Homeostasis and Feedback Homeostasis Maintaining Limits n Homeostasis

Homeostasis and Feedback

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

Examples of Maintaining Homeostasis n n n Keeping body temperature around 37 o. C Maintaining blood glucose level Keeping oxygen concentration steady

Dynamic Equilibrium n n 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

Control of Homeostasis: Feedback Systems n n 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) n Endocrine n Nervous

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

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

Feedback System n n AKA feedback loop Cycle of events in which the status of a body condition is continually monitored, evaluated, changed, remonitored, reevaluated and so on…

n n 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

Components of a Feedback System n n n 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.

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

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

Homeostasis and Disease n n 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

Disorder n Any disturbance of the structure or function of the body

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

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

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

Infectious disease n Pathogens invade a host and cause a disease

Local Disease n Affects one part or region of the body

Systemic Disease n Affects several body parts or the whole body

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

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

Pharmacology n The science that deals with the effects and uses of drugs in the treatment of disease

Diagnosis n 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

Aging and Homeostasis n n 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