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UNIT 9 The Nervous System sciencepeek.com Name __________________________________ Date _________________ Period _____ Part 3 - Membrane Potential 1. Every cell has a voltage, much like a battery has a voltage (between it’s two terminals). Voltage is a measure of how much a charge (positive or negative) “wants” to flow. The voltage across the cells of your body is the: 2. The inside (cytoplasm or cytosol) is _______________ compared to the outside of the cell (extracellular fluid) which is ______________. 3. When a neuron is at rest (not being stimulated) it maintains a _____________ _____________. 4. The average resting potential of many vertebrate neurons is: ________ millivolts (mV). 5. The sodium-potassium pump is the main contributor to the resting membrane potential of most cells. Fill in the general process of how it maintains this resting potential. 6. What is the second main contributor to the resting membrane potential, and which channel is more abundant? 7. Describe what an electrochemical gradient is, in your words so that you’ll be able to explain it on a test, hint hint! 8. The inside of a cell has a higher concentration of _____ ions and the outside has a higher concentration of _____ ions. 9. Describe the two types of polarization events that occur and label them with a simple graph. Page 1 of 2 UNIT 9 The Nervous System sciencepeek.com Part 4 - The Action Potential 10. Action potentials (or nerve impulses) are created when the membrane is depolarized to about _____ millivolts (mV). 11. Where on the neuron does the action potential originate? ____________________________________ 12. A threshold potential is: 13. Graded potentials are the result of activated gated ion channels whereas action potentials are caused by ___________________________________. 14. What are the two channels that are used to create action potentials? 15. What are the three phases of an action potential? 16. Fill in the sequence of events that occur during an action potential. 17. Describe the nature of action potentials. 18. Draw a myelinated neuron and show how action potential travel down the axon at the nodes of Ranvier. Page 2 of 2