Lecture 7 Action Potentials

Question 1

K channels

Answer 1

4 subunits

Question 2

Channel pore loop forms

Answer 2

Selectively permeable to K ions

Question 3

Scorpion toxins

Answer 3

Block potassium channel opening

Question 4

Mckinnon

Answer 4

x-ray crystal structures

Question 5

Mutations of specific k channels

Answer 5

inherited neurological disorders

Question 6

Importance of external K regulation concentration

Answer 6

Restin membrane potential is close to K because it is mostly permeable to K
Increase extracellular K depolarizes membrane

Question 7

BBB, Potassium spatial buffer by astrocytes

Answer 7

Mechanisms regulating the external potassium concentration

Question 8

Ligang-gate channels

Answer 8

Open in response to binding of specific chemical (ligand) to specific receptors (neurotransmitters and receptors)

Question 9

Voltage-gated channels

Answer 9

Open in response to changes in voltage across membrane

Question 10

Neurotransmitter binds to

Answer 10

receptor opening chanel

Question 11

Graded (local) potentials

Answer 11

small local changes in potential of neurons plasma membrane

Question 12

Depolarization

Answer 12

Cation enter cytosol, making membrane potential less negative, membrane potential approaches 0 mV

Question 13

Hyperpolarization

Answer 13

Cation exit cytosol or anion enter
Membrane potential become more negative

Question 14

Repolarization

Answer 14

Cell returns to resting MP
Anion enter cell, cations enter cytosol

Question 15

Change in MP depends on

Answer 15

Length of stimuli
number of ion channels open
types of ion channels open

Question 16

Reversible

Answer 16

when stimulus stops, neuron quickly returns to resting potential

Question 17

decremental

Answer 17

current is lost across membrane
useful for short-distance signaling only

Question 18

Actionpotentials

Answer 18

uniforms, rapid depolarization and repolarization of the MP

Question 19

AP generated

Answer 19

trigger zones (axolemma, axon hillock, initial segment of axon)

Question 20

Voltage gated channels

Answer 20

responsible for AP

Question 21

Types of VG channels

Answer 21

VG sodium ion channel
VG potassium ion channel

Question 22

Resting state

Answer 22

channels are closed; no potassium ions are able to cross plasma membrane

Question 23

Activated state

Answer 23

Channels are open; potassium ions are able to flow down concentration gradient

Question 24

VGSC resting potential

Answer 24

inactivation gate is open and activation gate is closed
No sodium ions are able to move

Question 25

VGSC activated state

Answer 25

voltage change opens activation gate

Question 26

VGSC inactivated state

Answer 26

inactivation gate is closed and activation gate is open Channel no longer allows sodium ions to move through; once AP is over channel returns to resting

Question 27

VGSC structure

Answer 27

4 domains, each has 6 transmembrane helices S1-6, pore loop

Question 28

S4 transmembrane

Answer 28

contains positively charged amino acids groups changes conformation moving towards extracellular surface opening pore

Question 29

AP depolarization

Answer 29

membrane potential rises towards 0; then becomes positive briefly

Question 30

AP repolarization

Answer 30

MP returns to negative value

Question 31

AP hyperpolarization

Answer 31

MP temporarily becomes more negative than resting MP

Question 32

AP steps write out fully

Answer 32

resting potential Rising phase overshoot falling phase undershoot

Question 33

Absolute refractory period

Answer 33

time from opening of Na channels until inactivation gate is closed enforces one-way transmission

Question 34

Relative refractory period

Answer 34

follows absolute period Most Na channels have returned to their resting state Some K channels still open