Basics of ion channels

Question 1

Who first demonstrated electricity in animal tissue?

Answer 1

Luigi Galvani in the 18th century.

Question 2

Who explained the ionic basis of the action potential?

Answer 2

Hodgkin and Huxley in 1952.

Question 3

What are the four main functions of the cell membrane?

Answer 3

Physical barrier, selective permeability, electrochemical gradient control, communication.

Question 4

What are the three states of ion channel gating?

Answer 4

Resting (closed), Activated (open), Inactivated (non-conductive).

Question 5

Where is sodium concentration higher, inside or outside the cell?

Answer 5

Outside.

Question 6

What are the two main types of sodium channels?

Answer 6

Voltage-gated (Nav) and epithelial sodium channels.

Question 7

What triggers voltage-gated sodium channels to open?

Answer 7

Membrane reaching threshold potential (~–55 mV).

Question 8

What is the role of epithelial sodium channels?

Answer 8

Regulate fluid composition in tissues like kidney, lung, and colon.

Question 9

Where is calcium concentration higher, inside or outside the cell?

Answer 9

Outside.

Question 10

Name the major types of voltage-gated calcium channels.

Answer 10

L-type, N-type, P/Q-type, R-type, T-type.

Question 11

What functions is calcium involved in?

Answer 11

Neurotransmission, muscle contraction, gene transcription, apoptosis.

Question 12

What can activate calcium channels polymodally?

Answer 12

Voltage, stretch, heat, intracellular messengers.

Question 13

Where is potassium concentration higher, inside or outside the cell?

Answer 13

Inside.

Question 14

Name the types of potassium channels.

Answer 14

Voltage-gated (Kv), Inwardly rectifying (Kir), K2P, Ca²⁺-activated (SKCa, IKCa, BKCa).

Question 15

What is the function of tandem pore domain (K2P) potassium channels?

Answer 15

Set resting membrane potential.

Question 16

What is the function of chloride channels?

Answer 16

Control volume, pH, and electrical properties of cells.

Question 17

Name three families of chloride channels.

Answer 17

Voltage-gated, CFTR, ligand-gated (GABA/glycine).

Question 18

What is the normal resting membrane potential?

Answer 18

–70 to –90 mV.

Question 19

What maintains the membrane potential?

Answer 19

Ion gradients and Na⁺/K⁺ ATPase pump.

Question 20

What is the role of the Na⁺/K⁺ ATPase?

Answer 20

Pumps 3 Na⁺ out and 2 K⁺ in to maintain gradients.

Question 21

What is the threshold potential for firing an action potential?

Answer 21

~–55 mV.

Question 22

What ions influx during depolarisation?

Answer 22

Na⁺ followed by Ca²⁺.

Question 23

What ion effluxes during repolarisation?

Answer 23

K⁺.

Question 24

What causes hyperpolarisation?

Answer 24

Continued K⁺ efflux past resting potential.

Question 25

What resets the membrane potential after an AP?

Answer 25

Na⁺/K⁺ ATPase pump.

Question 26

What is the absolute refractory period?

Answer 26

No AP can be fired; Na⁺ channels are inactivated.

Question 27

What is the relative refractory period?

Answer 27

AP can be fired but requires stronger stimulus.

Question 28

What triggers neurotransmitter release?

Answer 28

Calcium influx following depolarisation.

Question 29

What are common excitatory neurotransmitters?

Answer 29

Glutamate, acetylcholine (nicotinic), noradrenaline, dopamine.

Question 30

What are inhibitory neurotransmitters?

Answer 30

GABA, glycine.

Question 31

How does GABA inhibit neurons?

Answer 31

Opens Cl⁻ channels causing hyperpolarisation.

Question 32

How do calcium channel blockers work?

Answer 32

Reduce calcium influx → lower muscle contraction and blood pressure.

Question 33

How do potassium channel openers work?

Answer 33

Increase K⁺ efflux → hyperpolarise cell → reduce excitability.

Question 34

How do proton pump inhibitors work?

Answer 34

Block H⁺/K⁺ ATPase → reduce stomach acid.

Question 35

What do aquaporins do?

Answer 35

Control water flow across membranes.

Question 36

What is VMAT?

Answer 36

Vesicular monoamine transporter; loads NTs into vesicles.

Question 37

What is the role of ion channels in the nervous system?

Answer 37

They control ion movement to initiate and propagate action potentials.

Question 38

Why are ion channel modulators medically important?

Answer 38

They treat conditions like epilepsy, hypertension, anxiety, and GERD.