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Homeostasis. Defined : The maintenance of a constant internal environment Importance : Body processes work best in specific conditions. Homeostasis is like your home’s thermostat. Thermostat’s set point is 75ºF. heat. Inside temperature =. 72ºF. 73ºF. 74ºF. 75ºF. !*%!?%&#.

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Homeostasis

  • Defined: The maintenance of a constant internal environment

  • Importance: Body processes work best in specific conditions


Homeostasis is like your home s thermostat
Homeostasis is like your home’s thermostat

Thermostat’s set point is 75ºF

heat

Inside temperature =

72ºF

73ºF

74ºF

75ºF


Control system

!*%!?%&#

Control System

  • Sensors

    • Gather information about the internal and external environment

      • Ex: pressure sensors in your foot

  • Communication system

    • impulse (message) sent through the body

      • Ex: nerves connected from foot to brain.

  • Control Center

    • Interprets sensory information

      • Ex: Brain interprets pain in foot.

  • Targets

    • Body part that receives the final message

      • Ex: Muscles in foot, causes foot to move


Negative feedback loops
Negative Feedback Loops

  • Counter-actsany change that moves conditions away from a set point

    • REVERSES change

    • Ex: if your temp drops…you will shiver to reverse that

98.6

98.4

98.1

97.7

97.5

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96.8

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98.1

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Negative feedback loops1
Negative Feedback Loops

  • 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

98.6

98.8

99.2

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99.7

100.1

99.7

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98.8

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Positive feedback loop
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


Positive feedback loop1

platelets

blood vessel

fibrin

clot

white blood cell

red blood cell

Positive Feedback Loop

  • More examples…

  • Growth hormones stimulate cell division

  • Torn vessel stimulates release of clotting factors


Working together
Working Together

  • Thermoregulation: Maintenance of body temperature

    • Skin (sensors): sensors detect cold

    • Nervous system (communication system): electrical impulse sent to brain

    • Hypothalamus in brain (control center): releases hormones into blood stream

    • Muscles (target) : Hormones cause shivering


Homeostasis disruption

Beck Weathers, thought to be dead, survived a night exposed to Mt. Everest cold.

Homeostasis disruption

  • Some disruptions are temporary

    • Infections, fever, sore throats, muscle soreness

  • Some disruptions are too great for your body to control

    • Frost bite: Sensors are destroyed

    • Paralysis: Messages from brain can’t reach target

    • Can lead to death


Diabetes
Diabetes to Mt. Everest cold.

  • Defined: Inability to control blood sugar

  • 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

    • Blood pH decreases as glucose builds up

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glucose

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insulin

insulin

insulin

insulin

insulin

insulin

insulin

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Review
Review to Mt. Everest cold.

  • 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?