Capacitor: A structure with a gap over which a potential develops.
Capacitance: Ability to store electric charge.
3. Ion channels
Proteins: Building blocks of life.
Helix: Spiral.
Pore: Tunnel.
Gradient: Rate of change.
4. Membrane potential
Flux: Flow through a surface.
Diffusion: The spread of one medium in another.
Hyperpolarization: The cell potential decreases.
Depolarization: The cell potential increases.
Nernst equilibrium equation: E_ion = RT/(zF) log([ion]_out/[ion]_in) where E_ion is the reversal potential, R is the Avogadro gas constant, T the temperature in Kelvin, z the ions charge, F the Faraday constant, log the base 10 logarithm, [ion] is the ion concentration outside and inside the cell.
5. Cable properties
Dendrites: Branches of a neuron that receives impulses.
is impermeable to gases and small uncharged molecules
is permeable to ions and charged molecules
Question 1.2.3
How thick is the cell membrane?
0.5 nm
5 nm
50 nm
500 nm
Question 1.2.4
The phospholipid bilayer of the cell membrane can be represented as which electrical component?
Resistor
Inductor
Conductor
Capacitor
Question 1.2.5
What would be the approximate surface area of spherical cell with a 10 µm radius?
10 µm^2
100 µm^2
1000 µm^2
1 mm^2
Question 1.2.6
What would be the approximate capacitance of such a cell?
10 fF
10 pF
10 nF
10 µF
Question 1.2.7
Approximately how many positively charged ions would need to move from the outside to the inside of this cell in order to change the membrane potential by +70 mV?
4 hundred
6 thousand
4 million
8 billion
Question 1.3.1
Ion channels are made of what?
Lipids
Nucleic acids
Carbon nanotubes
Proteins
Question 1.3.2
What structural feature of an ion channel spans the lipid membrane?
Alpha helix
Beta sheet
Coiled coil domains
N-terminal domain
Question 1.3.3
The ion channel pore is largely composed of what?
Air
Water
Lipids
Metal
Question 1.3.4
Which statement about transporters (as opposed to ion channels) is not true?
Transporters move ions at slower rates than ion channels
Transporters passively transport ions along the electro-chemical gradient
Transporters can work against the electro-chemical gradient
Transporters do not have an aqueous pore
Question 1.3.5
Which of the following statements is not true
Ion channels are characterized by gating and selectivity
Ion channels can flip from open (conducting) to closed (non-conducting) states on the microsecond timescale
Changing the open probability of ion channels is an important way to regulate transmembrane current flow
Single ion channels can have unitary conductances of 10 nS
Question 1.3.6
Which of the following statements is not true?
Selectivity is a preference of ion channels to conduct a specific ion
The degree of selectivity can vary between different ion channels
The degree of ion selectivity is the same for all ion channels
There are many types of non-selective channels
Question 1.4.1
Ion flux through an ion channel is a passive process driven by electrochemical diffusion. Which statement is true?
There is no current flow if the ion concentrations are equal on both sides of the membrane.
There is no current flow if the electrical potential is equal on both sides of the membrane.
The electrical potential is more important than the concentration gradient.
For any given concentration of ions there is an electrical potential that prevents net current flow.
Question 1.4.2
What happens to a neuron which has a resting membrane potential of -70 mV, if potassium channels increase their open probability?
Hyperpolarization
Depolarization
Repolarization
Nothing
Question 1.4.3
The equilibrium potential
of a given ion across a membrane is the potential at which there is no net movement of that ion across the membrane due to electrochemical forces
of K+ across a typical nerve cell membrane is close to the resting potential of most neurons
of a given ion across a membrane is a function of the concentration of that ion on both sides of the membrane
all of the above are correct
Question 1.4.4
What are the approximate intracellular and extracellular concentrations of potassium for most mammalian neurons?
Intracellular 150 mM and Extracellular 5 mM
Intracellular 5 mM and Extracellular 150 mM
Intracellular 50 mM and Extracellular 100 mM
Intracellular 100 mM and Extracellular 50 mM
Question 1.4.5
What are the approximate intracellular and extracellular concentrations of chloride for most mammalian neurons?
Intracellular 120 mM and Extracellular 5 mM
Intracellular 5 mM and Extracellular 120 mM
Intracellular 25 mM and Extracellular 100 mM
Intracellular 100 mM and Extracellular 25 mM
Question 1.4.6
Calculate the reversal potential of a calcium selective conductance at 37 Celsius if the intracellular calcium concentration is 1 uM and the extracellular calcium concentration is 2 mM.
-90.0 mV
-103.5 mV
101.5 mV
203.0 mV
Question 1.5.1
What are the approximate dimensions of dendrites of typical neurons in the mammalian brain?
Length ~500 µm and Diameter ~1 µ
Length ~10 µm and Diameter ~10 nm
Length ~500 µm and Diameter ~10 nm
Length ~10 µm and Diameter ~1 µm
Question 1.5.2
What directly determines the membrane potential at any given time and location in a neuron?
Transmembrane current flux
Distribution of charges across the membrane
Axial current flow
Concentration of ions
Question 1.5.3
What do we learn about a dendrite if we know it's "length constant"?
Thickness of the dendrite
Axial resistance of the dendrite
Spatial attenuation of voltage along the dendrites at steady state
Length of the dendrite
Question 1.5.4
If we inject a subthreshold current pulse into the soma, what would we observe in recordings of membrane potential at the soma and at a distal dendrite?
The membrane potential changes would be faster and larger in the dendrite.
The membrane potential changes would be slower and smaller in the dendrite.
The membrane potential changes would be identical in the soma and dendrite.
It is not possible to evaluate without more information.
Question 1.5.5
When studying the cable properties of two different dendrites, what does it mean that Dendrite 1 has a smaller time constant than Dendrite 2?
For a given current pulse injection, Dendrite 2 needs less time to reach steady state membrane potential than Dendrite 1
For a given current pulse injection, Dendrite 1 needs less time to reach steady state membrane potential than Dendrite 2
Dendrite 2 has a lower membrane resistance than Dendrite 1
Dendrite 2 has a lower membrane capacitance than Dendrite 1
Question 1.5.6
When studying the cable properties of two different axons, what does it mean that Axon 1 has a smaller length constant than Axon 2?
Axon 2 needs less time to reach a given membrane potential than Axon 1
Axon 1 needs less time to reach a given membrane potential than Axon 2
In Axon 2 a change in membrane potential decays more rapidly with distance than in Axon 1
In Axon 2 a change in membrane potential decays less with distance than in Axon 1