NEUR 0010 - Chapter3

Question 1

How do action potentials contrast with passive electrical signals?

Answer 1

Don’t diminish over distance, fixed size and duration; similar to Morse code

Question 2

What is resting membrane potential?

Answer 2

The difference in electrical charge across a membrane; negative inside compared to outside

Question 3

What is the action potential?

Answer 3

A reversal of the resting membrane potential: depolarizes, makes it positive inside compared to outside

Question 4

What are the three main components that determine resting membrane potential?

Answer 4

Salty fluid bathing the membrane, the membrane, and the proteins in the membrane

Question 5

Why is it significant that the cytosol surrounding the neuronal membrane is composed mostly of water?

Answer 5

Because water is polar covalent: makes water an effective solvent of charged/polar molecules, which allows for ions

Question 6

What are three examples of protein use in the neuronal membrane?

Answer 6

Enzymes, cytoskeleton, and receptors

Question 7

What are the two most important functions/characteristics of ion channels in the neuronal membrane?

Answer 7

Ion selectivity and gating abilities

Question 8

What two conditions are required to allow ions to diffuse across a membrane?

Answer 8

The appropriate channels are present, and the appropriate concentration/electrical gradient is available to drive the ions over to whatever side

Question 9

What are the two main ways to move ions across a membrane?

Answer 9

Diffusion by concentration gradient, or by electrical field

Question 10

What is positive electrical current?

Answer 10

Current in the direction that positive charges move: from anode (+) to cathode (-)

Question 11

What are two important factors in determining ion movement through electric field?

Answer 11

Voltage (electric potential) = force exerted on a charge particle, determined by the different in charge between anode and cathode; and Conductance: ability of electrical charge to migrate from one point to another, depends on the electrical properties of the conducting substance, inverse of resistance

Question 12

What is the typical resting membrane potential for a neuron?

Answer 12

-65 mV

Question 13

What is equilibrium potential?

Answer 13

The potential establish when diffusion and electrical potential balance each other out: K+ ions move outside because of concentration gradient, but then are pulled back in by the large negative voltage inside the cell

Question 14

What is the typical equilibrium potential for a neuron?

Answer 14

-80 mV

Question 15

What size concentration gradient change is required to make a significant membrane potential change?

Answer 15

Tiny: miniscule ion concentration changes can cause huge shifts in membrane potential

Question 16

Why can a membrane store electrical charge and have capacitance?

Answer 16

Because it’s so thin: negative and positive ions are attracted to each other through the membrane, so cluster close to it, allowing charge to be localized near the membrane inner and outer surfaces

Question 17

What is the ionic driving force?

Answer 17

The difference between real membrane potential and the equilibrium potential )or Vm - Eion) for a particular ion

Question 18

What can be calculated from knowing the concentration difference across the membrane for a specific ion?

Answer 18

The equilibrium potential: whether it’s positive or negative, or exact value by Nernst equation

Question 19

What is the Nernst equation used for?

Answer 19

Calculating the value of the equilibrium potential for an ion using charge, temperature, and ratio of external and internal ion concentrations

Question 20

What is the Nernst equation?

Answer 20

Eion = (2.303)(RT/zF)log(ionO/ionI)

Question 21

What are the concentration distributions of K+, Na+, and Ca2+?

Answer 21

K+ concentrated on inside; Na+ and Ca2+ concentrated on outside

Question 22

How does the sodium potassium pump work?

Answer 22

Exchanges internal Na+ for external K+: 3 Na+ moves out, 2 K+ moves in

Question 23

How does the calcium pump work?

Answer 23

Drives Ca2+ out of the cytosol

Question 24

Why is the resting membrane potential closer to K+’s eq. pot. instead of Na+’s eq. pot, if the membrane is permeable to both ions?

Answer 24

Because it’s more permeable to K+ than Na+, so more K+ driven out than Na+ can leak in

Question 25

What is a pore loop?

Answer 25

The region in an ion channel subunit (here, K+ channels) that contributes to the selectivity filter to only allow K+ through

Question 26

How are neurons depolarized by K+?

Answer 26

Increasing outside concentration of K+ depolarizes neurons: makes it less negative

Question 27

How do astrocytes affect extracellular K+ concentration?

Answer 27

Pump K+ into their own cytosol to remove it from ECF: this increased internal K+ concentration in astrocytes is dissipated by the astrocytic processes network: potassium spatial buffering!