Introduction to optometry foundation year at city university of london Introductory biological sciences module Lesson 8 about the neurons. Everything you need to know about the neurons in the course.
Resting potential only exists locally on either side of the membrane
Neurones axoplasm and the extracellular fluid surrounding it is electrically neutral
Neuron at rest
Chemical force
Nature likes substances to be equally distributed, when it isn’t it
causes a concentration gradient. Substances flow down this
concentration gradient to reach equilibrium again.
A concentration gradient needs energy, and also releases
energy. Eg, hydroelectricity
Ion is a charged atom or
molecule, can be negatively charged (if more
electrons than protons) or positively charged (if
more protons than electrons)
Electrostatic force
Opposite ions attract, and need energy to force
ions apart. Energy is released when they come
together. There is potential energy to be released
when there are two separated electrical charges of
opposite signs. Measured in volts. 1mv=0.001v
Forces of nature
Two key potential forces (ways of harnessing energy to do work)
Physical concentration gradient and electrical gradient
Plasma membrane
In the body, + and - ions are balanced, but local ionic differences are maintained via the cells
plasma membrane
- Membrane contains phospholipid bilayer that
segregates the internal cytoplasm from external
extracellular fluid
- Plasma membrane can maintain a potential
for work if there’s more + ions on the outside
(extracellular fluid), and/or more - ions on the
inside (cytoplasm)
Ionic composition of a neuron
- more + ions outside the cell membrane, and
more - ions inside the cell membrane.
inside the cell outside the cell
high conc of K+ and A- (protein) High conc of Na+ and Cl-
small conc of Na+ and Cl- small conc of K+
net result- neuron is more negative on the inside than out
Ca measure the difference
using a voltmeter
In a neuron the difference is
70mV
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