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L22+23 Bioelectricity: Action Potentials and Synapses in Neurons

Description

• 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.
Mer Scott
Quiz by Mer Scott, updated more than 1 year ago
Mer Scott
Created by Mer Scott over 7 years ago
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Resource summary

Question 1

Question
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.
Answer
  • stimulus
  • Na+
  • depolarise
  • -59mV
  • voltage
  • excitatory
  • enters
  • exits
  • action potential
  • close
  • voltage gated K+ channels
  • K+
  • repolarisation
  • Hyperpolarisation

Question 2

Question
The refractory period is one mechanism that determines the direction of propagation of an action potential. Choose the correct statements about refractory periods.
Answer
  • There are two refractory periods.
  • The initial refractory period is the absolute refractory period.
  • The relative refractory period follows the absolute refractory period.
  • The relative refractory period is the shortest of the periods (in ms)
  • There is no response during the absolute period
  • The relative period requires a large stimulus
  • The absolute period is measured from the opening of voltage gated Na+ channels to the action potential
  • The relative period is measured from the action potential to the hyperpolarisation of the cell
  • The refractory period is an intrinsic feature of the Na+ channels

Question 3

Question
The mechanism of the refractory period:
Answer
  • depends on the inactive state of K+ channels after activation
  • relies on the fact that inactive channels do not respond to the electric field
  • prevents backward movement
  • relies on an inactive but open state

Question 4

Question
The action potential 'leaping' over the Nodes of Ranvier as it propagates is saltatory conduction.
Answer
  • True
  • False

Question 5

Question
Choose the incorrect statement about electrical synapses.
Answer
  • They are linked by gap junctions.
  • There is a direct connection between neurons.
  • Charge needs to be 'stored' at the terminus of the presynaptic neuron.
  • It is the fastest method of synapsing.

Question 6

Question
Choose the incorrect statement about chemical synapses.
Answer
  • There is no physical link between the two neurons.
  • The propagation of the action potential is direct.
  • A chemical messenger/neurotransmitter has to be 'stored' in the synaptic knob of the presynaptic neuron.
  • It is slower than electrical synapses.
  • The NMJ is an example of a specific chemical synapse.

Question 7

Question
Choose the correct statements about the structure of pre- and post- synaptic neurons.
Answer
  • Stimulus gated Na+ channels are most critical and most concentrated at the input zones of neurons.
  • Stimulus gated Ca+ channels at the presynaptic knob allow vesicle release.
  • Vesicles containing neurotransmitter reside in the postsynaptic knob.
  • Mitochondria are present at the synapse.

Question 8

Question
Without a higher concentration of calcium in the ECF compared to the ICF, you cannot trigger the release of vesicles in a synapse.
Answer
  • True
  • False

Question 9

Question
Stimulus gated channels also act as receptors.
Answer
  • True
  • False

Question 10

Question
If stimulus gated channels are Cl- or K+, hyperpolarisation occurs and this is inhibitory.
Answer
  • True
  • False

Question 11

Question
Which of these is not a method of closing/switching off a synapse?
Answer
  • Degradation by enzymes
  • Reuptake of neurotransmitter into the knob
  • Diffusion/reuptake of neurotransmitter into glia cells
  • Mitochondrial uptake of neurotransmitter

Question 12

Question
Choose the correct statement. EPSP is:
Answer
  • Excitatory Post Synaptic Potential (Net depolarisation)
  • Excitatory Pre Synaptic Potential (Net hyperpolarisation)
  • Electric Post Synaptic Potential (Net depolarisation)
  • Electric Post Synaptic Potential (Net hyperpolarisation)

Question 13

Question
IPSP stands for Inhibitory Post Synaptic Potential, and is a net depolarisation due to K+ or Cl- channels.
Answer
  • True
  • False
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