neurophys1,2

2018-04-17 10:45:39 -07:00
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@@ -538,17 +538,18 @@ For CaCl₂:  (58/2)log10(10/1) = +29 mV

 Since the Nernst equation is really just a linear equation of the form y = mx, you can think of this first term at the slope and the equilibrium potential for an ion varies linearly with the log of the concentration gradient. In other words there is 58 mV per tenfold change in the concentration gradient when we are talking about our potassium examples above, which is depicted here -->

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+<!-- 

 ## Electrochemical equilibrium

 <div><img src="figs/Neuroscience5e-Fig-02.05-2R_c30075c.png" height="500px"><figcaption>Neuroscience 5e Fig. 2.5</figcaption></div>


-Note:
-
 This plot depicts this equilibrium relationship for a hypothetical cell permeable only to potassium. 

+ -->
+
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 ## Electrochemical equilibrium summary
@@ -596,22 +597,17 @@ If our hypothetical battery holds the membrane at -58 mV, the equilbrium potenti
 At more negative membrane potentials than the nernst equilbrium potential we get net inward flow due to the stronger electrical driving force which in the case of potassium here is causing it to move against its chemical gradient.


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+<!-- 
 ## Membrane potential influences ion fluxes

 <figure><img src="figs/Neuroscience5e-Fig-02.06-2R_1ec257b.png" height="400px"><figcaption>Neuroscience 5e Fig. 2.6</figcaption></figure>


-Note:
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 The results of this thought experiment are displayed here, displaying the net movement of K⁺ ions into the cell when the membrane potential more negative or hyperpolarized than the K⁺ equilibrium potential, and net movement outward when the membrane potential is more positive or depolarized.
+ -->


-
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-## Both direction and magnitude of ion flux depend on the membrane potential
+<!-- ## Both direction and magnitude of ion flux depend on the membrane potential

 <div style="font-size:0.8em;">
 <div></div>
@@ -625,14 +621,13 @@ The results of this thought experiment are displayed here, displaying the net mo

 </div>

-Note:

 So to summarize, remember that both the direction (inward vs outward) and magnitude of charge flow or current depends on membrane potential. 

 Just remember Ohm’s law, I = V/R and rewrite it as Ix = (Vm - Ex)/R

 And we as scientists can experimentally vary...
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+ -->

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@@ -680,16 +675,6 @@ For a typical neuron at rest, pK : pNa : pCl = 1 : 0.05 : 0.45. Note that becaus
 - *"Expansion of the constant field equation to include both divalent and monovalent ions." (Spangler, S.G., Ala J Med Sci, 9: 218-223, 1972)*
 - [http://www.nernstgoldman.physiology.arizona.edu/using/](http://www.nernstgoldman.physiology.arizona.edu/using/)  

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-## Resting membrane and action potentials entail permeabilities to different ions
-
-<figure><img src="figs/Neuroscience5e-Fig-02.07-0_caebcb8.png" height="400px"><figcaption>Neuroscience 5e Fig. 2.7</figcaption></figure>
-
-
-Note:
-
-And as we will soon lecarn, the resting membrane potential and action potential voltage is mostly due to changes in K permeability and Na permeability across the neuronal membrane. As you can see in this figure, the resting membrane potential for a neuron is close to the EK eq potential due to much greater permeability for K. During an action potential Na permeability initially increases, until the Vm approaches the ENa  and then Na permeability decreases until the Vm again approaches the resting membrane potential and Pk increases.

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@@ -727,7 +712,7 @@ Cells are a bit like a semipermeable bag of electrolytes with different concentr
 | calcium (Ca<sup>2+</sup>), squid | 0.0001 | 10 | 100000 |
 | calcium (Ca<sup>2+</sup>), mammal | 0.0001 | 1–2 | 10000 |

-<figcaption>see also Neuroscience Table 2.1</figcaption>
+<figcaption>see also Neuroscience 5e Table 2.1</figcaption>
 </div>


@@ -770,12 +755,16 @@ Note:

 * Hypothesis– if axon resting potential (-65 mV) is predominantly due to K⁺ permeability then changing [K⁺]<sub>out</sub> should change the resting potential in a manner predicted by the Nernst equation
 	* Experiment– stick an electrode inside axon, one outside axon (in bath). Change the concentration of K⁺ in the bath and measure new membrane potential. Assume intracellular K⁺ is unchanged during experiment.
-	* Nernst equation prediction– resting potential will depolarize with a slope of 58 mV per tenfold change in K⁺ gradient
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+
+<!-- * Nernst equation prediction– resting potential will depolarize with a slope of 58 mV per tenfold change in K⁺ gradient -->

 Note:

 Alan Hodgkin, Andrew Huxley, Bernard Katz

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 ## K⁺ concentration gradient determines resting membrane potential
@@ -795,7 +784,6 @@ However it deviates from this expected relationship (shown by the black line), e

 **Because other ions, particularly Cl⁻ and Na⁺, are also slightly permeable and the contribution of these other ions is more evident at low K⁺ concentrations.**

-
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 ## Hodgkin and Katz– 1949 conclusions 1
@@ -874,41 +862,71 @@ As you can see on the left here changing extracellular [Na] changes the action p
 * During depolarization membrane becomes super permeable to Na⁺
 * There must be Na⁺ channels that are closed during rest but become open during an action potential, and closed again at the end of an action potential

-<figure><img src="figs/Neuroscience5e-Fig-02.07-0_caebcb8.png" height="200px"><figcaption>Neuroscience 5e Fig. 2.7</figcaption></figure>
+<!-- <figure><img src="figs/Neuroscience5e-Fig-02.07-0_caebcb8.png" height="200px"><figcaption>Neuroscience 5e Fig. 2.7</figcaption></figure> -->

 Note:

 So a summary of the Hodgkin and Katz experiment conclusions...

+
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+
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+## Resting membrane and action potentials entail permeabilities to different ions
+
+<figure><img src="figs/Neuroscience5e-Fig-02.07-0_caebcb8.png" height="400px"><figcaption>Neuroscience 5e Fig. 2.7</figcaption></figure>
+
+
+Note:
+
+And as we will soon lecarn, the resting membrane potential and action potential voltage is mostly due to changes in K permeability and Na permeability across the neuronal membrane. As you can see in this figure, the resting membrane potential for a neuron is close to the EK eq potential due to much greater permeability for K. During an action potential Na permeability initially increases, until the Vm approaches the ENa  and then Na permeability decreases until the Vm again approaches the resting membrane potential and Pk increases.
+
+
+---
+
+## The action potential– summary
+
+<figure><img src="figs/action_potential_ab5134f.png" width="800px"><figcaption></figcaption></figure>
+
+
+Note:
+
+And this is just a overall summary of what we have been discussing
+
+
+
+
+<!-- 
+
 ## Action potential form and nomenclature

 <div><figcaption class="big">(1) Squid giant axon, (2) frog motor neuron axon</figcaption><img src="figs/Neuroscience5e-Box-02C-0-1_6a18c85.png" width="800px"><figcaption>Neuroscience 5e Box 2C</figcaption></div>


-Note:
-
 The membrane potential rapidly depolarizes during the rising phase of an AP. Action potentials cause membrane to depolarize so much that the membrane potential transiently becomes positive with respect to the external medium, producing the overshoot. Then during repolarization, the membrane potential becomes even more negative than the resting membrane potential for a short time, giving the undershoot phase or ‘afterhyperpolarization’.  



 AHP due to voltage-gated K⁺ channels, including Ca²⁺ activated potassium channels— incr K⁺ permeability, and inactivation of Na⁺ permeability.

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 ## Action potential forms

 <div><figcaption class="big">(1) Frog motor neuron cell body, (2) guinea pig inferior olive neuron cell body, (3) cell body of purkinje neuron</figcaption><img src="figs/Neuroscience5e-Box-02C-0-2_f48aa34.png" width="800px"><figcaption>Neuroscience 5e Box 2C</figcaption></div>


-Note:

 Summation of many spikelets cause unlike most neurons, purkinje cells in cerebellum have dendrites that can initiate action potentials. The dendrites aren’t myelinated.

 Llinas Sugimori J Physiol 1980 Purkinje neurons

-<!-- Action potential forms
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+## Action potential forms

 cell body of a purkinje neuron

@@ -922,12 +940,3 @@ Llinas Sugimori J Physiol 1980 Purkinje neurons
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-## The action potential– summary
-
-<figure><img src="figs/action_potential_ab5134f.png" width="800px"><figcaption></figcaption></figure>
-
-
-Note:
-
-And this is just a overall summary of what we have been discussing