Nerve Impulses Flashcards
Multiple sclerosis ( MS ) is a disease that involves damage to the myelin sheaths of neurones. Movement in MS sufferers may be jerky or slow.
Damage to the myelin sheaths of neurones can lead to problems controlling the contraction of muscles.
Suggest one reason why.
Damage to the myelin sheaths of neurones can lead to problems controlling the contraction of muscles because:
- Action potentials travel more slowly
- So there would be a delay in muscle contration
Scientists investigated the use of substances called cannabinoids to control muscle problems caused by MS.
Cannabinoids are hydrophobic molecules.
In the body, they easily pass into neurones.
Explain why.
( Multiple sclerosis ( MS ) is a disease that involves damage to the myelin sheaths of neurones.
Movement in MS sufferers may be jerky or slow. )
Cannabinoids passes into neurones easily because:
- Cannabinoids are lipid-soluble
Cannabinoid receptors are found in the pre-synaptic membrane of neuromuscular junctions.
When a cannabinoid binds to its receptor, it closes calcium ion channels.
Suggest how cannabinoids could prevent muscle contraction.
( Scientists investigated the use of substances called cannabinoids to control muscle problems caused by MS.
Cannabinoids are hydrophobic molecules.
In the body, they easily pass into neurones. )
Cannabinoids could prevent muscle contraction because:
- It prevents the influx of calcium ions ( into the pre-synaptic membrane )
- So synaptic vesicles don’t fuse with the membrane
- Neurotransmitters don’t diffuse across the synapse
- No depolarisation occurs
Cannabinoids include substances found in cannabis that can enter brain tissue.
Scientists are developing artificial cannabinoids that can enter neuromuscular junctions but cannot enter brain tissue.
Suggest why these artificial cannabinoids would be better to use than cannabis when treating someone with MS.
( Scientists investigated the use of substances called cannabinoids to control muscle problems caused by MS.
Cannabinoids are hydrophobic molecules.
In the body, they easily pass into neurones. )
( Multiple sclerosis ( MS ) is a disease that involves damage to the myelin sheaths of neurones.
Movement in MS sufferers may be jerky or slow. )
Artificial cannabinoids would be better to use than cannabis when treating someone with MS because:
- They won’t affect the synapses in the brain
- So they won’t damage the brain
A biologist investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip.
She used microelectrodes to measure the maximum membrane potential of a Pacinian corpuscle and its sensory neurone when different pressures were applied to the fingertip.
The figure below shows the Pacinian corpuscle, its sensory neurone and the position of the microelectrodes.
( The figure shows a panician corpuscle )
( It is labelled with “ Microelectrode P “ and “ Microelectrode Q “ )
( “ Microelectrode P “ is located in the panician corpuscle, “ Microelectrode Q “ is located at the end of the neuron, between the myelin sheath )
( The sections of the panician corpuscle are also labelled, the head is labelled “ Pacinian corpuscle “, and the tail is labelled “ Sensory neurone “ )
The table below shows some of the biologist’s results.
Pressure applied to the fingertip:
1 ) None
2 ) Light
3 ) Medium
4 ) Heavy
Membrane potential at P / millivolts:
1 ) - 70
2 ) - 50
3 ) + 30
4 ) + 40
Membrane potential at Q / millivolts
1 ) - 70
2 ) - 70
3 ) + 40
4 ) + 40
Explain how the resting potential of - 70 mV is maintained in the sensory neurone when no pressure is applied.
The resting potential of - 70 mV is maintained in the sensory neurone when no pressure is applied by:
- The membrane is more permeable to potassium ions and less permeable to sodium ions
- So sodium ions are actively transported out and potassium ions are pumped in
Explain how applying pressure to the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode P.
( A biologist investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip.
She used microelectrodes to measure the maximum membrane potential of a Pacinian corpuscle and its sensory neurone when different pressures were applied to the fingertip.
The figure below shows the Pacinian corpuscle, its sensory neurone and the position of the microelectrodes.
( The figure shows a panician corpuscle )
( It is labelled with “ Microelectrode P “ and “ Microelectrode Q “ )
( “ Microelectrode P “ is located in the panician corpuscle, “ Microelectrode Q “ is located at the end of the neuron, between the myelin sheath )
( The sections of the panician corpuscle are also labelled, the head is labelled “ Pacinian corpuscle “, and the tail is labelled “ Sensory neurone “ )
The table below shows some of the biologist’s results.
Pressure applied to the fingertip:
1 ) None
2 ) Light
3 ) Medium
4 ) Heavy
Membrane potential at P / millivolts:
1 ) - 70
2 ) - 50
3 ) + 30
4 ) + 40
Membrane potential at Q / millivolts
1 ) - 70
2 ) - 70
3 ) + 40
4 ) + 40 )
Applying pressure to the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode P by:
- Pressure causes membrane to become deformed
- Sodium ion channels in the memebrane open and sodium ions move in
- The greater the pressure, the more sodium channels open
The membrane potential at Q was the same whether medium or heavy pressure was applied to the finger tip.
Explain why.
( A biologist investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip.
She used microelectrodes to measure the maximum membrane potential of a Pacinian corpuscle and its sensory neurone when different pressures were applied to the fingertip.
The figure below shows the Pacinian corpuscle, its sensory neurone and the position of the microelectrodes.
( The figure shows a panician corpuscle )
( It is labelled with “ Microelectrode P “ and “ Microelectrode Q “ )
( “ Microelectrode P “ is located in the panician corpuscle, “ Microelectrode Q “ is located at the end of the neuron, between the myelin sheath )
( The sections of the panician corpuscle are also labelled, the head is labelled “ Pacinian corpuscle “, and the tail is labelled “ Sensory neurone “ )
The table below shows some of the biologist’s results.
Pressure applied to the fingertip:
1 ) None
2 ) Light
3 ) Medium
4 ) Heavy
Membrane potential at P / millivolts:
1 ) - 70
2 ) - 50
3 ) + 30
4 ) + 40
Membrane potential at Q / millivolts
1 ) - 70
2 ) - 70
3 ) + 40
4 ) + 40 )
Membrane potential at Q was the same whether medium or heavy pressure was applied to the finger tip because:
- Threshold has been reached
- ( Thershold or above ) causes the all or nothing principle
Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed.
Explain how this results in slower responses to stimuli.
( A biologist investigated the stimulation of a Pacinian corpuscle in the skin of a fingertip.
She used microelectrodes to measure the maximum membrane potential of a Pacinian corpuscle and its sensory neurone when different pressures were applied to the fingertip.
The figure below shows the Pacinian corpuscle, its sensory neurone and the position of the microelectrodes.
( The figure shows a panician corpuscle )
( It is labelled with “ Microelectrode P “ and “ Microelectrode Q “ )
( “ Microelectrode P “ is located in the panician corpuscle, “ Microelectrode Q “ is located at the end of the neuron, between the myelin sheath )
( The sections of the panician corpuscle are also labelled, the head is labelled “ Pacinian corpuscle “, and the tail is labelled “ Sensory neurone “ )
The table below shows some of the biologist’s results.
Pressure applied to the fingertip:
1 ) None
2 ) Light
3 ) Medium
4 ) Heavy
Membrane potential at P / millivolts:
1 ) - 70
2 ) - 50
3 ) + 30
4 ) + 40
Membrane potential at Q / millivolts
1 ) - 70
2 ) - 70
3 ) + 40
4 ) + 40 )
Parts of the myelin sheaths surrounding neurones being destroyed results in slower responses to stimuli because:
- The impulse is unable to jump from node to node
- More depolarisation over the length is required
Malaria is a disease that is spread by insects called mosquitoes.
In Africa, DDT is a pesticide used to kill mosquitoes, to try to control the spread of malaria.
Mosquitoes have a gene called KDR.
Today, some mosquitoes have an allele of this gene, KDR minus, that gives them resistance to DDT.
The other allele, KDR plus, does not give resistance.
Scientists investigated the frequency of the KDR minus allele in a population of mosquitoes in an African country over a period of 10 years.
The figure below shows the scientists’ results.
( The figure shows a graph, “ Percentage of KDR minus allele in population “ against “ Year “ )
( The scale of “ Percentage of KDR minus allele in population “ is 0 - 60 )
( The scale of “ Year “ starts from 1999 - 2009 )
( The line graph starts from 0 in “ Percentage of KDR minus allele in population “ and reaches 54 in “ Percentage of KDR minus allele in population “ )
( The line graph is a staggered graph )
( At 2003, the “ Percentage of KDR minus allele in population “ is 20 )
Use the Hardy-Weinberg equation to calculate the frequency of mosquitoes heterozygous for the KDR gene in this population in 2003.
Show your working.
- Heterozygous = 2pq
- Frequency of mosquitoes heterozygous for the KDR gene in this population in 2003 = 0.32
Suggest an explanation for the results in the figure above.
( Malaria is a disease that is spread by insects called mosquitoes.
In Africa, DDT is a pesticide used to kill mosquitoes, to try to control the spread of malaria.
Mosquitoes have a gene called KDR.
Today, some mosquitoes have an allele of this gene, KDR minus, that gives them resistance to DDT.
The other allele, KDR plus, does not give resistance.
Scientists investigated the frequency of the KDR minus allele in a population of mosquitoes in an African country over a period of 10 years.
The figure below shows the scientists’ results.
( The figure shows a graph, “ Percentage of KDR minus allele in population “ against “ Year “ )
( The scale of “ Percentage of KDR minus allele in population “ is 0 - 60 )
( The scale of “ Year “ starts from 1999 - 2009 )
( The line graph starts from 0 in “ Percentage of KDR minus allele in population “ and reaches 54 in “ Percentage of KDR minus allele in population “ )
( The line graph is a staggered graph )
( At 2003, the “ Percentage of KDR minus allele in population “ is 20 ) )
The results above show:
- KDR minus has undergone a mutation to become a resistant allele
- DDT used provides a selection pressure
- Mosquitos with the KDR minus allele are more likely to survive and reproduce
- Leading to an increase in KDR minus allele in the population
The KDR plus allele codes for the sodium ion channels found in neurones.
When DDT binds to a sodium ion channel, the channel remains open all the time.
Use this information to suggest how DDT kills insects.
( Malaria is a disease that is spread by insects called mosquitoes.
In Africa, DDT is a pesticide used to kill mosquitoes, to try to control the spread of malaria.
Mosquitoes have a gene called KDR.
Today, some mosquitoes have an allele of this gene, KDR minus, that gives them resistance to DDT.
The other allele, KDR plus, does not give resistance.
Scientists investigated the frequency of the KDR minus allele in a population of mosquitoes in an African country over a period of 10 years.
The figure below shows the scientists’ results.
( The figure shows a graph, “ Percentage of KDR minus allele in population “ against “ Year “ )
( The scale of “ Percentage of KDR minus allele in population “ is 0 - 60 )
( The scale of “ Year “ starts from 1999 - 2009 )
( The line graph starts from 0 in “ Percentage of KDR minus allele in population “ and reaches 54 in “ Percentage of KDR minus allele in population “ )
( The line graph is a staggered graph )
( At 2003, the “ Percentage of KDR minus allele in population “ is 20 ) )
DDT kills insects by:
- Allowing neurones to stay depolarised
- So no action potentials are produced
Suggest how the KDR minus allele gives resistance to DDT.
( Malaria is a disease that is spread by insects called mosquitoes.
In Africa, DDT is a pesticide used to kill mosquitoes, to try to control the spread of malaria.
Mosquitoes have a gene called KDR.
Today, some mosquitoes have an allele of this gene, KDR minus, that gives them resistance to DDT.
The other allele, KDR plus, does not give resistance.
Scientists investigated the frequency of the KDR minus allele in a population of mosquitoes in an African country over a period of 10 years.
The figure below shows the scientists’ results.
( The figure shows a graph, “ Percentage of KDR minus allele in population “ against “ Year “ )
( The scale of “ Percentage of KDR minus allele in population “ is 0 - 60 )
( The scale of “ Year “ starts from 1999 - 2009 )
( The line graph starts from 0 in “ Percentage of KDR minus allele in population “ and reaches 54 in “ Percentage of KDR minus allele in population “ )
( The line graph is a staggered graph )
( At 2003, the “ Percentage of KDR minus allele in population “ is 20 ) )
KDR minus allele gives resistance to DDT by:
- The mutation changes the shape of the sodium ion channel
- DDT is no longer complementary to the sodium ion channels
A myelinated axon conducts impulses faster than a non-myelinated axon.
Explain this difference.
The difference between myelinated and non-myelinated axon are:
- Myelinated axons have depolarisation only at nodes
- In Myelinated axons, nerve impulese jump from node to node
- Action potential in myelinated axons don’t travel along the whole length
Doctors investigated the relationship between myelin in brain tissue and different types of dementia.
All types of dementia involve loss of mental ability.
The doctors measured the mean amount of myelin in samples of brain tissue from:
- a control group of 12 people without dementia
- 20 people with vascular dementia (VaD)
- 19 people with Alzheimer’s dementia (AD)
- 31 people with Lewy body dementia (LD).
The doctors’ results are shown in the figure.
The vertical bars show standard errors.
( The figure shows four bar graphs )
( The axis is “ Mean amount of myelin in samples of brain tissue / arbitrators units “ against “ Group of people “ )
( The four bar graphs are labelled “ Control “, “ VaD “, “ AD “ and “ LD “ respectively )
( The scale of “ Mean amount of myelin in samples of brain tissue / arbitrators units “ is 0 - 60 )
( In ranked order from highest to lowest; “ Control “, “ LD “, “ AD “ and “ VaD “ )
( Standard deviations don’t overlap )
The doctors used a statistical test to compare the results for AD and LD.
They obtained a value for P of 0.047.
What does this result show about the difference between the means for AD and LD?
Use the words probability and chance in your answer.
This result shows that the difference between the means for AD and LD is:
- Probability of obtaining this difference by chance
- Is less than 0.05
- ( So difference is significant )
A student who read this investigation concluded that there was a relationship between the amount of myelin in a person’s brain and whether or not they had dementia.
Do these data support this conclusion?
Give reasons for your answer.
( Doctors investigated the relationship between myelin in brain tissue and different types of dementia.
All types of dementia involve loss of mental ability.
The doctors measured the mean amount of myelin in samples of brain tissue from:
- a control group of 12 people without dementia
- 20 people with vascular dementia (VaD)
- 19 people with Alzheimer’s dementia (AD)
- 31 people with Lewy body dementia (LD).
The doctors’ results are shown in the figure.
The vertical bars show standard errors.
( The figure shows four bar graphs )
( The axis is “ Mean amount of myelin in samples of brain tissue / arbitrators units “ against “ Group of people “ )
( The four bar graphs are labelled “ Control “, “ VaD “, “ AD “ and “ LD “ respectively )
( The scale of “ Mean amount of myelin in samples of brain tissue / arbitrators units “ is 0 - 60 )
( In ranked order from highest to lowest; “ Control “, “ LD “, “ AD “ and “ VaD “ )
( Standard deviations don’t overlap ) )
The data may support this conclusion because:
- All dementia results are lower than the control group
- Error bars don’t overlap, so differences are signinficant
- However dementia may be due to other factors
- Because there’s signinficant differences in myelin in different demetia
