voltage gated K channels

Question 1

What is the general function of potassium (K⁺) channels?

Answer 1

regulate membrane potential, repolarization

Question 2

What are maxi-K channels (BK channels)?

Answer 2

large-conductance calcium-activated K⁺ channels that respond to both membrane voltage and intracellular calcium levels.

Question 3

What are the main structural components of maxi-K channels?

Answer 3

a subunit and B subunit
calcium binding domains

Question 4

What is the role of the α subunit in maxi-K channels

Answer 4

ion-conducting pore and contains both a voltage-sensor domain and intracellular calcium-binding sites that control the opening of the channel.

Question 5

What is the role of the B subunit in maxi-K channels

Answer 5

enhance the channel’s calcium sensitivity, influence the channel’s voltage dependence, and regulate the kinetics of gating.

Question 6

How does intracellular calcium influence maxi-K channel gating?

Answer 6

binds to the calcium-binding sites in the C-terminal of the α subunit, increasing the probability of channel opening even at lower voltages.

Question 7

What physiological processes are maxi-K channels involved in?

Answer 7

neuronal firing, smooth muscle contraction, vascular tone, and neurotransmitter release by controlling membrane repolarization

Question 8

How does the β1 subunit affect maxi-K channels in smooth muscle?

Answer 8

increases calcium sensitivity

Question 9

What effect does β4 subunit expression have on neuronal maxi-K channels?

Answer 9

regulates excitability

Question 10

What are the consequences of mutations in maxi-K channels?

Answer 10

hypertension, epilepsy, and cerebellar ataxia

Question 11

What are TREK channels and how are they activated?

Answer 11

part of the two-pore domain K⁺ (K2P) family. They are mechanosensitive and activated by membrane stretch, changes in temperature, pH, and certain lipids.

Question 12

What physiological role do TREK channels play?

Answer 12

regulate neuronal excitability, pain sensation by maintaining resting membrane potential

Question 13

How do TREK channels contribute to neuroprotection?

Answer 13

protect neurons during conditions like ischemia and hypoxia by hyperpolarizing the membrane, reducing neuronal excitability

Question 14

What are KATP channels and how are they regulated?

Answer 14

ATP-sensitive K⁺ channels They close when intracellular ATP levels are high and open when ATP is low, allowing K⁺ efflux to stabilize membrane potential.

Question 15

What is the physiological role of KATP channels in the pancreas?

Answer 15

In pancreatic β-cells, KATP channels regulate insulin secretion. When ATP levels are high after glucose metabolism, KATP channels close, leading to cell depolarization and insulin release.

Question 16

What are the clinical implications of KATP channel dysfunction?

Answer 16

neonatal diabetes, hyperinsulinism, and cardiomyopathies

Question 17

What is the rationale for using KATP channel inhibitors in the treatment of type 2 diabetes?

Answer 17

used to stimulate insulin secretion from pancreatic β-cells.
KATP inhibitors close these channels directly, bypassing ATP-mediated regulation, resulting in increased insulin secretion to help control blood glucose levels.

Question 18

What is the function of calcium-activated K⁺ channels (KCa) during the action potential?

Answer 18

contribute to afterhyperpolarization by allowing K⁺ outflow in response to increased intracellular calcium, which prolongs the refractory period.

Question 19

How do inward rectifier K⁺ channels (Kir) stabilize the action potential?

Answer 19

help stabilize the resting membrane potential and facilitate slow repolarization after action potentials, contributing to the overall excitability of the neuron