Scheme of Work Cambridge International as & a level

15.1.2 Compare the features of the nervous system and the endocrine system.

15.1.3 Describe the structure and function of a sensory neurone and a motor neurone and state that intermediate neurones connect sensory neurones and motor neurones.

15.1.4 Outline the role of sensory receptor cells in detecting stimuli and stimulating the transmission of impulses in sensory neurones.

15.1.5 Describe the sequence of events that results in an action potential in a sensory neurone, using a chemoreceptor cell in a human taste bud as an example.

15.1.6 Describe and explain changes to the membrane potential of neurones.

15.1.7 Describe and explain the rapid transmission of an impulse in a myelinated neurone with reference to saltatory conduction.

15.1.8 Explain the importance of the refractory period in determining the frequency of impulses.

15.1.9 Describe the structure of a cholinergic synapse and explain how it functions, including the role of calcium ions.

Refresh learners’ knowledge of membrane proteins involved in transport (Topic 4). Ask a series of questions that require learners to recall key terms. (F)

Learners investigate reflexes by comparing their reaction times when responding to sight, touch and sound. They can then analyse their data, using the t-test to assess the statistical significance of the differences, and evaluate their method. Help learners link their observations with the mechanism involving different types of neurone and how sensory receptor cells detect stimuli and stimulate the transmission of impulses in sensory neurones. (I)

Display diagrams or animations to show the outside and the inside of a neurone to explain the events associated with depolarisation. Learners prepare axes on graph paper and sketch the changes to potential as each stage is discussed. Learners annotate the graph, explaining what is occurring at different time points: resting potential, rising and falling phases of action potential, and refractory period. An excellent interactive demonstration of nervous impulses is at:

Animations to further support this activity include: www.sumanasinc.com/webcontent/animations/neurobiology.html and http://highered.mheducation.com/sites/0072943696/student_view0/chapter8/animation__voltage-gated_channels_and_the_action_potential__quiz_1_.html

Arrange learners into a long line and ask them to model how action potentials are propagated along neurones. Ask a learner at one end to ‘send an impulse’ by asking them to raise an arm and then lower it very quickly. The movement of the arm represents depolarisation. The learner next to them should then do the same, and so on, until the ‘impulse’ reaches the end of the line. Ask learners to suggest how a synapse can be represented by this model.

Challenge learners to convert between an image of a diagram (for example, photomicrographs of a longitudinal section of a nerve) and an image of a graph (for example, the journey of an impulse along the axon) or text. This helps them to apply their knowledge. (F)

Arrange learners into groups of four or five. Learners research the mechanism by which an impulse is transmitted across a synapse, using a range of sources. Give learners different numbers or colours and ‘rainbow group’ them to place all of those with the same number or colour together. Learners in their new groups then discuss their thoughts. Learners rearrange a set of diagrams to arrive at the correct sequence of events in synaptic transmission. Compare with an animation: www.sumanasinc.com/webcontent/animations/content/synaptictransmission.html (I)

Encourage learners to understand the key stages in the transmission of a nervous impulse by asking them what would happen if key components were missing – for example, calcium ions, sodium pumps, and so on. This prompts higher-order thinking as they are required to do more than simply recall the function of these particles. (F)