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L22+23 Bioelectricity: Action Potentials and Synapses in Neurons

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  1. 1The 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.
    1. Astimulus
    2. BNa+
    3. Cdepolarise
    4. D-59mV
    5. Evoltage
    6. Fexcitatory
    7. Genters
    8. Hexits
    9. Iaction potential
    10. Jclose
    11. Kvoltage gated K+ channels
    12. LK+
    13. Mrepolarisation
    14. NHyperpolarisation
  2. 2The refractory period is one mechanism that determines the direction of propagation of an action potential. Choose the correct statements about refractory periods.
    1. AThere are two refractory periods.
    2. BThe initial refractory period is the absolute refractory period.
    3. CThe relative refractory period follows the absolute refractory period.
    4. DThe relative refractory period is the shortest of the periods (in ms)
    5. EThere is no response during the absolute period
    6. FThe relative period requires a large stimulus
    7. GThe absolute period is measured from the opening of voltage gated Na+ channels to the action potential
    8. HThe relative period is measured from the action potential to the hyperpolarisation of the cell
    9. IThe refractory period is an intrinsic feature of the Na+ channels
  3. 3The mechanism of the refractory period:
    1. Adepends on the inactive state of K+ channels after activation
    2. Brelies on the fact that inactive channels do not respond to the electric field
    3. Cprevents backward movement
    4. Drelies on an inactive but open state
  4. 4The action potential 'leaping' over the Nodes of Ranvier as it propagates is saltatory conduction.
    1. AVerdadero
    2. BFalso
  5. 5Choose the incorrect statement about electrical synapses.
    1. AThey are linked by gap junctions.
    2. BThere is a direct connection between neurons.
    3. CCharge needs to be 'stored' at the terminus of the presynaptic neuron.
    4. DIt is the fastest method of synapsing.
  6. 6Choose the incorrect statement about chemical synapses.
    1. AThere is no physical link between the two neurons.
    2. BThe propagation of the action potential is direct.
    3. CA chemical messenger/neurotransmitter has to be 'stored' in the synaptic knob of the presynaptic neuron.
    4. DIt is slower than electrical synapses.
    5. EThe NMJ is an example of a specific chemical synapse.
  7. 7Choose the correct statements about the structure of pre- and post- synaptic neurons.
    1. AStimulus gated Na+ channels are most critical and most concentrated at the input zones of neurons.
    2. BStimulus gated Ca+ channels at the presynaptic knob allow vesicle release.
    3. CVesicles containing neurotransmitter reside in the postsynaptic knob.
    4. DMitochondria are present at the synapse.
  8. 8Without a higher concentration of calcium in the ECF compared to the ICF, you cannot trigger the release of vesicles in a synapse.
    1. AVerdadero
    2. BFalso
  9. 9Stimulus gated channels also act as receptors.
    1. AVerdadero
    2. BFalso
  10. 10If stimulus gated channels are Cl- or K+, hyperpolarisation occurs and this is inhibitory.
    1. AVerdadero
    2. BFalso

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Descripción
• List the events that must occur for the action potential to happen, know the two types of refractory period of the axon. • Know the two types of synapse and how they differ. • List the structures that make up a chemical synapse. • Explain the steps that must occur for synaptic transmission to occur. • Know the mechanisms that terminate the chemical signal.
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