Download International Baccalaureate Biology Option

International Baccalaureate
Biology Option A
Neurobiology and Behaviour
Introduction
Welcome to the International Baccalaureate Revision Guide for Option A.
Sections A1 to A3 form the common core and sections A4 to A6 are the Additional Higher Level
sections.
The format is the same as the Core Guides with key points, simple diagrams and large numbers of
Grey Box Questions and Self-test quizzes.
Pale blue boxes contain information that helps with understanding by providing additional information.
However you do not need to learn this.
Other coloured boxes, such as these green and yellow ones, contain
information that you do need to know.
The Option is tested, along with experimental skills and techniques linked to the Core material, in
Paper 3.
I would greatly value any feedback on this revision guide. Please feel free to email me at Oxford Study
Courses – [email protected]
Ashby Merson-Davies
Contents
A1 Neural Development ........................................................................................................................ 3
Neurulation – Formation of the Neural Tube ........................................................................................................... 3
Neuron Development............................................................................................................................................... 4
Neuron Migration ..................................................................................................................................................... 4
Synapse Development and Elimination ................................................................................................................... 4
Neural Pruning......................................................................................................................................................... 4
Plasticity of the Nervous System ............................................................................................................................. 5
Self-test quiz ............................................................................................................................................................ 6
A2 The Human Brain ............................................................................................................................. 7
Organisation of the Nervous Systems ..................................................................................................................... 8
The Autonomic Nervous System ANS ..................................................................................................................... 8
Electroencephalography EEG ................................................................................................................................. 9
The Pupil Reflex and Brain Death ........................................................................................................................... 9
Investigating Brain Function .................................................................................................................................... 9
Correlation between brain size and body size ....................................................................................................... 10
Brain function......................................................................................................................................................... 11
Self-test quiz .......................................................................................................................................................... 13
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IB Option A © Ashby Merson-Davies
A3 Perception of Stimuli ..................................................................................................................... 15
Receptors .............................................................................................................................................................. 15
The Human Eye..................................................................................................................................................... 15
Rods and Cones .................................................................................................................................................... 16
The retina .............................................................................................................................................................. 16
Optic Nerves and the Visual Cortex....................................................................................................................... 16
Colour vision .......................................................................................................................................................... 17
Olfactory Receptors ............................................................................................................................................... 17
The Human Ear ..................................................................................................................................................... 18
Sound .................................................................................................................................................................... 20
Movement of the Head .......................................................................................................................................... 21
Cochlear Implant ................................................................................................................................................... 21
Self-test quiz .......................................................................................................................................................... 23
A4 Innate and Learned Behaviour ..................................................................................................... 25
Reflexes ................................................................................................................................................................ 25
Reflex Conditioning ............................................................................................................................................... 26
Operant Conditioning............................................................................................................................................. 26
Imprinting ............................................................................................................................................................... 27
Latent Learning - Development of Birdsong .......................................................................................................... 27
Other examples of learning ................................................................................................................................... 28
Example of data analysis of invertebrate behaviour .............................................................................................. 29
Self-test quiz .......................................................................................................................................................... 31
A5 Neuropharmacology ...................................................................................................................... 32
Neurotransmitters and Synapses .......................................................................................................................... 32
Slow-acting neurotransmitters ............................................................................................................................... 34
Memory and learning ............................................................................................................................................. 34
Psychoactive drugs – the brain and personality .................................................................................................... 35
Addiction ................................................................................................................................................................ 37
Anaesthetics .......................................................................................................................................................... 37
Endorphins ............................................................................................................................................................ 37
Self-test quiz .......................................................................................................................................................... 39
A6 Ethology .......................................................................................................................................... 41
Migratory behaviour – Blackcap (Sylvia atricapilla) ............................................................................................... 41
Altruistic behaviour – Vampire bat (Desmodus rotundus)...................................................................................... 41
Foraging behaviour – Shore crab (Carcinus maenas) ........................................................................................... 42
Breeding strategies – Coho salmon (Oncorhynchus kisutch) ................................................................................ 42
Courtship behaviour – Birds of Paradise ............................................................................................................... 42
Synchronised oestrous – Lion (Panthera leo) ........................................................................................................ 43
Development and loss of learned behaviour – Blue tit (Cyanistes caeruleus) ....................................................... 43
Additional Examples .............................................................................................................................................. 44
Florida scrub jay (Aphelocoma coerulescens) ....................................................................................................... 44
Bluegill fish (Lepomis macrochirus) feeding on Daphnia ....................................................................................... 44
Oystercatchers (Haematopus ostralegus) feeding on limpets (Patella sp.) ........................................................... 44
Self-test quiz .......................................................................................................................................................... 45
Appendix .............................................................................................................................................. 46
Glossary ................................................................................................................................................................ 46
Answers to Grey Box Questions ............................................................................................................................ 46
Answers to Self-test quizzes.................................................................................................................................. 47
Acknowledgements ................................................................................................................................................48
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IB Option A © Ashby Merson-Davies
A2 The Human Brain
A2 The Human Brain
 Key points
 The brain begins as an expansion of the anterior part the neural tube.
 There are three regions.
eye
forebrain
midbrain
hindbrain
neural tube
umbilical
chord
hindbrain
tail
neural tube
A 28 day old embryo.
The developing brain viewed from above.
 Different regions of the brain have specific functions.
 The cerebral cortex:
 Forms a larger proportion of the brain.
 Is more highly developed in humans compared to other animals.
 Is enlarged principally by an increase in total area with extensive folding allowing it to fit
within the cranium (skull).
 The cerebral hemispheres are responsible for higher order functions.
The cerebral cortex is the
 The left cerebral hemisphere:
outer layer of the cerebral
 Receives sensory input:
hemisphere. (Think of the
 from the right side of the body
cortex as a coat.)
 from the right side of the visual field of both eyes (see page 17)
 Controls muscle contraction in the right side of the body.
 The right cerebral hemisphere is the same but for the left side of the body.
 Brain metabolism requires large energy inputs.
ventricle (fluid filled
space)
cerebral hemisphere
hypothalamus
pituitary gland
 A major endocrine
gland.
cerebellum
medulla oblongata
 Co-ordinates:
 Swallowing
 Breathing
 Heart rate
 Control of gut muscles
 Control of blood vessels
spinal cord
2.1 The human brain
The brain stem
The brain stem is made up of three regions connecting the spinal
cord to the main part of the brain. The medulla, or medulla
oblongata, is the one next to the spinal cord.
IB Option A © Ashby Merson-Davies
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A2 The Human Brain
Organisation of the Nervous Systems
Central Nervous System
Central Nervous System
Sensory
neurons
Somatic
System
Motor neurons
Sensory
neurons
Visceral
System
Sympathetic and
parasympathetic
motor neurons
Peripheral Nervous System
The somatic system is largely conscious and deals
mainly with surface receptors and the skeletal
muscles.
The visceral system is largely subconscious and
deals with systems such as heart, gut, breathing.
The motor neurons of the visceral system form the
ANS. In general these are antagonistic, e.g. for
the heart, sympathetic impulses speed it up and
parasympathetic impulses slow it down. (See core
guide SL page 115, HL page 151.)
The Autonomic Nervous System ANS
 Key points
 This controls the involuntary processes in the body – see medulla oblongata in the diagram on
the previous page.
 The brain stem controls most of the ANS output.
Broca’s area
 Part of the left cerebral
hemisphere.
 Controls speech.
 Damage to this area
results in the person
knowing what they want
to say but they can only
make sounds and are
unable to make
meaningful words and
sentences.
Nucleus accumbens
(in each
hemisphere)
 These are the pleasure or reward
centres of the brain.
 They release the neurotransmitter
dopamine in response to various
stimuli such as exercise, laughter,
sex, and drugs including cocaine
and heroine.
2.3 Nucleus accumbens
2.2 Broca’s area
You need to know the functions of three regions of the brain –
Broca’s area, nucleus accumbens and the visual cortex.
2.4 The cerebral cortex.
 This is divided into different lobes. (You do not need
to know the names.)
 It is 2 – 4mm thick.
 During human evolution the thickness has not
increased but the total surface area has.
 The cranium (skull) has enlarged to accommodate
some of this but the enlargement has principally
Occipital Lobe
been by becoming highly folded.
 The occipital lobe is the visual cortex containing
the visual processing centre which receives and
processes information from the retinas of both eyes
– see page 17.
2.5 Close-up of the cerebral
cortex showing the highly
folded structure
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 The olfactory bulb senses smell.
 The motor cortex deals with the planning, control,
and execution of voluntary movements.
 The somatosensory cortex receives information from
all the sensory receptors in the body, e.g.
thermoreceptors, chemoreceptors,
mechanoreceptors.
IB Option A © Ashby Merson-Davies