1. Homeostasis

2. What is Homeostasis? Homeostasis means “constant state”
Organisms maintain a relatively stable internal environment inside their body, even when the environment outside their body is changing
The body’s systems must maintain homeostasis so that essential life processes can be carried out in order to stay alive

3. What is Homeostasis?
For example, when you exercise, your body must keep your body temperature constant at about 98ºF even though your body’s activity is generating heat
Your body is also maintaining blood sugar levels, water & electrolyte balance, and blood pressure
Your body’s organ systems work together to carry out these tasks

4. How is Homeostasis Maintained?
To maintain homeostasis, the body must:
Detect changes in the environment
Process the sensory information
Respond to it appropriately

5. How is Homeostasis Maintained?
Detects change and sends a message to the control center
Receive the message and coordinates a response; Sends an output message to an effector
Responds to the output from the control center
RECEPTOR
(sense organs)
EFFECTOR
(muscles & glands)
CONTROL CENTER
(brain & spinal cord)

6. How is Homeostasis Maintained?
A good way to understand how homeostasis is maintained is to think of a thermostat on a heater
Heater has sensors (a receptor) to feel the room temperature
It has a control center to receive & process data
Depending on the data, the heating unit (the effector) will switch on or off to maintain a constant temperature

7. Stop & Summarize What is homeostasis?
What is the role of the following components in maintaining homeostasis:
Receptor:
Control Center:
Effector:

8. Two Types of Feedback
There are two ways homeostasis is maintained in your body
Negative Feedback
Positive Feedback

9. Negative Feedback Mechanisms
Negative feedback – when the change is BAD and needs to be corrected (returned to steady state)
It works by returning internal conditions back to a steady state when any variation from that state is detected

10. Negative Feedback Mechanisms
Negative feedback is the more common feedback mechanism in our bodies
Examples of negative feedback mechanisms:
Thermoregulation (body temperature)
Blood sugar levels
Blood pressure

11. Negative Feedback Mechanisms

12. Negative Feedback Mechanisms

13. Negative Feedback Mechanisms

14. Positive Feedback Mechanisms
Positive feedback – when the change is GOOD and should be amplified (increased)
It works by speeding up a biological process in order to achieve a particular outcome
Positive feedback stops when the end result is achieved

15. Positive Feedback Mechanisms
Positive feedback is less common in the body because it creates an escalated response, which is unstable (our body likes stability)
Examples of positive feedback:
Childbirth
Fever
Blood clotting (creation of scabs)
Lactation (production of milk)

16. Positive Feedback Mechanisms
This feedback only stops when the baby is born

17. Stop & Summarize
What is the difference between negative and positive feedback?
Why is positive feedback much less common than negative feedback?
How is a positive feedback loop stopped?