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BIO303: Neurobiology

Unit 2: Electrical Signaling   Our nervous system is amazingly responsive and powerful when reacting to information about the body and its environment. If you touch a very hot object, you instantly feel pain and automatically withdraw your hand. The entire process, from heat sensation to the coordination of motor function, happens within millisecondsin other words, faster than you can consciously think! This type of speed requires a very fast and strong signaling method known as electrical signaling. This unit explains this process in detail, teaching you how signaling is generated and how it is propagated. You will also learn about a few devastating diseases that occur when the process is compromised.

Unit 2 Time Advisory
This unit will take you 9.5 hours to complete.

☐    Subunit 2.1: 1.5 hours

☐    Subunit 2.2: 2 hours

☐    Subunit 2.3: 2 hours

☐    Subunit 2.4: 2 hours

☐    Subunit 2.5: 2 hours

Unit2 Learning Outcomes
Upon successful completion of this unit, the student will be able to: - explain what a resting membrane potential and the ionic basis of electric potential are; - define a voltage-dependent current, and describe how sodium-potassium channels function in a voltage-dependent current; - define threshold, depolarization, refractory periods, and the all-or-none principle; - compare and contrast channels and transporters; - compare and contrast voltage-gated and ligand-gated channels; - explain how signals are propagated; and - describe three diseases of electrical signaling.

2.1 Electric Potential   2.1.1 Resting Membrane Potential   - Web Media: YouTube: Great Pacific Media’s “The Nervous System: Neurons, Networks, and the Human Brain’s ‘Neuron Resting Potential’” Link: YouTube: Great Pacific Media’s “The Nervous System: Neurons, Networks, and the Human Brain’s ‘Neuron Resting Potential’” (YouTube)
 
Instructions: Watch this video about key components of the nervous system. This resource covers subsections 2.1.1 and 2.1.2.

 Watching this video should take approximately 4 minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Web Media: Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 4th Edition: “Animation 2.1: The Resting Membrane Potential” Link: Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 4th Edition: “Animation 2.1: The Resting Membrane Potential” (Adobe Flash)
     
    Instructions: Watch the entire animation. To begin, either click on “Step Through” or “Narrated.”  Then, click the play button on the webpage to begin the video.
     
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2.1.2 Relative Ion Concentrations   Note: This topic is covered by the video beneath subunit 2.1.1.

2.1.3 Nernst Equation and Ionic Basis of Electrical Potential   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “The Forces that Create Membrane Potentials” and “The Ionic Basis of the Resting Membrane Potential” Links: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “The Forces that Create Membrane Potentials” (HTML) and The Ionic Basis of the Resting Membrane Potential (HTML)

 Instructions: Read both webpages, click on any embedded hyperlinks,
and explore the figures.  

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  • Web Media: YouTube: LLKeeley’s “4. Nernst Equation and Calculations of Membrane Potentials” Link: YouTube: LLKeeley’s “4. Nernst Equation and Calculations of Membrane Potentials” (YouTube)
     
    Instructions: Watch this video for a brief introduction to calculating cell membrane potentials. Take some time to take notes on the formula provided.

    Watching this video should take approximately 4 minutes.
     
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2.1.4 Ion Channels   - Web Media: YouTube: Diane K. O'Dowd’s “Membrane Potential” Link:  YouTube: Diane K. O'Dowd’s “Membrane Potential” (YouTube)
 
Instructions: Watch this video that provides a visual explanation of membrane potential.

 Watching this video should take approximately 2 minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
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2.2 Action Potential   - Reading: W.H Freeman & Co.: Life -- The Science of Biology (7th ed.): “Chapter 44: The Action Potentials” Link: W.H Freeman & Co.: Life --The Science of Biology (7th ed.): “Chapter 44: The Action Potentials” (HTML and Adobe Flash)
 
Instructions: Click on each tab for “The resting membrane potential,” and read or listen to its contents. Then, navigate to “page 2,” click on each tab for “The action potential,” and read or listen to its contents.
 
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2.2.1 Voltage-Dependent Currents   - Web Media: YouTube: Garland Science’s “Action Potential” and 1Lecture.com’s “Action Potential Propagation in an Unmyelinated Axon” Link: YouTube: Garland Science’s “Action Potential” (YouTube) and 1Lecture.com’s “Action Potential Propagation in an Unmyelinated Axon” (Adobe Flash)
 
Instructions: Watch the linked videos above.

 Watching these videos should take approximately 5 minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

2.2.2 Sodium and Potassium Channels   - Web Media: YouTube: APBio Tutorials’ “Nerve Impulse” Link: YouTube: APBio Tutorials’ Nerve Impulse (YouTube)
 
Instructions: Watch the video linked above to learn how sodium and potassium channels function during a nerve impulse.

 Watching this video should take approximately 2 minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
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2.2.3 Squid Cell Example   - Web Media: YouTube: Alan Hodgkin’s “Action Potential from Squid” Link: YouTube: Alan Hodgkin’s “Action Potential from Squid” (YouTube)
 
Instructions: Watch the video linked above.

 Watching this video should take approximately 5 minutes.  
    
 Terms of Use: Please respect the copyright and terms of use
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2.2.4 Threshold   - Reading: The University of Texas’s Neuroscience Online: Professor John Byrne’s “Ch 1: Resting Potentials and Action Potentials” Link: The University of Texas’s Neuroscience Online: Professor John Byrne’s “Ch 1: Resting Potentials and Action Potentials” (HTML and Adobe Flash)
 
Instructions: Read the following sections: “Introduction to the Action Potential,” “Intracellular Recordings from Neurons,” and “Components of the Action Potential.”
 
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2.2.5 Depolarization   Note: This topic is covered in the reading assigned beneath subunit 2.2.4.

2.2.6 Refractory Period   - Reading: Biologymad.com: “Nervous System – Nerve Impulses” Link: Biologymad.com: “Nervous System – Nerve Impulses” (HTML)
 
Instructions: Click on the hyperlink titled “Propagation of Impulses,” and read the section “How are nerve impulses propagated?”
 
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2.2.7 All-or-None Principle   - Reading: Biologymad.com: “Nervous System – Nerve Impulses” Link: Biologymad.com: “Nervous System – Nerve Impulses” (HTML)
 
Instructions: Click on the hyperlink titled “Action Potential.” Then, scroll down the webpage until you reach the section titled “All or Nothing Law,” and read this entire section. 
 
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2.3 Ion Channels and Transporters   2.3.1 Channel vs. Transporter   - Reading: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” Link: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes”  (HTML)
 
Instructions: Click on the hyperlink titled “Membrane Currents,” and read the entire section to understand how channels and transporters work together.
 
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2.3.2 Voltage-gated Ion Channels   - Web Media: 1Lecture.com: “Voltage-Gated Channels and the Action Potential” Link: 1Lecture.com: “Voltage-Gated Channels and the Action Potential” (Adobe Flash)
 
Instructions: Watch the video linked above.

 Watching this video should take approximately 3 minutes.   
    
 Terms of Use: Please respect the copyright and terms of use
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2.3.3 Ligand-gated Ion Channels   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “Ligand-Gated Ion Channels” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “Ligand-Gated Ion Channels” (HTML)
 
Instructions: Read the entire webpage and click on the hyperlinks to the figures.
 
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2.3.4 Other Ion Channels   - Reading: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” Link: What Is Life:Lukas K. Buehler’s “Bioelectricity of Cell Membranes” (HTML)
 
Instructions: Click on the hyperlink titled “Synaptic Transmission,” and read the entire section to learn about the role of other ion channels in the nerve cell.
 
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2.3.5 Specificity of Ion Channels   - Reading: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” Link: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” (HTML)
 
Instructions: Click on the hyperlink for “Ion Selectivity,” and read the entire section. Ion channels can be remarkably specific and non-specific,depending on their purpose for the body. For example, potassium channels used in action potential are highly specific to potassium and will not allow other ions to sneak through. This is largely due to the thermodynamic properties of the channel, which is in turn based on the structure of the channel itself. Be sure to understand this connection, noting how structure determines specificity!
 
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2.3.6 Transport and Maintenance of Potential   - Reading: Biologymad.com: “Nervous System – Nerve Impulses” Link: Biologymad.com: “Nervous System – Nerve Impulses” (HTML)
 
Instructions: Click on the hyperlink for “Resting Membrane Potential,” and read this section to understand how membrane potential is maintained.
 
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2.4 Propagation of Signal   2.4.1 Bidirectional   - Web Media: YouTube: Khan Academy’s “Neuronal Synapses” Link: YouTube: Khan Academy’s “Neuronal Synapses” (YouTube)
 
Also available in:
iTunes U
 
Instructions: Watch the video linked above

 Watching this video should take approximately 20 minutes.   
    
 Terms of Use: This video is licensed under a [Creative Commons
Attribution-NonCommercial-NoDerives United States License 3.0](). It
is attributed to the Khan Academy. 

2.4.2 Unidirectional   - Reading: Biologymad.com: “Nervous System – Nerve Impulses” Link: Biologymad.com: “Nervous System – Nerve Impulses” (HTML)
 
Instructions: Click on the hyperlink titled “Propagation of Impulses,” and read the entire section. Although we saw this resource in section 2.3.6, work through this content again, paying attention to how the membrane potential over the entire nerve serves to propagate nerve impulses.
 
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2.4.3 Myelin and Nodes of Ranvier   - Reading: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” Link: What Is Life: Lukas K. Buehler’s “Bioelectricity of Cell Membranes” (HTML)
 
Instructions: Click on the hyperlink “Axonal Propagation and Myelination,” and read the entire section.
 
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2.4.4 Saltatory Conduction   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “Ch 3: Increased Conduction Velocity as a Result of Myelination” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc.,Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience 2nd Edition: “Ch 3: Increased Conduction Velocity as a Result of Myelination” (HTML)

 Instructions: Read this section of Chapter 3, click on any embedded
hyperlinks, and make sure to click on the figures at the end of the
text to enlarge and explore them.  
    
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2.4.5 Safety Factor   - Reading: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 4: Synaptic Transmission and the Skeletal Neuromuscular Junction” Link: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 4: Synaptic Transmission and the Skeletal Neuromuscular Junction” (HTML)
 
Instructions: Read the section on the “Physiology of Synaptic Transmission at the Neuromuscular Junction.”
 
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2.4.6 Synapse   - Reading: Biologymad.com: “Nervous System: Synapses” Link: Biologymad.com: “Nervous System: Synapses (HTML)
 
Instructions: Click on and read the section titled “Different Types of Synapses.”
 
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2.5 Diseases of Electrical Signaling   2.5.1 Tetrodotoxin   - Reading: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 4: Synaptic Transmission and the Skeletal Neuromuscular Junction” and “Ch 2: Ionic Mechanisms and Action Potentials” Links: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 4: Synaptic Transmission and the Skeletal Neuromuscular Junction” (HTML) and “Ch 2: Ionic Mechanisms and Action Potentials” (HTML)
 
Instructions: Click on the first link above, then scroll down to section 4.7 to read about the “Iontophoresis of ACh.” Then, click the second link posted above, and scroll down to section 2.5 to read about the “Pharmacology of the Voltage-Dependent Membrane Channels.”

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2.5.2 Multiple Sclerosis   - Reading: Imaginis: “What Causes Multiple Sclerosis?” Link: Imaginis: “What Causes Multiple Sclerosis?” (HTML)
 
Instructions: Read the webpage linked above.
 
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  • Web Media: YouTube: mPenn1’s “What Is Multiple Sclerosis?” Link: YouTube: mPenn1’s “What Is Multiple Sclerosis? (YouTube)
     
    Instructions: Watch the video linked above

    Watching this video should take approximately 2 minutes. 
     
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2.5.3 Channelopathies   - Reading: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 2: Ionic Mechanisms and Action Potentials” Link: The University of Texas’s Neuroscience Online: Dr. John Byrne’s “Ch 2: Ionic Mechanisms and Action Potentials” (HTML)
 
Instructions: Read the section on “Channelopathies.”
 
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  • Assessment: The Saylor Foundation’s “Unit 2 Assessment” Link: The Saylor Foundation’s “Unit 2 Assessment (PDF)

    Instructions: Complete this quiz after working through Unit 2. The questions are multiple choice, matching, or labeling diagrams. You can check your answers with The Saylor Foundation’s “Unit 2 Assessment Answer Key (PDF).