Investigating brain function/brain structure Flashcards
There are various ways of investigating brain structure and function.
(a) Compare the use of computed tomography (CT) with magnetic resonance imaging (MRI) for
studying brain structure.
(3)
- MRI has higher resolution, better image clarity.
- MRI can therefore identify smaller structures.
- MRI uses radio waves, CT uses X-rays.
- Both give 2D/3D images.
- MRI is noisy and more expensive.
Suggest why functional magnetic resonance imaging (fMRI) is considered better than CT for
studying brain function.
(2)
- fMRI can study brain activity directly.
- MRI identifies active areas, by greater blood flow, greater oxygen uptake, presence of more oxyhemoglobin.
- Can see brain activity over period of time (MRI).
- fMRI safer as does not use X-rays.
- No need for special dyes in fMRI.
The diagrams below show two MRI scans of the brain of a patient with a tumour. Scan 1 was
taken before treatment was carried out, and scan 2 after treatment.
‘image’-‘White tumour decreases in size across scans’.
(i) Suggest why the tumour appeared white in the scans.
(2)
(ii) Using the information in the diagrams, describe the effect of the treatment on this tumour.
(2)
-Tumour tissue differs from brain tissue.
-Energy source/magnetic scan/radio waves.
-Difference in blood supply between tumour and rest of brain.
-Tumour contains dividing/mutated cells.
/
-Treatment has been partially successful.
-Tumour reduced.
-In contact with less brain tissue.
(iii) Using the information in the diagrams, suggest two brain functions that may have improved
after treatment. Give a reason for your answer.
(3)
-image’-tumour reduced across scans, tumour located within front of brain.
- Think, learn, show emotions, memory, personality, reasoning.
- Because tumour is situated within frontal lobe/ cerebral hemispheres/ cerebrum.
Some of the drugs used to treat human disorders are proteins. Some of these proteins can
be synthesised by genetically modified bacteria.
(i) A restriction enzyme is used in Stage 1 of the genetic modification of bacteria, stage 1 is the isolation of the desired human gene, and plasmid, then placed into bacterial cell.
Explain why only one restriction enzyme is used in stage 1.
- Restriction enzyme cuts at specific base sequence of bases.
- Generating sticky ends.
- So easier to join together.
- Complementary sticky ends in human gene and plasmid.
(ii) Suggest how the addition of a chemical causes the human gene to be switched on in stage
2 of genetic modification of bacteria.
Stage 2, after bacterial cell has multiplied, chemical added to switch on isolated human gene.
(3)
- Chemical could be a transcription factor, or hormone.
- TF interacts at bacteria cell surface membrane.
- TF activated/ transcription initiation complex formed.
- Binds to promoter region.
- Transcription and production of mRNA.
(iii) Describe the structure of an organelle found in a bacterial cell that is involved in
synthesising human protein in stage 3 of bacteria gene modification.
(1)
-Ribosome has larger and smaller subunits/ ribosomal protein/ 2 subunits.
(iv) Suggest two advantages of injecting the protein into the vein of a patient rather than an artery in stage 4 of bacteria gene modification.
(2)
- Larger lumen so easier to put into blood.
- Less muscle, so thinner wall means more penetrable.
- Vein blood pressure less, so less damage to vein.
- Vein is easier to find, closer to surface of skin.
Domoic acid is a neurotoxin, produced by algae, that harms the brains of some mammals. This
neurotoxin damages brain cells that release a neurotransmitter called glutamate.
(i) Describe how a neurotransmitter, such as glutamate, is released from a brain cell
(4)
- Action potential arrives.
- Calcium ion channels open in pre-synaptic membrane of brain cell.
- Calcium ion channels enter via diffusion down concentration concentration gradient (high to low).
- Causes glutamate vesicles to fuse with pre-synaptic membrane.
- Neurotransmitter glutamate released via exocytosis.
(ii) Scientists have used magnetic resonance imaging (MRI) to provide evidence that domoic acid may damage the brains of California sea lions.
Suggest how MRI can provide this evidence.
(2)
- Damaged areas can be identified on MRI brain scan.
- These damaged areas known to be associated with release of glutamate.
- Comparison with and without domoic acid.
A blow to the back of the head may result in you seeing stars. Suggest why?
(1)
-The occipital lobe sits in the back cortex, and is involved with vision processing. Thus blow to this area would disturb vision.
Imagine that you are whizzing downhill on a bike and come across an unexpected sharp bend in the road. You need to apply the brakes, or turn the handle bars, what regions of the brain and brain stem are involved in the action?
(4)
- Frontal lobe.
- Parietal lobe.
- Motor cortex.
- Cerebellum.
Parkinson’s disease results in an inability to select and make appropriate movements. Suggest which lobe if the brain is damaged.
(1)
-Parietal lobe/basal ganglia
Name the functions of the cerebral hemisphere regions.
5
- Frontal lobe, involved in reasoning and emotions, also includes the primary motor cortex.
- Parietal lobe, involved in movement, memory and sensation.
- Occipital lobe, involved in vision, processing info. from the eyes.
- Temporal lobe, involved in speech and sound, and memory.
- Cerebellum, involved in balance, and coordinates movement from the motor cortex.
Physical damage causes brain damage. What are any other reasons?
- Lack of oxygen.
- Carbon monoxide poisoning.
- Infection.
- Tumours.
- Strokes.
- Genetic conditions.
