HomeostasisGive me some Feedback!

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Homeostasis*

* Maintaining of a stable internal environment

• Homeostatic Control Mechanisms – monitors aspects of the internal environment and corrects as needed. Variations are within limits. There are three (3) parts:

• Receptor - provides information about the stimuli

• Control Center - tells what a particular value should be (called the set point)

• Effector - elicits responses that change conditions in the internal environment

Homeostatic Control Mechanisms

Stimulus(Change occursin internalenvironment.) Response

(Change is corrected.)

Receptors Effectors(muscles or glands)

Control center(set point)

(Change is comparedto the set point.)

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Homeostatic Control Mechanisms

ReceptorsThermoreceptorssend signals to thecontrol center.

too high

too low

Normal bodytemperature37°C (98.6°F)

Control centerThe hypothalamusdetects the deviationfrom the set point andsignals effector organs.

Control centerThe hypothalamusdetects the deviationfrom the set point andsignals effector organs. If body temperature

continues to drop,control center signalsmuscles to contractInvoluntarily.

StimulusBody temperaturerises above normal.

EffectorsSkin blood vesselsdilate and sweat glandssecrete.

ResponseBody heat is lost tosurroundings, temperaturedrops toward normal.

ReceptorsThermoreceptorssend signals to thecontrol center.

EffectorsSkin bloodvessels constrictand sweat glandsremain inactive.

StimulusBody temperaturedrops below normal.

EffectorsMuscleactivitygeneratesbody heat.

ResponseBody heat is conserved,temperature rises toward normal.

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• There are two (2) types:

• Negative feedback mechanisms

• Positive feedback mechanisms

Homeostatic Control Mechanisms

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Negative feedback summary:

• Prevents sudden, severe changes in the body

• Corrects the set point

• Causes opposite of bodily disruption to occur, i.e. the ‘negative’

• Most common type of feedback loop

• Examples: body temperature, blood pressure & glucose regulation

Homeostatic Control Mechanisms

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Positive feedback summary:

• Increases (accelerates) the actions of the body

• short-lived

• do not require continuous adjustments

•Produces more instability and chaos in the body

•Controls only infrequent events that do not require continuous adjustments.

• Examples: blood clotting and child birth

Homeostatic Control Mechanisms

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Animation: Positive and Negative Feedback

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