Homeostasis:

Maintaining dynamic equilibrium in living

systems.[or keeping us alive]

So…what does it all mean?So…what does it all mean?

To keep the balance, an organism must sense changes in external and internal environment

respond to those changes

Examples: Cells in your brain are sensitive to changes (even small) in the levels of oxygen and sugar.

• low blood sugar triggers the liver to release stored sugar

• when you stand up quickly, blood pressure increases to keepoxygen flow to your brain.

Homeostasis is a characteristic of all living things.

Homeostasis

The body’s ability to maintain a relatively constant state.TemperatureWater BalanceGlucose LevelsOxygen & Carbon Dioxide Levels

And many, many more…

TemperatureTemperature

ColdSense: Neurons in our skin

Response: change in blood flowincreased heart rateconstriction of blood vessels close to the surfacekeeps brain, liver, and heart constant (core)

(37˚C)shivering

TemperatureTemperature

HotSense: Neurons in our skin

Response: change in blood flowdilation of blood vessels close to the surfacediverts blood flow away from internal organssweating

Homeostasis & Water Balance

The Urinary System:Disposing of Wastes

Waste Products

The body produces many waste materials each day.Wastes become toxic if they build up

Wastes and how they are disposed include:

The Urinary System

Rids the body of urea Liver converts ammonia into ureaKidneys are the main organ

Eliminate urea from the body (secretes)Adjusts fluid volumes and regulates blood pressure (restores and reabsorbs)Filters

125 mL of wateris filtered eachminute = 180 litersper day!

CO2 and the Effect On pH

Or why we breath hard during exercise!

• As we exercise breathing and heart rate increase.

• CO2 builds up in blood because of muscles burning nutrients to make energy.

• Increased CO2 causes the blood to become more acidic.

• The human body doesn’t tolerate changes in pH.

• As we exercise breathing and heart rate increase.

• CO2 builds up in blood because of muscles burning nutrients to make energy.

• Increased CO2 causes the blood to become more acidic.

• The human body doesn’t tolerate changes in pH.

• Special receptors in nerve cells in the aorta, brain, and arteries that lead to the head monitor the pH.

• When the pH begins to drift out of normal range (7.35 - 7.45), these receptors are engaged.

• This causes the brain to send signals to begin breathing at a faster rate.

• By breathing faster, more CO2 is exhaled bringing the pH back to normal.

• Special receptors in nerve cells in the aorta, brain, and arteries that lead to the head monitor the pH.

• When the pH begins to drift out of normal range (7.35 - 7.45), these receptors are engaged.

• This causes the brain to send signals to begin breathing at a faster rate.

• By breathing faster, more CO2 is exhaled bringing the pH back to normal.

• If too much CO2 is exhaled, like when one hyperventilates, the pH begins to drift the other way and becomes more alkaline.

• If this happens, the receptors register a lack of O2.

• The person will faint and the brain will slow breathing down to balance the amount of O2 in the body.

• One way to fix this is to have person inhale and exhale into a paper bag. The CO2 balance is regained and the breathing slows down.

• If too much CO2 is exhaled, like when one hyperventilates, the pH begins to drift the other way and becomes more alkaline.

• If this happens, the receptors register a lack of O2.

• The person will faint and the brain will slow breathing down to balance the amount of O2 in the body.

• One way to fix this is to have person inhale and exhale into a paper bag. The CO2 balance is regained and the breathing slows down.

So….what happens when something

goes wrong?

What Works Together?What Works Together?The hypothalamus: part of the nervous system

• Regulates water balance, body temperature, feeding,sleep, and works with the endocrine system.

The endocrine system: release chemical Messengers into the blood (hormones).

The nervous system, respiratory system,urinary system, circulatory system, digestive system, and so on…

To keep the balance!To keep the balance!

FeedbackFeedback

Negative feedback: changes that correct an abnormal situation i.e. dehydration (goes away from a situation)

Positive feedback: critical process must completed quickly. I.e. blood clot. (goes toward a situation)

In response to a condition, the body responds by adjusting internal conditions.