28.2 Mechanisms of Homeostasis

Sponge (Pg. 36)

1) Hypothesize how these climbers hang on to their body temperature.

28.2 Mechanisms of Homeostasis

1) Hypothesize how these climbers hang on to their body temperature.

• His body is working inside to provide energy and to maintain a stable body temperature.

28.2 Mechanisms of Homeostasis Set up Cornell Notes on pg. 37•Topic: 28.2 Mechanisms of Homeostasis

•Essential Question(s):1.On the top ½ of pg. 36 please create a double-bubble comparing and contrasting Negative and Positive feedback

2.On the bottom ½ of pg. 36 please draw your own negative feedback loop with a real example NOT used in class

2.1 Atoms, Ions, and Molecules

28.2 Mechanisms of Homeostasis

28.2 Mechanisms of Homeostasis

KEY CONCEPT Homeostasis is the regulation and maintenance of the internal environment.

28.2 Mechanisms of Homeostasis

• Homeostasis is the regulation and maintenance of the internal environment within the narrow ranges that support human life. It is a delicate balance.

• Temperature• Fluids• Salts• pH• nutrients

28.2 Mechanisms of Homeostasis

Conditions within the body MUST remain within a narrow range.

• Homeostasis involves keeping the internal environment within set ranges.

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• Human Internal Environment • Protects our cells from external changes• Is relatively constant, despite an ever-

changing outside environment (98.6 degrees)

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Your control center (brain) is like a thermostat•Has a set temperature (98.6)•If it is too hot- sends signals to effectors (sweat glands) to lower body temp (ex: sweat)•If too cold- sends signals to effectors to raise body temp (ex: shiver)

How does a thermostat work?•Air conditioner•Heater

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Stimulus: rising blood sugar

Response: blood sugar returns to normal= homeostasis

Negative Feedback: The control system (brain) sends signals/instructions to effectors (muscles and glands) to stabilize the body• activated by an imbalance•corrects an imbalance, brings body back to Homeostasis

Pancreas receptors detect high blood sugar

The control center signals the pancreas to secrete insulin

Effector: Insulin causes liver cells to take up sugar in the blood

28.2 Mechanisms of Homeostasis

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Change occurs in internal or external environment

100*

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ReceptorsSensors: Gather data, and Send signals to the control center

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The brain receives data, and compares it with “set point”, sends messages to effectors

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Work to return the body to balanced levels- delivers messages to target organs/glands

28.2 Mechanisms of Homeostasis

14Targets respond to change, and body returns to homeostasis

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Please complete a negative feedback loop for body temperature rising due to it being 110* outside

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Body temperature rises above 98.6 due to it being 110* outside

100*

Real life example:

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Skin sensory receptors send signals to brain

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The hypothalamus detects the difference from the set point: 98.6* and signals effectors

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Messages sent to sweat glands

28.2 Mechanisms of Homeostasis

20You sweat, body temperature lowers to normal (98.6)

28.2 Mechanisms of Homeostasis

How are negative feedback loops necessary for homeostasis?

• Feedback compares current conditions to set ranges.• Negative feedback counteracts change • Keeps environment stable

Negative Feedback LoopHolding breath, CO2

levels rise,

Control system forces exhale, inhale

O2 / CO2 level returns to normal

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Positive Feedback: Process by which changes cause additional similar changes, producing unstable conditions- pushes away from homeostasis

28.2 Mechanisms of Homeostasis

• Positive feedback increases change– Important when rapid change is needed

– EX: Torn vessel stimulates release of clotting factors

platelets

fibrin

white blood cellred blood cell

blood vessel

clot

28.2 Mechanisms of Homeostasis

At your table, please explain the difference between a negative feedback loop and positive feedback loop?

Negative feedback loop counteracts change away from set points. Positive feedback loops increases change away from set points.

28.2 Mechanisms of Homeostasis

Homeostasis is the regulation and maintenance of the internal environment within the narrow ranges that support human life.•Body temperature is normal•Normal amounts of blood and other bodily fluids

With your neighbor, please make a list of external or internal factors that would affect your body’s homeostasis.

28.2 Mechanisms of Homeostasis

• Disease

• Stress

• Lifestyle (drinking, smoking, diet)

• Injury

• Illness (fever, infection)

• Dehydration/Starvation

• Outside temperature

Please make a list of external or internal factors that would affect your body’s homeostasis. Pg. 37

28.2 Mechanisms of Homeostasis

A disruption of homeostasis can be harmful

• Sensors fail to detect changes

• Wrong messages sent• Messages fail to reach

their targets• Serious injuries

overwhelm the body• Viruses or bacteria

change the body’s internal chemistry

28.2 Mechanisms of Homeostasis

Short term effects

• Last a few days or weeks• Ex: A cold virus enters your body• Within a few days your immune system begins to kill the

virus

28.2 Mechanisms of Homeostasis

Long term effects

• Causes long term damage to the body• Ex: diabetes

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Homework

On the top ½ of pg. 37 draw a double-bubble map, comparing and contrasting negative and positive feedback. Make sure you give examples of each.

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Negative Feedback

Positive Feedback

Corrects an imbalance

Ex: temperature regulation

Returns body to homeostasis

Causes additional changes

Ex: Contractions during childbirth

Moves body away from homeostasis

stimuli

receptors

Control center

effectors