1. Homeostasis

2. What is Homeostasis? It’s about balance!
Homeostasis is the physiological state of the body in which internal conditions are kept within a range that is suitable for life processes.
The human body can deal with a range of environmental stimuli.
Humans operate best at :
37°C body temp
0.1% blood sugar
Blood pH of 7.35

4. How is Balance Maintained?
There are several body systems involved in the maintenance of homeostasis: Nervous System Endocrine System Musculoskeletal System Integumentary System Excretory System Reproductive System

5. How is Balance Maintained?
Homeostatic mechanisms involve the monitoring of internal and external conditions, as well as the changes the body undergoes to maintain balance.
Four components of homeostatic systems:
Sensor
Integrator (control centre)
Effector (Regulator)
Response
Example: Arterial stretch receptors (sensor) detect pressure changes (stimulus) in arteries which signals brain . The brain (integrator) then relays information to adjust the strength of the heart’s contractions (effector). Blood pressure will increase or decrease depending on the initial pressure (response).

6. Negative Feedback
Negative feedback systems are mechanisms that restore conditions to their original state. Classic example: Household thermostat Called negative feedback because a change in variable being monitored triggers control mechanism to counteract further changes.

7. Negative feedback

8. Positive Feedback Less common in the body and they reinforce changes.
Example: Birthing process
Progesterone drop initiates contractions
Contractions release oxytocin, which causes stronger contractions

9. Positive feedback

10. Thermoregulation Maintenance of body temperature.
Endotherms (like us mammals) maintain constant body temperatures despite surroundings.
Hypothalamus (in brain) is our thermostat (monitor).

11. Case Study: TEACUP THE FROZEN CAT!

13. Response to Heat
Brain detects a rise in body temp. Hypothalamus sends signal to sweat glands to start sweating and blood vessels to dilate. Evaporation cools body and more blood flows to skin where it loses heat.

14. Response to Cold
Hypothalamus sends message to organs and tissues to increase temperature. Blood vessels contract. Smooth muscles around hair follicles contract (goose bumps) to trap air near skin. Shivering to generate heat.

15. Prolonged Cold Exposure
Increase in brown fat (often found in babies).
Brown fat really efficient at generating heat.

16. Interesting thermoregulation
Exercise Endotherms - Some organisms exercise to maintain core body temperatures eg. Honey bees
Fur Distribution – Dogs have uneven distribution of fur and curl up when cold to cover exposed surfaces
Elephants have big ears!
Panting