The Nervous System: Membrane Potential-Lecture 9 Exam 2

Question 1

How is Resting Membrane Potential Difference (Vm) Measured?

Answer 1

-The difference in electrical charge between the inside & the outside of the cell/neuron

Question 2

What is the Resting Membrane Potential (Vm) is for a Typical Neuron

Answer 2

-70mV

Question 3

What Factors Contribute to the Resting Membrane Potential?

Answer 3

-Unequal distribution of ions across the membrane (due to the Na+/K+/ATPase pump)
-Differing membrane permeability to the ions

Question 4

Role of Ion Concentration Gradients & Membrane Permeability to Ions in Establishing a Membrane Potential

Answer 4

The resting potential is determined by concentration gradients of ions across the membrane and by membrane permeability to each type of ion

Question 5

Explain How the Sodium-Potassium ATP Pump Helps Maintain the Resting Membrane Potential

Answer 5

By moving sodium ions out and potassium ions into the cell membrane

Question 6

Polarization

Answer 6

-Difference between the charge on the inside of the cell compared to the
outside
-Positive outside the neuron/cell
-Negative inside the neuron/cell

Question 7

Depolarization

Answer 7

-Membrane potential becomes more positive
-Gains a positive charge or loses a negative charge

Question 8

Hyperpolarization

Answer 8

-Membrane potential becomes
more negative
-Gains a negative charge or loses a
positive charge

Question 9

Repolarization

Answer 9

The membrane potential returns to rest (-70 mV)

Question 10

Explain How Changes in Ion Permeability can Change Membrane Potential (i.e., depolarization, hyperpolarization, and repolarization)

Answer 10

The more permeable the membrane for a given ion, the more strongly the membrane potential tends to be driven toward the equilibrium value

Question 11

The Concept of Equilibrium Potential

Answer 11

The neuron’s membrane potential for a single ion

Question 12

Equilibrium Potentials for Na+ are estimated using an artificial cell

Answer 12

-ENa+ = +60 mV
-When Na+ channels open, the neuron’s membrane becomes more
permeable to Na+
-Na+ flows down its concentration/electrical gradient into the cell until it reaches its equilibrium potential

Question 13

Equilibrium Potentials for K+ are estimated using an artificial cell

Answer 13

-EK+ = -90 mV
-When K+ channels open, the neuron’s membrane becomes more
permeable to K+
-K+ flows down its concentration gradient out of the cell until it reaches its equilibrium potential

Question 14

Considering the equilibrium potentials for Na+ and K+, explain why the resting membrane potential for a typical neuron is -70 mV

Answer 14

The cell membrane is significantly more permeable to potassium ions (K+) than sodium ions (Na+) which is why the resting is closer to (K+)

Question 15

Determine how the membrane potential will change if the membrane of a neuron becomes permeable only to K+

Answer 15

Become more negative (hyper polarized)

Question 16

Determine how the membrane potential will change if the membrane of a neuron becomes permeable only to Na+

Answer 16

Becomes more positive (depolarized)

Question 17

Determine how the membrane potential will change if the membrane of a neuron becomes equally permeable to K+ and Na+

Answer 17

The membrane potential will move closer to a value between the equilibrium potentials of sodium & potassium

Question 18

Determine how the membrane potential will change if the membrane of a neuron becomes 40 times more permeable to Na+ than to K+

Answer 18

Becomes significantly more positive (depolarized)

Question 19

What does the Nernst equation calculate?

Answer 19

The membrane potential for a single ion

Question 20

What does the Goldman-Hodgkin-Katz (GHK) equation calculate?

Answer 20

The membrane potential that results from all ions that can cross the membrane