chapter 15 exam questions Flashcards
explain how a resting potential is maintained across the axon membrane in a neurone (3)
-potassium ions diffuse out
-sodium ions diffuse in
-sodium ions actively transported out and potassium ions in
-membrane is more permeable to potassium ions.
explain why the speed of transmission of impulses is faster along a myelinated vs non myelinated sheath (3)
non myelinated sheash- depolarisation occurs across whole length of axon
-myelinated sheath- saltatory conduction/impulses jump from node to node
-sheath provides electrical insulation.
A scientist investigated the effect of inhibitors on neurones. She added a
respiratory inhibitor to a neurone. The resting potential of the neurone
changed from –70 mV to 0 mV.
explain why (3)
-less ATP
-less active transport of ions
-electrochemical gradient not maintained.
Describe the sequence of events involved in transmission across a cholinergic
synapse.
Do not include details on the breakdown of acetylcholine in your answer (5)
-depolarisation of pre synaptic membrane
-calcium ion channels open and calcium ions enter.
-synaptic vesicles move towards/fuse with pre synaptic membrane and neurotransmitter/acetylcholine is released
-neurotransmitter diffuses across synapse
-binds to receptors on post synaptic membrane
-sodium ions enter leading to depolarisation
Dopamine is a neurotransmitter released in some synapses in the brain.
The transmission of dopamine is similar to that of acetylcholine.
Dopamine stimulates the production of nerve impulses in postsynaptic
neurones.
Describe how.
Do not include in your answer the events leading to the release of
dopamine and the events following production of nerve impulses at
postsynaptic neurones. (3)
-dopamine diffuses across synapse
-binds to receptors on post synaptic membrane
-stimulates entry of sodium ions and depolarisation.
Dopamine has a role in numerous processes in the brain including pain
relief. The release of dopamine can be stimulated by chemicals called
endorphins produced in the brain. Endorphins attach to opioid receptors on
presynaptic neurones that release dopamine.
Morphine is a drug that has a similar structure to endorphins and can
provide pain relief.
Explain how (2)
-morphine attaches to opiod receptors
-dopamine released
GABA is a neurotransmitter released in some inhibitory synapses in the
brain. GABA causes negatively charged chloride ions to enter postsynaptic
neurones.
Explain how this inhibits postsynaptic neurones (3)
-hyperpolarisation
-more sodium ions needed
-for depolarisation
Alzheimer’s disease (AD) is a non-reversible brain disorder that develops over a
number of years. At the start of 2014 the number of Americans with AD was
estimated to be 5.4 million. Every 30 seconds another person in America
develops AD.
5 In the brain of a person with AD there is a lower concentration of acetylcholine.
This affects communication between nerve cells and initially results in memory
loss and confusion. Some of the symptoms of AD that are associated with
communication between nerve cells are reduced by taking the drug donepezil.
Donepezil inhibits the enzyme acetylcholinesterase.
10 A gene mutation called E280A found on chromosome 14 causes early-onset AD
at a mean age of 49 years. The age at which the E280A mutation is expressed
to cause AD varies.
Yaramul is a town in a historically isolated region of the Andes Mountains. The
population of this town has the highest frequency of the E280A mutation in the
15 world. The origin of the E280A mutation in this population has been traced back
to a common ancestor in the 17th century. Natural selection has not reduced
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the frequency of the E280A mutation in the population.
This autosomal dominant mutation involves a change in triplet 280 from GAA to
GCA. Scientists analysed chromosome 14 from 102 individuals from Yaramul.
20 They recorded a sample size of 204 and detected 75 E280A mutations but only
74 potential AD cases. The scientists identified individuals with the mutation by
whole genome sequencing. They had decided that a DNA probe would not be a
suitable method to detect the E280A mutation
explain how donepezil could improve communication between nerve cells. (3)
-less acetylcholine inhibited
-acetylcholine attaches to receptors
-more sodium ions for depolarisation.
When a nerve impulse arrives at a synapse, it causes the release of
neurotransmitter from vesicles in the presynaptic knob.
Describe how (3)
-calcium ion channels open
-calcium ions diffuse in
-causes vesicles to fuse with pre synaptic membrane
This movement of mitochondria happens when nerve impulses arrive at the
synapse.
Suggest and explain one advantage of the movement of mitochondria
towards the presynaptic membrane when nerve impulses arrive at the
synapse (2)
mitochondria supply ATP
for active transport of ions
mutliple sclerosis is a disease involving damage to myelin sheaths of neurones. Movement in MS sufferers may be jerky/slow
damage to the myelin sheaths of neurones can lead to problems in controlling muscle contraction.
suggest how (2)
-action potentials don’t travel
-so muscles don’t contract
cannabinoid receptors are found in the pre synaptic membrane of neuromusclar junctions. When a cannabinoid binds to its receptor, sodium ion channels close.
suggest how cannabinoids prevent muscle contraction. (4)
-prevents influx of calcium ions into pre synaptic membrane
vesicles don’t bind to membrane
-neurotransmitter doesn’t diffuse across synapse
-no action potential generated.
cannabinoids include substances found in cannabis that can enter brain tissue. scientists are developing artifical cannabinoid sthat can enter neuromusclar junctions but can’t enter brain tissue.
suggest why they would be better to use than cannabis when treating someone with ms (2)
-won’t damage brain
-so only muscle affected
it is important that a neurotransmitter e.g. seretonin is transported back out of synapses. Explain why. (2)
-continues to bind to receptors
-keeps sodium ion channels open/continues to generate action potentials
synapses are uni directional. explain how acetyl choline contributes to synapses being unidirectional. (2)
-released from pre SN
-diffuses from high to low concentration
