Nervous System 1 - Membrane Potential

Question 1

What is plasticity?

Answer 1

The changing of the connectivity and physiological strength of synapses

Question 2

What are the 4 specialized sub regions for receiving/integrating inputs?

Answer 2

• Dendrites
• Cell body
• Axon
• Synaptic terminals

Question 3

What is Hyperpolarization?

Answer 3

Moving to a more negative potential

Question 4

What is Depolarization?

Answer 4

Going from resting potential to a more positive value

Question 5

What is repolarization?

Answer 5

Returning to a resting potential

Question 6

What is Vo?

Answer 6

Extracellular Voltage = 0 mV

Question 7

What is Vi?

Answer 7

Intracellular voltage

Question 8

What is Vm?

Answer 8

Membrane potential

Question 9

What is Vrest?

Answer 9

Resting potential

Question 10

What is Inward current?

Answer 10

Cations flowing into the cell or anions flowing out of the cell

Question 11

What is Outward current?

Answer 11

Cations flowing out of the cell and anions flowing in

Question 12

What is the sign of inward current?

Answer 12

Negative

Question 13

What is the sign of outward current?

Answer 13

Positive

Question 14

What is the charge of of cells at rest?

Answer 14

At rest the inside has a negative charge relative to the outside

Question 15

What is the Resting charge of cells due to?

Answer 15

Difference in ion concentrations and permeabilities across the membrane

Question 16

What cation is permeable to the cell at rest?

Answer 16

K+

Question 17

How is K+ permeable to the cell at rest?

Answer 17

It has leakage channels that are open at resting potential allowing it to leak out

Question 18

How are concentration gradients in a resting cell maintained?

Answer 18

By the active transport of K+ and Na+

Question 19

How must ions pass through the lipid bilayer?

Answer 19

Through ion channels

Question 20

What can gated channels open and close in response to?

Answer 20

Changes in the membrane voltage

Question 21

What are electrical signalling a result of?

Answer 21

Ions moving through ion channels

Question 22

What are the two ways channel activation can occur?

Answer 22

• Binding of a chemical ligand

* Changes in membrane potential (Vm)

Question 23

What are the two ways a Ligand can open a channel?

Answer 23

It binds to the protein or a phosphate group binds to the channel opening it

Question 24

How do voltage gated channels work?

Answer 24

When membrane potential becomes depolarized the channel can open and allow ions to cross the membrane

Question 25

How can channel inactivation (closure) occur?

Answer 25

Prolonged depolarization can cause the membrane to close

Question 26

What are the characteristics of Voltage dependant Na+ channels at rest?

Answer 26

The channels are closed because the activation gate within the channel is closed blocking sodium ions from entering the cell

Question 27

What is the state of Voltage dependant Na+ channels when the membrane is depolarized?

Answer 27

The activation gate is opened allowing sodium ions to flow into the cell down its concentration gradient

Question 28

When the cell is at rest where is the greater concentration of sodium ions?

Answer 28

Outside the cell

Question 29

When the cell is at rest where is the greater concentration of potassium ions?

Answer 29

Inside the cell

Question 30

What is the state of voltage dependant Na+ channels after 1 msec of depolarization?

Answer 30

The inactivation gate is closed preventing sodium from flowing into the cell

Question 31

What are Channelopathies?

Answer 31

Diseases arising from mutation of genes encoding ion channel subunits

Question 32

What could happen if a channel remains open for too long?

Answer 32

Cells become hyperexcitable

Question 33

What is the concentration of calcium ions relative to the cell?

Answer 33

Ca2+ ions are kept in extremely low concentration inside the cell

Question 34

What direction is the concentration gradient for Ca2+?

Answer 34

Ca2+ gets pushed into the cell

Question 35

What direction is the concentration gradient for Cl-?

Answer 35

It tends to get pushed into the cell

Question 36

What are the two driving forces on ions?

Answer 36

Chemical and Electrical driving forces

Question 37

What is the magnitude of chemical driving forces on ions proportional to?

Answer 37

The concentration gradient

Question 38

What is the electrical driving force on ions provided by?

Answer 38

Membrane potential

Question 39

What is Conductance (g)?

Answer 39

The ease with which ions flow across the membrane

Question 40

What is the equilibrium potential for ion x?

Answer 40

The membrane potential at which the current carried by ion x is 0

Question 41

What is the formula for the driving force on an ion?

Answer 41

Membrane potential - Equilibrium potential of ion

Question 42

What is the rule about membrane potential?

Answer 42

It will always move towards the equilibrium potential of the ion whose conductance increases

Question 43

What is the equation for calculate the Equilibrium potential for an ion?

Answer 43

Ex= (58/x) log [(conc. outside the cell)/(conc. inside the cell)

Question 44

Why is the resting membrane potential close to Ek?

Answer 44

Because the membrane is highly permeable to K+ and much less permeable to Na+