AHL Content Statements

• C2.2.8

  Depolarization and repolarization during action potentials
  

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  Include the action of voltage-gated sodium and potassium channels and the need for a threshold potential to be reached for sodium channels to open.
  

• C2.2.9

  Propagation of an action potential along a nerve fibre/axon as a result of local currents
  

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  Students should understand how diffusion of sodium ions both inside and outside an axon can cause the threshold potential to be reached.
  

• C2.2.10

  Oscilloscope traces showing resting potentials and action potentials

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  AOS: Students should interpret the oscilloscope trace in relation to cellular events. The number of impulses per second can be measured.

• C2.2.11

  Saltatory conduction in myelinated fibres to achieve faster impulses

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  Students should understand that ion pumps and channels are clustered at nodes of Ranvier and that an action potential is propagated from node to node.

• C2.2.12

  Effects of exogenous chemicals on synaptic transmission

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  Use neonicotinoids as an example of a pesticide that blocks synaptic transmission, and cocaine as an example of a drug that blocks reuptake of the neurotransmitter.

• C2.2.13

  Inhibitory neurotransmitters and generation of inhibitory postsynaptic potentials

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  Students should know that the postsynaptic membrane becomes hyperpolarized.

• C2.2.14

  Summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron

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  Multiple presynaptic neurons interact with all-or-nothing consequences in terms of postsynaptic depolarization.
  

• C2.2.15

  Perception of pain by neurons with free nerve endings in the skin

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  Students should know that these nerve endings have channels for positively charged ions, which open in response to a stimulus such as high temperature, acid, or certain chemicals such as capsaicin in chilli peppers. Entry of positively charged ions causes the threshold potential to be reached and nerve impulses then pass through the neurons to the brain, where pain is perceived.

• C2.2.16

  Consciousness as a property that emerges from the interaction of individual neurons in the brain

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  Emergent properties such as consciousness are another example of the consequences of interaction.

• B2.1.14

  Gated ion channels in neurons
  

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  Include nicotinic acetylcholine receptors as an example of a neurotransmitter-gated ion channel and sodium and potassium channels as examples of voltage-gated channels.

• C2.1.8

  Transmembrane receptors for neurotransmitters and changes to membrane potential

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  Use the acetylcholine receptor as an example. Binding to a receptor causes the opening of an ion channel in the receptor that allows positively charged ions to diffuse into the cell. This changes the voltage across the plasma membrane, which may cause other changes.