Name________________
Homeostasis and the Nervous System
In this activity, you and your partner will use the internet to explore what homeostasis is,
why it is important and how the nervous system works to help maintain it. Links are on
the nervous system page on our AP Biology wiki, so you don’t have to type them in.
This mostly has information pertaining to Targets I, II, and V.
Part 1 What is Homeostasis?
Go to the following website:
http://www.biology-online.org/articles/introduction-homeostasis.html
1.
In your words, what is homeostasis and why is it important to our survival?
2.
What roles do the following organs play in maintaining homeostasis? What do they
help maintain levels of? How do they get signals to do so?
a. Kidneys
b. Lungs
c. Skin
d. Liver
e. Pancreas
3.
This one is to be answered using your own nervous system command center (your
brain). Thinking on a cellular level, why is each of the following important for our
bodies to maintain? What would happen to molecules or cells if the value got too
high or too low? Use words from previous units.
a. pH
b. water concentration
c. glucose concentration
d. temperature
e. oxygen concentration
f. carbon dioxide concentration
Now go to the following website:
http://www.phys.unsw.edu.au/biosnippets/
Watch the definition and then click on “Analogy”
4. What is the function of a sensor?
5. What is the function of the control center?
6. What is the function of the effector?
7. What is negative feedback in your own words.
Now click on “In Humans”.
8. What might cause body temperature to decrease?
9. Though not strictly defined, what is meant by the afferent and efferent pathways?
10. What is the function of the hypothalamus? Where is it?
11. How would shivering increasing body temperature?
Go to the following website: http://www.bio.miami.edu/~cmallery/150/physiol/c44x10thermoreg.jpg
12. What other responses do we have to cold temperatures?
13. What responses do we have to warm temperatures?
14. How does temperature affect enzymes? Why is this important to organisms?
15. Can all organisms regulate their body temperature like humans can? If so, how? If not, how
does this fact affect them. Explain.
16. Based on the targets for this unit, other than the nervous system, what other system signals organs in
the negative feedback mechanisms that maintain homeostasis?
Part 2 – Neurons – Go to http://health.howstuffworks.com/brain1.htm
1. What is a neuron?
2. Name & describe the 3 basic parts of a neuron.
3. Label the parts of this neuron:
4. Name & describe 4 different types of neurons
Part 3 – The Sodium/Potassium Pump – View the animation.
Go to http://tinyurl.com/mmqrna2
1. How many positive sodium ions are being pumped out?
2. How many positive potassium ions are being pumped in?
3. Since the numbers are different could this cause an imbalance of charge on either side of the
membrane?
4. What molecule is providing the energy for this ion transport?
5. What is the process called when particles are being transported against the concentration
gradient across a membrane?
Action Potential-- Now go to the following website:
http://opl.apa.org/contributions/ITL/ap.htm
6. Draw the graph pictured below. Include axes labels, units, numbers and the labels on the
graph.
7. Watch the animation. When the line is at -70 millivolts, which ions are more plentiful
outside of the membrane (extracellular) and which are more plentiful inside of the membrane
(intracellular)?
8. When depolarization occurs, which ions move? Where do they move? How does this
change the membrane potential?
9. During repolarization, which ions move? Where do they move? How does this change the
membrane potential?
10. How does the membrane potential get back to -70 millivolts?
Part 4– The Nerve impulse & Synapse
In this section we will focus on the synapse. As you will recall, the synapse is the space
between the axon terminal of on neuron and the dendrites of another. It is important to
remember that the two neurons aren’t touching; they are just really close to each other.
Go to the following web site and answer the questions below:
http://tinyurl.com/msqkuhd
Note—You have to press next after watching the animation on each
page.
1. Label the following: Presynaptic Neuron, Vesicles, Dendrite, Synaptic Cleft,
Neurotransmitter, Postsynaptic Neuron, axon terminal
2. Neurotransmission occurs between the ______ __________ of one neuron and the
___________ of another.
3. At the synapse, information is transmitted from one neuron to another via what kind of
messengers?
4. An action potential is an ____________ signal.
5. Why are chemical messengers, or neurotransmitters, needed to get information across
the synapse?
6. What are ions?
7. Why are ions important for neurotransmission?
8. What are the 4 most common ions?
9. How do ions get across the neuron membrane?
10. An ion channel will only open when a specific _________________ binds to its
_____________ ________.
11. If enough ions flow into the post synaptic neuron, the neuron’s threshold will be reached
and the neuron will fire an ___________ ______________.
12. What are vesicles?
13. What effect does an action potential have on a vesicle?
14. What happens to the neurotransmitter once it has done its job?
15. What do mitochondria do?
16. List the 5 steps that take place in transmitting information across a synapse (these are
in the “Summary” section of the movie).
a.
b.
c.
d.
e.