Bio 219: Chp. 8 Neurophysiology: Ions & Membrane Potentials

Front 1

Fill in the blank: Ions diffuse through channels down an ______

Back 1

Ions diffuse through channels down an electrochemical gradient

Front 2

What is an electrochemical gradient?

Back 2

electrical gradient + chemical gradient

Front 3

Define: electrical gradient

Back 3

attraction or repulsion of electrical charges

Front 4

Define: chemical gradient

Back 4

concentration gradient

Front 5

What is an electrical potential?

Back 5

measure of electrical driving force (volts)

Front 6

What is the membrane potential?

Back 6

potentail (voltage) difference between intracellular fluid (ICF) and extracellular fluif (ECF)

Front 7

What is the resting membrane potential of an undisturbed cell?

Back 7

~ -70 millivolts (mV) (negative side)

Front 8

Fill in the blank: Neurons and muscle cells form _______.

Back 8

Neurons and muscle cells form excitable tissues function through electrical signals in form of changes in membrane potential

Front 9

Fill in the blank: Electrical forces exist between _______.

Back 9

Electrical forces exist between charged particles.

Front 10

Fill in the blank: To separate electrical charges requires _____.

Back 10

To separate electrical charges requires energy.

Front 11

Fill in the blank: When electrical changes are separated (e.g. across a membrane) they store energy as an _________.

Back 11

When electrical changes are separated (e.g. across a membrane) they store energy as an electrial potential (voltage)

Front 12

Fill in the blank: The strength of potential depends on the amount of __________.

Back 12

The strength of potential depends on the amount of charge separation.

Front 13

Fill in the blank: The membrane potential can be measured by inserting an ____ inside the neuron.

Back 13

The membrane potential can be measured by inserting an electrode inside the neuron.

Front 14

Fill in the blank: The potential difference this electrode and the electr????

Back 14

????

Front 15

What are the two factors that determine resting membrane potential?

Back 15

Passive mechanisms and active transport mechanisms

Front 16

What is a passive mechanism?

Back 16

relative mechanisms - differences in permeability to ions

Front 17

What is active transport mechanisms?

Back 17

Na+/K+ pump

Front 18

What is relative permeability?

Back 18

of the membrane to K+ versus Na+

Front 19

Group Question: How/why do you think clel can be more permeable to K+ rather than Na+?

Back 19

f

Front 20

What is a concentration gradient?

Back 20

of permeable ions (esp. K+ and Na+)

Front 21

Group Question: Place the following Na+ and K+ concentrations in the ECF or the ICF

Back 21

fdas

Front 22

Formation of the Resting Membrane Potential: a) K+ will diffuse down its concentration gradient (inside cell -> outside cell)

Back 22

chemical force "pulls" K+ out of the cell

Front 23

Formation of the Resting Membrane Potential: b) as K+ ions diffuse out of cell -> leave behind negative ions

Back 23

result = inside of cell is more negative electrical force is created (to pull K+ back into cell) this opposes chemical force

Front 24

Formation of the Resting Membrane Potential: c) K+ continues to diffuse out until the chemical force is equal but opposite to the electrical force

Back 24

K+ will reach equilibrium - no net movement of K+ in/out of cell

Front 25

What is Nerst Equation?

Back 25

calculates equilibrium potential (ion) of one ion

Front 26

What is the equilibrium potential of an ion?

Back 26

point at which electrical force exactly balances the chemical force of an ion

Front 27

What are the two most important ions to consider in formation of membrane potential?

Back 27

K+ and Na+

Front 28

Fill in the blank: Cell membranes are more permeable to _____ than _____ because …..

Back 28

Fill in the blank: Cell membranes are more permeable to K+ than Na+ because K+ has more channels

Front 29

Since there is more K+ channels there is …

Back 29

Since there is more K+ channels there is a greater tendency to drive membrane potential toward K+'s own equilibrium potential

Front 30

What is the first step in formation of the resting membrane potential?

Back 30

no membrane potential -> chemical force cause K+ to exit cell and Na+ to enter cell

Front 31

What is the second step in formation of the resting membrane potential?

Back 31

membrane is more permeable to K+ -> K+ flows out faster than Na+ -> inside of cell becomes more negative compared to outside cell

Front 32

What is the third step in formation of the resting membrane potential?

Back 32

Electrical force now opposes outflow of K+ and favors inflow of Na+

Front 33

What is the fourth step in formation of the resting membrane potential?

Back 33

K+ outflow slows down; Na+ inflow speeds up -> eventually membrane potential establishes (-70 mV in neurons)

Front 34

What is the fifth step in formation of the resting membrane potential?

Back 34

Na+/K+ pump counteracts leakage flows (Na+ leaking in/K+ leaking out) -> maintains Na+ and K+ gradients (steady state)