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Homeostasis August 11,12 2014.  The maintenance of relatively stable internal conditions  Dynamic process – the body is constantly regulating to keep.

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Presentation on theme: "Homeostasis August 11,12 2014.  The maintenance of relatively stable internal conditions  Dynamic process – the body is constantly regulating to keep."— Presentation transcript:

1 Homeostasis August 11,

2  The maintenance of relatively stable internal conditions  Dynamic process – the body is constantly regulating to keep conditions within acceptable ranges Homeostasis

3 What are some variables maintained by homeostasis? Examples of Homeostasis

4 Many variables are maintained by homeostasis. Examples include:  Temperature  Blood pH  Blood sugar  Water balance  Blood pressure  Ion balance Examples of Homeostasis

5 Homeostatic Control Mechanisms

6 Analogies Thermostat Cruise control others?

7

8 What is the... Variable? Stimulus? Receptor? Control center? Effector?

9 What is the... Variable? Stimulus? Receptor? Control center? Effector? Receptors aren’t shown on this picture, but there are two sets of thermoreceptors: some in the hypothalamus to measure internal temperature, and some in the skin to measure external temperature

10 You do: What is the... Variable? Stimulus? Receptor? Control center? Effector?

11 You do: What is the... Variable? Stimulus? Receptor? Control center? Effector? Receptors aren’t shown again, but there are two types of calcium receptors scattered throughout the body

12 Most homeostatic mechanisms are examples of negative feedback. In negative feedback, the output acts to change the direction of the stimulus. Example: If the body is hot, the hypothalamus will activate the sweat glands and dilate the blood vessels (the two outputs) … both of which will act to reduce the body temperature. Negative Feedback Mechanisms

13 Some processes in the body are positive feedback mechanisms. In positive feedback, the output enhances the stimulus Positive Feedback Mechanisms

14 Positive or Negative Feedback? Blood Clotting Blood Pressure Blood Pressure

15 Positive or Negative Feedback? Blood Clotting Blood Pressure Blood Pressure Positive – The output (platelet adhering) increases the original stimulus (platelet-attracting chemical) Negative– The output (decreased heart rate / increased diameter) decreases the original stimulus (high blood pressure)

16 In pairs, write a Venn diagram comparing and contrasting positive and negative feedback. Also, identify other examples of positive and negative feedback and be prepared to justify why they are examples. ** may be in or out of the body** (5 minutes) Positive and Negative Feedback

17 Most disease is caused by a disturbance of homeostatic mechanisms known as homeostatic imbalance. Homeostatic imbalance can result from  Aging  Genetic mutations  Pathogens  Environmental factors Homeostatic Imbalance

18 - 10 minutes - Congo Line review

19 Quiz next class! Homework

20 What were our objectives today and what did you learn? Closure

21 Study this diagram. 1)What is the stimulus? 2)What are the effectors? 3)Is this + or – feedback, and how can you tell? Exit Ticket

22 Identify the body system to which each organ belongs 4)Pancreas 5)Liver Ex) Which system cleans and returns body fluids to the blood stream? Exit Ticket


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