1. Mr. Mah Living Environment Lecture 10

2.  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 Surface  Inside the Cell

3. Mr. Mah Living Environment Lecture 10

4.  SWBAT evaluate a disruption in homeostasis and explain, through the use of a feedback mechanism, how the body compensates.

5.  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

6.  A balance between two opposite reactions.  Dynamic because there are changes taking place.  Equilibrium because there is a balance

7.  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

8. TThe variable produces a change in the body TThe three interdependent components of control mechanisms are: RReceptor – monitors the environment and responds to changes (stimuli) CControl center – determines the level of response to the stimulus EEffector – provides the actual response

9. Stimulus: Produces change in variable 1 2 3 Change detected by receptor Input: Information sent along pathway to Control Center 5 Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis Variable (in homeostasis) Imbalance Receptor (sensor) Control center 4 Output: Information sent along pathway to Effector Effector

10.  The response either depresses (negative) or enhances (positive) the stimulus  Negative 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)

11. 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

14. 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

15.  In positive feedback systems, the output enhances or exaggerates the original stimulus  Example: Regulation of blood clotting Figure 1.6

16. Receptors Control center (set point) Effectors (muscles or glands) Response (Change is corrected.) Stimulus (Change occurs in internal environment.) (Change is compared to the set point.)

17.  Disturbance of homeostasis or the body’s normal equilibrium  Overwhelming of negative feedback mechanisms allowing destructive positive feedback mechanisms to take over

18.  What would happen if the thyroid could no longer produce its hormones?  No negative feedback to hypothalamus and anterior pituitary