CONNECT! What was it like learning to ride a bike? What was it like learning to ride a bike? Could you ride in a straight line and balance, at first? Could you ride in a straight line and balance, at first? What happened if you couldn’t? What happened if you couldn’t? If you viewed your path from above on your first successful, independent ride, what would it look like? If you viewed your path from above on your first successful, independent ride, what would it look like?

Homeostasis is maintaining a stable internal environment even in a changing environment is maintaining a stable internal environment even in a changing environment

Responses to Environmental Change Organism Change (Stimulus) Reaction (Response) Plants Hot and dry weather Stomates close to conserve water Some species of bacteria Temp below a certain point Produce an “antifreeze” chemical Human Hears a loud noise at night Heart rate increases

Homeostasis is the maintenance of internal conditions within a narrow range that varies only slightly over time Homeostasis is the maintenance of internal conditions within a narrow range that varies only slightly over time it is necessary to keep every living thing alive it is necessary to keep every living thing alive

Blood Sugar Example Blood sugar levels show a rise after a meal but the body quickly restores these levels to equilibrium using the hormone insulin. Blood sugar levels show a rise after a meal but the body quickly restores these levels to equilibrium using the hormone insulin. This example illustrates why homeostasis can be considered dynamic equilibrium (or adjusting balance), since the body constantly monitors and makes adjustments to keep us alive. This example illustrates why homeostasis can be considered dynamic equilibrium (or adjusting balance), since the body constantly monitors and makes adjustments to keep us alive.

Homeostasis Graph

Chunk Time! Define homeostasis. Define homeostasis. Define stimulus and response. Define stimulus and response. Give examples of how plants, some bacteria, and humans respond to changes in their environment. Give examples of how plants, some bacteria, and humans respond to changes in their environment. Explain how the body maintains blood sugar level in a narrow range after a meal. Explain how the body maintains blood sugar level in a narrow range after a meal. Why is homeostasis also called “dynamic equilibrium”? Why is homeostasis also called “dynamic equilibrium”? Describe a graph of homeostasis – show it with your hands. Describe a graph of homeostasis – show it with your hands. What happens if the body condition continually increases or decreases? What happens if the body condition continually increases or decreases? Why do you think I chose a balance to be the background for the homeostasis notes? Why do you think I chose a balance to be the background for the homeostasis notes?

Connect! If you are the football player that catches the quarterback’s passes, what is your position? If you are the football player that catches the quarterback’s passes, what is your position? If you still have a house phone line, and it rings, what do you pick up? If you still have a house phone line, and it rings, what do you pick up? So…“receptor” is another word for _____. So…“receptor” is another word for _____.

A. Cell-to-cell Communication The “Ultimate Maintainer” is the cell membrane which is for allowing materials into and out of the cell as well as receiving messages from other cells The “Ultimate Maintainer” is the cell membrane which is for allowing materials into and out of the cell as well as receiving messages from other cells

HOMEOSTASIS CELL TO CELL COMMUNICATION NERVOUS SYSTEM ENDOCRINE SYSTEM RECEPTORS IN CELL MEMBRANE IS MAINTAINED BY IS ACHIEVED BY BOTH USING

How do the different parts of your body “know” how to play soccer when you want them to? How do the different parts of your body “know” how to play soccer when you want them to? How does your body “know” when to go through a growth spurt? How does your body “know” when to go through a growth spurt? It’s all about cell to cell communication and the two systems involved – the nervous and endocrine systems, which together coordinate and control our bodies by receiving and sending messages. It’s all about cell to cell communication and the two systems involved – the nervous and endocrine systems, which together coordinate and control our bodies by receiving and sending messages.

Chunk Time! What is the function of the cell membrane? What is the function of the cell membrane? How is homeostasis maintained? How is homeostasis maintained? How is cell-to-cell communication achieved? How is cell-to-cell communication achieved? What does “receptor” mean? What does “receptor” mean? What two systems coordinate and control our bodies by sending and receiving messages? What two systems coordinate and control our bodies by sending and receiving messages?

Nervous System Basically your body is “wired’ the same way the electric company has wired our homes for electricity. You have specific cells that carry messages for you called neurons (nerve cells). Basically your body is “wired’ the same way the electric company has wired our homes for electricity. You have specific cells that carry messages for you called neurons (nerve cells).

Neurons conduct electrical signals called impulses very quickly from one part of the body to another. It takes a fraction of a second for your brain to tell your body to move out of the way of a speeding car. Neurons conduct electrical signals called impulses very quickly from one part of the body to another. It takes a fraction of a second for your brain to tell your body to move out of the way of a speeding car.

Nerve cells secrete chemicals that signal adjacent nerve, muscle or gland cells. Nerve cells secrete chemicals that signal adjacent nerve, muscle or gland cells. These secretions are detected by specific receptor molecules on the cell membranes which receive the message. These secretions are detected by specific receptor molecules on the cell membranes which receive the message. The chemicals are called neurotransmitters.

Chunk! What is the proper name for a nerve cell? What is the proper name for a nerve cell? What is the job of nerve cells? What is the job of nerve cells? What kind of signals do nerve cells carry? What kind of signals do nerve cells carry? What are the chemicals called that neurons release at the end of the cell? What are the chemicals called that neurons release at the end of the cell? How does the next cell pick up the message? How does the next cell pick up the message? What is the gap between one neuron and the next called? What is the gap between one neuron and the next called?

What happens if homeostasis is not maintained in an organism? What happens if homeostasis is not maintained in an organism?