pptx, 2.39 MB
pptx, 2.39 MB
docx, 14.62 KB
docx, 14.62 KB
docx, 15.49 KB
docx, 15.49 KB
docx, 16.8 KB
docx, 16.8 KB
docx, 19.3 KB
docx, 19.3 KB

This fully-resourced lesson describes the structure of the human retina and explains how the rhodopsin in rod cells allows vision in low light intensity. The detailed PowerPoint and accompanying resources have been designed to cover points 9.7 (i), (ii) & (iii) of the Edexcel A-level Biology B specification but also makes links to previously covered topics such as cell structure and nervous transmission.

It is likely that students will be aware that the human retina contains rod and cone cells, so this lesson builds on that knowledge and adds the detail needed at this level. Students will discover that the optical pigment in rod cells is rhodopsin and that the bleaching of this into retinal and opsin results in a cascade of events that allows an action potential to be initiated along the optic nerve. Time is taken to go through the events that occur in the dark and then the students are challenged to use this as a guide when explaining how the events differ in the light. Key terms like depolarisation and hyperpolarisation, that were met in topic 9.5, are used to explain the changes in membrane potential and the resulting effect on the connection with the bipolar and ganglion cells is then described.

Cone cells are also introduced, with the main focus being their distribution in the centre of the fovea which is used to explain colour vision in bright light.

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Topic 9: Control systems (Edexcel A-level Biology B)

This bundle contains 15 lessons which are engaging and highly detailed in order to cover the difficult content as set out in topic 9 (Control systems) of the Edexcel A-level Biology B specification. The lesson PowerPoints and accompanying resources contain a wide variety of tasks which cover the following specification points: * Homeostasis is the maintenance of a state of dynamic equilibrium * The importance of maintaining pH, temperature and water potential in the body * The meaning of negative feedback and positive feedback control * The principles of hormone production by endocrine glands * The two main modes of action in hormones * The division of the autonomic nervous system into the sympathetic and parasympathetic systems * The transport of sodium and potassium ions in a resting potential * The formation of an action potential and the propagation along an axon * Saltatory conduction * The function of synapses * The formation and effects of excitatory and inhibitory postsynaptic potentials * The structure of the human retina * The role of rhodopsin * The distribution of rods and cone cells * The control of heart rate by the autonomic nervous system * The gross and microscopic structure of the kidney * The production of urea in the liver and its removal from the blood by ultrafiltration * Selective reabsorption in the proximal tubule * Control of mammalian plasma concentration * The differences between ectotherms and endotherms * The regulation of temperature by endotherms If you would like to sample the quality of this lesson bundle, then download the homeostasis, resting and action potentials and the formation of urea and ultrafiltration lessons as these have been uploaded for free.

£22.00

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