The brain Flashcards
Describe how dopamine acts as a neurotransmitter
- complains released from presynaptic membrane, from the synaptic knob and diffuses across synaptic cleft
- binds to receptors on post-synaptic membrane
- opens sodium ion channels
- initiating depolarisation/action potential in post synaptic neurone
Describe how use of MDMA could affect transmission of impulses in brain
MDMA prevents reuptake of serotonin
Blocking presynaptic receptors/binding to postsynaptic receptors
More action potentials produced
Explain how use of MDMA may cause development of symptoms of depression
MDMA use results in depletion of serotonin
Loss of receptors on post synaptic membrane
Lack of serotonin associated with depression
Describe how low serotonin levels can affect transmission of impulses in brain
Serotonin is a neurotransmitter
Less serotonin means fewer depolarisations of post synaptic membranes
Threshold not met
Less chance of action potential being produced
Explain how difficulty of treating Parkinson’s disease overcomes difficulty of drugs passing from blood into brain
L- dopa that can cross blood brain barrier
It is converted into dopamine
Explain how nicotine causes an action potential in the post-synaptic neurone that releases noradrenaline
Nicotine is similar in shape to acetylcholine
Increases permeability of membrane to sodium ions
Nicotine causes depolarisation of post-synaptic membrane
Depolarisation reaches threshold level
How can an increase in calcium ion uptake by the neurone lead to release in noradrenaline
Vesicles containing noradrenaline fuse with presynaptic membrane
Explain why inhibitors of acetylcholinisterase could be useful in treatments of Alzheimer’s disease
Acetylcholinesterase breaks down acetylcholine
Inhibitors prevent break down of acetylcholine
More acetylcholine is available to bind to post synaptic membrane
Therefore compensating for reduced production of acetylcholine
What happens at synapse leading to habituation
Repeated stimulus decreases permeability of presynaptic membrane
Fewer calcium ions moving into pre synaptic neurone
Fewer vesicles fusing with presyanptic membrane
Less neurotransmitters can bind to receptors in post synaptic membrane
Less neurotransmitter released and diffuse across gap
Action potential less likely to occur in post synaptic neurone
describe how PET scans can be used to investigate brain structure
radioactive tracer is absorbed in tissues
detects production of gamma rays
produces a 3D image
describe role of visual stimulation on development of visual cortex during critical period
occular dominance columns develop
neurones form synapses with these cells
impulses along neurones required to strengthen connections
stimulation during ciritical period is needed to form connections in viusal cortex
describe how ions and neurotransmitter molecules are involved in the transmission of an impulse
calcium ions are entering presynaptic neurone
vesicles fuse with presynaptic membrane
vesicles release neurotransmitters that diffuse across presynaptic cleft
neurotransmitter binds to receptors on post-synaptic membrane
sodium ions diffuse into post synaptic cell
action potential on post synaptic membrane occurs
explain how fMRI can be used to identify part of brain involved with interpreting information from visual cortex
detects blood flow in brain
increased blood flow = increased brain activity
oxyhaemoglobin absorbs fewer radio waves
cerebrum
vision and thinking
hypothalamus
thermoregulation
medulla
controls breathing and heart rate
cerebellum
movement and balance
Describe the functions of the enzymes used to genetically modify bacteria
restriction endonuclease used to cut plasmid
forming sticky ends
ligase enzymes used to add isolated gene to plasmid
ligase forms phopshodiester bonds by condensation reaction
recombinant DNA produced
IAA
causes cell elongation
alters pH of cell wall
regulates transcriprtion
makes cellulose cell wall more plastic
Explain how a single base mutation can lead to an altered primary structure of enzyme
change in triplet code
changes codon in mRNA
resulting in different amino acid
Explain how human genome sequencing can be used to identify the mutations associated with the condition
sequence the genome of people with the condition
sequence the genome of a number of people without the condition
compare base sequences to identify mutations found only in individuals with the condition
Explain why genetically modified bacteria delivering drugs ‘to the exact tissue in the body
where they’re needed and nowhere else’ would decrease side effects
drugs not delivered to other tissues
overall dosage needed is less
Describe how flies could be genetically modified to produce one form of the
human TAU protein.
extract mRNA for one form of the TAU protein
copy mRNA into DNA
use restriction enzymes to cut the DNA
insert the TAU DNA into the vector DNA
introduce vector into fertilised egg cell
Describe how bacteria can be genetically modified to produce a cytokine
isolate the gene for the cytokine
use a bacterial plasmid
cut the human DNA and plasmid using the same restriction enzyme
splice the gene and plasmid together using DNA ligase
put modified plasmids in bacterial cell
Give reasons why some people may be concerned about the use of genetically modified plant
transfer of antibitoic resistance gene to other microorganisms
Describe how scientists could produce this short sequence of RNA needed to treat
someone with a condition
transcription of DNA containing mutation to produce mRNA
using RNA polymerase and RNA nucleotides
Explain why the use of RNA technology can be described as personalised
medicine.
targets an individual’s specific mutation
RNA molecule used will be specific to each mutation/individual
Explain the electrical changes in an axon that allow these nerve impulses to be detected.
potential difference across axon changing (-70 to -55)
voltage gated sodium channels open
soidum ions move into axon, causing depolarisation
Sodium channels close and potassium channels open
potassium ions move out of axon, causing repolarisation of membrane
Compare and contrast the structure of a sensory neurone and a motor neurone
both have: cell body containing a nucleus, both have an axon, both have dendirtes at one end of neurone and terminal branches at the other end.
different location of cell body
glycolipids
sugar molecules joined by glycosidic bonds
describe the role of dendrites in a neurone
forms synapses with other neurones
receive impulses from other neurones
involved in summation
initiate an action potential to the axon
describe how adrenlaine changes the heart rate
adrenaline carried in blood
acts on sinoatrial node
increasing frequency of impulses produced by SAN that spread across heart
increasing rate at which heart cintracts
Describe the role of sodium ions in the functioning of a mammalian rod cell
sodium ions are pumped out the rod cell
in the light, sodiudm ions do not move back into rod cell so it is hyperpolarised
in the dark, sodium ions can move back into rod cell so it is depolarised
Explain why the plants were placed in a box in complete darkness.
plants respond to light and show phototropic responses
therefore light must be excluded to study geotropism/effects of gravity
putting plants in the dark prevents light having an effect. light is controlled
Explain how the IAA affects the growth of the coleoptile
IAA diffuses from the tip of the coleoptile
therefore can be taken up by cells in zone of elongation
which causes cell to elongate
this lowers pH in cellulose cell wall
causing coleoptile to grow towards light
Explain the effect of increasing light intensity on the current produced by a rod cell.
increasing light intensity decreases current
rhodopsin is broken down
more opsin binds to sodium-gated voltage channels
these close
making membrane impermeable to sodium ions
Describe the role of IAA (auxin) in the phototropic response of plants
IAA is produced in the tip of shoot
accumulates on the dark side of the shoot
stimulates cell elongation
causing shoot to grow towards light source
Dim light
Radial muscles contact to dilate pulils
Rod cells in dark
Sodium ions are pumped out
They diffuse back in so cell membrane is depolarised
Triggers release of neurotransmitters, which inhibit bipolar neurone so action potential isn’t fired
Rod cells in light
Light energy causes rhodopsin to break into retinal and opsin by bleaching
Sodidum ionn channels close so sodium ions can’t diffuse back in
Cell membrane is hyperpolarised
Bipolar neurone isn’t inhibited so it depolarises and if threshold is met, action potential is transmitted
How is myelinated neurone different
Depolarisation only happens at Nodes of Ranvier
Neurones cytoplasm conducts enough electrical charge to depolarise next node so impulse jumps from node to node
This is saltatory conduction
Red light
Pr is quickly converted into Pfr in red light
Far red light
Pfr is quickly converted into Pr
Darkness (photoreceptors)
Pfr is slowly converted into Pr
Daylight contains more
Red light
Describe role of enzymes involved in synthesis of personalised proteins in GMOs
DNA helicase breaks hydrogen bonds
RNA polymerase involved in making mRNA
forming phosphodiester bonds
Enzymes join amino acids together
Explain role of nervous system in bringing about increase in temperature of fingertip
Thermoreceptors detect increase in temperature
Hypothalamus detects it
More impulses sent along sympathetic begets
Leads to vasodilation
So more warm blood flowed near the skin surface
Why there might be a lighter part in fMRI scan
Due to more activity
Increase in blood flow to this region
fMRI signals not absorbed by oxygenated blood
Compare and contrast use of PET and CT
Both give info on function and structure
PET shows areas that are active
CT gives location/ size
CT uses X rays but PET uses radioactively labelled metabolite
Why does neurone become hyperpolarised
Potassium ions continue leaving axon
Preventing another depolarisation occurring - refractory period
Allowing time for neurone to reset
So nerve impulses travel in only one direction
