Option E: Neurobiology & Behaviour

            E1 Stimulus and response

2 hours

	Assessment statement	Obj	Teacher’s notes
E.1.1	Define the terms stimulus, response and reflex in the context of animal behaviour.	1	A stimulus is a change in the environment (internal or external) that is detected by a receptor and elicits a response. A reflex is a rapid, unconscious response.
E.1.2	Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli.	3	Aim 7: Data logging using an EKG sensor to analyse neuromuscular reflexes could be used.
E.1.3	Draw and label a diagram of a reflex arc for a pain withdrawal reflex, including the spinal cord and its spinal nerves, the receptor cell, sensory neuron, relay neuron, motor neuron and effector.	1	Include white and grey matter, and ventral and dorsal roots.
E.1.4	Explain how animal responses can be affected by natural selection, using two examples.	3	Use of local examples is encouraged. The bird Sylvia atricapilla (blackcap) breeds during the summer in Germany and, until recently, migrated to Spain or other Mediterranean areas for winter. However, studies show that 10% of blackcaps now migrate to the UK instead. To test whether this change is genetically determined or not (and, therefore, whether it could have developed by natural selection or not), eggs were collected from parents who had migrated to the UK in the previous winter and from parents who had migrated to Spain. The young were reared and the direction in which they set off, when the time for migration came, was recorded. Birds whose parents had migrated to the UK tended to fly west, wherever they had been reared, and birds whose parents had migrated to Spain tended to fly south-west. Despite not being able to follow their parents at the time of migration, all the birds tended to fly in the direction that would take them on the same migration route as their parents. This and other evidence suggests that blackcaps are genetically programmed to respond to stimuli when they migrate so that they fly in a particular direction. The increase in the numbers of blackcaps migrating to the UK for the winter may be due to warmer winters and greater survival rates in the UK. TOK: There are many poor examples of supposed links between animal responses and natural selection. It is easy for us to guess how the behaviour of an animal might influence its chance of survival and reproduction, but experimental evidence from carefully controlled trials is always needed to back up our intuitions.

 E2 Perception of stimuli

4 hours

	Assessment statement	Obj	Teacher’s notes
E.2.1	Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.	2	Details of how each receptor functions are not required. TOK: Other organisms can detect stimuli that humans cannot. For example, some pollinators can detect electromagnetic radiation in the non-visible range. As a consequence, they might perceive a flower as patterned when we perceive it as plain. To what extent, therefore, is what we perceive merely a construction of reality? To what extent are we dependent upon technology to “know” the biological world?
E.2.2	Label a diagram of the structure of the human eye.	1	The diagram should include the sclera, cornea, conjunctiva, eyelid, choroid, aqueous humour, pupil, lens, iris, vitreous humour, retina, fovea, optic nerve and blind spot.
E.2.3	Annotate a diagram of the retina to show the cell types and the direction in which light moves.	2	Include names of rod and cone cells, bipolar neurons and ganglion cells.
E.2.4	Compare rod and cone cells.	3	Include: ·  use in dim light versus bright light ·  one type sensitive to all visible wavelengths versus three types sensitive to red, blue and green light ·  passage of impulses from a group of rod cells to a single nerve fibre in the optic nerve versus passage from a single cone cell to a single nerve fibre.
E.2.5	Explain the processing of visual stimuli, including edge enhancement and contralateral processing.	3	Edge enhancement occurs within the retina and can be demonstrated with the Hermann grid illusion. Contralateral processing is due to the optic chiasma, where the right brain processes information from the left visual field and vice versa. This can be illustrated by the abnormal perceptions of patients with brain lesions.
E.2.6	Label a diagram of the ear.	1	Include pinna, eardrum, bones of the middle ear, oval window, round window, semicircular canals, auditory nerve and cochlea.
E.2.7	Explain how sound is perceived by the ear, including the roles of the eardrum, bones of the middle ear, oval and round windows, and the hair cells of the cochlea.	3	The roles of the other parts of the ear are not expected.

E3 Innate and learned behaviour

4 hours

	Assessment statement	Obj	Teacher’s notes
E.3.1	Distinguish between innate and learned behaviour.	2	Innate behaviour develops independently of the environmental context, whereas learned behaviour develops as a result of experience.
E.3.2	Design experiments to investigate innate behaviour in invertebrates, including either a taxis or a kinesis.	3	Examples include:         taxis—Planaria move towards food (chemotaxis) and Euglena move towards light (phototaxis)          Examples include: ·  taxis—Planaria move towards food (chemotaxis) and Euglena move towards light (phototaxis) ·  kinesis—woodlice move about less in optimum (humid) conditions and more in an unfavourable (dry) atmosphere.
E.3.3	Analyse data from invertebrate behaviour experiments in terms of the effect on chances of survival and reproduction.	3
E.3.4	Discuss how the process of learning can improve the chance of survival.	3
E.3.5	Outline Pavlov’s experiments into conditioning of dogs.	2	The terms unconditioned stimulus, conditioned stimulus, unconditioned response and conditioned response should be included. TOK: The extent to which Pavlov’s theory can be applied to different examples of learning could be considered.
E.3.6	Outline the role of inheritance and learning in the development of birdsong in young birds.	2

E4 Neurotransmitters and synapses

5 hours

	Assessment statement	Obj	Teacher’s notes
E.4.1	State that some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic transmission.	1
E.4.2	Explain how decision-making in the CNS can result from the interaction between the activities of excitatory and inhibitory presynaptic neurons at synapses.	3
E.4.3	Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission.	3	Include ways in which synaptic transmission can be increased or decreased. Details of the organization and functioning of the entire brain, and theories of personality or explanations for personality, are not required.
E.4.4	List three examples of excitatory and three examples of inhibitory psychoactive drugs.	1	Use the following examples. ·  Excitatory drugs: nicotine, cocaine and amphetamines ·  Inhibitory drugs: benzodiazepines, alcohol and tetrahydrocannabinol (THC).
E.4.5	Explain the effects of THC and cocaine in terms of their action at synapses in the brain.	3	Include the effects of these drugs on both mood and behaviour. Aim 8: The social consequences of these drugs could be considered, for the user, his or her family and the wider society.
E.4.6	Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion.	3

HL E6 Further studies of behaviour

	Assessment statement	Obj	Teacher’s notes
E.6.1	Describe the social organization of honey bee colonies and one other non-human example.	2	Detailed structural differences and the life cycle of honey bees are not expected.
E.6.2	Outline how natural selection may act at the level of the colony in the case of social organisms.	2
E.6.3	Discuss the evolution of altruistic behaviour using two non-human examples.	3
E.6.4	Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia.	2
E.6.5	Explain how mate selection can lead to exaggerated traits.	3	An example of this is the peacock’s tail feathers.
E.6.6	State that animals show rhythmical variations in activity.	1
E.6.7	Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.	2	Examples could include the diurnal activity variation of hamsters, coordinated spawning in corals, or seasonal reproductive behaviour in deer.

E 1.1 Define the terms stimulus, response and reflex in the context of animal behaviour.

Stimulus - Change in environment detected by a receptor and elicits a response.
Reflex - Rapid and unconscious response.
Response - Change in organism caused by a stimulus.

E 1.2 Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli. 

Receptors – Detect changes in the internal/external environment of an organism & convert stimuli into nerve impulses which are sent to the CNS (e.g., specialized nerve endings in the skin detecting temperature changes, mechanoreceptors in the cochlea of the ear).

Sensory neurons – Send nerve impulses from receptors to the CNS.

Relay neurons – Send nerve impulses up and down the spinal cord. Send electrical impulses from the sensory neuron and the motor neuron by linking the two neurons together.

Motor neurons – Send nerve impulses from the CNS (relay neuron) to the effector.

Synapse – Gap between two neurons controlling uptake/intake of sodium, potassium and chloride ions. 

Effector – Muscle cell/gland that carries out response to stimulus. Receives nerve impulses from motor neuron and carries out response specific to that stimulus.

E 1.3 Draw and label a diagram of a reflex arc for a pain withdrawal reflex. (Include the spinal cord and its spinal nerves, the receptor cell, sensory neuron, relay neuron, motor neuron and effector.

E 1.4 Explain how animal responses can be affected by natural selection, using two examples.

·       

                      Hedgehogs

•     Hedgehogs reflex to a threat such as cars is to curl up into a ball.
• ·       This however is ineffective against cars, and so the hedgehogs are squashed under the car tires.
• ·         Hedgehogs that have genetic variation and can run away from cars instead of curling up into a ball, are able to survive and have an increased change of surviving, reproducing and thus passing on their genes for this trait.
• ·        Over time, these genes will become more common in the hedgehog population.

      Blackcap birds

• ·         Blackcap birds breed in Germany in the summer and fly to Spain in the winter.

• ·        Now 10% of blackcap birds fly to Great Britain instead of Spain due to warmer winters.

• ·  Eggs from blackcap birds living in Great Britain and Spain were taken and reared in Germany away from their parents.

• · Blackcap birds from birds that flew to Spain were able to fly to Spain without the presence of their parents. Blackcap birds from birds that flew to Great Britain flew to Great Britain as well.

 ·         These birds are genetically determined to respond to external stimuli causing the birds to fly in a certain direction.

E 4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain.

• THC binds to cannabinoid receptors and prevents neurotransmitters from being released into the postsynaptic neuron, 
• causing hyperpolarisation of postsynaptic neuron
• Effects include a distorted sense of time and space/euphoria/increased appetite.

E 4.6 Discuss the causes of addiction.

• Addiction is dependency on a substance or activity. 
• Stopping is very difficult and causes severe mental/physical reactions
• Some individuals have a genetic predisposition for taking drugs due to polygenic inheritance.
• Drugs such as cocaine enhance the effect of dopamine
• Dopamine is released in response to a reward, e.g. food.
• Abuse of drugs hypothesized to lead to down-regulation of dopamine receptors
• High levels of dopamine needed for individual to feel happy.
• addiction is dependence on a substance (such as alcohol or other drugs) or
• an activity;
• stopping is very difficult and causes severe physical / mental reactions / 
• complex behaviour;
• predisposition may be determined by polygenic inheritance;
• significant role of environmental factors;
• dopamine released in response to reward / eg food;
• some drugs / heroin / cocaine enhance dopamine activity;
• abuse drugs hypothesized to lead to down-regulation of dopamine receptors;
• requires increasing amounts to achieve same effect;

Explain the processing of visual stimuli

Pigments in rod and cone cells detect light stimulus and convert light information into electrical information;

Nerve impulses are sent to bipolar neuron which are then sent to axons of ganglion cell;

Nerve impulses then sent to thalamus which are then sent to the visual cortex for processing.

Left and right optic nerves cross at the optic chiasma. Thus, information from the right visual field is processed in the left visual cortex. Visual cortex arranged in columns of cells alternating left and right eyes.

Explain edge enhancement

Two types of ganglion cells – Light falling on periphery stimulates one type of ganglion cell however the stimulation is reduced if light also falls on centre of receptive field. Both types of ganglion cell are thus more stimulated if the edge of light/dark areas is within the receptive field. This means that less stimulation occurs at the periphery

Hardest IB Biology Option E neurobiology & Behaviour questions

Hardest IB Biology Option E neurobiology & Behaviour questions

E. 4.2 Explain how decision-making in the CNS can result from the interaction between the activities of excitatory and inhibitory presynaptic neurons at synapses.

Excitatory neurons transmit excitatory nerve impulses to synapse which increase potential difference at axon hillock.

Inhibitory neurons transmit inhibitory nerve impulses that decrease potential difference at axon hillock. Summation of many excitatory nerve impulses can override decreased potential difference caused by inhibitory nerve impulses neurons at axon hillock,  and can cause an action potential if the potential difference reaches threshold value of -50 mV. Therefore, several nerve impulses must be transmitted to synapse in order to cause an action potential, leading to a decision being made in the CNS.

E. 4.3 Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission.

Inhibitory psychoactive drugs decrease postsynaptic transmission, depressing arousal levels whereas excitatory drugs amplify postsynaptic transmission, stimulating arousal levels. Inhibitory drugs such as alcohol and benzodiazepines combine with and enhance the effects of the GABA neurotransmitter, reducing neuron activity of the postsynaptic membrane.

Excitatory drugs such as nicotine,

psychoactive drugs may increase or decrease transmission (to
the post-synaptic membrane);
may increase the release/delay the breakdown/interfere with
storage/uptake/reabsorption of neurotransmitters;
may mimic the action of neurotransmitters;
inhibitory drugs may reduce the effect of excitatory neurotransmitters /
increase the effect/release of inhibitory neurotransmitters;
inhibitory drugs can hyperpolarize the post-synaptic neuron;                         3 max

E. 4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain.

Cocaine is an excitatory psychoactive drug that attaches to the dopamine pumps on presynaptic membrane. COCAINE PREVENTS REMOVAL OF DOPAMINE NEUROTRANSMITTERS and thusDOPAMINE STAYS IN THE SYNAPTIC CLEFT causing a CONSTANT STIMULATION OF THE POSTSYNAPTIC NEURON. This results in EUPHORIA, INCREASED ENERGY, ALERTNESS AND HEART RATE. Cocaine in the form of crack is rapidly absorbed and therefore the STATE OF EUPHORIA IS INTENSE BUT SHORT. DEPRESSION CAN FORM AFTER THE EUPHORIA WEARS OFF and dopamine levels in the brain plummet, causing the DRUG USER TO CRAVE THE DRUG IN ORDER TO FEEL HAPPY AGAIN, LEADING TO ADDICTION. BODY GRADUALLY PRODUCES LESS DOPAMINE, so the drug user becomes dependent on cocaine.

E. 4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion.

Addiction can be caused by social factors including peer pressure in gangs where individuals are expected to take part in drug use or otherwise face social exclusion and a lack of respect from other members.

Some individuals become addicted to drugs because drugs trigger secretion of dopamine which causes users to feel happy when they would otherwise feel depressed due to poverty and social deprivation. Users crave these feelings of pressure and thus become addicted to the drug. For this reason, many drugs are potentially addictive, but not every drug user becomes addicted.

addictive drugs trigger secretion of dopamine which causes feelings
of pleasure/well-being/reward / users become dependent on feelings;
genetic predisposition is most common with addiction to alcohol;
social factors affect the incidence of addiction;
it is not certain that a person who is genetically predisposed will
develop addiction when exposed to the drug / OWTTE;
although many drugs are (potentially) addictive, not every user
becomes an addict;

                         named social factors which must be explained:
e.g. cultural traditions / peer pressure;
social deprivation / traumatic life experiences / mental problems;     

E. 5.1 Label on a brain diagram five parts of the brain, including the cerebral hemisphere, hypothalamus, pituitary gland, cerebrum and medulla oblongata.

E. 5.2 Outline the functions of each of the parts of the brain labelled in E.5.1

Cerebral hemisphere - Integrating centre for high complex functions such as emotions, learning and memory (ELM).

Hypothalamus - Maintains homeostasis, coordinates nervous and endocrine systems, secretes hormones of posterior pituitary and releases factors that regulate anterior pituitary. 

Pituitary gland - Posterior lobe stores and releases hormones produced by hypothalamus and anterior lobe. Produces and secretes hormones regulating body functions.

Medulla oblongata - Controls automatic and homeostatic activities, e.g. swallowing, digestion, vomiting and breathing and heart activity.

Cerebellum - Coordinates unconscious functions including movement and balance.

E. 5.3 Explain how animal experiments, lesions and FMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions. (Include one specific example for each).

FMRI:

·    FMRI is a non-harmful method which can be undertaken on patients to investigate and diagnose stroke and ADHD.

·    Subject is given stimulus designed to stimulate brain activity.

·    When a certain region of brain is stimulated, blood flow increases in that area.

·    FMRI records changes in blood flow and can show sequential use of brain.

·    Thus, the stimulus investigated can be potentially linked to the region of the brain where blood flow increases.

·    However, not all brain activity is recorded, so that some investigations may be flawed.

non invasive; it records changes in blood flow;a subject is given stimulus which is designed to stimulate brain activity;
active parts of the brain have increased blood flow;degree of activity can be represented (by different colours);
links stimulus with certain part of the brain;
brain activity visualized by coloured images;
allowing sequential use of the brain to be visualized;
temporal activities can be recorded as well;
collaboration between brain parts;but not all brain activity is detected by MRI; 6 max

fMRI gives a more specific knowledge of stimulated area/activation;

e.g. used to study/diagnose ADHD/dyslexia/recovery from strokes/music

comprehension / other valid examples;

non-invasive / no damage to brain;

can study healthy subjects;

involves blood flow/supply/oxygenation;

not neuronal connections (so requires interpretation);

good spatial but poor temporal resolution;

problem of statistical interpretations of model;

LESIONS:

Lesions from accidents/birth provide information about loss of specific brain area.
E.g. research on split brain patients led to understanding of functional roles of left and right hemispheres
However, many actions of body can be caused by many different areas of brain.
Damage may be to several parts of the brain so results unclear.
Data difficult to interpret due to complexity of reactions.



lesions (from accidents/birth) indicate effect of loss of area;
e.g. split brain patients led to understanding of different functional roles of left and right hemispheres
many actions of the body involve different areas of the brain;
damage may be to several/many parts so results unclear;
difficult to interpret due to complexity of reactions;

E. 5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of blood to the gut.

Explain sympathetic and parasympathetic control of blood flow to the gut.
Sympathetic and parasympathetic nervous systems that are part of autonomic nervous system (ANS) have antagonistic actions.
Smooth muscle in blood vessels controlled by sympathetic and parasympathetic nerves.
Sympathetic system releases noradrenaline which constricts blood vessels so that blood flow to gut is decreased.
Parasympathetic system releases acetylcholine which dilates blood vessels so that more blood can flow to gut.

sympathetic and parasympathetic nervous systems are part of the autonomic
system; have antagonistic actions;
smooth muscle in blood vessels controlled by sympathetic and parasympathetic nerves;
sympathetic system release noradrenaline;
constricting blood vessels to gut; decreases blood flow to gut;
parasympathetic system releases acetylcholine;
dilates blood vessels to gut; increases blood flow to gut; 6 max

E.5.5 Explain the pupil reflex.

• Light shone into one eye causes both pupils to constrict.
• Photoreceptors in retina detect light stimulus.
• Impulses sent down sensory neuron to brain
• Medulla oblongata of brain processes impulses
• Messages sent to circular muscles of iris which contract, causing pupil constriction.

E.5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this.

• Pupil reflex is nervous pathway involving the brain stem and cerebrum controlled by autonomic nervous system
• Light shone into eye would normally cause pupil contraction.
• No pupil contraction indicates that synapses are not functioning
• This may indicate brain death involving the death of both the brain stem and the cerebrum
• However, some drugs, e.g. barbiturates, may interfere with pupil reflex.
• Brain stem may be functioning, but the individual's cerebrum may not function, resulting in a vegetative state, which could be regarded as the "death" of a person.

shine light in eye to see if pupil constricts;
pupil reflex is a cranial reflex controlled by the brainstem;

opening the eyelid lets light into the eye and stimulates the retina;
a reflex will cause the pupil to constrict if the brain is intact;
failure of the pupil to constrict indicates brain damage;
this could be an indication of brain death;

(if pupil reflex is lost) patient is most likely brain dead;

some drugs (barbiturates) / nerve damage may interfere with pupil reflex;

whole brain death is brain stem and cerebrum;

failure of pupil to respond to light indicates brain stem death;
without brain stem function, life cannot continue;
cerebrum involves higher order brain function;
non-functioning cerebrum with functioning brain stem is vegetative state;
some would argue this is the death of the person;
though brain stem function alone may be able to maintain homeostasis;      


Discuss the concept of brain death and how it can be diagnosed.

·         Brain death is legal definition of death

·         Some cases of coma recoverable whereas others are irreversible, for example

·         Damage to the medulla oblongata is usually irreversible.

·         Doctors have to diagnose damage to decide treatment

·         Doctors test whether brain stem is functioning to decide whether to save patient’s life.

·         Light is shone into eye and according to pupil reflex, pupil should constrict to avoid damage from light to eye.

·         If no pupil constriction occurs, brain death is plausible.

·         More than one test is used to diagnose brain death.

it is a legal/medical definition of death;
some cases of coma are irreversible / some cases of coma may recover;
damage in the medulla (oblongata) is generally permanent;
doctors have to diagnose damage to decide treatment;
use tests of brain stem function to decide whether to preserve patient’s life /
without brain stem function life cannot continue;
test pupil reflex / shine light into eye;
if pupils do not constrict with light this suggests brain death;
more than one test used to diagnose brain death;
no response to pain or cranial reflexes;
legal/ethical definition needed for organ donation / long term use of life-support
machines may be inappropriate / bioethical considerations;

E.5.7 Outline how pain is perceived and how endorphins can act as painkillers.

• Pain receptors in skin and other body parts detect stimuli such as chemical substances.

endorphins released by pituitary gland (during stress, injury

or exercise);

endorphins block transmission of impulses at synapses involved

in pain perception;

bind to receptors in the membrane neurons (involved in)

sending pain signal;

block release of neurotransmitters;

E 6.3 Discuss the evolution of altruistic behaviour using non-human examples. 6 marks

·    Altruistic behaviour occurs in social animals and may increase the survival rate of the group and thus the species.

·    It does this by helping close relatives/siblings to increase their chances of passing on genes to the next generation due to natural selection

·    Altruistic behaviour may be harmful to the animal itself but beneficial to other animals.

·    Altruistic behaviour usually occurs in the same species and animals that are genetically closely related

·    Altruistic behaviour is an example of kin selection because the reproductive success of relatives is enhanced.

·    If altruism was a negative trait, it may have disappeared.

altruistic behaviour may be harmful to the animal itself but beneficial to other
animals;

occurs in social animals;

usually occur in the same species;

need not happen between genetically related animals from one population;

altruistic behaviour often occurs in animals which are genetically closely related;

altruistic behaviour may increase the survival rate of the group and thus the species;

helping close relatives or siblings increases the chances of passing on genes to the

next generation;

due to natural selection;

this is called inclusive fitness;

enhancing reproductive success of relatives is called kin selection;

if altruism was a negative trait it would / may have disappeared;altruistic species do just as well as non altruistic species belonging to the same order;

E 6.4 Outline the examples of how foraging behaviour optimizes food intake.


Bluegill fish foraging for Daphnia

E 6.5 Explain how mate selection can lead to exaggerated traits.

E.g. Peacock's tail feathers


E 6.7 Outline two examples illustrating the adaptive value of rhythmical behaviour patterns and state that animals show rhythmical variations in activity.

• Animals show rhythmical variations in activity
• Rhythmical behaviour is behaviour that repeats itself through cycles of time (e.g. daily or monthly and so on). 
• For example, barred owls are most active at night, to avoid competition from other organisms such as hawks, which are diurnal, so that they can hunt the same meadow as the hawks without conflict.
• This increases the owl's ability to find food, and thus increases the survivability of the whole species.
• Red deer breed in October so that the offspring are born and reared in late spring, where the temperatures are warmer whilst the fruitfulness of the vegetation from the winter is maintained. The warmer temperatures provide an environment that increases chances of survivability of the offspring, and thus the survivability of the whole population o organisms.