Lecture 2, Chapter 4&7

Question 1

What is diffusion?

Answer 1

Random movement of molecules from high energy state to lower total energy

Question 2

Find some reading on membrane potentials is highly recommended!

Answer 2

!

Question 3

What are the driving forces acting on solutes that determine net diffusion?

Answer 3

1. Chemical (concentration gradient high to low)
2. Electrical (charge attraction) opposite ions attract. Only important for charge particles like ions (K+, Na+, Cl-)

Question 4

Ions can move in or out regardless of the chemical or electrical gradients but must think of ______ diffusion

Answer 4

Net

Question 5

Does glucose have a charge?

Answer 5

No not charge but polar just like water, so glucose is only affected by chemical gradients

Question 6

Charged molecules are affected by what type of gradients?

Answer 6

Both chemical and electrical gradients

* electrochemical gradient

Question 7

Can a electrical gradient overpower a strong chemical gradient?

Answer 7

Yes

Question 8

Separation of charge across a cell membrane. Difference between outside and inside the cell

Answer 8

Membrane potential. Produces a voltage measured in millivolts

Question 9

A difference in voltage between two points?

Answer 9

Potential difference = E

Question 10

Difference in voltage across the plasma membrane, always given in terms of voltage inside the cell relative to voltage outside the cell.

Answer 10

Membrane potential***

Question 11

Difference in voltage across the plasma membrane when I saw is at rest, not receiving or sending signals

Answer 11

Resting Vm

Question 12

A relatively small change in membrane potential produce by some type of stimulus that triggers the opening or closing of ion channels, strength is relative to strength of stimulus
-dif. Levles

Answer 12

Graded potential

Question 13

Graded potentials produced in the post synaptic cell in response to neurotransmitters binding to receptors

Answer 13

Synaptic potential

Question 14

Graded potentials produced in response to a stimulus acting on a sensory receptor.
(Hands, touch receptors, sensory neuron)

Answer 14

Receptor potential

Question 15

A large, rapid change in membrane potential produced by depolarization of an excitable cells plasma membrane to the threshold.
(Pain- three for small pain, 50 for intense pain, how many and how often…)

Answer 15

Action potential

Question 16

The membrane potential that counters the chemical force acting to move an ion across the membrane, thereby putting the ion at equilibrium

Answer 16

Equilibrium potential

Question 17

The millivolts at which an action potential is initiated.

Answer 17

Threshold potential***

Question 18

Potential that will generate an action potential

Answer 18

Threshold potential?

Question 19

A cell is in equilibrium and has equal concentrations of sodium and potassium and chloride between inside and outside in what case?

Answer 19

Only when the cell is dead

Question 20

The cell membrane is completely impermeable to sodium potassium and chloride but the membrane contains….

Answer 20

Na+,K+ pumps (uses ATP to pump)

2 K+ in and 3 Na+ out**

Question 21

What is the primary active transport on the cell membrane?

What charge does it create on the inside and outside of the cell?

Answer 21

Sodium potassium pump

This will cause more negative inside the cell and positive on the outside of the cell

Question 22

What if a typical cell is only permeable to potassium (K+)?

Answer 22

The electrical and chemical gradient will eventually reach equilibrium

Question 23

Hypothetical membrane potential where the chemical an electrical gradients for the ions are equel opposite

Answer 23

Equilibrium potential

Question 24

What is the Nernst equation?

Answer 24

E(ion) = (61mV/z) log [I]o/[I]i

E= equilibrium potential of ion I
Z= valence of ion I
[I]o=ECF Concentration of ion I
[I]i=ICF concentration of ion I 

If the particular ion equals that calculated concentration then it is in equilibrium

Question 25

What can change the resting membrane potential?

Answer 25

Changes in ionic concentrations

Question 26

-

Answer 26

• Na+/K+ pump
•  relative permeability of membrane to different ions (determined by presence of ion channels - Leak channels in this case.

Question 27

Need to know the Goldman-Hodgkinz-Katz (GHK) equation!!!

Answer 27

This equation takes into account of shared permeability

Kind of like a weighted average

Question 28

At rest, a cell (neuron or skeletal muscle) is about 20 times more permeable to ____ than ____.

Answer 28

K+, Na+

Question 29

Changes in membrane permeability are mediated by…

Answer 29

Ion channels

Question 30

What are the different types of ion channels?

Answer 30

• Leak channel
• ligand gated channels
• voltage-gated channels

Question 31

This channel is always open and has no gates

Answer 31

Leak Channels

Question 32

This channel needs to be unlocked, signaling molecules. Regulated by some compound like a neurotransmitter or hormone; usually rasies Vm to threshold.
(response may be small or big)

Answer 32

Ligand gated channels

Question 33

These channels are regulated by changes in voltage (membrane potential)

Answer 33

Voltage-gated channels

Question 34

Triggered when the Vm (membrane potential) reaches threshold potential

Answer 34

The action potential**^

Question 35

Where are leak channels, ligand-gated channels, and voltage-gated channels found? 

Answer 35

Leak- everywhere
Ligand- gated- are only on dendrites and soma
Voltage-gated channles- only on axon (underline action potential)

Question 36

Action potential is all-or-none changes in Vm triggered at _________.

There are three phases (depolarization, repolarization, hyperpolarization)

Answer 36

Axon hillock (base of axon)

Question 37

What are the three phases of action potential?

Answer 37

• depolarization phase (due to increased Na+ perm, 100x more perm)
• repolarization phase (due to increased K+ perm)
• hyperpolarization phase (due to increased K+ perm) 

Question 38

What kind of channels underline action potential?

Answer 38

Voltage-gated

V-gated Na+ channel

• 2 gates
  1. Activation gate
  2. Inactivation gate

Question 39

V-gated Na+ channel…
At rest: activation gate ________; inactivation gate is _______.

Threshold: activation gate _______; ____ goes in.

Brief time later: inactivation gate ______; _____ Na+ stops 

Answer 39

Closed, open

Opens, Na+

Closes, inward

• Gates do not return to at rest configuration untill Vm drops below threshold

Question 40

In activation is (slow or quick)?
And inactivation is?

Does Na+ go up or down dor each? 

Answer 40

Inactivation is creaky and slow, Na+ goes down

Activation gate is quick and sodium goes up

Question 41

This channel only has one gate and it is closed at rest and activated by threshold Vm, Time course much like the sodium in activation gate (slow), must go below threshold too close.

Answer 41

K+ Channel

Question 42

V-gated K+ channels has how many gates?

At rest it is…

Answer 42

One

Closed

Question 43

Is Na+ or K+ voltage-gated channel slower?

Answer 43

K+ is slower than Na+ activation gate

Question 44

How does the puffer fish toxin call People?

Answer 44

It binds voltage-gated sodium channels

Question 45

How does potassium chloride effectively euthanize animals?

Answer 45

Voltage can’t drop past threshold. The action potential becomes a one and done

Question 46

Explain the conduction of action potentials down axons

Answer 46

Na+ entry during action potential spreads to adjacent region of the cell causing it to depolarize to threshold and generate an action potential

This repeats down Axon until reaches axon terminal