Homeostasis

Homeostasis

• A condition of equilibrium (balance) in the body’s internal environment

• Continually disrupted by internal and external stimuli

• Usually disruptions are mild and temporary because body respond

Feedback System

Cycle of events - body is constantly monitored

Made up of three basic components

• Receptor

• Control center

• Effector

Receptor (first step)

Body structure that monitors changes in a controlled condition

Sends input to the control center

• Nerve ending of the skin in response to temperature change

Control Center

Brain

Sets the range of values to be maintained

Evaluated input received from receptors and generates output command

Nerve impulses and hormones

• Brain acts as a control center receiving nerve impulses from slin temperature receptors

Effector

Receives output from the control center

Produces a response or effect that changes the controlled condition

• Body temperature drops, brain sends impulse to skeletal muscles to contract

Negative Feedback Loop

• Reveres a change in a controlled condition

• Original stimulus is reversed

• Most body feedback systems go through this

  • Used for conditions that need frequent adjustment - blood pressure, body temp., blood sugar

Negative Feedback: Regulation of Blood Pressure

• External or internal stimulus increases BP

• Baroreceptors detect higher BP

• Send nerve impulses to brain for interpretation

• Response sent via nerve impulse sent to heart and blood vessels

• BP drops and homeostasis is restored

• Drop in BP negates the original stimulus

Positive Feedback Loop

Strenghthen or reinforce a change in one of the body’s controlled conditions

Original stimulus intensifies

Normal childbirth

Positive Feedback: Normal Childbirth

• Uterine contractions cause cervix to open

• Stretch-sensitive receptors in cervix send impulse to brain

• Oxytocin is released into the blood

• Contractions enhanced and baby pushes farther down the uterus

• Cycle continues to the birth of the baby (no stretching)

Disorder - Homeostatic Imbalance

Any abnormality of normal structure or function

Disease - Homeostatic Imbalance

A specific illness with a distinct set of recognizable characteristics

Symptoms

Changes in body function felt by a patient

Signs

Change in body function that can be observed by a doctor

Diagnosis - Homeostatic Imbalance

The skill of distinguishing one disease from another

Epidemiology - Homeostatic Imbalance

Tracking how diseases transmit and spread through population

Pharmacology - Homeostatic Imbalance

The science of hoe drugs interact with the body to restore balance

Moderate Imbalance

Disorder or disease may occur

Severe Imbalance

Death

Aging

Increases vulnerability to stress and disease