Anatomy Homeostasis

1. Anatomy Homeostasis

2. I. Homeostasis and Disease • Homeostasis – is the maintenance of a relatively constant internal environment. • The ability to maintain the balance depends on two factors • The status of the physiological systems involved. • The nature of the stress that’s imposed.

3. Homeostasis is a “balancing act” that must adapt to sudden or gradual changes in our environment, arrival of pathogens, injuries… • Homeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world • The internal environment of the body is in a dynamic state of equilibrium • Chemical, thermal, and neural factors interact to maintain homeostasis

4. What contributes to or effects this balancing act? • Age, health, and genetics affect our ability to maintain homeostasis. If the physio-logical values go outside the normal range it can affect other systems and can be fatal.

5. Disease is the failure to maintain homeostatic conditions. It can start in a specific cell/tissue and continue throughout the body. • The body often overcomes some diseases, for example the flu.

6. II. Homeostatic Regulationand Control Mechanisms • Homeostasis regulation is the adjustment of physiological systems to preserve balance/to keep the internal environment within desired limits (simply put… it is the communication within the body to maintain homeostasis) • Two homeostatic pathways are involved: (stop see if students have read pg. 9-11)

7. 1. Afferent pathway- carrying to or toward a center (receptor carries to the control center). • Efferent pathway –carrying away or away from (the control center sends a message to the effector).

8. B. Control Mechanisms • Variable produces a change in the body • Receptor monitors the environments and responds to changes (stimuli)- sends to the control center. • Control center determines the set point at which the variable is maintained (decides what message to send to the effector) • Effector provides the means to respond to the stimulus. It is a cell or organ that responds to the command of the control center. The response then “feeds back” to influence the stimulus (variable).

9. Case study A Spill at Parsenn Bowl: Knee injury and Recovery

10. Figure 1.4

11. Negative Feedback In negative feedback systems, the output shuts off the original stimulus Example: Regulation of blood glucose levels Figure 1.5

12. Positive Feedback In positive feedback systems, the output enhances or exaggerates the original stimulus Example: Regulation of blood clotting Figure 1.6

13. Review: Feedback mechanisms regulate biological systems • Feedback mechanisms allow biological processes to self-regulate • Negative feedback means that as more of a product accumulates, the process that creates it slows and less of the product is produced • Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is produced

14. Fig. 1-13 A Negative feedback  Enzyme 1 B D Enzyme 2 Excess D blocks a step D D C Enzyme 3 D (a) Negative feedback W Enzyme 4 X Positive feedback + Enzyme 5 Excess Z stimulates a step Z Y Z Z Enzyme 6 Z (b) Positive feedback

15. Homeostatic Imbalance: • is a disturbance of homeostasis or the body’s normal equilibrium. • overwhelms the usual negative feedback mechanisms allowing destructive positive feedback mechanisms to take over.