chatgpt lMembrane and Action Potential

Flashcard 1
Q: What is membrane potential?

The difference in electrical charges across a cell membrane, reflecting the electrical polarity of the cell interior relative to the exterior.

Flashcard 2
Q: What is resting membrane potential?

A: Membrane potential measured when a cell is in a steady, unstimulated state. Typically around 70 mV for neurons.

Flashcard 3
Q: Which ions primarily determine membrane potential?

A: Potassium (K⁺) and sodium (Na⁺), along with negatively charged intracellular proteins.

Flashcard 4
Q: What is the range of resting membrane potential in excitable tissues?

A: Approximately -70 to -90 mV.

Flashcard 5
Q: How does potassium contribute to the resting membrane potential?

A: Through potassium leak channels, K⁺ passively exits the cell, making the inside negative and outside positive.

Flashcard 6
Q: What role does the sodium potassium pump play?

A: Actively pumps 3 Na⁺ out and 2 K⁺ in to maintain ion gradients and resting membrane potential.

Flashcard 7
Q: What is the Nernst potential for potassium?

A: The equilibrium potential for K⁺, typically around 90 mV.

Flashcard 8
Q: What triggers an action potential in neurons?

A: A stimulus strong enough to depolarize the membrane to the threshold (~55 mV), opening voltage

Flashcard 9
Q: What is depolarization?

A: When Na⁺ influx makes the membrane less negative and eventually positive, reaching up to +40 mV.

Flashcard 10
Q: What happens after the membrane reaches +40 mV during an action potential?

A: Sodium channels inactivate, and voltage gated potassium channels open, allowing K⁺ efflux to repolarize the membrane.

Flashcard 11
Q: What is the refractory period?
A: A period after depolarization during which sodium channels are inactivated, preventing another immediate action potential.

A: A period after depolarization during which sodium channels are inactivated, preventing another immediate action potential.

Flashcard 12
Q: How does hyperpolarization occur?

A: Excess K⁺ efflux after repolarization makes the membrane potential more negative than resting, approaching -80 to -90 mV.

Flashcard 13
Q: What maintains the resting membrane potential after hyperpolarization?

A: Sodium potassium pumps restore normal ion concentrations, keeping the inside negative and outside positive.

Flashcard 14
Q: Describe the structure of a neuron.

A: Composed of a cell body (with nucleus), dendrites (receive signals), axons (transmit signals), myelin sheath (insulates), nodes of Ranvier (voltage gated Na⁺ channels), and axon terminals (synapse with target cells).

Flashcard 15
Q: What is saltatory conduction?

A: Rapid propagation of action potentials along myelinated axons, jumping from one node of Ranvier to another.

Flashcard 16
Q: How do neurotransmitters transmit signals across synapses?

A: Action potentials open voltage gated calcium channels in axon terminals, causing Ca²⁺ influx and neurotransmitter release into synaptic cleft.

Flashcard 17
Q: Difference between excitatory and inhibitory neurotransmitters?

Excitatory (e.g., acetylcholine, glutamate): depolarize postsynaptic membrane → promote firing

inhibitory (e.g., GABA, glycine): hyperpolarize postsynaptic membrane → suppress firing

Flashcard 18
Q: How do ligand gated ion channels work?

A: Open in response to chemical signals (neurotransmitters), allowing specific ions (Na⁺, K⁺, Cl⁻, Ca²⁺) to enter or exit, altering membrane potential.

Flashcard 19
Q: What is the role of voltage gated Na⁺ channels during action potential?

A: Facilitate passive Na⁺ influx, leading to depolarization; inactivate after peak to prevent overstimulation.

Flashcard 20
Q: What is the role of voltage gated K⁺ channels?

A: Allow K⁺ efflux during repolarization to restore membrane potential and contribute to hyperpolarization.

Flashcard 21
Q: How does calcium contribute to neurotransmitter release?

A: Ca²⁺ influx into axon terminals triggers synaptic vesicle fusion and neurotransmitter release.

Flashcard 22
Q: How do sodium potassium pumps use energy?

A: Use ATP hydrolysis to move 3 Na⁺ out and 2 K⁺ in against concentration gradients.

Flashcard 23
Q: What is the significance of the resting membrane potential being closer to K⁺ equilibrium?

A: Because the membrane is more permeable to K⁺ (via leak channels), the resting potential is more negative, near -70 to -90 mV.

Flashcard 24
Q: How does the membrane ensure one way propagation of action potentials?

A: Refractory periods prevent backward activation of Na⁺ channels, ensuring the signal moves downstream.