L32 Resting Neuron & Neural transmission Flashcards
What did Luigi Galvani notice?
That as he used the laden to produce a spark of electricity a frog’s leg would twitch.
What did Luigi Galvani think he discovered?
Spiritus anomalous - essentially what makes humans come to life/work.
What did Alessandro Volta propose?
He disputed Galvani’s logic that nerves contained electricity and instead proposed that they were electrically stimulated.
Which 2 fundamental discoveries allowed the elucidation of basic neural function?
1) microelectrodes- small electrodes
2) Discovery of giant squid axon
What is the effect of axon size on conduction?
The bigger the axon the faster the conduction
If you stuck two electrodes on the surface of an axon why would the potential difference be 0?
Because they are both sitting in the same medium despite being away from each other. You would only see a potential difference if one electrode was on the surface of the axon and the other was protruding inside the axon thus you would be able to measure the difference in the electrical signal of the inner neurone versus the outside - this you would find to be negative as neurones have negative resting potential.
How can you measure the electrical potential of a neurone?
You essentially need to stick two electrodes away from each other but in the same axon. This proved difficult before the 2 fundamental discoveries of a giant squid axon and microelectrodes as typically axons were very small and electrodes were very big.
What the typical resting potential?
-60 millivolts
What are electrical signals?
Changes in the resting potential
What are the two ways in which a resting potential can change?
Hyperpolarisation- become more negative
Depolarisation- become more positive
What is the ionic composition of a resting neurone ( describe ions present on the inside and outside of the axon)?
Within the inside of the axon there is lots of Potasium
(K+) and other large negative ions. On the outside of the axon there are lots of sodium and chloride ions ( Na+ & Cl-)
What forces can act upon an ion?
Chemical force - going from an area of high concentration to an area of low concentration
Electrostatic force- The ion will be attracted to the opposite polarity.
What 2 factors determine the movement of an ion across a membrane?
The size of the electrochemical gradient
The permeability of the membrane
What allows very small amounts of ions to pass across a membrane?
Leaky channels
What does the sodium potassium pump do?
Counteract the effects of the leaky channels.
It pushes 3 Na+ ions out for every 2K+ in.
