1. Homeostasis
Pages 332 – 341
Section 7.1 & 7.2

2. Homeostasis
The process of maintaining the body’s internal environment, despite changes in the external environment.
This makes sure that the body’s organs and cells are operating at ideal conditions, and thus are most efficient.

3. Factors that are regulated
Blood pressure
Blood pH
Body temperature
Water levels
Blood glucose levels
Heart rate
Respiratory rate

4. Homeostasis continued
Also called dynamic equilibrium because small changes are constantly occurring.
All homeostatic control systems have:
A monitor (sensory receptors that detect imbalance)
Coordinating center (relays information)
Effectors (works to restore balance, usually muscles and glands)
These systems of control are called feedback loops

5. Negative Feedback Loop
Mechanisms that work to restore the system to normal levels.
Negative feedback ensures that small changes do not get too large.
Ex. When body temperature rises, you begin to sweat in order to lower temperature.
The most common type of feedback loop

6. Positive Feedback Loop
When the change in a system causes the system to amplify the change.
Less common
Ex. During childbirth, as the baby moves towards the cervix, more oxytocin is released, which increases contractions.

7. Thermoregulation The maintaining of body temperature.
Ectotherms (fish, amphibians, reptiles) depend on the air to regulate body temperature.
Endotherms (mammals and birds) maintain a constant body temperature via internal systems.
Normal body temperature in humans = 37°C
Hypothalamus acts as the ‘thermostat’

8. Homework Read p. 332-341 Questions: p. 337 #1-9 p. 341 #1-7
* Pay special attention to understanding thermoregulation as this is a great example of a negative feedback loop!