Scheme of Work Cambridge International as & a level

Syllabus ref. and Key Concepts (KC)	Learning outcomes
Suggested teaching activities
14.1 Homeostasis in mammals KC2 KC5	14.1.1 Explain what is meant by homeostasis and the importance of homeostasis in mammals. 14.1.2 Explain the principles of homeostasis in terms of internal and external stimuli, receptors, coordination systems, effectors and negative feedback. 14.1.3 State that urea is produced in the liver from the deamination of excess amino acids. 14.1.4 Describe the structure of the human kidney. 14.1.5 Identify, in diagrams, photomicrographs and electron micrographs, the parts of a nephron and its associated blood vessels and structures. 14.1.6 Describe and explain the formation of urine in the nephron. 14.1.7 Relate the detailed structure of the Bowman’s capsule and proximal convoluted tubule to their functions in the formation of urine. 14.1.8 Describe the roles of the hypothalamus, posterior pituitary gland, antidiuretic hormone (ADH), aquaporins and collecting ducts in osmoregulation.	To prepare learners for the topic of homeostasis, hold a quiz to refresh and review learners’ understanding of key terms related to glucose in respiration (Topic 12), and transport across membranes, cell signalling and osmosis (Topic 4). (F) Host a discussion with learners to identify the physiological factors that are maintained at a set point (e.g. temperature, blood glucose concentration, blood pH / carbon dioxide concentration, water balance / water potential, metabolic wastes) and explain the importance of maintaining the balance. Use this opportunity to revise the source of excretory substances, e.g. urea is produced in the liver from the deamination of excess amino acids. Learners identify analogies to describe the role of homeostasis in the body. Examples include a cooking oven with a thermostat, a thermostatically controlled water bath, central heating systems, and air-conditioned rooms. During the subsequent discussion, discuss homeostasis and link the analogies to key terms. Write these on the board such as stimulus (internal and external), receptor, coordination centre, effector and response. Learners record a summary of the discussion in the form of a flow diagram, including these key terms. Show a short animation of the movement of substances that occur in a nephron. An example is found at www.sumanasinc.com/webcontent/animations/content/kidney.html. Pause the animation at regular intervals for learners to discuss, in small groups, and give a summary sentence that describes the events. Learners convert a diagram of a nephron into a sketch of a graph to show the change in the contents of a nephron. To make this more challenging, provide learners with only 60 seconds to do this, or to add labels to their work to illustrate the roles of the hypothalamus, posterior pituitary gland, antidiuretic hormone (ADH), aquaporins and collecting ducts in osmoregulation. (I) Learners draw diagrams of transverse and longitudinal sections of kidney tissue, including detail showing the tubules in different planes, labelling glomerulus, renal convoluted tubule (proximal and distal), Bowman’s capsule, loop of Henle and collecting duct. You could provide histology images, such as: https://webpath.med.utah.edu/RENAHTML/RENALIDX.html and www.histology.leeds.ac.uk/urinary/kidney.php, (I) A key skill is being able to recognise structures in electron micrographs. Good sources of kidney sections include https://wellcomecollection.org/works/h2parxes and https://wellcomecollection.org/works/ask2jkuq Other images can be found at https://www.dartmouth.edu/~emlab/gallery/ Learners prepare a table to show the visible features that can be used to distinguish different parts of the nephron, including their functions. Place an emphasis on listing structures that adapt cells in these regions to their functions, e.g. microvilli and mitochondria in the epithelial cells lining the proximal convoluted tubule. (F)