1. Stimulus & Response From ksnow.wikispaces.com/file/view/Stimulus-Response-Tropisms.PPT

2. Stimulus Achange in organism’s environment A change in organism’s environment

3. Types of Stimuli   A stimulus can either be external or internal.   External stimuli- come from factors found in the environment. Examples- temperature, predators, presence of water or food, etc   Internal stimuli- come from factors within an organism Examples- germs, dehydration, lack of energy, pain

4. Stimulus Is this stimulus external or internal?

5. Response An organisms reaction to change.

6. Response

7. Homeostasis Homeo- same Stasis- state of balance The purpose of response to stimuli in organisms is to maintain homeostasis, a balance within it’s internal systems.

8. Examples  Stimulus = Is this internal or external? Is this internal or external?  Response =  Stimulus = Is this internal or external? Is this internal or external?  Response = Lack of water Wilting Bacteria or Virus Fever

9. General Adaptation Syndrome  Three phase pattern of physiological response to stress  Alarm phase  Occurs when homeostasis is disrupted and the body prepares for “fight or flight”  Homeostasis  a balanced physical state in which all the body’s systems function smoothly  A stressor is interpreted by the cerebral cortex and triggers the autonomic nervous system  ANS  the portion of the central nervous system that regulates bodily functions that a person does not normally consciously control This & next 4 slides from faculty.spokanefalls.edu/InetShare/AutoWebs/barrym/Unit%202.ppt

10. General Adaptation Syndrome  ANS has 2 branches: sympathetic and parasympathetic  The sympathetic branch energizes the body for fight or flight by signaling the release of several stress hormones  The parasympathetic branch slows the body down after stress reaction  The hypothalamus determines the overall reaction to stressors  Controls sympathetic NS and directs stress response

11. General Adaptation Syndrome  Epinephrine secreted by adrenal glands  Strengthens heart beat  Dilates bronchioles  Increases oxygen intake  Stimulates release of glucose (sugar)  Dilates pupils to improve vision  ACTH (adrenocorticotrophic hormone)  Releases cortisol, making nutrients readily available  Endorphins released to relieve any physical pain

12. General Adaptation Syndrome  Resistance phase  Begins almost immediately after beginning of alarm phase  Body adjusts in order to return to homeostasis  Parasympathetic nervous system helps keep energy levels under control  Basically the body works overtime, until the body can’t function anymore, or the stressor is eliminated.

13. General Adaptation Syndrome  Exhaustion phase  Occurs after continuous alarm and resistance reactions  Physical and emotional energy to battle stress have been depleted  Adaptation energy stores have been depleted  Is the physical and mental foundations of our ability to cope with stress  Superficial stores are readily accessible and used for everyday stressors  Can be replenished  Deep stores are accessed following use of superficial stores

14. Tropisms  Tropism = plant’s growth response toward or away from a stimulus

15. Tropisms  Positive tropism  Negative tropism

16. Tropisms  Tropism = plant’s growth response toward or away from a stimulus  Positive tropism = plant grows toward a stimulus  Negative tropism

17. Tropisms  Tropism = plant’s growth response toward or away from a stimulus  Positive tropism = plant grows toward a stimulus  Negative tropism = plant grows away from a stimulus

18. Hydrotropis m Hydrotropism = a plant’s roots grow toward water Is this positive or negative?

19. Phototropism Plants grow toward a source of light Animation: http://botanical-online.com/animation8.htm

20. Examples

21. Thigmotropism A plant grows toward or away from pressure Positive turns toward pressure Negative turns away from pressure

22. Geotropism  A plant grows with or against gravity  Also called Gravitropism Negative- A plant’s stems or trunk grow up, against the pull of gravity. Positive- A plant’s roots grow down, with the pull of gravity Animation: http://botanical-online.com/animation4.htm

23. Regardless of the slope of the land, the tree grows up against gravity. Regardless of the position a seed is planted in, the roots grow down with gravity and the stem up against gravity.

24. Working Together   Plant tropisms work together to maintain homeostasis within the plant + geotropism + phototropism - geotropism + hydrotropism