1. I can explain mechanisms of homeostasis
Objective:
I can explain mechanisms of homeostasis
Agenda:
Finish presentations
White Board Movements
Notes homeostasis
Worksheet
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2. Levels of Structural Organization
Chemical – atoms combined to form molecules
Cellular – cells are made of molecules
Tissue – consists of similar types of cells
Organ – made up of different types of tissues
Organ system – consists of different organs that work closely together
Organism – made up of the organ systems
***The purpose of the 11 organ systems is for the human body to maintain homeostasis.

3. § Homeostasis—
Definition– Maintenance of stable conditions in the internal environment
Importance of homeostasis:
Homeostasis is essential for survival of cells– Why?
Cells make up the body systems
Homeostasis is the central theme of physiology– How? via cells/body systems

4. Factors under homeostatic control
nutrients
gases
waste products pH
salt and other electrolytes
temperature
volume and pressure

5. 5 Maintain Body (organ) systems Homeostasis Is essential for survivalof
Make up
Cells 5

6. Feedback Loops for Reflex Control

7. § Regulation of homeostasis by Negative feedback--A
Definition– change in a factor (controlled variable) triggers a physiological response that seeks to restore the factor by OPPOSING the initial change
Example—control of room/body temperature

8. § Regulation of homeostasis by Negative feedback--B
Three components of a control system
Sensor (receptor)– monitors the control variable (for example, room temp.); what is the sensor?
Integrating (control) center– it compares the sensor’s input with the set point and sends instructions to effector
Effector– action component that . . .
Figure 1.9 (a-b)

9. Sensor?
Integrating center?
Effector?

10. Fig. 1.9(b) Fluctuation of room temperature around the thermostatic set point

11. Fig. 1.10 Negative feedback in human thermoregulation.
Figure 1.11

12. § Positive feedback & rapid change--A
Definition– change in a factor triggers a physiological response that AMPLIFIES an initial change
Example— in the birth of a baby; how?

13. Figure 1.12--Positive feedback in childbirth
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17. § Positive feedback & rapid change--B
Details of birth of a baby
Uterine contractions push the baby against the cervix
the stretching of the cervix triggers nerve impulses
brings about oxytocin secretion
The hormone oxytocin causes even stronger powerful contractions of the uterus