jackman/biol125-lectures
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

into neurotrans

Browse Source
This commit is contained in:
ackman678
2020-10-28 21:56:06 -07:00
parent 8ffd442701
commit 93d862046c
8 changed files with 1635 additions and 1588 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
neurophysiology2.md
View File

@@ -12,6 +12,10 @@
<div><img src="figs/Neuroscience5e-Fig-02.07-0_2233a33.png" height="200px"><figcaption>Neuroscience 5e Fig. 2.7</figcaption></div>
<div style="font-size:0.5em;">
<!-- date: -->
</div>
Note:
We learned last time that the experiments of Hodgkin, Huxley, and Katz showed that the Vm during an AP approaches ENa. And they thought that this might be due to changes in permeability for Na in the cell membrane that changes during the course of an action potential. Thus Hodgkin and Huxley hypothesized that APs can be explained by ion channels that change their permeability due to voltage— that these channels are voltage-gated.
@@ -290,18 +294,18 @@ TTX and TEA experiments from Moore 1967 J Gen Physiol; Armstrong and Binstock, 1
* Another way of describing permeability is using membrane conductance (*g*). Conductance (measured in siemens, *S*) is the reciprocal of resistance
* *g = 1/R*
* Ohm’s law:
* <span class= "fragment fade-in">Ohm’s law:
* *I = V/R*
* *I = gV*
* For an ion *x*,
* *I<sub>x</sub>* = ionic current flow, *E<sub>x</sub>* = equilibrium potential
* The membrane potential (*V<sub>m</sub>*) minus the equilibrium potential (*E<sub>x</sub>*) is the electrochemical driving force acting on an ion, thus *V = V<sub>m</sub> - E<sub>x</sub>*
* *I<sub>x</sub> = g<sub>x</sub>V*
* *I<sub>x</sub> = g<sub>x</sub>(V<sub>m</sub> - E<sub>x</sub>)*
* Solve for *g*:
* *g<sub>x</sub> = I<sub>x</sub>/(V<sub>m</sub> - E<sub>x</sub>)*
* *I<sub>x</sub>* determined from measurement of current changes plus or minus ion (or during pharmacological inhibition)
* *E<sub>x</sub>* calculated from Nernst equation using concentrations of inside and outside ions
* *I<sub>x</sub> = g<sub>x</sub>(V<sub>m</sub> - E<sub>x</sub>)*</span>
* <span class= "fragment fade-in">Solve for *g*:
* *g<sub>x</sub> = I<sub>x</sub>/(V<sub>m</sub> - E<sub>x</sub>)* </span>
* <span class= "fragment fade-in">*I<sub>x</sub>* determined from measurement of current changes plus or minus ion (or during pharmacological inhibition)</span>
* <span class= "fragment fade-in">*E<sub>x</sub>* calculated from Nernst equation using concentrations of inside and outside ions</span>
</div>
@@ -393,7 +397,7 @@ Can also see increases in K conductance during the AP, but this K+ conductance (
Note:
The threshold is a point of criticality in the system like trying to balance on a knifes edge. Just imagine any self-organized phenomena in nature: a snow field suddenly turning into an avalanche, liquid water turning into gas or solid forms, videos of cats or korean pop stars suddenly going viral. The point at which the states of these systems veer on the edge of order or disorder is the point of criticality also known to physicists as a phase transition.
The threshold is a point of criticality in the system like trying to balance on a knifes edge. Just imagine any self-organized phenomena in nature: a snow field suddenly turning into an avalanche, liquid water turning into gas or solid forms, videos of cat memes suddenly going viral. The point at which the states of these systems veer on the edge of order or disorder is the point of criticality also known to physicists as a phase transition.
---
@@ -548,6 +552,31 @@ figure comparing action potential propagation speed in an unmyelinated and myeli
action potential genaration occurs only at specific points, the nodes of Ranvier, along the myelinated axon
--
## Multiple sclerosis
* Disease caused by myelination defects and loss of neurons
* Seems like an autoimmune disease
* 1/750 of population in US get multiple sclerosis (MS)
* 1/40 risk if a parent has it
* 1/3 if an identical twin gets it
* Genetic and environmental risk factors
Note:
onset between ages 20-40.
blindness, motor weakness, paralysis.
ultimate cause of MS remains unclear. Immune system contributes to damage and is key component. Immune cells in CSF and injection of myelin in animals can cause EAE. Autoimmune disorder. Or persistent infection with a human retrovirus?
* women to men ratio 3/2
* Genetic component is likely the effect of multiple genes
---
## The Nobel Prize in Physiology or Medicine (1963)
@@ -587,25 +616,3 @@ Note:
---
## Multiple sclerosis
* Disease caused by myelination defects and loss of neurons
* Seems like an autoimmune disease
* 1/750 of population in US get multiple sclerosis (MS)
* 1/40 risk if a parent has it
* 1/3 if an identical twin gets it
* Genetic and environmental risk factors
Note:
onset between ages 20-40.
blindness, motor weakness, paralysis.
ultimate cause of MS remains unclear. Immune system contributes to damage and is key component. Immune cells in CSF and injection of myelin in animals can cause EAE. Autoimmune disorder. Or persistent infection with a human retrovirus?
* women to men ratio 3/2
* Genetic component is likely the effect of multiple genes