1. Unit 12:Human Regulation and Reproduction
Assignment 3: Homeostatic Feedback Loops

2. Learning Outcomes
To know some of the body systems / organs which have a role in Homeostasis.
To understand the difference between positive and negative feedback and be able to state/explain examples of each.

3. Starter Activity Write a definition of HOMEOSTASIS.

4. Homeostasis What is homeostasis?
The maintenance of a constant internal environment in a continually changing external environment.
What is controlled by Homeostasis?
Write down as many examples of Homeostasis as you can think of.

5. Did you get… Regulation of: Temperature Water balance pH Blood glucose
Menstrual cycle
Heart rate
Breathing rate
Metabolism
Ion balance

6. Question: Which body systems / organs are involved in homeostasis
How are they involved?

7. Feedback Loops Negative feedback reverses the change
Positive feedback keeps the change going in the same direction.
Most homeostatic mechanisms are controlled by negative feedback

8. Negative Feedback Mechanisms
Push a system back to its original equilibrium position E.g. Imagine you are out walking in the country. As you walk, the sun rises higher in the sky and the air temperature increases. Your body senses that your internal temperature is rising above 37C and you start to sweat, which reduces your body temperature by evaporating water from your skin, returning your temperature to normal

10. Task
Draw a feedback loop for thermoregulation

12. Thermoregulation

13. Glucoregulation
When learning about hormones, we covered the action of insulin / glycogen on blood glucose.
Draw a feedback loop for glucoregulation

15. Osmoregulation
Now try drawing a feedback loop for balancing water content:
(Osmoregulation)

17. POSITIVE FEEDBACK MECHANISMS–
Push a system to a new state of equilibrium
E.g., Imagine you are lost on a high snowy mountain.
When your body senses that it is cooling below 370C, various mechanisms such as shivering help to raise your internal temperature again, but if these are insufficient to restore normal
body temperature, your metabolic processes start to slow down, as, like most chemical reactions, they happen more slowly at lower temperatures.
As a result you become lethargic and sleepy and move around less and less, allowing your body to cool even further. Unless you are rescued at this point, your body will reach a new equilibrium – you will die of hypothermia

22. Feedback loops