1. Homeostasis and Feedback Loops

2. Definitions Homeostasis –balance in the body
Stimulus- something in the environment that causes a change (can be internal)
Response – action of organism as a result of stimulus
Feedback mechanisms/loops – processes by which the body maintains levels

3. 1) receptor (nerve) recognizes stimulus
Steps
1) receptor (nerve) recognizes stimulus

4. 2)sensory neuron transmits a message from the receptor, to a control center

5. 3)message is carried to a control center (brain),
message is interpreted, and the correct ordered

6. 4) Motor neuron carries message from control center to effector organ dictating response

7. Effector organ
5) Effector organ receives message and conducts the response

8. Afferent vs. Efferent pathway
Afferent pathway
= message to the brain
Efferent pathway = message from the brain

9. Positive Feedback Loop
Body responds by increasing stimulus stimulus
Ie. Oxytocin in childbirth
- chemical increases rate of contractions until the child is born

10. Graph of Positive Feedback
X-axis is time
Y-axis is hormone secreted

11. Negative Feedback loops
Body’s response counters the change
Tries to maintain a median
Ie. Blood glucose, temp, blood O2/CO2 levels