This pages gives outline details of the content of Option A for SL & HL together. There are essential questions and lists of student skills and applications. Helpful for revision. Student can check their understanding and prioritise areas for revision.

A.1 Neural development

• Embryonic chordates form a neural tube by in-folding of the ectoderm followed by elongation of the tube formed.
• Differentiation of cells in the neural tube produces neurons.
• Immature neurons migrate to their final location.
• Each immature neuron grows an axon in response to chemical stimuli.
• Some axons extend out of the neural tube to reach other parts of the body.
• Note: Terminology relating to embryonic brain areas or nervous system divisions is not required.

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• Multiple synapses are formed by developing neurons.
• Synapses that are not used do not persist.
• Neural pruning involves the loss of unused neurons.
• The nervous system has plasticity, the ability to change with experience.

A2 The Human Brain

• The brain is formed from expansion of the anterior part of the neural tube.
• Brain metabolism requires a lot of energy.

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• Skill: Identification of parts of the brain in a photograph, diagram or scan of the brain, including the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.
• The brain stem contains the autonomic nervous system which controls involuntary processes in the body. For example: Swallowing, breathing and heart rate  coordinated by the medulla.
• Application: Use of the pupil reflex to evaluate brain damage.

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  The cerebral cortex is larger (in proportion) and more highly developed in humans than other animals.
• An increase in the total area of the cerebral cortex has extensive folding so it fits within the cranium.
• The cerebral hemispheres are responsible for higher order functions.
• Different parts of the brain have specific functions. For example; Visual cortex, Broca’s area and nucleus accumbens.
• Application: Use of animal experiments, autopsy, lesions and fMRI to identify the role of different brain parts.
• The left cerebral hemisphere receives sensory input from sensory receptors in the right side of the body and the right side of the visual field in both eyes and vice versa for the right hemisphere.
• The left cerebral hemisphere controls muscle contraction in the right side of the body and vice versa for the right hemisphere.

A3 Perception of stimuli

• Receptors detect changes in the environment. e.g. Humans sensory receptors - mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.
• Application: Detection of chemicals in the air by the many different olfactory receptors.

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• Rods and cones are photoreceptors located in the retina - they differ in their sensitivities to light intensities and wavelengths.
• Bipolar cells send the impulses from rods and cones to ganglion cells.
• Ganglion cells send messages to the brain via the optic nerve.
• The information from the right field of vision from both eyes is sent to the left part of the visual cortex and vice versa. (covered in the cerebral cortex work in section A2.)

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• Structures in the middle ear transmit and amplify sound.
• Sensory hairs of the cochlea detect sounds of specific frequency.
• Impulses caused by sound perception are transmitted to the brain via the auditory nerve.
• Hair cells in the semicircular canals detect movement of the head.

A4 Innate and learned behaviour - HL

Understandings:

• Innate behaviour develops independently of the environment (is not learned) it is inherited.
• Reflexes are involuntary responses (Autonomic)
• A reflex arc is made of the neurons that make up reflexes.
• Reflex conditioning is the formation of new associations between stimulus and response.
• Learned behaviour develops as a result of experience (of stimuli in the environment).
• Imprinting is a type of rapid learning which occurs at a particular life stage and which is not 'unlearned' through other types of learning.
• Operant conditioning is type of learning through trial and error experiences.
• Gaining a skill or knowledge is called 'learning'.
• Encoding information, storing it and then accessing the information is Memory.

A5 Neuro-phamacology - HL

Understandings:

• Neurotransmitters can excite nerve impulses in postsynaptic neurons or inhibit them (It depends on the neurotransmitter).
• The summation of excitatory and inhibitory neurotransmitters received from pre-synaptic neurons either initiates or inhibits nerve impulses in post-synaptic neurons.
• The modulation of fast synaptic transmission in the brain involves different slow-acting neurotransmitters.
• These slow-acting neurotransmitters cause changes in neurones leading to memory and learning.
• Postsynaptic transmission in the brain can be increased or decreased by psychoactive drugs.
• Aesthetics can decrease or prevent neural transmission between sensory receptors and the CNS.
• Stimulant drugs (nicotine, cocaine or amphetamines) mimic the sympathetic nervous system and stimulate neural transmission.
• Sedative drugs (benzodiazepines, alcohol or tetrahydrocannabinol (THC)) can decrease neural transmission.
• Three factors can lead to Addiction;
  • genetic predisposition, social environment and dopamine secretion.

A6 Ethology - HL

Understandings:

• The study of animal behaviour in natural conditions is called Ethology.
• Animal behaviour can be changed by natural selection when it has a genetic basis. For example Migratory behaviour in blackcaps.
• Natural selection increases the frequency of behaviour that improves the chances of survival and reproduction in a population. For example foraging behaviour in shore crabs through (learning) optimal prey choice or breeding strategies in coho salmon populations.
• Learning can increase the frequency of behaviour in a population more rapidly than natural selection of innate behaviour. It promotes the spread of the behaviour, or it can reduce the frequency of a dangerous behaviour.
• Feeding on cream from milk bottles in blue tits as an example of the development and loss of learned behaviour.