Lecture 1 – Chapter 2: Electrical Signals of
Nerve Cells
Learning outcomes I:
Understand that:
• Neurons generate electrical signals to transmit and store information
• Electrical signals are based on the flow of ions across the membrane
• Selective permeability to different ions and the non-uniform distribution of these ions give rise to
electrical signals
Know:
• The concepts of resting membrane potential and action potential.
• Know the importance of action potentials for neuronal signalling
• Understand how information is coded in action potentials (frequency)
• Know how to differentiate the resting membrane potential from the action potential
Injecting current in presynapse:
Membrane fusing at the active zone.
Accumulation of active proteins in the electron dense active zone, especially calcium channels on the
presynaptic membrane. These calcium channels are voltage-gated. When they open you get massive
influx of calcium. This changes the membrane potential in presynapse. This calcium will bind to
Synaptotagmin on the vesicles in the presynapse. When they bind calcium, they get a super high
affinity for the plasma membrane.
Electrical signals are fundamental for brain function:
Resting potential is always around -50;-90 depending on the
type of neuron.
A. Receptor potentials in skin touch receptors
B. Synaptic potential upon activation single synapse.
Stimulate one neuron by injecting current into a neuron that
innervates another neuron and record the neuron.
C. Action potential when threshold potential is reached
,Lots of sodium (Na+) channels in the axon hillocks.
This is the location were action potentials are
generated.
How Ion Movements Produce Electrical Signals:
Potassium (K+) has a high concentration inside the
neuron and a low concentration extracellular.
Sodium (Na+) has a low concentration intracellular
and a high concentration extracellular. You can
hardly find charged proteins extracellular but you
do intracellular. Also, there is a high concentration
chloride extracellular and a low concentration
intracellular.
Active transporters create ion gradients:
Sodium-potassium pump is used to keep the sodium and
potassium concentrations. This consumes 20-40% of total
brain energy. 2 K+ ions in, 3 Na+ ions go out.
Ion channels allow membrane passage:
Ion channels open/close upon changes in membrane
potential.
,At rest:
- K+-channels open
- Na+ channels closed
Diffusion and electrical forces:
1. At rest K+-channels are open
2. K+ diffuses outside → negative potential inside
3. Electrical force pulls positive K+ ions back to the cell
4. At rest no net movement of K+ - equilibrium potential
, Lecture 2 – Chapter 2,3,4
Action Potentials are Generated by Ion
Currents
LEARNING OUTCOMES
1) You know that neurons generate electrical signals to transmit and store information;
2) You understand that that the selective permeability to different ions and the non-uniform
distribution of these ions give rise to electrical signals;
3) You can reconstruct, step-by-step, how an action potential generates and propagates (in a drawing
for example);
4) You understand the importance of scientific research for the acquisition of this knowledge.
Concepts:
Electric current = Current is the flow of electrical particles (the amount of charge per second)
Resistance = an electrical quantity that measures how the device or material reduces the electric
current flow through it (opposite of Conductance)
Voltage = Difference in charge between two points. This difference creates energy that will “push”
charges to move – POTENTIAL energy
Capacitors = electronic components that can store charge; and capacitance is the amount of charges
a capacitor can store.
Voltage → difference in levels of water
Current → flow of water
Resistance → the narrow tube
Capacitor → two boilers with water
Diffusion:
Diffusion will occur faster when water is warmer. Because the
molecules will move faster. Also, if we shake the bottle of water
with a solution, it will diffuse quicker since we put a mechanic
force in it.
Nerve Cells
Learning outcomes I:
Understand that:
• Neurons generate electrical signals to transmit and store information
• Electrical signals are based on the flow of ions across the membrane
• Selective permeability to different ions and the non-uniform distribution of these ions give rise to
electrical signals
Know:
• The concepts of resting membrane potential and action potential.
• Know the importance of action potentials for neuronal signalling
• Understand how information is coded in action potentials (frequency)
• Know how to differentiate the resting membrane potential from the action potential
Injecting current in presynapse:
Membrane fusing at the active zone.
Accumulation of active proteins in the electron dense active zone, especially calcium channels on the
presynaptic membrane. These calcium channels are voltage-gated. When they open you get massive
influx of calcium. This changes the membrane potential in presynapse. This calcium will bind to
Synaptotagmin on the vesicles in the presynapse. When they bind calcium, they get a super high
affinity for the plasma membrane.
Electrical signals are fundamental for brain function:
Resting potential is always around -50;-90 depending on the
type of neuron.
A. Receptor potentials in skin touch receptors
B. Synaptic potential upon activation single synapse.
Stimulate one neuron by injecting current into a neuron that
innervates another neuron and record the neuron.
C. Action potential when threshold potential is reached
,Lots of sodium (Na+) channels in the axon hillocks.
This is the location were action potentials are
generated.
How Ion Movements Produce Electrical Signals:
Potassium (K+) has a high concentration inside the
neuron and a low concentration extracellular.
Sodium (Na+) has a low concentration intracellular
and a high concentration extracellular. You can
hardly find charged proteins extracellular but you
do intracellular. Also, there is a high concentration
chloride extracellular and a low concentration
intracellular.
Active transporters create ion gradients:
Sodium-potassium pump is used to keep the sodium and
potassium concentrations. This consumes 20-40% of total
brain energy. 2 K+ ions in, 3 Na+ ions go out.
Ion channels allow membrane passage:
Ion channels open/close upon changes in membrane
potential.
,At rest:
- K+-channels open
- Na+ channels closed
Diffusion and electrical forces:
1. At rest K+-channels are open
2. K+ diffuses outside → negative potential inside
3. Electrical force pulls positive K+ ions back to the cell
4. At rest no net movement of K+ - equilibrium potential
, Lecture 2 – Chapter 2,3,4
Action Potentials are Generated by Ion
Currents
LEARNING OUTCOMES
1) You know that neurons generate electrical signals to transmit and store information;
2) You understand that that the selective permeability to different ions and the non-uniform
distribution of these ions give rise to electrical signals;
3) You can reconstruct, step-by-step, how an action potential generates and propagates (in a drawing
for example);
4) You understand the importance of scientific research for the acquisition of this knowledge.
Concepts:
Electric current = Current is the flow of electrical particles (the amount of charge per second)
Resistance = an electrical quantity that measures how the device or material reduces the electric
current flow through it (opposite of Conductance)
Voltage = Difference in charge between two points. This difference creates energy that will “push”
charges to move – POTENTIAL energy
Capacitors = electronic components that can store charge; and capacitance is the amount of charges
a capacitor can store.
Voltage → difference in levels of water
Current → flow of water
Resistance → the narrow tube
Capacitor → two boilers with water
Diffusion:
Diffusion will occur faster when water is warmer. Because the
molecules will move faster. Also, if we shake the bottle of water
with a solution, it will diffuse quicker since we put a mechanic
force in it.
