5.2

Question 1

What are ion channels?

Answer 1

Specialized membrane-embedded proteins that conduct ions selectively.

Question 2

What factors influence ion selectivity?

Answer 2

Properties of the pore and the size/charge of the ion with its hydration shell.

Question 3

What determines the magnitude of ionic current flow?

Answer 3

Channel density and individual channel conductance.

Question 4

What is gating in ion channels?

Answer 4

The process of opening and closing ion channels in response to stimuli.

Question 5

How are Na⁺ and Ca²⁺ voltage-gated channels structured?

Answer 5

One α-subunit with four internal repeats (domains), each with 6 TM segments.

Question 6

How are K⁺ voltage-gated channels structured?

Answer 6

Four separate α-subunits, each with one domain of 6 TM segments.

Question 7

What segment acts as the voltage sensor?

Answer 7

The fourth transmembrane segment (S4) in each domain.

Question 8

What does the voltage sensor detect?

Answer 8

Changes in membrane electric field or charge distribution.

Question 9

What happens when the threshold voltage is reached?

Answer 9

A conformational change opens the channel.

Question 10

What happens when the membrane voltage is below threshold?

Answer 10

The channel remains closed.

Question 11

What role do voltage-gated channels play in action potentials?

Answer 11

They initiate, propagate, and terminate the action potential.

Question 12

What does Na⁺ influx cause?

Answer 12

Membrane depolarisation (rising phase of AP).

Question 13

What does K⁺ efflux cause?

Answer 13

Membrane hyperpolarisation (repolarising phase of AP).

Question 14

What triggers NaV activation?

Answer 14

Membrane depolarisation.

Question 15

What is “fast inactivation”?

Answer 15

NaV channels close within 1–2 ms after opening.

Question 16

What are CNS NaV subtypes?

Answer 16

NaV1.1, NaV1.2, NaV1.3.

Question 17

What are PNS NaV subtypes?

Answer 17

NaV1.7, NaV1.8, NaV1.9.

Question 18

What NaV subtype is found in skeletal muscle?

Answer 18

NaV1.4.

Question 19

What NaV subtype is found in cardiac tissue?

Answer 19

NaV1.5.

Question 20

What is the axon initial segment (AIS)?

Answer 20

A region with high NaV density where action potentials are generated.

Question 21

Which NaV subtype propagates action potentials forward?

Answer 21

NaV1.6.

Question 22

Which NaV subtype is involved in back-propagation?

Answer 22

NaV1.2.

Question 23

What drug classes target NaV channels?

Answer 23

Local anaesthetics and anti-epileptic drugs.

Question 24

How do local anaesthetics block NaV channels?

Answer 24

They bind to receptors lining inside the pore to physically block ion flow.

Question 25

What natural toxins target NaV channels?

Answer 25

Tetrodotoxin (TTX) and others block the pore externally. | Animal toxin

Question 26

What is the main function of Kv channels in neurons?

Answer 26

Repolarisation and control of firing frequency.

Question 27

How many Kv families exist?

Answer 27

12 (Kv1 to Kv12).

Question 28

What role do Kv channels play in resting membrane potential?

Answer 28

They help set the resting potential.

Question 29

What are three types of Kv modulators?

Answer 29

Metal ions, small organic molecules (200–500 Da), venom peptides (3–6 kDa).

Question 30

How can Kv modulators affect channel function?

Answer 30

By blocking the pore (internal or external) or altering the voltage sensor.

Question 31

What are the two main CaV channel types?

Answer 31

High voltage activated and low voltage activated.

Question 32

What is typical intracellular [Ca²⁺]?

Answer 32

~100 nM.

Question 33

What does CaV opening increase [Ca²⁺] to?

Answer 33

>1 μM.

Question 34

What is CaV's role in action potentials?

Answer 34

Activates calcium-dependent K⁺ channels to assist in repolarisation.

Question 35

What is CaV's role in neurotransmission?

Answer 35

Provides the calcium needed for vesicle fusion and neurotransmitter release.

Question 36

Why are CaV channels attractive drug targets?

Answer 36

Their role in excitability and neurotransmission links them to various neurological disorders.

Question 37

What is the primary mechanism of CaV blockers?

Answer 37

Reduce neuron excitability by altering depolarisation and firing frequency