1. Mechanisms of Homeostasis

2. Homeostasis is like your home’s thermostat
Thermostat’s set point is 75ºF
heat
Inside temperature =
75ºF
74ºF
73ºF
72ºF

3. Defined: Process where the body maintains a constant internal environment
Importance: Internal reactions & enzymes work best in specific conditions
Control systems adjust to internal/external changes
Changes controlled: pH, temp, fluids

4. Control Systems Sensors (aka: receptors)
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Sensors (aka: receptors)
Gather information about the body and environment
Ex: skin senses pressure
Communication Center
Messages sent throughout the body to respond
Ex: Impulse travel through your nerves
Control Center
Receives information from the sensors
Ex: Brain interprets the impulse
Targets
Body part that changes its activity
Ex: Muscles in foot stretch/contract abruptly

5. Negative Feedback Loops
Regulates most of the body
Reverses any change that moves conditions from a set point
Ex: if your temp drops…you will shiver to reverse that
97.5
97.7
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97.2
98.1
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98.1
97.7
97.5
96.8

6. Negative Feedback Loops
Regulates most of the body
Reverses any change that moves conditions from a set point
Ex: if your temp drops…you will shiver to reverse that
Ex: If your temp rises…you will sweat to reverse that
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99.2
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7. Negative Feedback Loop: Cold Response

8. Negative Feedback Loop: Breathing

9. Positive Feedback Loop
Increases the changes away from set points
Important when rapid change is needed
Ex: Pregnancy contractions
Uterus contractions begin slowly
Oxytocin released to speed up the contractions
Negative feedback would reverse and stop the contractions. But if the contractions stopped, would the baby be delivered?
Ask yourself…
If this was negative feedback, what would happen next?
So how will the body respond to the contractions if it’s positive feedback?

10. Working Together Thermoregulation: Maintenance of body temperature
Skin: sensors detect cold
Nervous system: electrical impulse sent to brain
Endocrine system: releases hormones into blood stream
Muscles: Hormones cause shivering

11. Homeostasis disruption
Beck Weathers, thought to be dead, survived a night exposed to Mt. Everest cold.
Some disruptions temporary
Infections, fever, sore throats, muscle soreness
Some disruptions too great for your body to control
Frost bite: Sensors are destroyed
Paralysis: Messages from brain doesn’t reach target

12. Diabetes & Homeostasis
Normally
Glucose in blood rises after meals
Pancreas releases insulin
Cells remove the glucose
Type 1
Immune system destroys pancreas cells
Pancreas unable to make insulin
Blood pH decreases as glucose builds up
Type 2
Pancreas does not make enough insulin
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13. Kobe Kuiz Define homeostasis.
Name and describe the four parts of the “control system.”
What is negative feedback?
What is positive feedback?
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.
What is diabetes?
How does Type I and Type II diabetes differ?