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Warm-Up Quiz Hormones are secreted by
endocrine glands or cells into the blood. Only _____________ ___________with receptors for the hormone will respond to the signal.TARGET CELLS
What are the two places you can find cell receptors?Cell SurfaceInside the Cell
SWBAT evaluate a disruption in homeostasis and explain, through the use of a feedback mechanism, how the body compensates.
Homeostasis
Body's ability to maintain stable internal environment
Typically maintained with communication of the nervous and endocrine systems
Think about thirst, blood sugar, and body temperature?
Also known as Dynamic Equilibrium
Dynamic Equilibrium A balance between two opposite
reactions. Dynamic because there are changes
taking place. Equilibrium because there is a balance
Feedback Mechanism A release of chemicals or a reaction that helps
maintain equilibrium with in a system.
Example: hammer to knee A change in the environment is called a
stimulus. A response is the manner in which the
organism reacts to the stimulus. (knee jerk reflex)
Ex. cold, hot, fear
Homeostasis Control Mechanisms
The variable produces a change in the body
The three interdependent components of control mechanisms are:
Receptor – monitors the environment and responds to changes (stimuli)
Control center – determines the level of response to the stimulus
Effector – provides the actual response
Stimulus:Produceschangein variable
1
2
3
Changedetectedby receptor
Input:Informationsent alongpathway to Control Center
5Response ofeffector feedsback to influencemagnitude of stimulus andreturnsvariable tohomeostasis
Variable (in homeostasis)
Imbalance
Imbalance
Receptor (sensor)
Controlcenter
4
Output:Information sentalong pathway to Effector
Effector
Homeostatic Control Mechanisms
Feedback
The response either depresses (negative) or enhances (positive) the stimulusNegative Feedback
Response turns off stimulus (ex. your air conditioning at home, heart rate, breathing rate, oxygen)
Positive Feedback Response increases stimulus Rare in body (ex. Blood clotting)
Negative Feedback
• Prevents sudden, severe changes in the body
• Corrects the set point (balance point)• Causes opposite of bodily disruption to
occur, i.e. the ‘negative’• Limits chaos in the body by creating
stability• Most common type of feedback loop• Examples: body temperature, blood
pressure & glucose regulation
• Increases (accelerates) the actions of the body
• Produces more instability in the body
• Produces more chaos in the body
• There are only a few types necessary for our survival
• Positive feedback mechanisms are short-lived
• Controls only infrequent events that do not require continuous adjustments
• Considered to be the uncommon loop
• Examples: blood clotting and child birth
Positive Feedback
Positive Feedback In positive
feedback systems, the output enhances or exaggerates the original stimulus
Example: Regulation of blood clotting
Figure 1.6
Maintenance of Life
Receptors
Control center(set point)
Effectors(muscles or glands)
Response(Change is corrected.)
Stimulus(Change occursin internalenvironment.)
(Change is comparedto the set point.)
Homeostatic Imbalance
Disturbance of homeostasis or the body’s normal equilibrium
Overwhelming of negative feedback mechanisms allowing destructive positive feedback mechanisms to take over
Thyroid Problems
What would happen if the thyroid could no longer produce its hormones?
No negative feedback to hypothalamus and anterior pituitary