Summary Neuroscience
Lecture 1&2: membrane potential
Resting membrane potential
Learning objectives:
-knowing the difference between active and passive conduction
-be able to explain what the equilibrium potential or reversal potential is
-understanding how the resting membrane potential is established
-knowing which ions are important for the resting membrane potential
-knowing for which ions the permeability changes during the action potential
-knowing how to calculate the resting membrane potential when the membrane is
permeable for 1 ion, or multiple ions
Electrical signals in the brain
All the output of the brain is generated by electrical signals.
Electrical signals in nerve cells
These cells translate a stimulus into a
receptor potential.
Nerve cells are connected with each other
through synapses. An axon potential arises
and must be translated into a chemical signal
to convene its message to its next neuron. It
does so by releasing neurotransmitters
which will be sensed by the post-synaptic
transmitter in the synapse and that will
generate this synaptic potential.
An action potential is a signal when a neuron
is being activated (for instance by receptors
or other neurons) leading to depolarization
and an action potential→ very strong short
pulse.
When we try to distinguish the different signals, we see
- A different source
- The amplitude of the action potential is much bigger
- The time of depolarization is shorter in the action potential
,What are the requirements for electrical signaling between nerve cells?
- must be fast
- travel long distances
- should not loose strength over distance (reliability> amplitude must stay the same)
The action potential is quite preserved in animals, making studying them easier.
Active and passive signals
We have a neuron and two electrodes (electrophysiology). With one we can stimulate the
neuron and the other record the signal in the neuron.
You stick the electrode inside the cell, measuring the potential inside versus outside
(reference electrode in a bath) and you measure the potential difference between these two
electrodes. Nerve cells are hyperpolarized, they have a negative resting membrane
potential. If you have the electrode in the bath, you measure the (before inserting) you do
not have a potential difference=0. When you insert the measuring electrode in the cell, you
measure the cell's resting potential (-65).
We give a negative injection (e-) of a current and then we see as a response a negative
reflection of this current potential. If you give a twice as big negative injection, then the
hyperpolarization will be twice as strong. This is called passive responses.
When we give a positive stimulus (below threshold) resulting in depolarization. When we
increase the amplitude of the positive stimulus twice (reaching threshold), we get an active
response, an action potential. What will happen if we give even stronger stimulation? →the
action potential will not change but the firing frequency is increased (can be explained by
the membrane potential).
,→ doesn’t work when you have a long axon
Extra: Excitation and inhibition
Active and passive signals are deviations from the resting membrane potential
What determines the resting membrane potential?
, Resting membrane potential is the electrical potential difference measured across the
membrane (inside with respect to outside→ reference electrode necessary)
• Based on two membrane properties:
-lipid bilayer is impermeable for ions
-specialized ion channels can conduct ions selectively (only one ion group can pass)
• Based on two principles in physics:
-diffusion of particles
-electrical forces between electrical charges
The chance of particles diffusing to lower
concentration is higher than vice versa.
Know the charges by heart
Lecture 1&2: membrane potential
Resting membrane potential
Learning objectives:
-knowing the difference between active and passive conduction
-be able to explain what the equilibrium potential or reversal potential is
-understanding how the resting membrane potential is established
-knowing which ions are important for the resting membrane potential
-knowing for which ions the permeability changes during the action potential
-knowing how to calculate the resting membrane potential when the membrane is
permeable for 1 ion, or multiple ions
Electrical signals in the brain
All the output of the brain is generated by electrical signals.
Electrical signals in nerve cells
These cells translate a stimulus into a
receptor potential.
Nerve cells are connected with each other
through synapses. An axon potential arises
and must be translated into a chemical signal
to convene its message to its next neuron. It
does so by releasing neurotransmitters
which will be sensed by the post-synaptic
transmitter in the synapse and that will
generate this synaptic potential.
An action potential is a signal when a neuron
is being activated (for instance by receptors
or other neurons) leading to depolarization
and an action potential→ very strong short
pulse.
When we try to distinguish the different signals, we see
- A different source
- The amplitude of the action potential is much bigger
- The time of depolarization is shorter in the action potential
,What are the requirements for electrical signaling between nerve cells?
- must be fast
- travel long distances
- should not loose strength over distance (reliability> amplitude must stay the same)
The action potential is quite preserved in animals, making studying them easier.
Active and passive signals
We have a neuron and two electrodes (electrophysiology). With one we can stimulate the
neuron and the other record the signal in the neuron.
You stick the electrode inside the cell, measuring the potential inside versus outside
(reference electrode in a bath) and you measure the potential difference between these two
electrodes. Nerve cells are hyperpolarized, they have a negative resting membrane
potential. If you have the electrode in the bath, you measure the (before inserting) you do
not have a potential difference=0. When you insert the measuring electrode in the cell, you
measure the cell's resting potential (-65).
We give a negative injection (e-) of a current and then we see as a response a negative
reflection of this current potential. If you give a twice as big negative injection, then the
hyperpolarization will be twice as strong. This is called passive responses.
When we give a positive stimulus (below threshold) resulting in depolarization. When we
increase the amplitude of the positive stimulus twice (reaching threshold), we get an active
response, an action potential. What will happen if we give even stronger stimulation? →the
action potential will not change but the firing frequency is increased (can be explained by
the membrane potential).
,→ doesn’t work when you have a long axon
Extra: Excitation and inhibition
Active and passive signals are deviations from the resting membrane potential
What determines the resting membrane potential?
, Resting membrane potential is the electrical potential difference measured across the
membrane (inside with respect to outside→ reference electrode necessary)
• Based on two membrane properties:
-lipid bilayer is impermeable for ions
-specialized ion channels can conduct ions selectively (only one ion group can pass)
• Based on two principles in physics:
-diffusion of particles
-electrical forces between electrical charges
The chance of particles diffusing to lower
concentration is higher than vice versa.
Know the charges by heart
