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Ch 10 Nervous System What is an Action Potential?
Physiology
Visit these web sites and answer the questions as you go through the
various tutorials.
PART 1. Begin this tutorial by going to the following website:
http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf
and choose the ACTION POTENTIAL TUTORIAL
A. First define these terms using the INTRODUCTION PART:
1. Action potential (based on charges)
2. Schwann Cell
3. Myelination versus speed of action potential
4. Neuron membrane polarity
5. Draw a neuron membrane below showing which side is positively vs negatively charged
6. List all ions involved in an action potential
B. Now go to the RESTING POTENTIAL PART.
1. Explain the sodium-potassium pump that maintains resting potential.
2. Draw a cell membrane below that is in RESTING POTENTIAL.? Show the two types of
gates and ions in two different colors (DO THIS FOR ALL OF THE DRAWINGS
THAT FOLLOW) . Next do the exercise in this part. Which ions are on the inside vs. the
outside?
C. Next view the DEPOLARIZATION PART which is the first step in an action potential.
1. Explain what DEPOLARIZATION is.
2. Next do the exercise to see how a cell membrane becomes depolarized. Draw a cell
membrane below that is depolarized showing all ions along with all gates. Show which
gates are closed and which are opened. What gate(s ) did you manipulate and how?
D. Now view the REPOLARIZATION PART.
1. Explain what REPOLARIZATION is.
2. Next do the exercise to see how a cell membrane becomes repolarized. Draw a cell
membrane below that is repolarized showing all ions along with all gates. Show which gates
are closed and which are opened. What gate(s ) did you manipulate and how?
E. Now continue the tutorial by viewing RETURN TO RESTING POTENTIAL.
1. Which protein is responsible for restoring the original concentrations of potassium and sodium
ions?
2. Now sketch a cell membrane that has returned to resting potential showing all ions and
proteins involved. What has happened to the K and Na gates?
3. Fill in the blanks. An animal uses ________________ of its energy to maintain
__________________.
F. Finish the tutorial by ZOOMING OUT. Watch the animation. What is a nerve impulse (also
called an action potential)?
****MAKE SURE YOU GO THROUGH THE SUMMARY AT THE END OF THE
MODULE. YOUR OBJECTIVE IN THIS LESSON IS TO UNDERSTAND WHAT AN
ACTION POTENTIAL IS ON A CHEMICAL LEVEL. COULD YOU EXLPLAIN THIS
BACK TO ME AS AN ESSAY QUESTION?
G. Now view this carton about action potentials. Does this whole process make sense to you? If
not go back and review it again.
http://brainu.org/files/movies/action_potential_cartoon.swf
PART 2. NOW FOR MORE PRACTICE ON THIS CONCEPT:
Work through the entire tutorial on GET BODY SMART from your text book site and answer
the questions that follow.
Go to the Nervous System and then do all TUTORIALS under the
following to help prepare for the next quiz on this part of Ch 10.
NEUROPHYSIOLOGY
http://highered.mcgraw-hill.com/sites/0072919329/student_view0/index.html
Do not go through the entire program
Go through the following parts and subparts. The red topics come up first and if you click on this
topic you will get the subtopics below that are in blue.
Overview of Neuron Cell Membranes
• Ion Channel Proteins
• Na+/K+ Pump (ATPase)
Resting Membrane Potentials
• Introduction to the Resting Axon
• Distribution of Ions in a Resting Axon
Neuron Action Potentials
• Sequence of Events
• Myelinated and Unmyelinated Axons
• Propagation Along Unmyelinated Axons
 Propagation Along Myelinated Axons
• Propagation Rates Compared
AN ACTION POTENTIAL
1. Information moves along the axon of a neuron in the form of an electrochemical change
known as what?
2. At rest, there is a potential difference across the cell membrane of -70 mV. Why?
3. The inside of the membrane is negatively charged. Explain why.
4. The outside of the membrane is positively charged relative to the inside. Explain why.
5. Describe the distribution of Na+ and K+ in and out of the cell.
6. When a small stimulus is applied to the cell membrane, what channels open and what diffuses
in which direction?

As a result, there is a local change in the ____________ in a relatively small region of the
plasma membrane.
7. Watch the animation. What is occurring?
DEPOLARIZATION
1. If the stimulus is strong enough, the neuron fires an_____________.
2. When the amount of stimulus causes the membrane to depolarize to threshold, what occurs?
3. Depolarization abruptly stops when what occurs?
4. Watch the animation. What is occurring?
REPOLARIZATION
1. The same voltage changes that cause the voltage-activated Na+ channels to close causes what
event to occur next?
2. After the Na+ channels inactivate, the rapid movement of ____________ out of the cell results
in a rapid_____________.
3. Watch the animation. What is occurring?
HYPERPOLARIZATION
1. K+ channels open and close slowly. As a result, what occurs?
2. This causes a slight _______________________called the after potential.
3. Although the voltage-activated channels are closed, what happens to the potassium?
4. Watch the animation. What is occurring?
RESTING POTENTIAL
1. Shortly after the negative after potential occurs, what happens next?
2. The sodium-potassium pump acts to re-establish the original ion concentrations by doing
what?
3. Watch the animation. What is occurring?
PART 3. Now go to this web site again and choose SYNAPTIC TRANSMISSION
http://outreach.mcb.harvard.edu/materials.htm
A. Begin with LEARNING AND MAKING THE CONNECTIONS and THE NEURON.
1. Sketch a neuron and label the parts as shown on the animation.
2. Sketch a synapse and label all parts as shown on the animation.
B. Next go to the SYNAPSTIC TRANSMISSION PART.
1. Draw 2 neurons and show how an impulse travels.
2. When an action potential reaches the end of the axon, what occurs?
3. Beginning with the inward surge of calcium, list ALL steps involved in the release and
restoration of the neurotransmitters.
B. Now go to the last EXERCISE.
1. What happened to your neurons that enabled you to learn this game?
PART 4. Now go to this web site:
http://bcs.whfreeman.com/thelifewire/content/chp44/4403s.swf
Watch this animation and explain how a neurotransmitter can begin the action potential that was
described in the last tutorial. (This ties in the neuromuscular junction we talked about in Ch 9.)
PART 5 . Next, go to this web site:
http://www.blackwellpublishing.com/patestas/animations/actionp.html
1. What is the difference between a myelinated axon and an unmyelinated axon?
2. Explain the difference of an action potential as travels down an unmyelinated axon versus
a myelinated axon. Salta