--- marp: true theme: default html: true --- # Quick check: feedback loops and what goes wrong Year 9 Biology · Coordination and control --- ## Today **We are learning to** a few quick questions on tracing a negative feedback loop in two examples, and finding which part has failed in a disorder. Taught in class; use this to check yourself. - I can name the parts of a feedback loop in an example. - I can say the set point for body temperature and blood glucose. - I can say which part of a loop fails in a disorder and what follows. --- ## Why it matters > Your body keeps glucose and temperature steady all day. What happens when one part of the loop stops working? --- ✅ Check ## Parts of the loop **Which part of the temperature loop is it?** Groups: Receptor · Control centre · Effector Temperature sensors in the skin and blood · The hypothalamus in the brain · Sweat glands · Muscles that shiver · Nerve endings that detect cold * Answer: Temperature sensors in the skin and blood → Receptor; The hypothalamus in the brain → Control centre; Sweat glands → Effector; Muscles that shiver → Effector; Nerve endings that detect cold → Receptor --- ✅ Check ## Blood glucose **Blood glucose rises after a meal. What reverses the change?** - Insulin makes blood glucose rise further - More glucose is released from the liver - Nothing: it stays high until the next meal - Insulin is released, cells take up glucose, and blood glucose falls back towards its set point * Answer: Insulin is released, cells take up glucose, and blood glucose falls back towards its set point --- ✅ Check ## Set points **Which pair names a feedback example and its set point?** - Insulin, about 37 °C - Body temperature, about 37 °C - Sweating, about 37 °C - Shivering, about 5 mmol/L * Answer: Body temperature, about 37 °C --- ✅ Check ## The whole loop **On a hot day, match each part of the temperature loop.** | | | |---|---| | `Body temperature held near 37 °C` | A. Corrective response | | `Exercise raises body temperature to 38 °C` | B. The return is detected | | `Sweating and more blood flow to the skin` | C. A change away from the set point | | `The hypothalamus detects 37 °C again, so sweating slows` | D. Set point | * Answer: Body temperature held near 37 °C → D. Set point; Exercise raises body temperature to 38 °C → C. A change away from the set point; Sweating and more blood flow to the skin → A. Corrective response; The hypothalamus detects 37 °C again, so sweating slows → B. The return is detected --- ✅ Check ## Type 1 diabetes **In type 1 diabetes the pancreas stops making insulin. What happens to blood glucose after a meal?** - It stops being measured - It falls too low - It stays too high, because cells are not told to take up glucose - It stays at the set point * Answer: It stays too high, because cells are not told to take up glucose --- ✅ Check ## Sweat glands **A person's sweat glands do not work. Which part of the temperature loop has failed, and what is the consequence?** - Nothing: sweating is not needed - The receptor: they cannot feel heat - The set point: it is lower than normal - The effector: they cannot cool by sweating and can overheat in hot weather * Answer: The effector: they cannot cool by sweating and can overheat in hot weather --- ✅ Check ## Where is the fault? **Which part of the loop has failed?** Groups: Receptor · Control centre · Effector Cold sensors in the skin send no signals · The brain does not process the signal · Muscles do not shiver when told to * Answer: Cold sensors in the skin send no signals → Receptor; The brain does not process the signal → Control centre; Muscles do not shiver when told to → Effector --- ✅ Check ## Exit ticket **Name the parts of a negative feedback loop for body temperature.** * Receptor (skin and blood sensors), control centre (hypothalamus), effector (sweat glands, muscles, skin blood vessels), return towards 37 °C.