Mechanisms of Homeostasis

Homeostasis• Defined: Process

where the body maintains a constant internal environment

• Reactions & enzymes work best in specific conditions

• Control systems adjust to changes

– pH, temp, fluids

Thermostat senses cold room

Heater is activated

Warm air released

Room gets back to normal

Thermostat turns heater offHypothalamus senses you are cold

Hypothalamus activates muscles to shiver

Heat is generated

Body temp returns to normal

Hypothalamus turns off

Control Systems• Sensors (aka: receptors)

– Gather information about the body– Ex: skin senses pressure from

bowling ball• Communication Center

– Messages sent throughout the body

– Ex: Impulse travels through your nerves

• Control Center– Receives information from the

sensors– Ex: Brain receives the impulse

• Targets– Body part changes its activity– Ex: Brain tells foot muscles to pull

away

!*%!?%&#

Negative Feedback Loops• Regulates most of

the body• Reverses the

change– Ex: if your

temp drops…you will shiver to reverse that

– Ex: If your temp rises…you will sweat to reverse that

How Negative Feedback Makes You Breathe

Positive Feedback Loop• Does not stop the

change, but…• Speeds up the change• Ex: Birth Contractions

– Contractions of a pregnant woman start slow

– Oxytocin released– Contractions speed

up to push out baby

Thermoregulation

• Defined: Maintenance of body temperature• Example of homeostasis• Many organ systems working together

– Skin: sensors provide feedback to brain– Nervous & Endocrine system: send messages to/from brain– Muscles: Start to shiver

• Some changes can be too great for your body to control

• Examples:– Frost bite: Sensors

are destroyed– Paralysis: Messages

from brain doesn’t reach target

– Infection: fever, sore throat, soreness

Homeostasis disruption

Long Term: Diabetes

• Normally (good)

– Glucose in blood rises after meals

– Pancreas releases insulin

– Cells remove the glucose

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Long Term: Diabetes

• Normally (good)

– Glucose in blood rises after meals

– Pancreas releases insulin

– Cells remove the glucose

• Type 1 (bad)

– Immune system destroys pancreas cells

– Pancreas unable to make insulin

– Blood pH decreases as glucose builds up

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Long Term: Diabetes

• Normally (good)

– Glucose in blood rises after meals

– Pancreas releases insulin

– Cells remove the glucose

• Type 1 (bad)

– Immune system destroys pancreas cells

– Pancreas unable to make insulin

– Blood pH decreases as glucose builds up

• Type 2 (bad)

– Pancreas does not make enough insulin

– Blood pH decreases as glucose builds up

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glucose

glucose

glucose

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Kobe Kuiz1) Define homeostasis.

2) Name and describe the four parts of the “control system.”

3) What is negative feedback?

4) What is positive feedback?

5) Is the following example positive or negative feedback?During heavy exercise your body loses water when you sweat. As a result of water loss, your body redirects the remaining water inside your body to vital parts of your body to replenish these vital organs.

6) What is diabetes?

7) How does Type I and Type II diabetes differ?