Brain and behaviour session 2: how do neurons
communicate information?
Electrical symbols in the brain – a historical perspective – Rene Descartes – dualism,
brain communicates with the body via fluids - Luigi Galvanni – frog muscles twitched
when struck by lightning – nephew would stimulate criminal’s bodies with electricity
to try bring them back to life (Shelley Frankenstein)
Bando Mitsugoro VIII and puffer fish – ate the liver of puffer fish – contain
tetrodotoxin most poisonous as it interferes with electrical signalling in the brain in
voltage-gated ion channels
The resting membrane potential – neuron: cell body, dendrites (receive info), axon
(sends info), membrane (lipid bilay-fatty substance separation of in and out) contains
two proteins: ion channels: protein inserted in the neuronal membrane allowing the
movement of ions along the gradient from high to low, and, ion pumps: move ions
from inside to outside or outside to inside move against concentration gradient
require energy to move an electrical charge
To forces which control movement: electrical negative to positive and diffusion from
high to low
K+ and Cl- improve communication of neurons k+ diffuse between the neuronal
membrane diffusion forces allow K+ to move increasing the charge of the 2 nd
chamber and electrical forces move the ion back in order to balance out the
potential of the membrane this causes an electrochemical equilibrium (-50/-60
millivolts – resting membrane potential)
Na+ K+ pump allows for the imbalance of ions to generate an electrical charge. Ion
pump move K+ from out to in and Na+ from in to out causing a high concentration of
K+ inside and Na+ outside and for every two K+ that enter the neuron, three Na+
move outside, this causes a net loss of positive ions inside the neuron this causes a
small electrical charge (brain uses 20% of energy)
The action potential with a stimulating electrode you are able to inject a positive or
negative charge and with a recording electrode you are able to find the resting
membrane potential (imbalance of Na+ and K+ caused mainly by potassium
producing an equilibrium of -55/-65) if negative current if injected in to neuron it
makes it more negative causing hyperpolarisation (negative)and takes it further
away from the threshold of -50 millivolts making it less likely to fire an action
potential when a small positive charge is injected this causes depolarisation
(positive) however when a large amount of positive electricity is injected it causes
the charge to spike creating an action potential
Voltage-gated Na+ and K+ channels: at resting membrane potential the voltage-gates
of ion channels are closed these gates only open when the charge is at the threshold,
sodium open faster than potassium channels
Voltage sensitive gates open at threshold allowing a flood of sodium to rush into the
neuron which causes the charge to become positive with a higher concentration of
sodium as a result potassium leaves the neuron as it is part of a higher concentration
this results in the neuron becoming more negatively charged as potassium channels
have a delayed closing of the gates this is in order to try reach equilibrium (resting –
depolarize – repolarize – hyperpolarize - resting)
communicate information?
Electrical symbols in the brain – a historical perspective – Rene Descartes – dualism,
brain communicates with the body via fluids - Luigi Galvanni – frog muscles twitched
when struck by lightning – nephew would stimulate criminal’s bodies with electricity
to try bring them back to life (Shelley Frankenstein)
Bando Mitsugoro VIII and puffer fish – ate the liver of puffer fish – contain
tetrodotoxin most poisonous as it interferes with electrical signalling in the brain in
voltage-gated ion channels
The resting membrane potential – neuron: cell body, dendrites (receive info), axon
(sends info), membrane (lipid bilay-fatty substance separation of in and out) contains
two proteins: ion channels: protein inserted in the neuronal membrane allowing the
movement of ions along the gradient from high to low, and, ion pumps: move ions
from inside to outside or outside to inside move against concentration gradient
require energy to move an electrical charge
To forces which control movement: electrical negative to positive and diffusion from
high to low
K+ and Cl- improve communication of neurons k+ diffuse between the neuronal
membrane diffusion forces allow K+ to move increasing the charge of the 2 nd
chamber and electrical forces move the ion back in order to balance out the
potential of the membrane this causes an electrochemical equilibrium (-50/-60
millivolts – resting membrane potential)
Na+ K+ pump allows for the imbalance of ions to generate an electrical charge. Ion
pump move K+ from out to in and Na+ from in to out causing a high concentration of
K+ inside and Na+ outside and for every two K+ that enter the neuron, three Na+
move outside, this causes a net loss of positive ions inside the neuron this causes a
small electrical charge (brain uses 20% of energy)
The action potential with a stimulating electrode you are able to inject a positive or
negative charge and with a recording electrode you are able to find the resting
membrane potential (imbalance of Na+ and K+ caused mainly by potassium
producing an equilibrium of -55/-65) if negative current if injected in to neuron it
makes it more negative causing hyperpolarisation (negative)and takes it further
away from the threshold of -50 millivolts making it less likely to fire an action
potential when a small positive charge is injected this causes depolarisation
(positive) however when a large amount of positive electricity is injected it causes
the charge to spike creating an action potential
Voltage-gated Na+ and K+ channels: at resting membrane potential the voltage-gates
of ion channels are closed these gates only open when the charge is at the threshold,
sodium open faster than potassium channels
Voltage sensitive gates open at threshold allowing a flood of sodium to rush into the
neuron which causes the charge to become positive with a higher concentration of
sodium as a result potassium leaves the neuron as it is part of a higher concentration
this results in the neuron becoming more negatively charged as potassium channels
have a delayed closing of the gates this is in order to try reach equilibrium (resting –
depolarize – repolarize – hyperpolarize - resting)
