General anesthetics act on the neurotransmitters in neuron synapses. Explain the effect of anesthetics on patients and how they affect synaptic transmission.

a. patient loses awareness/does not feel pain/analgesia

b. interfere/block neural/synaptic transmission between «areas of» sensory perception and the CNS
OR
block «sensory» neural pathways to the brain that detect pain

c. increase presynaptic inhibition
OR
block receptors on the presynaptic membrane

d. increase release of inhibitory neurotransmitters
OR
prevent release of excitatory neurotransmitters

e. inhibit binding of neurotransmitters «to receptors» on postsynaptic membrane

f. decrease «likelyhood of» depolarization of the postsynaptic neuron
OR
hyperpolarize the postsynaptic neuron

g. prevent propagation of action potential on the postsynaptic neuron

h. vital physiological functions/breathing/maintenance of blood pressure continue to function

i. the effects are reversible

j. anesthetics mimic effect/stimulate release of endorphins «which are natural painkillers»/OWTTE

Outline the neural control of the process of swallowing.

Describe an example of learned behaviour.

a. «usually» autonomic reflex

b. «usually» involuntary/automatic
OR
not controlled consciously

c. coordinated by medulla «oblongata»

d. can be voluntary/consciously controlled «by cerebral cortex»

a. learned behaviour is behaviour that is taught or received through experience

Allow other definition.

b. named organism 

eg: Chimpanzees.

Allow human, people, etc, providing it is explicitly written.

c. named/description of behaviour

eg: Sticks used to spear juicy grubs.
eg: learning a language.

State the function of the bones in the middle ear.

Explain the role of the hair cells in the cochlea.

amplify/transmit the sound/vibrations

a. hair cells located within the organ of Corti
OR
hair cells are mechanoreceptors

b. hairs/cilia of hair cells move/vibrate with the movement of the liquid/fluid in the cochlea

c. amount of movement is proportional to the amplitude/loudness of the sound

d. frequency/wavelength/pitch distinguished by different hair cells/according to position of hair cells/length of hairs/cilia

e. hair cells transmit impulses to auditory nerve/brain

Outline the benefits of using fMRI in this experiment.

Compare and contrast the effects of THC and CBD on the areas of the brain studied.

State the function of the visual cortex.

a. «fMRI» allows imaging through magnetic resonance

b. to measure the amount of activity/blood flow in different parts of the brain
OR
to identify the parts of the brain that are activated

c. non-invasive/indirect observation/real time observation

a. THC causes a negative/inhibitory mean activation of parahippocampus whereas CBD causes a positive/excitatory one
OR
THC and CBD cause opposite effects on parahippocampus

b. both cause a positive/excitatory «mean activation» of the visual cortex

c. «magnitude» of mean activation of both ingredients is minute on parahippocampus compared to visual cortex/OWTTE

d. mean activation due to THC lower than CBD for both «parahippocampus and visual cortex»
OR
mean activation due to THC lower than placebo whereas higher for CBD for both

e. other valid comparison/contrast between the two drugs

processing visual information/signals from the optic nerve/OWTTE

Approximately 350 000 people worldwide have received cochlear implants. Outline the use of cochlear implants in patients with hearing problems.

State the part of the ear that is responsible for detecting movement of the head.

Describe the role of bipolar cells in the eye.

a. microphone outside the ear pick up sounds 

b. sound waves converted to electronic/digital signals 

c. electronic impulses sent to electrode in cochlea 

d. «electrode» directly stimulates auditory nerve 

e. signals «generated by implant» sent to brain which recognizes signals as sound

semicircular canals

a. transmit the signals from the photoreceptors «rods and cones» to the ganglion cells 

b. groups of/more than one rod cell synapse with one bipolar cell 

c. one cone cell synapses with one bipolar cell 

d. once light is absorbed bipolar cell depolarizes 

e. activates/depolarizes a ganglion cell

Outline the development of axons in immature neurons.

State one activity controlled by the medulla oblongata.

a. axon grows from an «immature» neuron 

b. chemical stimuli trigger the growth/direction of axon 

c. only one axon develops per neuron 

d. some axons extend beyond neural tube to reach other parts of body

gut muscles / heart rate/cardiac centre / vasomotor / breathing/ventilation rate / reflex centre of vomiting/coughing/sneezing/swallowing

Explain two methods that scientists have used to determine the different functions of the brain.

first method: [3]

a. name of first method eg: lesion studies

b. how the first method works eg: carry out an autopsy

c. what can be learned from the first method eg: relate the position of the lesion to observed changes in behaviour

second method: [3]

d. name of second method eg: fMRI

e. how the second method works eg: inject dye into blood OR active parts of the brain have dyed blood flowing to them

f. what can be learned from the second method eg: known stimulus activates specific region of the brain that is detected

Allow other verifiable methods.

A study examined the effects of four weeks of intensive training in athletes on vertical jumping performance and neuromuscular learning. The graph shows the results for jumping height.

Outline the effect of training on jumping performance.

List the different types of neurons involved in a reflex arc.

Predict whether an animal such as a laboratory rat could be encouraged to learn a new behaviour pattern.

Using an example, describe how innate behaviour may increase the chances of survival of a species.

a. jumping performance shows an improvement «during the first two/three weeks»
OR
no/little improvement as error bars all overlap 

b. «during the period of this investigation» it reaches a plateau 

c. the investigation was over a short time and is not conclusive of the effects of training over a longer period

a. sensory/afferent neuron 

b. motor/efferent neuron 

c. relay neuron/interneuron

Two correct for [1]
Three correct for [2]

a. operant conditioning/classical conditioning/trial and error experiences 

b. behaviour could be modified by positive/negative reinforcement 

c. animal makes an association between a particular behaviour and a consequence

Accept reward/punishment and/or examples such as food/electric shock.

a. innate behaviour inherited/develops independently of environment
OR
Changes in innate behaviour depend on change in frequency of alleles that cause the behaviour ✓

b. example of an innate behaviour ✓

c. description of the behaviour ✓

d. outcomes affecting survival

eg
b. synchronized oestrus in female lions

c. female lions can share responsibilities / females can suckle each other’s cubs allowing some mothers to hunt

d. cubs are more likely to survive when they are raised in a group «nursery» rather than by a solitary mother /group of male cubs can leave pride together helping each other

State the most common length of M. edulis eaten by the C. maenas population.

Suggest reasons for the length you stated in (a) being the most common length of M. edulis that C. maenas eat.

17.5 mm OR 15 mm to 20 mm

a. larger mussels too much effort to open OWTTE
OR
best ratio between effort and energy return 

b. smaller mussels means more individuals have to be eaten for the same return on effort 

c. greater time/predator exposure spent during foraging to obtain required daily energy 

d. it «may be» the most common size available
OR
«correct mussel» size favoured by natural selection 

e. the claws are best adapted to prey on mussels of this size

The diagram shows the mechanism of action of the psychoactive drug cocaine.

Suggest how cocaine might influence the brain.

Dopamine acts as a slow-acting neurotransmitter. Outline one function of slow-acting neurotransmitters.

Outline the structure of a reflex arc.

State the type of receptor that detects odours.

a. «cocaine» is an excitatory drug  OWTTE
OR
excitatory influence on the brain 

b. increase the concentration/level of dopamine in the synapse  OWTTE

c. prolonged effect/continuous stimulus of dopamine on the brain/postsynaptic neuron 

d. addiction/dependence on high levels of dopamine for the same effect/addiction

a. they contribute to memory/learning 

b. they modulate fast synaptic transmission «in the brain» 

c. by causing the release of secondary messengers in the postsynaptic neuron

a. receptor cell  

b. sensory neuron passes stimulus 

c. to interneuron/relay neuron 

d. which transmit response to motor neuron 

e. effector

Award marking points for a clearly annotated diagram.
eg:

olfactory «receptor»
OR
chemoreceptor

Graph 1 shows the range of light wavelengths detected by the three types of cone cells in normal colour vision. Graph 2 shows the range of light wavelengths detected by a person with one form of colour blindness. Each line shows a different type of cone cell.

Deduce, with a reason, the difference in colour perception between people with normal colour vision and those with this type of colour blindness.

Explain how sounds of different wavelengths are distinguished by the ear.

difference in colour perception:

a. cannot distinguish red and green 

reason:

b. green and red cones detect very similar wavelengths
OR
peak of altered green shifts to the right
OR
range of altered green wider «than normal green»

a. «movement of eardrum and ossicles» causes vibration of cochlear fluid 

b. hair cells in different position «along the basal membrane» have hair/cilia of different length  OWTTE

c. different hair/cilia vibrate at different wavelengths 

d. «different hair cells send different» nerve signals in the auditory nerve

Label the parts I and II on the images.

Structure Y will eventually elongate to form two structures. State the names of these two structures.

1. 

2. 

State the condition that arises if the closure of structure X is incomplete during embryonic development.

The diagrams show a rat brain and a human brain. They are not drawn to scale.

Distinguish between the cerebral cortex of the human brain and of the rat brain.

a. I: neural groove/plate/fold 

b. II: ectoderm

a. brain 

b. spinal cord

spina bifida

a. human cortex larger than rat cortex 

b. human cortex proportionally larger than other brain parts than rat cortex  OWTTE

c. surface area «of cortex» larger for humans 

d. more infolding of the surface of the cerebral cortex in humans

Explain how psychoactive drugs affect the nervous system.

a. psychoactive drugs act upon the central nervous system/alter brain function;

b. psychoactive drugs are addictive;

Stimulants:
c. increase postsynaptic transmission;

d. mimic the stimulation provided by the sympathetic nervous system
OR
mimic action of natural stimulating neurotransmitters e.g. acetylcholine;

e. example: e.g. nicotine/cocaine/amphetamine;

Sedatives:
f. decrease postsynaptic transmission;

g. mimic inhibition (of the parasympathetic nervous system)
OR
mimic action of natural inhibiting neurotransmitters e.g. dopamine;

h. example: e.g. benzodiazepines/alcohol/tetrahydrocannabinol (THC);

Most candidates displayed a considerable knowledge about psychoactive drugs, but only the strongest candidates could provide focused answers and sufficient detailed mechanisms for both stimulants and sedatives on synapses.

Label the cerebellum on the diagram.

State a function of the cerebellum.

On the diagram, label one named structure that produces hormones.

Outline one method that can be used to investigate the function of different parts of the brain.

label to cerebellum

TefiM / istockphoto.com

controls/coordinates (motor) movements/balance

label to pituitary
OR
label to hypothalamus;

Alternative 1:
a. fMRI;

b. scan detects changes in blood flow/oxygen in blood
OR
more active parts of brain receive more blood flow;

Alternative 2:
c. lesions/autopsy;

d. part of the brain damaged
OR
loss of function detected;

Alternative 3:
e. stimulation during open brain surgery;

f. reaction observed;

The “f” must be written for fMRI.

Description must relate to method named.

The vast majority of candidates could label the cerebellum correctly, but fewer could state its function.

Most candidates could correctly label one named structure producing hormones.

The majority of candidates could name one method to investigate the function of different parts of the brain, mainly fMRI, but the change in blood flow was obscure for some or lacked sufficient details; other valid methods were seen, such as lesions, autopsy or open surgery.

Describe the changes occurring in this neuron from day 1 to day 2.

Suggest other processes that may occur during neural development.

Suggest what can happen to neurons that are unused in the nervous system.

a. branches (of dendrites/axons) formed
OR
new/more dendrites formed;

b. dendrites/axons grow/get longer;

a. neural tube differentiation/formation;

b. neuron (may) migrate to other parts;

c. axon (may) extend beyond the neural tube/myelinates;

d. synapses develop;

e. neural pruning;

Do not accept “connection” instead of “synapse”.

a. neural pruning;

b. neurons are destroyed / apoptosis

Many candidates could describe at least one change occurring, but many used terminology for processes occurring at later stages that were not shown on the photographs.

Most candidates suggested correctly at least one other process, and stronger candidates suggested two.

The vast majority of candidates correctly suggested neural pruning.

Evaluate the hypothesis that females prefer to mate with males whose feathers are a brighter blue.

Explain how natural selection can cause mate selection behaviour patterns to develop in a species such as eastern bluebirds.

Another type of behaviour is altruistic behaviour. Outline an example of altruistic behaviour.

Strengths:
a. (slight) increase in mate choice at higher male brightness index;

Weaknesses:
b. dots are scattered without a trend/no clear correlation
OR
most females choose mates around normal (brightness);

c. insufficient data/information provided;

Allow any other data-based statement.

a. natural selection favours specific types of mate selection/behaviour;

b. (behaviour/mate selection) increases the chances of survival/reproduction;

c. chosen organisms/males will leave more offspring;

d. pass on gene(s) for behavior to offspring;

e. (behaviour/allele) will become more prevalent/frequent in a population;

vampire bats share blood to ensure survival;

Other verified, outlined example.

Most candidates managed to provide at least one evaluation statement, but it was difficult for many to provide a complete evaluation.

It was difficult for many to provide focused answers for this question, although most candidates could provide valid partial explanations.

A large number of candidates could outline a valid example, but many answers lacked precision, either because "vampire" bats were not specified or the behaviour description was absent; a number of irrelevant examples were seen, including examples of human behaviour.

Outline how the human brain can reorganize itself following a stroke.

State the area of the human brain that may have been damaged when the following symptom is present:

A lack of muscle control on the left side of the body

State the area of the human brain that may have been damaged when the following
symptom is present.

Difficulty in swallowing

activities/functions spread across the brain

OR

activities/functions taken over by other areas of the brain

right motor cortex

OR

right cerebral hemisphere

medulla «oblongata»

State which group has the lowest percentage of cerebral cortex mass.

Suggest advantages of the cerebral cortex containing a high percentage of the brain’s neurons.

Suggest a role for the cerebral cortex in rodents such as rats and mice.

Explain how the cerebral cortex in humans differs from other mammals.

rodents

a. more neurons means more synapses/connections

b. higher cognitive ability

c. capacity for information processing increased

OWTTE

[Max 2 Marks]

a. sensory function

b. information processing

c. memory/learning

d. motor function

Do not accept “language”

[Max 1 Mark]

a. parts/lobes/proportions more highly developed in humans «than in other animals»

b. folding/wrinkles/sulci/gyri

c. increases surface area

d. larger mass of cerebral cortex «relative to body mass»

e. enables higher order functions

Do not accept answers that only refer to the “brain” in general instead of the “cortex”

[Max 3 Marks]

State the effect of simulated ship noise on foraging behaviour.

Predict the consequences on C. maenas of increasing noise related to human activity.

foraging behaviour disrupted more «in the presence of simulated ship noise»

a. affects searching for food/foraging/selecting optimum prey

b. increased risk of starvation/less food «for survival»

c. cause migration/relocation/moving to other foraging area

d. individuals less distracted by noise will survive

    OWTTE

    OR

    leads to natural selection

e. decline in population

[Max 3 Marks]

Explain the use of a local anesthetic during surgery to remove the cataract.

Describe red-green colour blindness.

a. reduction/elimination of pain

    OR

    to block sensory perception

b. blocks synaptic transmission between «sensory neurons and CNS»

    OWTTE

c. allows patient to remain aware

d. prevent reflex causing blinking/eye movement

    OWTTE

[Max 2 Marks]

a. sex/X-linked «genetic trait»

b. results from absent/defective cone cells

c. cannot distinguish between red and green

[Max 2 Marks]

Outline how this experiment shows learned behaviour.

Deduce, with a reason, whether the patient is left-handed or right-handed.

Define, with an example, operant conditioning.

Define, with an example, imprinting.

Outline the effects of slow-acting neurotransmitters.

a. with each trial the drawings get better/less errors
OR
each day the patient becomes better at drawing the star ✔

b. by day 3 the patient makes few mistakes/less fluctuations ✔

c. even though left hand went through fewer trials, still an improvement ✔

d. practice improves the behaviour
OR
learning occurs «over time» with repetition ✔

right handed, as the patient made fewer mistakes with this hand  Must give reason for the mark
OR
right handed as fewer trials with left hand
OR
not possible to draw conclusion as the trends are the same for both but left hand trials end after a few trials ✔

Must give reason for the mark

OWTTE

a. learning by trial and error
OR
reward/punishment to reinforce behaviour ✔

b. example ✔

eg: mice given food when finding their way across a maze will perform better the second time

a. a form of learning where the young animal fixes its attention on the first object seen ✔

b. example ✔

eg: a duckling seeing a human after hatching will follow that human

a. slow-acting neurotransmitters affect learning/memory ✔

b. «slow-acting neurotransmitters» trigger the release of secondary messengers «in postsynaptic neuron» ✔

c. synaptic transmission is enhanced
OR
increase in the number of receptors in the postsynaptic membrane ✔

d. modulate/reduce/increase fast synaptic transmission «in the brain» ✔

State what happens to unused neurons.

Predict how mental activity might delay the onset of Alzheimer’s disease.

Autism appears early in life and affects how a person communicates and relates to others. There is evidence that autism could be caused by a surplus of synapses. Using all of the information provided, suggest two possible causes of a surplus of synapses in people with autism.

neuron pruning
OR
synapses removed

Do not accept “apoptosis”.

a. more synapses maintained with stimulation/mental activity/OWTTE

b. strong mental activity prevents «neuron» pruning

a. most synapses are formed during childhood/before birth
OR
first years of childhood most important for brain development

b. more synapses «than normal» may be formed «during childhood/before birth in autism»

c. «in autism» pruning of neurons does not occur «causing excess of synapses»
OR
normal synapse elimination does not remove extra synapses

Compare and contrast the rank order of body mass and brain volume in the six species of mammals.

Predict the difference that would be seen if the cerebral cortex of a human and a gorilla were compared.

State one function of each of the following areas of the brain.

Broca’s area

State one function of each of the following areas of the brain.

Nucleus accumbens

State one function of each of the following areas of the brain.

Medulla oblongata

similarity:

a. as body size increases, brain volume increases for smaller mammals
OR
«weak» positive correlation ✔

contrast:

b. humans do not fit the trend/are the exception ✔

a. human cortex has a larger total volume/is larger than gorilla’s ✔

b. human cortex has more folding/area «to accommodate within the cranium» ✔

speech production/language processing ✔

cognitive processing of motivation/pleasure/reward
OR
modulates the effects of «the neurotransmitter» dopamine
OR
involved in learning ✔

swallowing/breathing/heart rate/digestion/sneezing/coughing/vomiting ✔

Label the cerebellum on image I.

State one function of the cerebellum.

State the difference in the cerebral cortex between the two images of the brain.

A person with Alzheimer’s disease typically has a reduced nucleus accumbens. Predict how this will affect the person.

The images show the differences in glucose uptake between the brain of a person without Alzheimer’s disease (image I) and the brain of a patient with Alzheimer’s disease (image II). The key indicates the levels of glucose uptake.

Deduce the implications of reduced glucose uptake in the brain of a patient with Alzheimer’s disease.

cerebellum properly labelled

[Source: Reprinted by permission from Springer Nature: Nature, Pathways towards and away from Alzheimer’s disease, Mark P. Mattson, © 2004]

balance
OR
coordination
OR
motor control

a. «image II shows» reduction in size/volume/total amount of tissue/lobes 

b. «image II shows» increased space between foldings 

c. «image II shows» reduced surface area

Allow vice versa for image I.

a. reduced cognitive function/processing/memory 

b. reduced reward/pleasure perception 

c. depression

OWTTE.

a. brain metabolism requires large energy inputs
OR
glucose is the only source of energy of the brain 

b. «less glucose» means there is less respiration/metabolic reactions 

c. less cognitive/functional/synaptic activity 

d. some cell death

State the type of sensory receptors that detect sound.

Suggest one reason for hearing loss caused by extended exposure to high intensity sound.

Outline the role of the ear in balance perception.

mechanoreceptor

a. permanent injury/loss of hair cells / sensory hairs in cochlea 

b. damage to bones in the middle ear / damage the connections between the ossicles 

c. ruptured eardrum

a. (3) semicircular canals are perpendicular/at right angles/help sense movement 

b. movement (of head) causes fluid in canals/inner ear to move 

c. deflects/bends hair cells

d. (Hair cells) send messages to brain via auditory nerve 

Outline how an immature neuron develops an axon.

Explain neuroplasticity in terms of the developing neurons.

a. neurons initially produce multiple dendrites/prolongations 

b. an axon develops in response to chemical stimuli

a. neurons that are stimulated develop more dendrites «than those not stimulated» 

b. more dendrites allow for more synapses 

c. developing neurons form multiple/new synapses 

d. synapses that are stimulated/used many times are fortified 

e. neural pruning involves the loss of unused neurons/synapses 

f. plasticity of the nervous system allows it to change with environment/experience/to reorganize following damage
OR
some neurons can regenerate

The diagram shows one of the stages in neurulation.

Describe what happens next in neurulation.

Explain the causes of spina bifida in vertebrates.

Explain the process of neural pruning.

a. neural plate moves/folds/bends inwards to form a groove 

b. cells multiply/edges increase in height 

c. borders/edges of neural plate join/form neural crest 

d. neural tube forms/separates from rest (of ectoderm)

a. spine/spinal cord does not form properly
OR
incomplete closure of embryonic neural tube/ tissues around the neural tube do not fuse 

b. lack of folic acid/folate (B9 vitamin) in pregnancy 

c. genetic/family history 

d. exposure to certain medication/environmental conditions during pregnancy

a. development of vertebrate nervous system results in overabundance of neurons/connections 

b. unused neurons/synapses are lost 

c. neurons destroy themselves by programmed/natural cell death/apoptosis 

d. removal of dendrites from neurons

Drug misuse and abuse are major health problems in the world. The diagram shows the correlation between physical harm and dependence for various psychoactive drugs.

Identify an example of inhibitory drug shown in the diagram.

Addiction may be affected by social environment. Outline one other named factor that can affect addiction to drugs.

Distinguish between innate behaviour and learned behaviour in the development of birdsong.

Outline an example of a change in animal behaviour as a result of natural selection.

benzodiazepines / alcohol / THC /barbiturates

EITHER

a. genetic predisposition 

b. metabolic/enzyme differences (e.g. in processing of alcohol) 

OR

a. dopamine secretion 

b. addictive drugs trigger (higher) secretion/extracellular levels of dopamine (which causes positive effect on mood) 

a. innate behaviour is controlled by genes/inherited while learned is not inherited 

b. the early birdsong pattern is genetically determined/innate 

c. learned behaviour occurs as a result of experience while innate is independent of environment 

d. (Later) birds modify their (early) song pattern based on learning from adults/other birds/the environment

Note that mpa and mpc have two parts that are both required for the mark to be awarded. They are comparisons.

a. named animal and traditional behavior 

b. natural selection pressure with resulting animal response

Accept common or general names of organisms.

Examples of change in colour (peppered moth) are not behavioural changes.

Example:

a. blackcap/warbler migrates to Spain 

b. warmer winters in UK / more food resulting in selection of those migrating to UK / increased numbers / greater survival 

OR

a. native green lizards traditionally occupy the lower branches and trunks of Florida’s trees 

b. now live in upper branches due to pressure caused by competition of Invasive brown lizard (Over 20 generations/15 years developed sticky foot pads to hold on to smoother branches) 

OR

a. House finches in California are sedentary/do not migrate 

b. Introduced into New York (about 1940) and increasing numbers migrate south during the winter months to warmer conditions/more food

The brain requires a large energy input. Suggest one reason for this.

Outline the functional magnetic resonance imaging (fMRI) technique for brain research.

a. brain cells/neurons carry out large amount of metabolic activity 

b. maintenance of resting potential requires energy/ATP
OR
functioning of Na-K pumps requires energy/ATP

a. (measures brain activity by) detecting changes associated with blood flow 

b. more active parts of brain receive more blood flow 

c. activity leads to change in magnetization between oxygen-rich and oxygen-poor blood 

d. scans/images are taken while the subject is exposed to a stimulus/activity

Explain, using examples, the neurological effects of inhibitory psychoactive drugs.

a. examples are benzodiazepines / THC / cannabis / alcohol 

b. block / decrease synaptic transmission 

c. causing less transfer of information to the brain / decreasing brain activity 

d. benzodiazepines increase effect of GABA 

e. GABA is an inhibitory neurotransmitter 

f. Increase permeability of neural membrane to chloride ions/hyperpolarizes the neuron 

g. alcohol enhances effect of GABA 

h. «alcohol» also decreases activity of glutamate, an excitatory neurotransmitter 

i. THC/cannabis can block cannabinoid receptors 

j. «THC» inhibits release of neurotransmitters that excite postsynaptic neurons/membranes 

k. use of psychoactive drugs can lead to dependence/addiction / alter dopamine levels

State the effector in this reflex arc. 

With reference to the experiments on habituation, state the effect of repeated stimulation on the level of neurotransmitter in the synapses.

With reference to the withdrawal of the siphon in Aplysia californica, explain the concept of summation.

Amphetamines act on synapses that use dopamine as a neurotransmitter by increasing the release of dopamine into the synaptic cleft. Outline the effect this would have on human synaptic transmission.

muscle «that retracts gill»

less neurotransmitters/dopamine are released «to the synaptic cleft by presynaptic interneurons»

a. summation is the sum of all depolarization impulses/neurotransmitters released in the synapse/synaptic cleft of the effector/motor neuron 

b. in control more excitatory than inhibitory so effect would be excitatory 

c. less of each in habituated so not enough to produce action potential in the effector/motor neuron

a. amphetamines are stimulants 

b. increases the release of dopamine in the presynaptic neuron 

c. blocks reuptake by presynaptic neuron 

d. more dopamine in the synaptic cleft 

e. increased binding on / transmission by the postsynaptic neuron

Outline the trend in large tree finch song frequency.

Describe the role of inheritance and learning in birdsongs.

a. (the pattern/unit is) a low frequency followed by higher frequency;

b. the same pattern/unit is repeated;

c. range limited to specific frequencies;

a. early birdsong pattern is genetically determined/innate;

b. later birdsong pattern is modified based on learning from adults/other birds;

OWTTE

Most candidates could generally outline the trend, but some had difficulty expressing it clearly and correctly.

Most candidates knew that birdsongs had an inherited and a learned component; it was more difficult for some to accurately put it into words and attribute the role of birds of the same species in the learning process.

Compare and contrast innate behaviour and learned behaviour.

a. behaviour is observable impulse/reaction of an organism to «internal and external» stimuli 

b. exhibited behaviour results from the combination of inherited traits, experience and environment
OR
exhibited behaviour is a result of the combination of innate and learned behaviour

Award [5 max] if no similarities are given.

A dog owner wants to teach a dog to stop jumping up on people.

[Source: © Nevit Dilmen]

Explain how operant conditioning could be used to train the dog.

a. operant conditioning consists of trial and error ✔

b. operant conditioning uses the consequences of the behaviour to modify the behaviour ✔

c. this can be carried out by positive reinforcement
OR
reward the desired behaviour ✔

d. showing the dog affection/food when it does not jump up ✔

e. can be negative reinforcement
OR
stopping a negative consequence when the appropriate behaviour is observed ✔

f. hold the dog until it no longer wants to jump up ✔

g. can be positive punishment
OR
a negative consequence to undesired behaviour ✔

h. hitting the dog when it jumps up/pushing the dog down/show anger at the dog ✔

i. negative punishment
OR
taking away a desired item ✔

j. tying the dog up/isolating the dog to another place when it jumps up/remove attention/ ignore dog ✔

This longer response question was well answered, and stronger candidates often scored full marks. Even students without a specific knowledge of operant conditioning achieved some marks. Many spent much of the time writing about Pavlov’s experiments, which are irrelevant to this answer. Others wrote about Skinner boxes, which do address operant conditioning but are not directly relevant to the question being asked. Few students showed detailed knowledge or understanding of the distinction between positive and negative reinforcement.

Label the diagram to show part of the visual cortex of the brain.

Outline how the diagram can be identified as a human brain and not the brain of a monkey.

Explain how studies of lesions have helped to identify the functions of different parts of the brain.

[Source: https://pixabay.com/vectors/brain-anatomy-human-medicine-150935/]

Accept any label within marked area

a. the cerebral hemispheres are larger «relative to rest of brain» ✔

b. the cerebral cortex forms a larger proportion of the brain ✔ 

c. there is extensive folding of the cerebral cortex ✔

a. lesions are areas of brain injury ✔

b. diagnosed in living people using MRI/CAT scan/PET scan ✔ 

c. autopsies reveal the position and extent of lesions
OR
animal experimentation ✔

d. the behaviour/functioning of patient with lesion was observed ✔

Other possible techniques: cerebral arteriogram/angiogram, diffusion weighted MRI

Many candidates identified the correct region of the brain.

Few candidates were able to demonstrate the subject-specific vocabulary required to answer this question with clarity. Most did not refer to the cerebral cortex or even cerebrum, instead using vague terms like “brain.” Where students added detail, it was often about the frontal lobe, something this question was not addressing.

Students who did poorly on this question showed the same weaknesses already mentioned in earlier questions. They were unable to define what a lesion was, and few attempted to address the question directly. Rather than explaining how studies of lesions have helped identify functions of the brain, many candidates only described the relationship between parts of the brain and their functions. Nevertheless, a lenient interpretation of the marking point regarding observed changes in patients’ behaviours due to lesions in the brain allowed many students to achieve 1 mark.

Outline innate and learned behaviour.

innate behaviour : [3 max]

a. inherited «from parents»/controlled by genes

b. develops independently of environment

    OR

    not modified by experience/learning

c. species specific/shared by all members of species

d. developed by natural selection/increases chance of survival/reproduction

e. valid example of innate behaviour

Only mark the first example if more provided

learned behaviour : [3 max]

f. develops as a result of experience/environmental stimulus

g. is a process of gaining new knowledge or skills

h. not inherited «from parents»

    OR

    not controlled by genes

i. may or may not increase chance of survival and reproduction

j. valid example of learned behaviour

Only mark the first example if more provided

[Max 6 Marks]

Describe the process occurring in the diagram.

State what would occur in the embryo immediately after stage IV.

Outline the consequences of incomplete closure of the neural tube in humans.

a. the process is neurulation ✔

b. ectoderm tissue differentiates to form the neural plate ✔

c. the neural plate «changes shape and» folds ✔

d. «the ends join» to form the neural tube ✔

elongation «of the neural tube» ✔

a. this leads to condition spina bifida ✔

b. some of the vertebrae may not form correctly
OR
incomplete closing of the backbone ✔

c. spinal cord may protrude ✔

d. «may» cause paralysis ✔

This question was fairly well answered by most candidates, and it appears that the process of neurulation is covered well by teachers choosing this option. However, as stated before, students struggled to communicate the process clearly, finding it hard to delineate the steps in an organised, sequential manner. There was also some confusion among weaker students regarding the three primary germ layers during embryonic development – all three layers were suggested by these students. They also used subject-specific terminology such as “neural plate,” “neural fold” and “neural tube” incorrectly.

Most students did not state the correct process here, instead writing about longer term events in the nervous system, or excessively generic terms like “differentiation” and “organ development.”

Candidates’ answers to this question tended to be good predictors of how well they scored on the whole option. Students with little to no knowledge and understanding scored 0 marks. An equal number were able to score 1 mark, usually the marking point for identifying the result as spina bifida, while students who scored well on the whole paper successfully communicated another aspect of the condition. This question is also a good example of the need for students to understand what is being asked first. The question asks students to outline the consequences, but a number of students wrote in some detail about the effect of folic acid deficiency during pregnancy as a cause. One reason for this response may be that the cause of spina bifida has been a question in a recent paper.

The drawing shows male and female Emperor birds of paradise (Paradisaea guilielmi ) found in Papua New Guinea.

Suggest how the external features and courtship behaviour of these birds of paradise affect reproductive success.

a. males’ long feathers/plumage/bright colours attract mate
OR
dance/vocalizations attract mate ✔

b. males compete for the females to reproduce ✔

c. characteristics also make males more vulnerable to predation ✔

d. males survive despite having huge tails/extreme features ✔

e. «natural selection» has benefited the most colourful/attractive males with best reproductive success/fitness/passing genes to offspring ✔

OWTTE

Calculate the difference in the number of former users of MDMA and those who have never used the drug making an error before a correct response.

Outline the evidence that MDMA leads to impulsive behaviour.

Explain the effect MDMA has on the metabolism in the brain. 

6

a. MDMA «former» users made quicker responses AND made more errors than those who never used drugs ✔

b. quick responses with errors suggest impulsive behaviour ✔

c. possible impulsive behaviour was reason for taking drug rather than a consequence
OR
drug users could always have shown impulsive behaviour
OR
study shows correlation, not causation ✔

a. MDMA increases the release of serotonin ✔

b. occurs in synapses of brain cells ✔

c. MDMA binds to serotonin transporters so MDMA not removed from synapse ✔

d. MDMA also causes increased dopamine/norepinephrine secretion ✔

e. these neurotransmitters influence our mood/cause euphoria
OR
may lead to memory problems ✔

This may have been the most successfully answered question on paper 3, and almost all candidates achieved this mark.

While many students did achieve at least 1 mark here, few connected the data with impulsive behavior. In addition, this question showed that students still need guidance on how to make sure their writing is clear. Many lost a mark because they were unable to express that they were looking at number of errors and time taken to give an answer.

This question was not answered well. Few candidates addressed synaptic transmission as the key element when explaining an effect on brain metabolism. Very few students achieved full marks on this question.

Discuss the effect of endorphins on the central nervous system (CNS) and in pain relief.

a. pain receptors/ends of sensory neurons send impulses to cerebral cortex creating sensation of pain ✔

b. endorphins interfere with neural transmission between areas of pain perception and CNS ✔

c. endorphins produced/secreted «primarily» by pituitary gland ✔

d. endorphins secreted during times of physical exercise/emotional stress ✔

e. endorphins bind to «opiate» receptors at «pre/post»synaptic membrane ✔

f. prevent neurotransmitters binding to postsynaptic membrane/cell ✔

g. decrease transmission at postsynaptic membrane
OR
are inhibitory neurotransmitters ✔

h. effects have slow onset but last long time «minutes/hours» ✔

i. act as natural painkiller
OR
produce feeling of euphoria ✔

Many had a vague idea about the effect of endorphins and limited their answers to a few memorized elements, not thinking about expanding their answer to their understanding of the nervous system at the cell or synapse level. A few excellent and extensive answers were nevertheless seen.

Identify the parts of the ear labelled X and Y.

X:

Y:

Describe the use of cochlear implants in deaf patients. 

Identify the area of the brain which is labelled with the white arrow in the fMRI.

Compare the general patterns of activation in the brain shown when all of the individuals in the study processed language.

Suggest one reason for two different language groups being used in the study.

Outline how fMRI is used in brain studies.

Suggest what might result if a deaf individual who uses sign language has a lesion in the Broca’s area of the brain.

X: semicircular canals ✔

Y: eardrum/tympanic membrane ✔

a. sound picked up by microphone relayed electronically to speech processor ✔

b. speech processor filters background noise/selects only speech frequencies ✔

c. «radio» signal from transmitter to receiver/stimulator which converts it to electric signal ✔

d. «electrical impulses» sent to electrode «array» in cochlea
OR
cochlear implant bypasses the hair cells in the cochlea ✔

e. electrode/electrical signal stimulates auditory nerve «fibers in cochlea» ✔

f. signals «generated by implant» sent to brain «which recognizes signals as sound» ✔

OWTTE

cerebrum/cerebral hemisphere ✔

a. all «deaf and hearing» people show common pattern of brain activation/engage similar tissues ✔

b. all show two distinct areas, one in frontal/anterior region and another in back/posterior region ✔

a. to see whether results are valid/held across different cultural/linguistic groups ✔

b. to see whether results are specific to only one language ✔

a. active parts of brain receive increased blood flow ✔

b. harmless dye injected to make blood flow visible ✔

c. brain activity for specific tasks can be observed «in real time» ✔

they might make mistakes in signing/naming/repetition «which is what they use to “speak”» ✔

Generally correct answers although some inadvertedly inverted X and Y.

Most had a general idea of how cochlear implants work, but a large number could either not use the correct terminology (provided in the diagram), nor distinguish between sound waves, electrical impulses, nerve impulses and/or structure their answer in a logical or chronological order.

Most did generally well in the different subparts of this question.

Most did generally well in the different subparts of this question, but many stated differences when a comparison requires only similarities.

Most did generally well in the different subparts of this question.

The use of fMRI was well outlined.

Also, many, although they knew that Broca's area controls production of language, ignored the fact that sign language was specified in the question and focused on verbal language.

Distinguish between learned behaviour and innate behaviour.

Evaluate how the data supports the hypothesis that honeybees are able to learn to use cues to find the path through new mazes.

Suggest an advantage of such behaviour.

Not necessary to answer within a table.

a. trained bees made few mistakes/were successful ✔

b. trained bees could use cues on two different mazes so able to remember «overtime»
OR
bees who did well on training maze continued to do well on other mazes ✔

c. «approximately» same percentage/frequency of successful bees on training and other two mazes ✔

d. most control/untrained bees unable to find path through maze without mistakes
OR
most control/untrained bees always made mistakes ✔

[Source: reprinted from Neurobiology of Learning and Memory, 72, S.W. Zhang et al, Honeybee Memory: Navigation by Associative Grouping and Recall of Visual Stimuli, 180–201, Copyright 1999, with permission from Elsevier]

Accept converse statements.

a. return to flowers with nectar
OR
«more chance» to obtain food ✔

b. increases chances of survival «if they can learn directions to and from food» ✔

Most produced correct answers, but some had difficulties pairing distinctions of the same type.

Most did well on evaluating the data, but it was more difficult for some to suggest an advantage of the behaviour and apply it to the bees.

Most did well on evaluating the data, but it was more difficult for some to suggest an advantage of the behaviour and apply it to the bees.

Suggest a reason for the plateau in the graph when only one crab is present in the cage.

Determine whether foraging by crabs is dependent on number of prey (mussels) or number of predators (crabs).

Outline the role of natural selection in animal behaviour.

a. has eaten its full ✔

b. feeding depends on ratio of predator to prey
OR
when «certain» ratio of predator to prey is reached feeding/graph levels off ✔

c. prefers certain size mussel so only preys on these ✔

[Source: reprinted from B D Griffen and D G
Delaney, Ecology, 88 (12), pages 3012–3021,
copyright 2007, with permission, the Ecological
Society of America]

a. «foraging» depends on number of predators/crabs ✔

b. mean number of mussels/prey consumed per crab decreases as number of crabs increases ✔ Accept vice versa.

c. crabs compete for prey/mussels ✔

d. both «prey and predator» affect foraging success ✔

a. genetically based/innate behavior can be passed on to offspring ✔

b. behavior increases chances of survival and reproduction ✔

c. will increase in frequency/become more prevalent in a population ✔

Most candidates figured out that the plateau occurred when the crab could eat no more but it was more difficult for certain to determine that the foraging depends on the number of predators and to justify it.

Most candidates figured out that the plateau occurred when the crab could eat no more but it was more difficult for certain to determine that the foraging depends on the number of predators and to justify it.

Most candidates could only partly outline the role of natural selection in animal behaviour.

Define neurotransmitter.

Describe how local anesthetics act on the nervous system.

Describe the main role of slow-acting neurotransmitters in memory and learning.

chemical substance that transmits message across synapses/from one cell to another ✔

OWTTE
Do not accept "connection" instead of "synapse".

a. interfere with neural transmission between areas of sensory perception and the CNS ✔

b. blocks nerve transmission/impulses to pain centres in the CNS ✔

c. inhibit the function of an ion channel «sodium channel» in nerve cells ✔ OWTTE

d. no changes in awareness/consciousness/sense perception in other areas ✔ Accept vice versa

e. suppress excitatory synaptic transmission ✔

f. some increase the intensity of inhibitory synaptic transmission ✔

a. may cause the release of secondary messengers «in post-synaptic neuron» ✔

b. secondary messengers can persist for long time ✔

c. «secondary messengers» may enhance the synaptic connections between neurons OWTTE
OR
«secondary messengers» strengthen neural pathways «involved in memory/learning»
OR
«secondary messengers» increase the number of receptors in the postsynaptic membrane ✔

d. modulate/reduce/increase fast synaptic transmission «in the brain» ✔

Courtship behaviour leads to mate selection. Describe innate behaviour.

Explain the implications of courtship behaviour in natural selection.

Outline operant conditioning, giving an example.

a. innate behavior is independent of environment ✔

b. innate behaviour is controlled by genes/inherited ✔

c. innate behaviour is present at birth OWTTE
OR
doesn't change through time/experience ✔

a. «courtship behaviour» is inherited/innate
OR
variations exist ✔ OWTTE

b. fittest animals have the best courtship behaviour ✔

c. «courtship behaviour» allows members of a species to identify each other
OR
«courtship behaviour» results in mate selection ✔ OWTTE

d. «courtship behaviour» increases chances of mating/reproductive success ✔

e. «courtship behaviour» also make organisms more vulnerable to predation ✔

f. «allows» best courtship to be passed on to the next generation/offspring ✔

a. when an animal learns to associate a reward with a certain kind of behaviour OWTTE
OR
trial and error learning
OR
positive reinforcement
OR
associative learning ✔

b. example: animal training ✔

Explain how the human eye is able to distinguish between different colours of light.

a. (white) light is a mix of different wavelengths which correspond to different colours seen 

b. light hits the back of the eye /retina 

c. cones are photoreceptors in the retina/concentrated in fovea 

d. cone cells are sensitive to a specific wavelength/specific colours/contain different pigments 

e. three types of cone cells respond to red, blue or green light 

f. different colours are perceived by the relative degree of stimulation of different cone cells 

g. single cone cell passes impulses to a single nerve fibre/ganglion cell 

h. (stimulation of) cones require bright light/ colour vision is less in dim light 

i. genetic disorders can cause absence of red/green/some pigments / colour blindness

On the diagram, draw an arrow showing the direction of the light.

Identify the cells labelled A and B.

A:

B:

Photoreceptors in the retina sense light. State the name of another type of receptor with an example of the stimulus it detects.

Explain, using the diagram, how the visual stimuli from the right eye reach the visual cortex of the brain.

[Source: reprinted by permission from Springer Nature: Nature Reviews Neuroscience
Parallel processing in the mammalian retina, Heinz Wässle, 2004, Nat Rev Neurosci 5,
747–757 (2004) doi:10.1038/nrn1497]

Accept any arrow pointing upwards.

A: bipolar cell
B: ganglion cell ✔

Both required.

a. mechanoreceptors «detect» pressure ✔

b. chemoreceptors «detect» chemical substances/pH ✔

c. thermoreceptors «detect» temperature ✔

Mark only the first answer if more than one receptor is mentioned.
Accept valid other receptors with the correct function.

a. «right» eye receives information/stimuli/light from both «left and right» visual fields ✔

b. light from the left visual field goes to the right side of the retina ✔ Accept vice versa.

c. impulses «from retina» carried along the optic nerve ✔

d. «optic» nerves cross at «optic» chiasma ✔

e. impulses from the left side of the retina go to the left side of the brain ✔ Accept vice versa.

Accept any of these points made on an annotated diagram.

The human brain is larger than the brain of many animals. Identify one other difference between the human brain and the brain of a sheep.

Outline the main feature of neural pruning.

State the name of the part of the brain that controls breathing rate.

Explain the need for the adult human brain to be supplied continuously with a relatively large supply of blood.

a. larger cerebral cortex in human brain ✔ Do not accept larger brain for human as it is in the stem.

b. higher folding in human brain
OR
increased surface area in human brain ✔

c. angle of spinal cord more vertical in human
OR
angle of spinal cord more horizontal in sheep ✔

a. loss of unused neurons ✔ Accept apoptosis or programmed neuron death.

b. loss of unused synapses
OR
reducing the number of synapses
OR
leaving more efficient synaptic configurations ✔ Do not accept "connection" instead of "synapse".

medulla «oblongata» ✔ Do not accept "brain stem".

a. the brain contains a very large number of neurons and therefore consumes large amount of energy ✔ OWTTE

b. «large» requirement for oxygen/glucose to provide energy for «aerobic» cell respiration ✔

c. energy used to sustain the electric charges of neurons
OR
energy used to sustain the membrane potential of neurons
OR
energy used to produce neurotransmitters ✔

d. brain has continuous activity that requires continuous supply of oxygen/glucose ✔ OWTTE

Identify the structures labelled X and Y in the diagram.

Identify the structure in the inner ear that is in contact with the stapes.

Explain the function of the semicircular canals.

a. X: pinna ✔ 

b. Y: auditory/cochlear/acoustic nerve ✔

oval window ✔

a. semi-circular canals are concerned with balance/head movement ✔

b. movement of the head causes fluid/liquid/endolymph in the canals to move ✔

c. hair cells detect this movement and transmit information to brain ✔

d. along the vestibular nerve ✔

e. three canals allow us to detect movement in all directions/planes ✔

Not many could identify X “pinna” and used less specific terms instead. More identified Y “auditory nerve” correctly.

This question was surprisingly difficult for candidates to answer correctly. While there were many incorrect answers, the most notable ones involved other bones of the middle ear, again revealing that students need to read the questions more carefully, as the question specifically asked about a structure in the inner ear. Of course, this could also mean that students are unclear where the middle ear ends and the inner ear begins.

Students who knew that semicircular canals are involved in balance tended to score 2 or 3 marks here, with weaker students scoring 0 marks because they wrote about hearing. Stronger students distinguished themselves by using appropriate terminology about hair cells (rather than hair).

Explain the effect of a named stimulant drug on the nervous system. 

General effects of any stimulant drugs: [3 max]
a. addictive/causes tolerance/addiction ✔

b. increase dopamine release ✔

c. speed up activity of CNS/alertness/euphoria/suppress appetite ✔

d. have symptoms of withdrawal when stop «chronic» use ✔

Drug name: [1 mark] 
e. name of «chosen» stimulant drug ✔ Award this mark for a stimulant drug only, e.g. nicotine, cocaine or amphetamines.

Cocaine:
f. chronic use may cause psychological craving/paranoia/arrhythmia/hypertension/stroke ✔

g. cocaine attaches to dopamine pumps/transporters «on presynaptic membrane»
OR
blocks uptake/recycling
OR
causes dopamine to persist in the synaptic cleft ✔

h. amplifies synaptic transmission
OR
causes constant stimulation of postsynaptic neuron ✔

Nicotine:
f. nicotine stimulates synaptic transmission of cholinergic synapses ✔

g. causes strong mood changes ✔

h. large doses have a calming effect ✔

Amphetamines: Accept ecstasy instead
f. chronic use can «permanently» damage dopamine system
OR
cause problems with memory/learning ✔

g. amphetamines/ecstasy stimulate synaptic transmission of adrenergic synapses ✔

h. longer lasting effect than cocaine ✔

Award [3 max] for either cocaine, nicotine or amphetamines. Mark only the first drug explained.

Outline the process that could result in spina bifida during neural tube development.

a. neural tube formed by infolding of ectoderm/outer tissue layer ✔

b. «spina bifida» caused by «embryonic» neural tube not closing off completely ✔

c. « spina bifida» results in backbone vertebrae/spinal cord not closing/fusing properly ✔

Award marks for marking points in an annotated diagram.

Most candidates knew what spina bifida is but had a bit more difficulty expressing how it occurs using appropriate terminology. Many confused ectoderm with neural plate.

Explain how the eye detects stimuli and sends information to the brain.

a. photoreceptors/cones/rods detect «reflected» light/stimulus ✔

b. cones found in fovea «of retina» and rods found all over retina ✔

c. rods active in low-intensity/dim light ✔

d. cones active in high-intensity/bright light ✔

e. rods give black and white vision ✔
OWTTE

f. cones detect colours ✔
OWTTE

g. bipolar neurons/cells synapse with multiple rods but «only» with individual cones ✔
OWTTE

h. bipolar neurons/cells «in the retina» form synapses with ganglion cells ✔

i. electrical/nerve impulses travel to brain/occipital lobe via the optic nerve ✔

j. right field of vision from both eyes sent to the left part of the visual cortex through the chiasma «and vice versa» ✔

Allow answers in annotated diagrams