Membrane and Action Potentials

Question 1

Concentration of K+ is greater __________.

Answer 1

Inside a cell

Question 2

Concentration of K+ inside of cell

Answer 2

120-140 mM

Question 3

Concentration of K+ outside of cell

Answer 3

5 mM

Question 4

Concentration of Na+ is greater __________.

Answer 4

Outside of cell

Question 5

Concentration of Na+ inside of cell

Answer 5

10-15 mM

Question 6

Concentration of Na+ outside of cell

Answer 6

150 mM

Question 7

Concentration of Cl and HCO- is greater _________.

Answer 7

Outside of cell

Question 8

Concentration of Cl inside of cell

Answer 8

5-40 mM

Question 9

Concentration of Cl outside of cell.

Answer 9

130 mM

Question 10

Concentration of HCO- inside of cell

Answer 10

12-25 mM

Question 11

Concentration of HCO- outside of cell

Answer 11

25 mM

Question 12

Electroneutrality

Answer 12

Cations and Anions balancing each other outside of cell (155 mM)

Question 13

Ions want to move _____ their concentration gradients.

Answer 13

down

Question 14

When ions continue to move down their concentration gradients, what happens?

Answer 14

The sign of their charge begins to accumulate where they diffuse to (so they began to be pushed in the opposite direction across the membrane – b/c they want to work down their electrical AND concentration gradient – remember that like charges repel)

Question 15

Responsible for asymmetrical concentration gradient across the cell membrane

Answer 15

ATPase Pump

Question 16

ATPase Pump

Answer 16

pumps three sodium ions out of the cell for every two potassium ions pumped in

Question 17

What can be used to calculate the membrane voltage across a cell’s membrane?

Answer 17

Nernst equation

Question 18

What is Nernst equation?

Answer 18

(2.3) x (RT/ZF) x [Log(Concentration of ion on outside/concentration of ion on inside)]

Question 19

What is R in the nernst equation?

Answer 19

8.314 J/(mol x K)

Question 20

What is T in the nernst equation?

Answer 20

Temperature in kelvin

Question 21

What is Z in the nernst equation?

Answer 21

Ion’s valence

Question 22

What is F in the nernst equation?

Answer 22

Faraday’s Constant: 96,500 C/mol

Question 23

Under standard conditions, what is (2.3) x (RT/ZF) in the nernst equation equal to?

Answer 23

60

Question 24

What the membrane voltage of the membrane if only K+ is permeable across the membrane?

Answer 24

-87 mV - inside the cell with respect to outside the cell

only K+ gradient determines this voltage if it is the only permeable ion

Question 25

What the membrane voltage of the membrane if only Na+ is permeable across the membrane?

Answer 25

+60 mV - inside the cell with respect to outside the cell

Question 26

What are the units of the nernst equation?

Answer 26

mV (1 mV = 0.001 V)

Question 27

What happens if we stimulate a nerve and it leaves its resting state?

Answer 27

It enters it's active state and makes Na+ ions to become more permeable (causing them to want to work down their electrochemical and concentration gradients; This happens when too much K+ has left the cell)

Question 28

Increasing the membrane's Na+ permeability can lead to ________.

Answer 28

Depolarization (decrease in membrane potential)

Question 29

How can depolarization be accomplished?

Answer 29

By stimulating a nerve

Question 30

What happens when when the initial depolarization exceeds the threshold potential (specific minimum value of the membrane potential for a cell to trigger action potential)?

Answer 30

Na+ ions burst into the cell and trigger an action potential

Question 31

When an action potential is generated, which ion becomes more permeable across the membrane and in what direction does it move?

Answer 31

Na+ ions, They burst into the cell

Question 32

When does the influx of Na+ ions into the cell discontinue?

Answer 32

When the membrane potential reaches the equilibrium potential for Na+ (60+)

Question 33

What occurs when the membrane potential reaches the equilibrium potential for Na+ (60+)?

Answer 33

The membrane potential (inside the cell) is balanced with the concentration gradient of Na+

Question 34

What happens during the refractory period?

Answer 34

1) Na+ channels close and becoming temporarily inactive | 2) The neuron will not generate an action potential b/c the Na+ channels are closed (to prevent further depolarization)

Question 35

What happens during re-polarization?

Answer 35

1) Na+ channels close shut 2) K+ channels open and leave the cell 3) hyper-polarization

Question 36

What is hyper-polarization?

Answer 36

When the membrane potential passes above it's normal resting potential (the cell eventually reach equilibrium)

Question 37

Multiple action potentials can happen at once in one cell? (TRUE/FALSE)

Answer 37

FALSE - ONLY ONE AP can happen AT ONE POINT IN TIME IN A CELL

Question 38

The ability of a neuron to conduct a current depends on what?

Answer 38

The cross-sectional area of the neuron

Question 39

Neurons with larger cross-sectional area conduct an AP ______ and ________ than a small diameter neuron.

Answer 39

farther, faster (more efficient)

Question 40

Which of the following increases the rate at which action potentials are conducted? A. Myelinated B. Unmyelinated

Answer 40

Myelinated

Question 41

What types of cells help to myelinate neurons?

Answer 41

Glial cells (they attach themselves to unmyelinated regions of neurons, rotate around the neuron a number of times to create a myelin sheath)

Question 42

Nodes of Ranvier

Answer 42

1) Regions between myelin on a myelinated neuron (AP "jumps" from node to node) 2) Plasma membrane at each node depolarizes during an AP 3) High density of Na+ channels for depolarization

Question 43

Which nervous system are oligodendrocytes (type of glial cell) located in?

Answer 43

CNS

Question 44

Which nervous system are schwann cells (type of glial cell) located in?

Answer 44

PNS

Question 45

What does myelin act as?

Answer 45

an electrical insulator that prevents transfer of ions across plasma membrane of the axon (Thus, there are only channels (Na+ in particular) at the nodes of Ranvier)

Question 46

Saltatory Conduction

Answer 46

Impulse jumping from node to node on an axon that is myelinated