Electrical signaling

Question 1

Examples of downstream events signaled by ion channels opening/closing

Answer 1

Action potential, muscle contraction, secretion;, etc

Question 2

neurotransmission

Answer 2

transduction of chemical signals to electrical signals

Question 3

excitation-contraction coupling

Answer 3

when electrical signals are turned into chemical signals

Question 4

when an electrical signal is used to transduce other, or more, electical signals

Answer 4

action potentials, happen in nerve and muscl

Question 5

what is an example of a spontaneous electrical signal

Answer 5

pacemaker activity in the heart, assembly of ion channels

Question 6

techniques to measure ion channel activity

Answer 6

intracellular microelectrode, voltage clamp and patch clamp

Question 7

voltage clamp

Answer 7

allows scientists to keep membrane potential constant, while currents flowing across the membrane are measured. Recording and reference electrodes.

Question 8

patch clamp

Answer 8

glass pipets able to pull off a section of membrane to watch single ion channels or groups of ion channels

Question 9

T/F. There are only two states of ion channels.

Answer 9

True, open and closed

Question 10

hydration shell

Answer 10

waters surrounding ions which are affected by charge density - affects ion selectivity in ion channels. Li larger hydration shell than K

Question 11

ohms law

Answer 11

conductance = current / membrane voltage

Question 12

what is the “battery” of a living cell?

Answer 12

ion pump, concentration gradient driving force

Question 13

What does the x-intercept of a conductance graph represent?

Answer 13

That the current is zero at that point, both the nernst and reversal potential, and electrochemical equilibrium. Slope is conductance

Question 14

T/F. Ion channels have either an activation gate or an inactivation gate.

Answer 14

False, they all have both

Question 15

Two types of channel gating

Answer 15

Voltage and ligand gating

Question 16

voltage gating

Answer 16

channel opening/closing variable depending on membrane potential itself

Question 17

action potentials arise from the combined actions of three ion channels

Answer 17

leak K channels, Na channels, and delayed rectifier K channels

Question 18

leak K channels: 3 characteristics

Answer 18

open at rest, low conductance, close upon depolarization

Question 19

Na channels: 3 characteristics

Answer 19

closed at rest, open upon depolarization, inactivate within 1-2 ms of opening

Question 20

delayed rectifier K channels: 3 characteristics

Answer 20

closed at rest, open upon depolarization, 10-fold slower to open than Na channels

Question 21

describe the time course of an action potential

Answer 21

1. Leak channels open at rest
2. Membrane depolarizes, leak channels close and Na opens
3. Na current reaches threshold = leak K current, overwhelms leak K current and you get spike in membrane potential
4. Na channels inactivate, delayed K channels open, membrane repolarizes
5. Leak channels open, delayed K channels close, membranes return to resting potential

Question 22

what ensures that only a single action potential is fired at a given part of the membrane for a given time?

Answer 22

refractory period where ion channels are returning to resting potential. Sodium channels which have opened are inactivated

Question 23

How does depolarization spread down a nerve fiber?

Answer 23

Charge spreads through cytoplasm just enough to stimulate adjacent region to depolarize and fire it’s own action potential, which goes down the line

Question 24

Why does an action potential only travel in a single direction?

Answer 24

Because of desensitization of sodium channels and refractory period

Question 25

Give an example of a disease that arises from defects in voltage gated ion channels?

Answer 25

Long QT syndrome in heart, prolongation of action potential leads to cardiac arrhythmias. Or mutations in HERG K+ channels (delayed rectifier) makes them fail to open and delays repolarization

Question 26

How can Na channel spontaneously close once it is opened?

Answer 26

Ball and chain model, where a part of the channel forms a ball that is attracted to an open channel, allowing it to block and inactivate channel once open.