8839983
Descrição
Questão 1
Questão
The timing and sequence of events leading up to and when carrying out an action potential in a neuron are critical.
Firstly, [blank_start]stimulus[blank_end] gated [blank_start]Na+[blank_end] channels open, and begin to [blank_start]depolarise[blank_end] the cell. If the threshold potential of [blank_start]-59mV[blank_end] is reached, the [blank_start]voltage[blank_end] gated Na+ channels open and the cell begins to rapidly depolarise (an [blank_start]excitatory[blank_end] function) as Na+ [blank_start]enters[blank_end] the cell. When the membrane potential reaches +30mV it is at it's maximum, and this is is the [blank_start]action potential[blank_end] which causes propagation along the axon without losing amplitude. At +30mV, the Na+ channels [blank_start]close[blank_end] and the [blank_start]voltage gated K+ channels[blank_end] open. [blank_start]K+[blank_end] rapidly leaves the cell, and [blank_start]repolarisation[blank_end] occurs. [blank_start]Hyperpolarisation[blank_end] beyond the RMP usually occurs.
The cell is returned to RMP by pumping the ions against their gradient, which is done by Na+/K+ ATPase.
Responda
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stimulus
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Na+
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depolarise
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-59mV
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voltage
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excitatory
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enters
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exits
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action potential
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close
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voltage gated K+ channels
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K+
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repolarisation
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Hyperpolarisation
Questão 2
Questão
The refractory period is one mechanism that determines the direction of propagation of an action potential. Choose the correct statements about refractory periods.
Responda
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There are two refractory periods.
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The initial refractory period is the absolute refractory period.
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The relative refractory period follows the absolute refractory period.
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The relative refractory period is the shortest of the periods (in ms)
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There is no response during the absolute period
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The relative period requires a large stimulus
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The absolute period is measured from the opening of voltage gated Na+ channels to the action potential
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The relative period is measured from the action potential to the hyperpolarisation of the cell
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The refractory period is an intrinsic feature of the Na+ channels
Questão 3
Questão
The mechanism of the refractory period:
Responda
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depends on the inactive state of K+ channels after activation
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relies on the fact that inactive channels do not respond to the electric field
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prevents backward movement
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relies on an inactive but open state
Questão 4
Questão
The action potential 'leaping' over the Nodes of Ranvier as it propagates is saltatory conduction.
Responda
- True
- False
Questão 5
Questão
Choose the incorrect statement about electrical synapses.
Responda
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They are linked by gap junctions.
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There is a direct connection between neurons.
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Charge needs to be 'stored' at the terminus of the presynaptic neuron.
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It is the fastest method of synapsing.
Questão 6
Questão
Choose the incorrect statement about chemical synapses.
Responda
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There is no physical link between the two neurons.
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The propagation of the action potential is direct.
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A chemical messenger/neurotransmitter has to be 'stored' in the synaptic knob of the presynaptic neuron.
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It is slower than electrical synapses.
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The NMJ is an example of a specific chemical synapse.
Questão 7
Questão
Choose the correct statements about the structure of pre- and post- synaptic neurons.
Responda
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Stimulus gated Na+ channels are most critical and most concentrated at the input zones of neurons.
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Stimulus gated Ca+ channels at the presynaptic knob allow vesicle release.
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Vesicles containing neurotransmitter reside in the postsynaptic knob.
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Mitochondria are present at the synapse.
Questão 8
Questão
Without a higher concentration of calcium in the ECF compared to the ICF, you cannot trigger the release of vesicles in a synapse.
Responda
- True
- False
Questão 9
Questão
Stimulus gated channels also act as receptors.
Responda
- True
- False
Questão 10
Questão
If stimulus gated channels are Cl- or K+, hyperpolarisation occurs and this is inhibitory.
Responda
- True
- False
Questão 11
Questão
Which of these is not a method of closing/switching off a synapse?
Responda
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Degradation by enzymes
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Reuptake of neurotransmitter into the knob
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Diffusion/reuptake of neurotransmitter into glia cells
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Mitochondrial uptake of neurotransmitter
Questão 12
Questão
Choose the correct statement. EPSP is:
Responda
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Excitatory Post Synaptic Potential (Net depolarisation)
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Excitatory Pre Synaptic Potential (Net hyperpolarisation)
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Electric Post Synaptic Potential (Net depolarisation)
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Electric Post Synaptic Potential (Net hyperpolarisation)
Questão 13
Questão
IPSP stands for Inhibitory Post Synaptic Potential, and is a net depolarisation due to K+ or Cl- channels.
Responda
- True
- False
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