Action Potentials & Permeability

Question 1

The best way to observe neuron electrical signals is to use

Answer 1

intracellular microelectrode

Question 2

electrical signals produced by neurons are caused by

Answer 2

responses to stimuli

Question 3

Two types of electrical potentials

Answer 3

Receptor potentials and Synaptic Potentials

Question 4

Receptor potentials are due to the activation of

Answer 4

sensory neurons by external stimuli, such as light, sound, or heat

Question 5

synaptic potentials allow…

Answer 5

transmission of information from one neuron to another

Question 6

A fundamental problem for neurons is that their axons are not good electrical conductors.

1) How do they compensate for this?
2) What does this compensation allow them to do?

Answer 6

1) neurons have evolved a “booster system”
2) allows them to conduct electrical signals over great distances despite their intrinsically poor electrical characteristics.

Question 7

The electrical signals produced by the neurons “booster system” are called

Answer 7

action potentials

Question 8

What is an action potential?

Answer 8

a) an active response generated by the neuron

b) is a brief (about 1 ms) change from negative to positive in the transmembrane potential

Question 9

the amplitude of the action potential is

Answer 9

independent of the magnitude of the current used to evoke it

larger currents do not elicit larger action potentials

Question 10

the intensity of a stimulus is encoded in the ______ of action potentials rather than in their _________

Answer 10

Frequency

amplitude

Question 11

If the membrane potential is made more negative than the resting potential this leads to______; if more positive, ________

What happens as a result?

Answer 11

Hyperpolarization: nothing very dramatic happens

Depolarization: if it passes the threshold potential, an action potential occurs

Question 12

Differences in the intensity of a stimulus between action potentials, receptor potentials, and synaptic potentials

Answer 12

action potentials: intensity is encoded by frequency; not amplitude

receptor potentials: amplitudes are graded in proportion to the magnitude of the sensory stimulus

synaptic potentials: amplitude varies according to the number of synapses activated and the previous amount of synaptic activity.

Question 13

Electrical potentials are generated across the membranes of neurons because

Answer 13

(1) there are differences in the concentrations of specific ions across nerve cell membranes, and
(2) the membranes are selectively permeable to some of these ions.

Question 14

ion concentration gradients are established by proteins known

Answer 14

active transporters

Question 15

What are active transporters?

Answer 15

Proteins that actively move ions into or out of cells against their concentration gradients.

Question 16

The selective permeability of membranes is due largely to

Answer 16

Ion channels

Question 17

What are ion channels?

Answer 17

proteins that allow only certain kinds of ions to cross the membrane in the direction of their concentration gradients

Question 18

generate the resting membrane potential, action potentials, and the synaptic potentials and receptor potentials that trigger action potentials

Answer 18

Ion Transports and Ion Channels

Question 19

Electrical Gradient

Answer 19

Difference in + and – charges across a membrane

Question 20

Concentration Gradient

Answer 20

Difference in distribution of ions across a membrane

Question 21

responsible for the resting membrane potential

Answer 21

A continual resting efflux of K+

Question 22

the equilibrium potential, can be predicted by a simple formula called….

What is that formula?

Answer 22

Nernst equation

Question 23

To measure the Electrochemical Equilibrium in an Environment with More Than One Permeant Ion use

Answer 23

the Goldman equation

Question 24

Hodgkin and Katz showed that the inside-negative resting potential arises because

Answer 24

(1) the membrane of the resting neuron is more permeable to K+ than to any of the other ions present, and
(2) there is more K+ inside the neuron than outside.

Question 25

while the resting neuronal membrane is only slightly permeable to Na+, the membrane becomes extraordinarily permeable to Na+ during the ______ and ______ phase

Answer 25

rising phase and overshoot phase