Homeostasis and Feedback

1. Homeostasis and Feedback

2. Homeostasis: Maintaining Limits • Homeostasis is the maintenance of relatively stable conditions • Ensures the body’s internal environment remains steady despite changes both inside and outside the body

3. Examples of Maintaining Homeostasis • Keeping body temperature around 37oC • Maintaining blood glucose level • Keeping oxygen concentration steady

4. Dynamic Equilibrium • Homeostasis can fluctuate over a narrow range the is compatible with life. • If certain levels fall outside this range for a prolonged period of time death may result

5. Control of Homeostasis: Feedback Systems • Every body structure contains homeostatic devices that work to keep the internal environment within normal limits • 2 body systems control most homeostatic devices (part of the life process called regulation) • Endocrine • Nervous

6. Nervous Control of Homeostasis • The nervous system detects changes from the normal state and sends out nerve impulses to organs to counteract the change

7. Endocrine Control of Homeostasis • Corrects changes by secreting chemicals called hormones into the blood • Hormones affect specific body cells where they cause responses that restore homeostasis

8. Feedback System • AKA feedback loop • Cycle of events in which the status of a body condition is continually monitored, evaluated, changed, remonitored, re-evaluated and so on…

9. Each condition in the body that is monitored in such a way is called a controlled condition • Any disruption that causes a change in a controlled condition is called a stimulus

10. Components of a Feedback System • Receptor – monitors change • Control Center – sets a range of acceptable values, evaluates input from the receptor and sends output to an effector • Effector – a body structure that receives output from the control center and produces a response or effect that changes the controlled condition.

11. Negative Feedback Systems • Reverses the change in a controlled condition • EX – BP, BGL, HR, Temp

12. Positive Feedback System • The effector produces a response that enhances or reinforces the initial change in the controlled condition. • EX – Childbirth, Ovulation, Blood Clotting • Happens in stimuli that are do not happen very often

14. Homeostasis and Disease • If 1 or more components of the body lose their ability to contribute to homeostasis, the normal balance among all the body’s processes may be disturbed. • This may result in a disease, disorder or even death

15. Disorder • Any disturbance of the structure or function of the body

16. Disease • A more specific term for an illness that is characterized by a specific set of signs and symptoms

17. Symptoms • Subjective changes in body function that are not apparent to an observer • Ex – nausea or headache

18. Signs • Objective changes that a clinician can observe and measure • Ex – bleeding, swelling, fever, rash

19. Infectious disease • Pathogens invade a host and cause a disease

20. Local Disease • Affects one part or region of the body

21. Systemic Disease • Affects several body parts or the whole body

22. Pathology • The science that deals with the nature, causes and development of abnormal conditions that occur from the disease process

23. Epidemiology • The science that deals with the why, when and where diseases occur and how they are transmitted in a human community

24. Pharmacology • The science that deals with the effects and uses of drugs in the treatment of disease

25. Diagnosis • The identification of a disease or disorder based on a scientific evaluation of a patient’s signs and symptoms, medical history, physical examination and sometimes lab tests

26. Aging and Homeostasis • Aging is a normal process characterized by a progressive decline in the body’s ability to restore homeostasis. • Produces observable changes in structure and function and increases vulnerability to stress and disease