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DP IB Biology: HL

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Home / IB / Biology: HL / DP / Topic Questions / 6. Human Physiology / 6.5 Neurones & Synapses / Structured Questions: Paper 2


6.5 Neurones & Synapses

Question 1a

Marks: 3
a)
The image shows a representation of a neurone.uqsE6XvR_e-1a

Identify structures X-Z in the image.

[3 marks]

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    Question 1b

    Marks: 1
    b)

    Branching from structure X of the neurone in part a) are structures known as dendrites.

    State the role of dendrites in the nervous system.

    [1 mark]

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      Question 1c

      Marks: 2
      c)

      Describe the structure of from the image in part a).

      [2 marks]

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        Key Concepts
        Myelination

        Question 1d

        Marks: 2
        d)

        It has been estimated that a neurone without structure Y present can conduct nerve impulses at speeds of 0.5 m s-1 whereas a neurone with structure Y present can conduct impulses at speeds of 150 m s-1.

        Calculate how many times faster impulse conduction is in the presence of structure Y than without structure Y.

        [2 marks]

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          Key Concepts
          Myelination

          Question 2a

          Marks: 3
          a)

          The graph below shows changing membrane potential in an axon within a human leg.

          action-potentials-sq

          At 0.5 ms:

          i)

          Identify the type of membrane potential present in the axon.

          [1 mark]

          ii)

          Explain how this membrane potential has been achieved.

          [2 marks]

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            Key Concepts
            Resting Potential

            Question 2b

            Marks: 1
            b)

            At 1 ms in the graph in part a) the membrane is stimulated.

            State what happens within the membrane at 1 ms as a result of this stimulation.

            [1 mark]

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              Key Concepts
              Action Potential

              Question 2c

              Marks: 3
              c)

              Explain the shape of the curve between 1 - 1.8 ms in the graph in part a).

              [3 marks]

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                Key Concepts
                Action Potential

                Question 2d

                Marks: 2
                d)

                Assuming the intensity of stimulation remains constant, calculate how many complete action potentials will occur in 1 second in the graph shown in part a). Note that there are 1000 ms in a second.

                [2 marks]

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                  Key Concepts
                  Action Potential

                  Question 3a

                  Marks: 2
                  a)

                  The graph below shows the changes in membrane potential that take place in a neurone during a single action potential.

                  action-potential-sq

                  Stages 1 and 5 can be identified as the neurone in its resting state, and during stage 4 the neurone is said to be hyperpolarised.

                  Identify stages 2 and 3 in the graph.

                  [2 marks]

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                    Question 3b

                    Marks: 2
                    b)

                    Explain the change in membrane potential taking place during stage 3 in the graph in part a).

                    [2 marks]

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                      Key Concepts
                      Action Potential

                      Question 3c

                      Marks: 3
                      c)

                      The table below contains a series of statements that describe the propagation of a nerve impulse a long an axon.

                        Sodium ions diffuse along the inside of the axon from an area of high concentration to an area of low concentration
                        A new action potential is generated in the neighbouring section of the axon
                        The recent influx of sodium ions creates a sodium gradient between the stimulated part of the axon and the neighbouring section.
                        If a depolarisation threshold is reached new sodium ion channels open

                      Identify the correct sequence of events by writing the numbers 1-4 in the blank boxes. The first event should be number 1, and so on.

                      [3 marks]

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                        Question 3d

                        Marks: 1
                        d)

                        State the role of the refractory period in the propagation of action potentials.

                        [1 mark]

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                          Key Concepts
                          Action Potential

                          Question 4a

                          Marks: 3
                          a)

                          The image below shows a representation of a junction between two neurones.

                          synapse-sq

                          Identify structures A-C.

                          [3 marks]

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                            Key Concepts
                            Synapses

                            Question 4b

                            Marks: 2
                            b)

                            Part a) shows that the junctions between neurones contain molecules known as neurotransmitters.

                            Outline how neurotransmitters interact with the structures labelled D to bring about an action potential in the new neurone.

                            [2 marks]

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                              Key Concepts
                              Synapses

                              Question 4c

                              Marks: 1
                              c)

                              Once its role is complete the neurotransmitter needs to be broken down and recycled in order for the junction between neurones to continue functioning.

                              Identify an enzyme that is involved with the breakdown of neurotransmitter molecules.

                              [1 mark]

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                                Key Concepts
                                Acetylcholine

                                Question 4d

                                Marks: 1
                                d)

                                Neonicotinoids are chemicals used in some types of pesticide. Neonicotinoids have a similar function to certain neurotransmitters in the nervous systems of insects, with one major difference being that the enzyme in part c) cannot break them down.

                                Suggest why the enzyme in part c) cannot break down neonicotinoids.

                                [1 mark]

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                                  Question 5a

                                  Marks: 3

                                  One mark is available for clarity of communication throughout this question.

                                  a)

                                  Outline the role of the myelin sheath in nerve transmission.

                                  [3 marks]

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                                    Key Concepts
                                    Myelination

                                    Question 5b

                                    Marks: 5
                                    b)

                                    Draw a labelled diagram of a neurone.

                                    [5 marks]

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