Student Response Sheet

1. What do we call electrical messages that are sent down the axon of a neuron? Action potentials

2. In one sentence, describe how the electricity in an action potential is generated. Generated by the opening of gated sodium channels

3. Draw a diagram of the cell membrane of the axon. Label the following on your drawing: cell interior, cell exterior, Na+ channels, K+ channels, Na+/K+ pump.

4. The main component of cell membranes are fats called phospholipids. Use the Internet to research the structure of a phospholipid. Label a phospholipid on your diagram.

5. What do these terms hydrophilic and hydrophobic mean and how do they relate to the structure of a cell membrane? Hydrophilic is the ability to dissolve in to something. Hydrophobic means not having the ability to mix with water. They relate to the structure of the cell membrane, because some things may be able to mix with in the cell, and others may not be able to.

6. Return to your cell membrane diagram. Use a yellow marker or colored pencil to color the parts of a phospholipid that are hydrophilic. Use a black marker or colored pencil to color in the parts of the molecules that are hydrophobic.

7. Add Na+ and K+ ions to your cell membrane drawing to show the placement of ions when the cell is at rest. Think about which side will have more K+ and which side will have more Na+.

8. How does the location of these ions relate to the overall membrane potential (charge) at this point? Place (-) signs on the side that is now negative and (+) signs on the side that is now positive.

9. The Na+/K+ pump pumps 3 Na+ ions out of the cell for every 2 K+ ions it brings into the cell. Is this specialized protein working via active or passive transport? Explain your reasoning. Passive transport because the protein is working

10. What causes the inside of the membrane to reverse charge and begin the action potential? Ca++ ions are allowed to enter the cell after a neurotransmitter opens up a gated ion channel. This begins the opening of voltage gated ion channels, which allow Na+ down its gradient into the cell, allowing the action potential down the axon.

11. Draw a graph of the action potential broken down into four steps as in the Internet activity. Make sure to label the axes and add units. Highlight or shade each step in a different color.

12. Beneath the graph, use the color marker or pen that corresponds to the step to describe in words what happens in the membrane during this step. Make sure to relate what is happening in the membrane to the value for membrane potential shown on the graph. Add a title to each step.

13. Which membrane protein is responsible for restoring the original concentration of Na+ and K+? Sodium potassium pump

14. What happens when the action potential reaches the end of the axon at the axon terminals? How does one neuron communicate with another neuron and complete the circuit? Causes neurotransmitters to be released in the synapse. Communicate through action potential.