2. Mechanisms of Homeostasis

3. Homeostasis Process where the body maintains a constant internal environment Reactions & enzymes work best in specific conditions Control systems adjust to internal/external changes –pH, temp, fluids

4. Control Systems Sensors (aka: receptors) –Gather information about the body and environment –Ex: skin senses pressure Communication Center –Messages sent throughout the body to respond –Ex: Impulse travel through your nerves Control Center –Receives information from the sensors –Ex: Brain interprets the impulse Targets –Body part that changes its activity –Ex: Muscles in foot stretch/contract abruptly !*%!?%&#

5. Negative Feedback Loops Regulates most of the body Counters changes in the body that move conditions away from a set point –Reverses the change Keeps internal environment stable

7. Positive Feedback Loop Increases the changes away from set points Important when rapid changes needed Ex: Oxytocin released –When uterus contractions begin, oxytocin released to speed up the contractions (not stop them)

8. Working Together Thermoregulation: Maintenance of body temperature –Skin: sensors provide feedback to brain –Nervous & Endocrine system: send messages to/from brain –Muscles: Start to shiver

9. Homeostasis disruption Sensors fail Wrong messages sent Message doesn’t reach target Serious injury Microorganism infection Short Term –Temporary discomfort (usually)

10. Long Term: Diabetes Normally –Glucose in blood rises after meals –Pancreas releases insulin –Cells remove the glucose Type 1 –Immune system destroys pancreas cells –Pancreas unable to make insulin –Blood pH decreases as glucose builds up Type 2 –Pancreas does not make enough insulin –Blood pH decreases as glucose builds up insulin glucose insulin glucose