Lecture 2: Membrane Potentials

Question 1

Most of the bodies solutes are ___ and thus carry a ____ charge

Answer 1

Ions
Net Electrical

Question 2

Cause ions to move across cell membranes

Answer 2

Gradients

Question 3

Separation of ___ takes place across the membrane

Answer 3

Charge

Question 4

The electrical potential is called the

Answer 4

Membrane potential

Question 5

Membrane potentials are determined by 3 factors:
1. _____ of ions on the inside and outside
of the cell.
2. ____ of the cell membranes to those
ions through ion channels
3. Activity of _____ that maintain
[ion] across the membranes

Answer 5

Concentration
Permeability
Electrogenic pumps

Question 6

All cells have different concentrations of ___ across the membrane (esp Na+, K+, Cl-), as well as ____ charged proteins to which the cell membrane is ____

Answer 6

Ions
Negatively
Impermeable

Question 7

Typical resting potential is ___ mV

Answer 7

70

Question 8

Resting membrane potential: Constant membrane potential in:
• ____ cells
•____ cells at rest

Answer 8

Nonexcitable
Excitable

Question 9

Minus sign means inside of cell is ___ compared to outside

Answer 9

Negative

Question 10

Ions responsible for generating resting potential are the cations ___ and ___, as well as____ anions.

Answer 10

Na+ and K+
intracellular

Question 11

Na+ greater concentration in the ___, moderate permeability
• K+ higher concentration in the ___, high permeability
• A- only in the ___, no permeability

Answer 11

ECF
ICF
ICF

Question 12

The Na+–K+ pump: __ Na+ out of the
cell for every 2___K+ in
•Inside becomes ___ compared to
outside
•Primary role of the pump is to actively
___ Na+ and K+ concentration
gradients

Answer 12

3. 2
   NEGATIVE
   MAINTAIN

Question 13

In a cell that is permeable to just one ion, the membrane potential that exactly opposes the concentration gradient is called the _____
or E(ion)

Answer 13

equilibrium potentiaL

Question 14

The greater the ____ of
the plasma membrane for a
given ion, the greater the
tendency for that ion to drive
the membrane potential toward
the ion’s own ____
potential

Answer 14

Permeability
Equilibrium

Question 15

At rest, a membrane is 50-75
times as permeable to
___, therefore ____
influences resting membrane
potential to a greater extent

Answer 15

Potassium
Potassium

Question 16

Nerve and muscles cells are excitable cells and can change their resting membrane potential to produce ______

Answer 16

Electrical signals

Question 17

Neurons use signals to receive, process, initiate, and transmit ____
◦ Muscle cells use signals initiate ___ ___

Answer 17

Messages
Muscle contractions

Question 18

Changes in membrane potential are brought about by ___ movements
• Net inward flow of +ve ions compared with resting state → _____
• Net outward flow of +ve ions compared with resting state →_____

Answer 18

Ion
Depolarization
Hyperpolarization

Question 19

______: membrane becomes less polarized than at resting potential
_______: membrane returns to resting potential after having been depolarized
_____: membrane becomes more polarized than at resting potential

Answer 19

Depolarization
Repolarization
Hyperpolarization

Question 20

Recall that ions can only cross membranes via specific ____

Answer 20

Channels

Question 21

Types of gated channels:
1. ____ gated
2. _____ gated
3. ____ gated
4. _____ gated

Answer 21

Voltage
Chemically
Mechanically
Thermally

Question 22

2 basic forms of electrical signals
• ____ potentials
• _____ potentials

Answer 22

Graded
Action

Question 23

_____ potentials
Local changes in membrane potential
•Occur in a small, specialized region of excitable cell membranes
•Usually produced by specific triggering events that causes gated ion channels to open in a
specialized region of the membrane generally chemically- or mechanically–gated

Answer 23

Graded

Question 24

The magnitude of this
graded potential is related to
the magnitude of the
____ event
• The _____ the trigger, the
larger the _____
graded potential
• The ____ the duration of
the triggering event, the
longer the duration of the
_____ potential

Answer 24

Triggering
Stronger
Depolarizing
Longer
Graded

Question 25

Current can be ___ across membrane
• Because of this leak, the local current
progressively _____ with increasing
distance from origin
• Graded potentials have limited
signaling ____

Answer 25

Lost
Decreases
Distance

Question 26

Graded potentials can sum to
initiate ______

Answer 26

Action potentials

Question 27

The ____ equation is used to calculate the resting membrane potential that results from the contribution of all ions that can cross the membrane

Answer 27

GHK - Goldman-Hodgkin-Katz equation