The Brain, Behaviour & Disease (Edexcel A Level Biology (A) SNAB): Flashcards

It holds more neurones, so more connections can form.

More connections allow more complex processing.

The hypothalamus, which releases ADH if the blood is too concentrated.

It is very complex and its tissues are delicate.

Different regions work together, so they cannot easily be studied in isolation.

It uses X-rays from many angles.

Denser tissue absorbs more, showing physical structures and any damage.

It uses a magnetic field and radio waves.

It shows soft tissue at higher resolution and avoids the X-ray risk of CT.

It shows brain function in real time.

It detects oxygenated blood flow, indicating which regions are active.

It measures the ratio of oxygenated to deoxygenated haemoglobin.

Active regions receive more oxygenated blood and 'light up'.

A radioactive tracer (e.g. labelled glucose) is injected.

It collects in active regions, which the scanner detects as areas of high radioactivity.

CT and MRI show only structure.

fMRI and PET show structure and function in real time.

The strong magnetic field can interfere with medical devices such as pacemakers and insulin pumps.

Tumours, which show up clearly in the images.

An fMRI scan shows brain function in real time by detecting oxygenated blood flow.

False.

CT scans use X-rays and are not recommended for pregnant patients or children.

MRI scans are considerably more expensive.

The visual cortex is the region of the cerebral cortex where visual information is processed.

The critical period is the early period after birth during which both eyes must be stimulated for the visual cortex to develop normally.

They are strengthened.

They become permanent parts of the visual cortex.

They are lost and cannot be reformed.

This can cause blindness if an eye is not stimulated.

So the neurones in the visual cortex are organised correctly.

Without stimulation, the connections do not form properly.

Blindness in that eye.

The lost synapses cannot be reformed later.

Hubel and Wiesel, using animal models.

At the back of the brain, within the cerebral cortex.

The early period when both eyes must be stimulated for normal visual development is called the critical period.

False.

Synapses lost during the critical period cannot be reformed.

Synapses, which allow visual information to be transferred and processed.

That visual experience shapes brain development.

Early stimulation is essential for the visual cortex to wire correctly.

The human brain is hard to study directly, being complex and delicate.

Some animals have a similar brain structure, so findings can reasonably be applied to humans.

A model is something that provides a representation of real events, such as an animal model of the human brain.

The development of the brain's visual cortex.

They deprived animal models of vision in one eye and studied the effects.

Ocular dominance columns are groups of neurones in the visual cortex that respond to input from only one eye.

The kittens became blind in that eye.

The ocular dominance columns for the closed eye were smaller and those for the open eye larger.

No blindness resulted and the ocular dominance columns did not change.

This showed early stimulation is essential during development.

That light stimulation to both eyes in early development is essential.

Without it, the ocular dominance columns cannot develop normally.

For: it allows testing of medicines without endangering humans.

Against: it can cause suffering and raises ethical concerns.

It avoids endangering human lives.

Many view it as more ethically acceptable for medical research.

Groups of neurones in the visual cortex that respond to input from only one eye are called ocular dominance columns.

False.

Adult cats showed no blindness — the effect only occurred during the early critical period.

Because those animals have a similar brain structure to humans.

Habituation is when an animal learns not to respond to a repeated stimulus that has no positive or negative consequence.

Responding to stimuli uses energy.

Habituation avoids wasting energy on non-threatening stimuli, conserving it for essential processes.

Fewer calcium ions enter the presynaptic neurone.

So less neurotransmitter is released.

Fewer receptors are bound, so fewer sodium channels open.

Threshold is not reached, no action potential forms, and the effector does not respond.

The nervous system responds to it again.

For example, a constant sound that suddenly gets louder.

Humans no longer noticing a constant smell or sound after a while.

Or wild animals losing their fear of harmless humans.

Gently touch the snail and time how long it takes to re-emerge from its shell.

As it habituates, the re-emergence time gets shorter with repeated touches.

To control variables.

This ensures any change in response is due to habituation, not a different stimulus.

To use the same end-point each time.

This makes the timings comparable and reliable.

A gradual decrease in re-emergence time with each touch.

This shows the snail is becoming habituated.

During habituation, fewer calcium ions enter the presynaptic neurone, so less neurotransmitter is released.

True.

Snails should be handled gently and returned to the exact location they came from.

A neurotransmitter is a chemical that transmits nerve impulses across a synapse.

A shortage of dopamine.

It results from the loss of dopamine-producing neurones in the brain.

Dopamine is involved in muscle control.

Too little of it causes tremors, slow movement and stiffness.

Less dopamine binds to postsynaptic receptors, so fewer sodium channels open.

Depolarisation and action potentials are reduced, so movement is impaired.

It binds to and activates dopamine receptors on the postsynaptic membrane.

This mimics the effect of dopamine.

A chemical that is converted into dopamine in the neurones.

An example is L-dopa.

Low levels of serotonin.

Noradrenaline and dopamine are also linked to depression.

They prevent the reuptake of serotonin at synapses.

This raises overall serotonin levels in the brain.

They inhibit the enzymes that break down neurotransmitters in the synaptic cleft.

More neurotransmitter remains available.

Parkinson's disease is caused by a shortage of the neurotransmitter dopamine, which controls movement.

False.

SSRIs prevent the reuptake of serotonin, increasing its levels in the brain.

Gene therapy and stem cell therapy.

Both aim to restore dopamine production in the brain.

Any two of:

• Causing more neurotransmitter to be produced or released

• Mimicking a neurotransmitter at receptors

• Preventing neurotransmitter breakdown or reuptake

Any two of:

• Preventing production or release of neurotransmitter

• Blocking receptors so neurotransmitter cannot bind

• Causing neurotransmitter to leak out and be destroyed

Serotonin.

MDMA increases the amount of serotonin in the brain.

It inhibits the reuptake of serotonin into the presynaptic neurone.

It also triggers further release of serotonin.

Extreme euphoria and enhanced touch and bodily sensations.

Serotonin affects mood, anxiety and sleep.

The symptoms of Parkinson's disease.

It is converted into dopamine by the enzyme dopa-decarboxylase.

Unlike dopamine, L-dopa can cross from the blood into the brain.

It cannot cross the barrier between the blood and the brain.

L-dopa is given instead because it can cross.

More nerve impulses are transmitted in movement-control areas of the brain.

This gives better control of movement.

MDMA increases serotonin in the brain by inhibiting its reuptake into the presynaptic neurone.

True.

Its similar structure allows it to be converted into dopamine in the brain.

By binding to and activating receptors on the postsynaptic membrane.

This triggers a response as if the real neurotransmitter were present.

Personalised medicine is the development of targeted drugs to treat disease in individuals with different genotypes.

Its sequence data is stored in databases.

Genes and proteins involved in disease can be found and analysed to design drugs.

A drug can be designed to target that specific protein.

For example, an enzyme inhibitor if an enzyme is involved in the disease.

Testing drugs on cells cultured in a lab.

These are genetically identical to certain groups of patients.

It identifies people at high risk of specific diseases.

They can then take action, e.g. preventative surgery or lifestyle changes.

Doctors can predict how well they will respond to specific treatments.

Treatments can then be selected based on genotype.

High research costs could raise drug prices.

This may mean only wealthier people can access it.

Insurance companies or employers could discriminate unfairly.

For example, raising insurance costs for people with certain genetic variants.

If it is not predicted to be effective for them.

This can be distressing when no other treatment is available.

Using information about a person's genes to design their medical treatment is known as genomic medicine.

True.

Combining genome and clinical data reveals patterns that indicate disease risk.

Someone with a breast cancer gene mutation can have surgery in advance.

This reduces their risk of developing the disease.

A GMO is an organism that contains recombinant DNA — a gene transferred into it from another organism.

Restriction enzymes cut the gene out.

PCR then makes many copies of it.

It is inserted into a plasmid vector using DNA ligase.

The plasmid then carries the gene into the bacterial cell.

A vector is something that carries the desired gene into another cell, such as a plasmid or a bacterium.

The bacteria are grown in large fermenters with nutrients.

They multiply and produce the protein, which is then isolated and purified.

Human insulin and human blood clotting factors.

A bacterium acts as a vector to infect the plant cells.

Alternatively, a 'gene gun' fires DNA-coated pellets into the cells.

The gene is injected into the nucleus of a zygote.

The zygote is implanted into a surrogate and develops into a GM animal.

From its milk.

For example, human blood clotting proteins.

In genetic engineering, small loops of bacterial DNA used to carry genes into cells are called plasmids.

Large quantities of a pure human protein (e.g. insulin) can be made reliably and cheaply.

There are ethical concerns, especially about modifying animals and about GM crops intended for human consumption.

Nature = the influence of genetic factors.

Nurture = the influence of environmental factors.

Genes and environment interact and are hard to isolate.

One factor would have to be completely removed to study the other.

Animals of the same species have similar genes.

So differences in brain development from varied environments are likely due to nurture.

Nurture (environment).

Since their genes are identical, differences must be environmental.

They are genetically different but share a similar environment.

This helps separate genetic effects from environmental ones.

The trait is largely determined by genetic factors (nature).

They compare children of similar age from different cultures.

Differences suggest nurture; similarities suggest nature.

The environment outside the womb has not yet influenced the baby.

So abilities present at birth are likely due to nature.

If the trait still develops despite damage, nurture is important.

If it fails to develop, nature is more important.

Because identical twins are genetically identical, any differences between them raised apart must be due to nurture.

True.

Their shared genes and similar IQ scores imply a strong genetic influence.

A gene is switched off and the animals raised alongside unaltered ones.

Differences in brain development are then likely due to that gene.