Homeostasis and Feedback

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

Examples of Maintaining Homeostasis

Keeping body temperature around 37oC Maintaining blood glucose level Keeping oxygen concentration steady

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

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

Nervous Control of Homeostasis

The nervous system detects changes from the normal state and sends out nerve impulses to organs to counteract the change

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

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…

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

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

Reverses the change in a controlled condition EX – BP, BGL, HR, Temp

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

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

Disorder

Any disturbance of the structure or function of the body

Disease

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

Symptoms

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

Signs

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

Infectious disease

Pathogens invade a host and cause a disease

Local Disease

Affects one part or region of the body

Systemic Disease

Affects several body parts or the whole body

Pathology

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

Epidemiology

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

Pharmacology

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

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

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