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