Lab I

partially complete

Which equation gives you the reverse/equilibrium potential of an ion?

Nernst equation

What is the reverse/equilibrium potential of an ion?

the membrane potential in which there’s no net movement of that ion across the membrane (diffusional and electrical force balance each other out)

What is Ex?

reverse/equilibrium potential of an ion (mV)

What is z?

the charge of an ion

What is R?

universal gas constant (8.314)

What is T?

temperature in Kelvin

What is F?

Faraday constant (96485)

Which ions are more concentrated outside of the cell?

Na, Ca, Cl

Which ions are more concentrated inside of the cell?

K

Ions move to bring the membrane potential closer to their

reverse/equilibrium potential

How do ions move to bring the membrane potential closer to their reverse/equilibrium potential?

• if the membrane potential is more negative than the reverse/equilibrium potential, negative ions exit and positive ions enter

• if the membrane potential is more positive than the reverse/equilibrium potential, negative ions enter and positive ions exit

How would elevated extracellular K+ impact potassium’s reverse/equilibrium potential?

• will increase reverse/equilibrium potential

• K+ will flow into the cell

Which equation gives you the membrane potential of a cell?

Goldman equation

What is Pion?

the permeability of an ion

Which equation allows you to calculate the current of an ion?

Ohm’s Law

What is I?

current of an ion (amperes)

What is g?

conductance of the ion channel (siemens)

What does a negative current indicate?

positive ions flowing into the cell

What does a positive current indicate?

positive ions flowing out of the cell

What is Vm?

Membrane potential (mV)

What is a current?

the flow of electrical charge carried by ions

What happens when Vm = Ex?

no driving force, no net current

Why do immature neurons have more intracellular Cl?

higher expression of NKCC1 transporter (brings chloride into the cell)

Why do mature neurons have more extracellular neurons?

KCC2 transport becomes more prominent (moves chloride out of cell)

Decreasing intracellular chloride concentrations allow the neuron to…

develop and mature

Types of potassium leak channels

TWIK-1, 2

TERK-1, 2

TASK-1, 2

Why is Vm of most cells close to EK?

because potassium leak channels are abundant, so resting membrane potential is close to potassium’s equilibrium potential

Type of sodium leak channel

NALCN

Membrane is how many times more permeable to K+ than Na+?

40x

Types of channels

• voltage-gated

• ligand-gated

• mechanically-gated

• leak channels

Why are hydrogen ions important?

• essential for transport of some NTs into their synaptic vesicles

• power ATP synthase

Why is magnesium important?

plugging the NMDA receptor

what is mM?

millimolar (millimoles of solute/liters of solution)

milli (m)

x 10^-3

micro (μ)

x 10^-6

nano (n)

x 10^-9

pico (p)

x 10^-12

Transporters that maintain membrane potential

• sodium potassium pump

• PMCA

• NCX

• KCC2

sodium potassium pump

• pump

• pumps 3 sodium out

• pumps 2 potassium in

PMCA

• pump

• pumps calcium out

NCX

• passive

• allow sodium in

• allow calcium out

KCC2

• passive

• allows chloride out alongside potassium

What do SERCA pumps do?

pump calcium from cytoplasm into ER for storage

What types of molecules is the membrane permeable to?

• small hydrophobic molecules (CO2)

• small uncharged polar molecules (H2O)

What types of molecules is the membrane impermeable to?

• large uncharged polar molecules (glucose)

• ions (Na+)

Why does an EPSP happen when GABA binds and lets in chloride in an immature neuron?

• immature neurons have high intracellular Cl- concentrations

• GABA binding lets Cl- out

• Vm becomes more positive and reaches threshold for an EPSP