Chapter 12.2 : Electrical Potentials

Question 1

What are the four types of electrical potentials?

Answer 1

Resting Membrane Potentials
Local Potentials
Action Potentials
Receptor Potentials

Question 2

All cells have a _____ membrane potential

Answer 2

resting

Question 3

Nerves have resting potential when

Answer 3

not stimulated

Question 4

Dendrites exhibit local potentials (similar to receptor potentials) after

Answer 4

stimulus moves resting potential towards threshold

Question 5

Local potentials are

Answer 5

graded, decremental, reversible, and either excitory or
inhibitory

Question 6

If stimulus great enough it spreads to the

Answer 6

trigger zone (axon hillock)

Question 7

If a local potential stimulus reaches trigger zone then it initiates an action potential that

Answer 7

travels down axon (all or none and uni-directional)

Question 8

Electrical potential

Answer 8

a difference in the concentration of
charged particles separated by a barrier (the unit membrane)

Question 9

Voltage values may vary depending on

Answer 9

tissue type

Question 10

Voltage

Answer 10

separation of ions

Question 11

Electrical current

Answer 11

the flow of ions

in the body, currents created by movement of ions (e.g. Na+ or K+) through gated channels in the plasma membrane

Question 12

gated channels

Answer 12

are opened or closed by various stimuli
(voltage / ligand / mechanical)

Question 13

regulated gates enables cell to allow ____ ___ ___ /// results in _______ ______ /// creates mechanism that can be used to ______ cellular events

Answer 13

ions to flow ; electrical currents ; regulate

Question 14

All living cells are polarized // called the

Answer 14

resting membrane potential (RMP)

Question 15

resting membrane potential (RMP)

Answer 15

charge difference across the plasma
membrane

Question 16

What number is the resting potential?

Answer 16

-70 mV RMP

Question 17

negative value means

Answer 17

there are more
negatively charged particles on the inside of
the membrane than on the outside (like a little
battery)

Question 18

nervous and muscle tissue may ____ their
resting membrane potential // sequentially
_______ and ______ gates to first
reverse then restore the charge across the
membrane // excitable tissue

Answer 18

alter ; opening ; different

Question 19

RMP exists because of

Answer 19

unequal electrolyte distribution across
membrane

Question 20

resting membrane is much less _______ to Na+
than K+

Answer 20

permeable

Question 21

70% of the energy requirement of the nervous system is
used to power what pump

Answer 21

Na+/K+ ATPase pump

Question 22

Na+/K+ ATPase pump

Answer 22

Transmembrane protein channels // moves out 3 Na+
and moves in 2 K+ for each ATP consumed

Question 23

Local potential

Answer 23

Current movement across dendrite and soma

response is initiated at the dendrite then spreads
across the soma to trigger zone

Question 24

If stimulus great enough then local potential reaches the trigger
zone /// achieves “threshold” and an _______ ______ results

Answer 24

action potential

Question 25

Other names for local potentials are

Answer 25

end plate potential or receptor potential

Question 26

Local potential occurs when a neuron

Answer 26

is stimulated by chemicals, light, heat or mechanical disturbance

Question 27

Sodium ions move into neuron at dendrites or somas when a
neuron is

Answer 27

stimulated

Question 28

depolarization

Answer 28

Voltage measured across the membrane
drifts toward zero

– Stimulus opens the Na+ gates and allows Na+ to rush in to the cell
– Na+ inflow neutralizes some of the internal negative charge

Question 29

There are four characteristics that distinguish local potentials from the action potentials. What are they?

Answer 29

Graded
Decremental
Reversible
Either excitatory or inhibitory

Question 30

Graded

Answer 30

• vary in magnitude with stimulus strength
• stronger stimuli open more Na+
  gates

Question 31

Decremental

Answer 31

• get weaker the farther they spread from the point of
  stimulation
• voltage shift caused by Na+ inflow diminishes rapidly
  with distance

Question 32

Reversible

Answer 32

• get weaker the farther they spread from the point of
  stimulation
• voltage shift caused by Na+ inflow diminishes rapidly
  with distance

Question 33

Either excitatory or inhibitory

Answer 33

• E.g. / the neurotransmitter glycine make the
  membrane potential more negative
• hyperpolarize membrane // less likely to
  produce an action potential // inhibitory

Question 34

Action potentialsis a more ______ change than local potential

Answer 34

dramatic

Question 35

Does an action potential resemble a positive feedback loop or a negative feedback loop?

Answer 35

positive feedback mechanism

Question 36

Produced by voltage-regulated ion gates in the plasma
membrane at

Answer 36

axon hillock

Question 37

the axon hillock is the same thing as the

Answer 37

trigger zone

Question 38

How many gates per um2 are on a soma?

Answer 38

50-75

Question 39

How many gates per um2 are on a trigger zone?

Answer 39

350-500

Question 40

Between the soma and the trigger zone, which one cannot generate an action potential and which one is where the action potential is generated?

Answer 40

soma cannot generate an action potential

trigger zone where action potential is generated

Question 41

if local potential spreads all the way to the _______ // can
open gates at axon hillock and generate an _______

Answer 41

trigger zone ; action potential

Question 42

action potential

Answer 42

is a rapid up-and-down shift in the membrane voltage

Question 43

threshold

Answer 43

critical voltage which local potentials must reach in order to open the voltage-regulated gates at axon hillock

Question 44

___mV is threshold value in neurons

Answer 44

-55

Question 45

Action potential occurs so fast it is often referred to as a “____”

Answer 45

spike

Question 46

Four Phases

Answer 46

Resting – Depolarization – Repolarization - Hyperpolarizing

Question 47

In an action potential only a thin layer of the _____ next to the cell membrane is affected /// very few ____ are involved

Answer 47

cytoplasm ; ions

Question 48

characteristics of action potential versus a local potential

Answer 48

all-or-none law
non-decremental
irreversible

Question 49

all-or-none law

Answer 49

if threshold is reached, neuron fires at its maximum voltage

if threshold is not reached it does not fire

Question 50

non-decremental

Answer 50

does not become weaker with distance

Question 51

irreversible

Answer 51

once started goes to completion and can not be stopped

Question 52

refractory period

Answer 52

the period of resistance to stimulation

Question 53

during an action potential and for a few milliseconds after, it is
difficult or impossible to stimulate that region of a neuron to

Answer 53

fire again.

Question 54

two phases of the refractory period

Answer 54

absolute refractory period
relative refractory period

Question 55

absolute refractory period

Answer 55

• no stimulus of any strength will trigger AP
• as long as Na+ gates are open
• from action potential to RMP

Question 56

relative refractory period

Answer 56

• only especially strong stimulus will trigger new AP
• K+ gates are still open and any affect of incoming Na+
  is opposed by the outgoing K+

Question 57

refractory period is occurring only at a _______ of the neuron’s membrane at one time. Other parts of the neuron can be
______ while the small part is in refractory period

Answer 57

small patch ; stimulated

Question 58

for communication to occur, the nerve signal must
travel to the

Answer 58

end of the axon (reach synaptic knobs)

Question 59

saltatory conduction

Answer 59

the nerve signal seems to jump from node to node

Question 60

Saltatory Conduction is faster than conduction speed in an _______ fibers

Answer 60

unmyelinated