
the
many
detection
different
of
chemicals
olfactory
in
the
air
by
receptors.
in
retina.
✔
label
a
diagram
of
the
structure
of
the
human
to
show
eye.
✔
rods
and
light
intensities
cones
differ
and
in
their
sensitivities
to
wavelengths.
✔
annotate
types
✔
bipolar
cones
✔
✔
cells
to
send
ganglion
cells
the
optic
nerve.
the
information
from
both
visual
the
ganglion
from
rods
messages
to
the
brain
via
✔
explain
✔
describe
of
from
the
right
is
sent
to
and
vice
versa.
the
eld
left
of
part
vision
of
✔
the
structures
in
the
middle
amplify
sound.
sensory
hairs
specic
wavelengths.
ear
transmit
and
✔
✔
impulses
of
caused
transmitted
to
hair
the
cells
the
in
movement
of
by
the
cochlea
sound
brain
detect
via
the
semicircular
the
sounds
perception
retina
in
which
light
the
cell
moves.
how
a
is
red–green
normal
label
light
detected
of
the
eye.
colour-blindness
trichromatic
diagram
by
the
as
a
variant
vision.
structure
of
the
human
explain
how
sound
waves
are
detected
by
the
of
explain
the
use
of
cochlear
implants
in
deaf
patients.
are
auditory
canals
the
ear.
✔
✔
of
direction
ear.
✔
✔
the
and
cells.
send
eyes
cortex
impulses
diagrams
and
nerve.
detect
head.
161
A
N E U R O BI O LO G Y
AND
BE H AV IO U R
Living
In Topic 3.4, you studied the
inheritance of traits.
the
organisms
environment.
chemoreceptors,
olfactory
have
Humans’
in
the
that
sensory
thermoreceptors
receptors
chemicals
receptors
in
the
nose
are
are
able
receptors
and
to
detect
are
changes
in
mechanoreceptors,
photoreceptors.
chemoreceptors,
as
For
they
example,
detect
air.
SAMPLE STUDENT ANSWER
• meaneept detect
Odorants are very small molecules with varied chemical formulae.
mechanical forces and movement.
Volatile odorants that enter the nose are detected by millions of
olfactory neurons. The discriminatory capacity of the mammalian
• ceeept detect
olfactory system is so specic that a vast number of volatile chemicals
chemicals.
are perceived as having distinct odours.
• Teeept detect
The table shows the response of olfactory receptors to dierent
dierences in temperature.
substances. Acids and alcohols with the same number have the same
• Pteept detect light.
formula except for the rst carbon, where one has an acid and the other
an alcohol group.
cea
oaty eept
t
(ant)
1
2
3
4
5
6
7
8
9
10
acid 1
alcohol 1
acid 2
alcohol 2
acid 3
alcohol 3
acid 4
alcohol 4
Key
response
no response
a) State the name given to the type of receptor the olfactory receptors
belong.
This
▼ This
answer
is
too
answer
is
answer
could
have
achieved
0/1
marks:
vague—the
a)
correct
[1]
Smell
receptors.
chemoreceptors.
) Identify the receptor that:
()
[2]
detects most odorants
() does not perceive the odorants shown.
This
answer
could
have
achieved
2/2
marks:
Remember that in the options the
examiners are expecting more in-
(i)
4
depth knowledge of the topics.
(ii)
9
) Identify the chemical that is the least perceived by these
receptors.
This
▲ Only
two
response
to
receptors
this
show
chemical.
answer
[1]
could
have
achieved
1/1
marks:
a
Alcohol
2
) A slight alteration of the odorant will be perceived as a completely
dierent smell. Comment on this statement referring to the results
obtained in this experiment.
162
[2]
A .3
This
answer
could
have
achieved
2/2
PEr cEPTioN
▲ Recognizing
substance
with
the
same
chemical
formula
as
ones
scored
from,
changing
the
rst
carbon
group
from
acid
(for
example,
acid
1
and
alcohol
1),
is
perceived
different
receptors,
thus
smelling
by
by
If
a
change
in
group
can
be
then
this
is
a
true
acid
and
number
one
mark.
to
be
were
The
compared
the
were
fact
that
perceived
different
second
receptors
mark.
Another
completely
considered
a
for
slight
could
have
commenting
this
alteration,
the
same
had
completely
mark
different.
that
substances
gained
completely
that
the
to
both
alcohol
with
another
,
the
apart
s T im u li
marks:
alcohol
A
of
change
was
been
that
not
scored
perhaps
only
a
slight
statement.
alteration.
The
eye
is
organism
from
the
organ
with
both
that
vision.
eyes
is
sent
can
The
to
receive
light
information
the
left
part
stimuli
from
of
the
the
and
right
visual
provide
field
cortex,
of
the
vision
and
vice
versa.
Exape A .3.1.
The
a
drawing
cross
shows
section
human
of
the
eye.
a)
Label
I
to
b)
Outline
IV
.
II
the
function
I
of
I.
IV
c)
State
the
the
name
tissue
of
containing
In exams you may be asked to
photoreceptors.
III
Solution
a)
I:
lens;
optic
identify some par ts of the eye
including the sclera, cornea,
II:
retina,
nerve;
IV:
III:
conjunctiva, eyelid, choroid,
cornea.
aqueous humour, pupil, lens, iris,
vitreous humour, retina, fovea,
b)
The
function
of
the
lens
is
to
bend
the
light
rays
so
they
are
optic nerve and blind spot.
focused
c)
on
the
retina.
cones
are
photoreceptors
Retina
Rods
and
located
in
the
retina.
Rods
and
• r are photoreceptors that
cones
differ
in
their
sensitivities
to
light
intensities
and
wavelengths.
detect monochromatic images.
Impulses
travel
cells
pass
they
from
to
the
rods
and
ganglion
cones
cells
to
that
bipolar
carry
cells.
the
From
the
information
bipolar
to
the
• cne are photoreceptors that
detect colour.
brain
through
the
optic
nerve.
• bpa e send the impulses
from rods and cones to ganglion
Exape A .3.2.
cells.
The
diagram
shows
part
of
the
retina
of
the
human
eye.
• Gangn e send messages to
the brain via the optic nerve.
D
A
B
C
a)
Label
parts
A to
D
in
the
diagram.
163
A
N E U R O BI O LO G Y
AND
BE H AV IO U R
b)
Draw
c)
Annotate
from
d)
an
the
Describe
arrow
the
eye
showing
diagram
to
the
to
direction
show
the
of
light.
direction
of
the
nerve
impulse
brain.
red–green
trichromatic
the
colour-blindness
as
a
variant
of
normal
vision.
Solution
a)
A:
bipolar
b)
Arrow
from
left
c)
Arrow
from
ganglion
d)
Trichromacy
retina,
cell;
the
the
properly
these
colours.
close
to
cell;
C:
cone;
D:
rod
right
cell
that
and
that
the
Because
together
in
from
three
person
cones
work
very
ganglion
means
giving
blindness
B:
top
types
normal
detect
person
the
the
to
bottom
of
cones
vision.
red
has
light
In
spectrum,
of
most
present
red–green
and
difficulty
wavelengths
are
green
in
red
in
the
colour-
light
do
not
distinguishing
and
affected
green
light
people
are
have
• oe are the bones of the
problems
with
both
these
colours.
middle ear (hammer, anvil and
stirrup) that transmit and amplify
sound.
The
ear
is
the
organ
of
hearing.
Sound
waves
are
detected
by
the
ear
• seny a of the cochlea
through
the
movement
of
the
eardrum
and
ossicles.
The
eardrum
detect sounds of specic
and
ossicles
amplify
the
sound.
This
causes
the
vibration
of
cochlear
wavelengths.
fluid.
• The aty ne e sends
hair
All
along
cells.
the
These
basal
hair
membrane
cells
are
in
of
the
different
cochlea
positions
there
and
are
sensory
have
cilia
of
impulses caused by sound
different
lengths.
These
cilia
different
nerve
signals
vibrate
at
different
wavelengths,
each
perception to the brain.
sending
• ha e in the semicircular
canals detect movement of the
by
sound
nerve.
perception
Hair
cells
in
are
the
in
the
transmitted
semicircular
auditory
to
the
canals
nerve.
brain
detect
via
Impulses
the
caused
auditory
movement
of
head.
thehead.
outer ear
middle ear
inner ear
The discovery that electrical
ossicles (bones)
stimulation of the auditory
semicircular
system can create a perception of
pinna
hammer
anvil
stirrup
canals
sound has had a huge impact on
oval
the treatment of hearing loss and
auditory
window
impairment. Cochlear implants can
ner ve
now be used to help those who are
deaf to hear. Sounds are detected
by an external microphone placed
on the external ear. These sounds
are transmitted through wires to
electrodes that are implanted in
round
the cochlea of the inner ear. The
window
electrodes then transmit the sound
as electrical impulses to the
eardrum
oval window
(membrane)
(membrane)
auditory nerve, which carries the
message to the brain, allowing
hearing.
fge A .3.1.
164
Structure of the ear
cochlea
A .4
A .4
I N N AT E
AND
i N N AT E
LEARNED
ANd
lE ArNEd
bE h Av io u r
B E H AV I O U R
✔
learning
is
the
acquisition
✔
memory
is
the
process
of
skill
or
(Ahl)
( AHL)
knowledge.
Y  knw:
✔
innate
so
✔
behaviour
develops
is
inherited
independently
autonomic
and
referred
as
from
of
involuntary
the
parents
and
accessing
environment.
responses
of
encoding,
storing
and
information.
are
Y  e ae t:
to
reexes.
✔
✔
reex
arcs
comprise
the
neurons
that
explain
the
withdrawal
reex
of
the
hand
from
mediate
a
painful
stimulus.
reexes.
✔
✔
reex
conditioning
involves
forming
describe
Pavlov’s
experiments
into
reex
new
conditioning
in
dogs.
associations.
✔
✔
learned
behaviour
develops
as
a
result
explain
the
role
of
inheritance
and
learning
in
of
the
development
of
birdsong.
experience.
✔
✔
imprinting
particular
is
learning
life
consequences
stage
of
occurring
and
is
at
analyse
independent
of
operant
survival
reproduction.
is
a
form
of
learning
Behavioural
trial
and
patterns
terms
of
the
behaviour
effect
and
on
chances
of
draw
error
can
be
a
labelled
diagram
of
a
reex
arc
for
a
that
pain
of
invertebrate
in
behaviour.
conditioning
consists
from
experiments
the
✔
✔
data
a
withdrawal
reex.
experiences.
inherited
or
learned.
Inherited
behaviours
are
In Topics 3.3 and 3.4 you
said
to
be
innate.
Learned
behaviour
develops
as
a
result
of
experience.
studied inheritance of alleles
through meiosis and in Topic 6.6
Exape A .4.1.
you studied reproduction.
Compare
and
contrast
learned
and
innate
behaviour.
Solution
feate
innate
leane
type of behaviour in humans
yes
yes
Laboratory experiments and
field experiments both have
their strengths and limitations.
inherited
yes
no
instinctive
yes
no
affected by the environment
no
yes
can be modified by experience
no
yes
produces variability in a population
no
yes
Laboratory experiments have the
advantages that it is much more
possible to precisely control the
variables and it is far easier to
replicate the experiment. However,
the ar tificial setup of a laboratory
Reflexes
are
an
example
involuntary
responses
the
that
neurons
forming
new
of
are
mediate
innate
behaviour.
referred
reflexes.
to
as
Autonomic
reflexes.
Reflex
Reflex
conditioning
and
arcs
comprise
involves
study can produce unnatural
behaviour or biased results. Field
studies have the advantage that
the results are more likely to
associations.
reflect real life and therefore have
dorsal root
cell body of
more validity. Predictions and
(sensory ganglion)
relay neuron
results obtained in the laboratory
cell body of
do not always correspond with
sensory neuron
studies performed on organisms in
spinal ner ve
field conditions.
impulses from
receptor
grey
impulses to
ventral root
cell body of
eector
(motor neuron)
motor neuron
matter
fge A .4.1.
Learned
The reflex arc
behaviour
develops
as
a
result
of
experience.
165
A
N E U R O BI O LO G Y
AND
• ipntng is learning occurring
BE H AV IO U R
Exape A .4.2.
at a par ticular life stage and is
independent of the consequences
a)
of behaviour.
With
respect
between
a
to
Pavlov’s
conditioned
experiments
and
an
with
dogs,
unconditioned
distinguish
stimulus.
• opeant ntnng is a form of
b)
Outline
the
differences
between
classic
conditioning,
as
seen
in
learning that consists of trial and
Pavlov’s
dogs,
Describe
an
and
operant
conditioning.
error experiences.
c)
example
of
imprinting.
• leanng is the acquisition of skill
or knowledge.
• mey is the process of
Solution
a)
An
unconditioned
encoding, storing and accessing
therefore
information.
salivation
neutral
innately
.
in
The
b)
Both
or
The
conditioned
for
the
classic
and
stimulus
reflexes
reaction
is
a
the
a
learning
is
a
voluntary
learned
is
independent
duckling
as
it
either
learned
of
the
first
occurring
would
human
follow
its
bell,
and
a
or
in
that
is
response,
sound
before
Operant
error
classic
for
food.
behaviours
operant
and
becomes
learned.
depends
which
will
conditioning
experiences.
conditioning
at
a
of
particular
behaviour.
after
mother
hatching
life
stage
and
An
example
and
follows
before they scored was
recorded. They were then
asked to train for two
weeks and the same test
was performed again. The
results are shown in the
graph.
gnirocs erofeb slairt fo rebmun
ball . The number of trials
subdivisions on the Y axis,
15
10
mean
5
0
trained
a) State the highest number of trials attempted by an untrained student
and by a trained student before scoring a basket.
[1]
therefore it is hard to give the exact
This
answer
could
have
achieved
1/1
marks:
answer. The markscheme will have
a range, but you should not give
18
trials
for
untrained
and
5
for
trained
a range, but an exact number. The
reason for this is that if your range
) Calculate the dierence in the mean number of trials before scoring
is larger and does not match the
between untrained and trained students.
range in the markscheme, you do
This
answer
could
have
not score a mark.
Untrained =
T
rained
=
4
Difference
166
=
9
trials
trials
5
trials
achieved
1/1
marks:
is
is
duck.
not trained
This graph does not show the
a
a
that
20
score a basket using a
is
It
is
SAMPLE STUDENT ANSWER
Students were asked to
on
conditioning
punishment
trial
triggers
previously
reflexes.
consequences
a
a
conditioning
while
on
a
is
involve
while
of
automatically;
naturally
conditioned
Classic
behaviour
sees
a
hearing
behaviour.
consists
of
stimulus
reward
depending
learning
that
to
stimulus
food
stimulus
conditioning
learned
that
behaviour
Imprinting
human
to
the
a
response
of
sound
triggers
response
to
response
control
of
the
environment.
therefore
form
in
operant
by
in
example
a
smell
unconditioned
salivation
controlled
there
c)
with
conditioned
example
triggers
sight
dogs.
stimulus,
associated
stimulus
The
[1]
A .5
N E u r o P h A r m A c o lo G Y
) Deduce whether scoring a basket is an innate or learned
▼ This
behaviour.
reason
This
[2]
answer
could
have
achieved
1/2
answer
must
of
answer
In
this
to
a
incomplete.
given
for
“deduce”
the
A
choice
question.
marks:
case,
learned
Learned
is
be
(Ahl)
the
behaviour
because
once
is
students
behaviour
.
were
trained,
required
) Explain how training aects the nervous system.
nearly
[3]
to
half
the
score
the
number
of
a
was
basket
number
trials
before
training.
This
answer
could
Developing
many
not
of
have
neurons
connections
used
do
unused
stimuli.
neurons.
basket,
not
form
neurons,
so
so
and
while
Neural
there
A . 5
is
less
is
that
some
not
there
are
used
faster
will
be
the
are
are
loss
between
a
by
neurons
used
that
involves
interference
accessed
are
so
Synapses
pruning
synapses
that
synapses,
neurons.
reinforces
others
marks:
multiple
information
T
raining
3/3
between
persist.
Neurons
reinforced
achieved
lot
are
these
to
help
score
a
pruned.
N E U R O P H A R M A C O L O G Y
✔
anesthetics
( A H L )
act
by
interfering
with
neural
Y  knw:
transmission
✔
communication
between
neurons
can
be
the
reception
✔
some
in
of
manipulation
chemical
the
release
neurons
excite
✔
and
nerve
others
stimulant
in
and
by
the
✔
inhibit
addiction
can
be
predisposition,
impulses
postsynaptic
are
initiated
neurons
as
or
a
the
drugs
provided
dopamine
nerve
sensory
CNS.
mimic
the
stimulation
sympathetic
nervous
system.
impulses
them.
✔
of
and
messengers.
neurotransmitters
postsynaptic
of
areas
altered
perception
through
between
affected
social
by
genetic
environment
and
secretion.
inhibited
result
of
the
Y  e ae t:
summation
of
all
excitatory
neurotransmitters
received
and
from
inhibitory
✔
presynaptic
explain
✔
many
the
action
of
excitatory
and
inhibitory
neurotransmitters.
neurons.
different
modulate
fast
slow-acting
synaptic
✔
neurotransmitters
transmission
in
explain
the
the
action
of
slow-acting
neurotransmitters
in
memory
explain
on
and
learning.
brain.
✔
✔
memory
in
and
neurons
learning
caused
by
involve
the
stimulants
changes
effects
and
two
the
nervous
system
of
two
sedatives.
slow-acting
✔
describe
the
effect
✔
explain
✔
evaluate
data
(ecstasy)
on
of
anesthetics
on
awareness.
neurotransmitters.
✔
psychoactive
either
drugs
increasing
or
affect
the
brain
decreasing
how
endorphins
can
act
as
painkillers.
by
showing
the
impact
of
MDMA
postsynaptic
serotonin
and
dopamine
transmission.
metabolism
Neurotransmitters
are
chemicals
released
neuron
neurotransmission.
by
vesicles
in
the
in
the
brain.
presynaptic
In Topic 6.5 you studied neurons
that
enable
They
are
chemical
messengers
and synapses.
which
transmit
synapse.
neurons
in
Some
and
others
postsynaptic
and
signals
inhibitory
from
one
neuron
neurotransmitters
inhibit
neurons
as
them.
a
excite
Nerve
result
neurotransmitters
of
to
another
nerve
impulses
the
across
impulses
are
summation
received
from
the
in
neural
postsynaptic
initiated
of
all
the
presynaptic
or
inhibited
excitatory
neurons.
167
A
N E U R O BI O LO G Y
AND
BE H AV IO U R
Exape A .5.1.
An innovative method of
treating cancer patients is
Explain
how
nerve
impulses
depend
on
the
summation
of
through immunotherapy. Because
excitatory
and
inhibitory
messages.
it is a relatively new treatment,
there is little data about the
long-term effects of immune cell
therapy. There are still concerns
about long-term survival as well as
pregnancy complications in female
patients treated with these cells.
Some immune therapy drugs have
been approved, although they
produce serious side effects.
Patient advocates have pressed for
the speeding up of drug approval
processes, encouraging more
tolerance of risk .
Solution
The
axon
neurons.
of
one
There
More
than
same
postsynaptic
effects
of
a
given
released,
being
and
neurotransmitters. They excite
they
affect
only
can
than
neuron.
a
of
of
an
does
a
They
or
excitatory
rise
effect
can
the
action
above
potential.
the
of
The
excitatory
prevent
the
neurotransmitter
slow-acting.
to
of
the
is
occur.
millisecond
attach
The
must
action
not
with
combining
signals
potential
cancels
other
neurons.
synapse
involves
excitatory
fast-acting
less
form
balance
an
action
of
between
neurotransmitters
when
the
be
take
one
the
membrane
Inhibitory
dendrites
neurotransmitters.
generation
reached,
therefore
neurotransmitters
on
The
the
can
neurotransmitters
neurotransmitters.
Neurotransmitters
• stant are excitatory
for
the
Summation
inhibitory
depending
inhibitory
threshold
and
with
connections
neuron
neuron.
signals.
threshold
of
connects
multiple
presynaptic
form
inhibitory
effect
be
excitatory
potentials
and
one
neuron
can
to
The
cross
receptors
fast-acting
the
in
synapse
the
and
postsynaptic
nerve impulses in postsynaptic
neuron
which
are
protein
ion
channels.
Slow-acting
neurotransmitters
neurons.
on
• seate are inhibitory
neurotransmitters. They inhibit
the
more
cause
other
than
the
hand
one
can
take
neuron.
release
of
hundreds
They
do
secondary
not
of
act
milliseconds
through
messengers.
ion
to
act.
They
channels,
Examples
of
affect
but
instead
slow-acting
nerve impulses in postsynaptic
neurotransmitters
are
noradrenalin,
dopamine
and
serotonin.
neurons.
Psychoactive
drugs
affect
the
postsynaptic
transmission.
brain
by
either
increasing
or
decreasing
• satn is the result of
Stimulant
drugs,
such
as
nicotine,
cocaine
all excitatory and inhibitory
or
amphetamines,
mimic
the
stimulation
provided
by
the
sympathetic
neurotransmitters received from
nervous
system.
Sedatives
such
as
benzodiazepines,
alcohol
or
presynaptic neurons.
tetrahydrocannabinol
(THC)
mimic
inhibition. Anesthetics
act
by
• sw-atng netantte
interfering
with
neural
transmission
between
areas
of
sensory
perception
act through secondary messengers.
and
the
central
nervous
system
(CNS).
They
prevent
the
transmission
They modulate fast synaptic
of
nerve
of
sodium
impulses
by
binding
to
sodium
channels,
inhibiting
the
influx
transmission in the brain.
ions
through
these
channels. Addiction
can
be
affected
by
• mey and eanng involve
genetic
predisposition,
social
environment
and
dopamine.
changes in neurons caused by
slow-acting neurotransmitters.
Exape A .5.2.
a)
Outline
the
effect
of
benzodiazepines
and
alcohol
on
the
nervous
system.
b)
State
the
c)
Outline
effect
the
of
use
MDMA on
of
synapses.
anesthetics
in
surgery
.
Solution
a)
Both
benzodiazepines
synaptic
transmission.
receptors
Alcohol
b)
c)
for
enhances
alcohol
which
the
effect
neurotransmitter
MDMA is
also
dopamine
levels
called
in
reuptake.
Anesthetics
act
This
as
by
ketamine
interferes
perception
the
as
CNS,
inhibitory
GABA and
It
increases
enhancing
with
neural
glutamate
neural
sedatives,
increase
affecting
the
effect
of
neurotransmitter.
decreases
the
glutamate.
ecstasy
.
prevent
an
of
interfering
with
and
is
synapses,
preventing
act
Benzodiazepines
excitatory
such
168
GABA,
and
its
serotonin
release
from
between
pain
and
and
transmission. Anesthetics
receptors
transmission
preventing
the
being
areas
of
duringsurgery
.
active.
sensory
A .6
A . 6
E T H O L O G Y
E T h o lo G Y
(Ahl)
( A H L )
✔
explain
migratory
behaviour
in
blackcaps
is
an
Y  knw:
example
✔
behaviour
can
be
innate
or
ethology
is
the
study
of
animal
behaviour
change
natural
selection
observed
explain
animal
can
change
the
frequency
behaviour
that
increases
reproduction
in
population.
learned
will
behaviour
population
innate
how
or
be
example
the
chances
become
more
of
explain
natural
blood
of
by
the
behaviour
and
selection.
sharing
in
vampire
development
natural
can
lost
spread
from
it
survival
optimal
prevalent
through
more
foraging
example
✔
✔
of
of
bats
as
altruistic
selection.
behaviour.
and
a
by
behaviour
of
✔
✔
basis
conditions.
an
✔
genetic
in
✔
natural
the
learned.
its
✔
of
explain
of
prey
affecting
than
in
shore
chances
of
crabs
survival
as
an
by
choice.
breeding
populations
a
rapidly
behaviour
increasing
as
strategies
an
chances
example
of
in
Coho
of
behaviour
survival
and
salmon
reproduction.
behaviour.
✔
explain
courtship
example
of
mate
in
birds
of
paradise
as
an
selection.
Y  e ae t:
✔
✔
explain
how
natural
selection
favours
explain
in
types
of
✔
describe
examples
✔
describe
different
behaviours
foraging,
crabs
oestrus
in
female
lions
a
pride
as
an
example
of
innate
behaviour
behaviour.
that
Shore
synchronized
specic
such
of
types
as
breeding
(Carcinus
innate
of
animal
strategies
maenas)
reproduction
behaviours.
migration,
✔
learned
explain
blue
altruistism,
and
choose
increases
loss
courtship.
middle-sized
mussels
to
of
feeding
tits
of
the
as
an
chances
survival
and
offspring.
on
cream
example
learned
of
of
from
the
milk
bottles
development
in
and
behaviour.
feed
In Topic 5.2 you studied natural
on
in
preference
to
large
mussels,
despite
the
fact
they
provide
less
selection.
energy
.
larger
This
is
mussels
example
of
because
is
not
the
time
worth
increasing
the
the
taken
to
trouble.
chances
of
break
This
the
harder
foraging
survival
by
shells
of
behaviour
optimal
prey
is
an
choice.
SAMPLE STUDENT ANSWER
a) The sketch shows the growth rate of two types of the same species of
migratory sh (Coho salmon, Oncorhynchus kisutch). The mean age at
maturity is shown with a circle.
7
fish 1
stinu y ratibra / ezis
6
fish 2
5
4
3
2
1
0
0
2
4
6
8
10
12
age / years
Use the graph to explain breeding strategies in Coho salmon populations
as an example of behaviour aecting the chances of survival and
reproduction.
[6]
169
A
N E U R O BI O LO G Y
▲ This
The
in
answer
student
the
types
graph
of
is
uses
to
very
the
and
complete.
BE H AV IO U R
This
answer
One
part
could
have
achieved
6/6
marks:
information
explain
salmon
AND
the
their
different
of
the
population
stays
in
one
habitat,
reaching
a
breeding
strategies.
small
the
Experiments to test
hypotheses on the migratory
size.
graph
when
T
hese
that
they
sh
2.
size
before
are
reaches
become
T
he
called
other
a
plateau
adults,
sh
jacks.
rst
which
grow
at
a
T
hese
is
are
represented
(Fish
at
slower
a
1).
T
he
younger
rate,
dot
age
reaching
by
shows
than
a
larger
behaviour of blackcaps have been
returning
to
the
breeding
site.
T
hese
are
called
carried out. Birds are tagged and
followed through GPS recordings. The
hooknoses.
T
he
hooknoses
are
usually
larger
in
size
so
they
bird known as the blackcap (Sylvia
ght
to
fertilize
females,
while
the
smaller
jacks
do
not
ght
atricapilla) traditionally migrated
but
hide
and
T
he
larger
wait
for
the
right
moment
to
fertilize
females.
from its summer breeding grounds in
Central Europe to warmer areas in
jacks
may
behave
like
the
hooknoses,
as
it
is
Spain and Portugal for the winter.
difcult
for
them
to
hide.
Lately they have been seen to
migrate to the UK. The abundance of
garden birds increased with levels of
Many
birds
show
sexual
dimorphism.
This
means
the
males
are
bird feeding. Studies found that
very
different
may
have
from
the
females.
The
males
may
be
very
colourful
or
blackcaps migrating to the UK from
distinctive
feathers
to
attract
females.
Others
show
special
paradise
show
both
Germany had become adapted to
courtship
behaviours
such
as
dances.
Birds
of
of
eating food supplied by humans. In
these
behaviours,
in
a
very
exaggerated
manner.
Females
choose
their
contrast blackcaps migrating to
mates
according
to
selection
to
their
plumage
and
dance.
Natural
selection
has
led
Spain had bills adapted to feeding on
the
of
these
exaggerated
traits.
fruit such as olives. The birds
migrating to the UK have an
evolutionary advantage, as they
Exape A .6.1.
need to travel less so expend less
a)
Outline
the
behaviour
of
feeding
on
cream
from
milk
bottles
by
energy. Therefore the genetic basis
blue
tits.
of behaviour has been changed by
natural selection.
b)
Outline
one
increases
way
the
in
which
chances
of
synchronized
survival
and
oestrus
in
reproduction
female
of
lions
offspring.
Solution
a)
Blue
tits
started
behaviour
are
few
bottles
of
b)
the
soon
blue
are
tits
no
to
feed
spread
on
showing
longer
development
cream
from
throughout
this
behaviour,
delivered
and
loss
milk
Europe.
of
bottles.
probably
door-to-door.
a
learned
This
Nowadays
This
there
because
is
an
milk
example
behaviour.
The advantage of synchronized oestrus in female lions is that the
females have their cubs and are lactating all at same time, therefore
some females can suckle and take care of others’ cubs while they
hunt. The cubs are more likely to survive when they are raised in a
nursery rather than by a solitary mother. Another advantage is that a
group of male cubs of the same age leave the pride at the same time,
so can compete for dominance of another pride more effectively
.
170
A .6
E T h o lo G Y
(Ahl)
Pate pe  optn A
Pe 1
Pe 4 (Ahl)
The growth of the axon and one dendrite were measured
Outline the processes occurring when a person touches
in a developing neuron. The graph shows the length of
a rough surface with their hand and then moves the
the axon and dendrite from the tip to the cell body over
hand away.
time.
Pe 5 (Ahl)
The volume of the left and right nucleus accumbens was
measured in tetrahydrocannabinol (THC) consumers
350
and compared with those of control par ticipants who do
300
not consume cannabinoids. The bar graph shows the
250
results of several recordings.
axon
200
1000
dendrite
150
800
100
50
0
0
1
2
3
4
5
6
7
8
time / days
mm / emulov
3
sertemorcim / pit ot ydob morf ecnatsid
400
600
400
200
a) State the process occurring in this neuron from day 1
0
control
to day 7.
THC
control
left
THC
right
) Calculate the difference in length of the axon and
dendrite after 7 days’ growth.
a) State the mean volume of the left nucleus
accumbens in THC consumers.
) Explain the difference in trend of growth of the axon
and dendrite.
) Compare the volume of the accumbens in THC
consumers and control par ticipants.
) Outline what could happen to the dendrite if it is not
used.
) Explain the effect of THC on the nervous system.
Pe 2
Pe 6 (Ahl)
The following is a magnetic resonance image (MRI) of a
Common vampire bats (Desmodus rotundus) feed only
human brain.
on blood and die after 70 h of fasting. Unfed bats often
receive food from other bats by regurgitation. The graph
shows the changes in weight at the time of feeding
compared to the pre-feeding weight (100%) of donor
and recipient bats before and after blood donation.
120
cerebellum, hypothalamus and pituitary gland.
% / gnideef-erp thgiew egatnecrep
a) On the image, label the medulla oblongata,
100
80
before
60
after
40
20
) Explain how functional MRI can be used to detect the
functions of different par ts of the brain.
0
donor
recipient
Pe 3
Explain how, in humans, colour in the environment is
detected by the eyes and relayed to the brain.
Using the data, explain blood sharing in vampire bats is
an example of the development of altruistic behaviour
by natural selection.
171