Topic 9: Control Systems C/W 18/10/2016 Estimate: 12 x double lessons, mid topic test after 6 lessons Multiple choice quiz after 6 lessons End of topic test after 12 lessons

C/W 18/10/2016 Homeostasis Know that homeostasis is the maintenance of a state of dynamic equilibrium Understand the importance of maintaining pH, temperature and water potential in the body Understand what is meant by negative feedback and positive feedback control

Key Definitions Homeostasis – Maintenance of a state of dynamic equilibrium in the body, despite changes in the external or internal conditions 18/10/2016

What factors do we need to control in our body? pH Temperature -Thermoregulation Water potential In your exercise books, say why it is important that these 3 variables are controlled. 18/10/2016

pH Keeps protein structures stable Synoptic link – Topic 1 – Protein Structure – Primary, Secondary, Tertiary, Quateranry pH Keeps protein structures stable Enzymes can function at their optimum acitivity Structure of cell membranes can remain stable. Link with transport of Carbon Dioxide away from body cells. 18/10/2016

Core temperature Synoptic link – Enzyme structure and active site Enzyme activity maintained at optimum levels to control cellular reactions Maintains integrity of cell membranes to control movement in and out of cells. 37C Water potential Water potential of body fluids must remain within narrow limits to avoid osmotic effects that could damage or destroy the cells 18/10/2016

What does homeostasis involve? Synoptic link – Enzyme structure and active site What does homeostasis involve? Changes in the body are detected by sensors, also called receptors. They send messages to effectors that either work to reverse the change or to change or to increase it in a number of different feedback systems. Effectors are usually muscles or glands. 18/10/2016

C/W 18/10/2016 Checkpoints Know that homeostasis is the maintenance of a state of dynamic equilibrium Understand the importance of maintaining pH, temperature and water potential in the body Understand what is meant by negative feedback and positive feedback control

Feedback systems Most feedback systems in mammals are negative feedback system. They provide a way of maintaining a condition such as a concentration of a substance, within a narrow range. A change in conditions is registered by receptors and as a result effectors are stimulated to restore the equilibrium. Next…. Complete negative feedback activity. 18/10/2016

Using the card sort and template Sort the negative feedback cards onto the correct template. We will go through this as a class. You should then draw out a neat version of this in your exercise books. 18/10/2016

Negative Feedback Systems Norm (normal level of a particular factor) Negative Feedback Systems Fall to a lower level Rise to a higher level Receptor Detects change Receptor Detects change Communication (1) by hormonses or (2) by nervous system via coordination centre Communication (1) by hormonses or (2) by nervous system via coordination centre Effector Carries out response which brings about corrective change Effector Carries out response which brings about corrective change Norm (normal level of a particular factor) Rise to normal level Fall to normal level 18/10/2016

C/W 18/10/2016 Checkpoints Know that homeostasis is the maintenance of a state of dynamic equilibrium Understand the importance of maintaining pH, temperature and water potential in the body Understand what is meant by negative feedback and positive feedback control

Definitions Negative feedback – Provides a way of maintaining a condition within a narrow range. A change in condition is registered by receptors and as a result effectors are stimulated to restore the equilibrium. Positive Feedback – Where effected work to increase an effect that has triggered a response. 18/10/2016

Positive Feedback 18/10/2016

Positive Feedback mechanisms Baby pushes against cervix – cervix stretches Stretch receptors in cervix send impulses to brain Brain stimulates pituitary to release oxytocin Oxytocin makes uterus contract harder pushing baby against cervix No return to homeostasis. This causes contractions to become stronger and more frequent. 18/10/2016

C/W 18/10/2016 Checkpoints Know that homeostasis is the maintenance of a state of dynamic equilibrium Understand the importance of maintaining pH, temperature and water potential in the body Understand what is meant by negative feedback and positive feedback control

Questions What is homeostasis and why is it so important in living organisms? In the past, homeostasis was described as the maintenance of a steady internal state. Why do you think this definition has changed? Suggest why there are many negative feedback systems in mammals and relatively few positive feedback systems. 18/10/2016

Answers What is homeostasis and why is it so important in living organisms? In the past, homeostasis was described as the maintenance of a steady internal state. Why do you think this definition has changed? Suggest why there are many negative feedback systems in mammals and relatively few positive feedback systems. 18/10/2016

Exam Questions Complete the data analysis questions relating to Homeostasis. We will mark these in in class. You have 20 minutes to complete. You will then put them in the Exam Practice section of your folder. 18/10/2016

Topic 1 recap… 1. 2. 3. 4. 5 18/10/2016

Topic 1 recap… ANSWERS 1. 2. 3. 4. 5 18/10/2016

This relates to the following specification point: 18/10/2016