2. Membrane potentials

Question 1

An electrical potential (potential difference) that exists across the plasma membrane

Answer 1

membrane potential

Question 2

Charged solutes in body in the ECF are mostly ions, what are they?

Answer 2

Sodium (Na+) = major cation, chloride(Cl-) and bicarbonate(HCO3-) = major anions

Question 3

charged solutes in the ICF are mostly ions and charged molecules, what are they?

Answer 3

proteins, amino acids, and nucleotides = anions potassium (K+) and magnesium (Mg+) = cations

Question 4

Body fluids are electrically _____

Answer 4

neutral

Question 5

what is the principle of macroscopic electroneutrality?

Answer 5

Body fluids are electrically neutral

Question 6

Are body fluids 100% electrically neutral?

Answer 6

No, ICF has small amount of excess negative charge and ECF has small amount of excess positive charge.

Question 7

Charge difference across the plasma membrane is called what?

Answer 7

membrane potential

Question 8

what units is membrane potential measured in?

Answer 8

millivolts (mV)

Question 9

Size of the potential difference is indicated by the _______ of the membrane potential

Answer 9

magnitude

Question 10

A negative membrane potential indicates that the ______has excess _______charge and the ______has excess ________charge

Answer 10

ICF; negative; ECF; positive

Question 11

A positive membrane potential indicates that the _____has excess ________ charge and the ____has excess ________charge

Answer 11

ICF; positive; ECF; negative

Question 12

Membrane potentials are important for body function. They help drive movement of ______across the plasma membrane, which is important for processes such as _____ ________and _______ ___________, ________ absorption, and _______ _________ ___________.

Answer 12

solutes; plasma filtration; urine production; nutrient; action potential production

Question 13

When membrane potentials are produced, net ion movement is first determined by several driving forces, what are they called? and what other name do they have?

Answer 13

chemical driving force (chemical potential), electrical driving force (electrical potential), together they are called the electrochemical driving force (electrochemical potential gradient)

Question 14

Movement of ions down their __________ ________will change the membrane potential

Answer 14

electrochemical gradient

Question 15

the membrane potential at which an ion’s chemical driving force and the electrical driving force are equal to one another and in opposite directions

Answer 15

equilibrium potential

Question 16

What net ion movement is found at the equilibrium potential?

Answer 16

none

Question 17

ions will move in direction that

Answer 17

brings them closer to the equilibrium potential

Question 18

Do ions contribute to membrane potential?

Answer 18

yes, they all do

Question 19

Which ions contribute the most to membrane potential?

Answer 19

cl- K+ Na+

Question 20

The greater permeability of K+ causes the ICF to be slightly what compared to the ECF? Why is that?

Answer 20

negative, bc K+ have a greater tendency to diffuse from ICF to ECF

Question 21

What structure helps maintain the membrane potential by moving potassium ions and sodium ions up their concentration gradients?

Answer 21

sodium-potassium ATPase pumps

Question 22

sodium-potassium ATPase pumps also contribute to the ICF being slightly negative, why is that?

Answer 22

the pumps move fewer K+ than Na+