Membrane and Action Potential

Question 1

What is the definition of resting membrane potential (RMP)?

Answer 1

The electrical potential of the cell at rest, mainly due to the asymmetrical distribution of ions across the plasma membrane.

Question 2

What is the typical RMP for a neuron?

Answer 2

-50 to -80 mV (commonly around -70 mV).

Question 3

What is the primary ion responsible for establishing RMP?

Answer 3

K+ (potassium) ions.

Question 4

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

Answer 4

It contributes about 20% to the resting membrane potential.

Question 5

What is an action potential?

Answer 5

A rapid change in membrane potential that occurs when a neuron or muscle cell is stimulated.

Question 6

What is the threshold for action potential generation in neurons?

Answer 6

-40 to -55 mV.

Question 7

What does the term ‘all-or-none law’ refer to?

Answer 7

Once a stimulus reaches the threshold, further increasing the stimulus amplitude will not result in a bigger response.

Question 8

What are the two types of refractory periods?

Answer 8

• Absolute refractory period
• Relative refractory period

Question 9

What is the duration of action potential in cardiac muscle?

Answer 9

~300 ms (ranging from 200-400 ms).

Question 10

Fill in the blank: The RMP for skeletal muscle is ______.

Answer 10

-90 to -80 mV.

Question 11

What is the significance of the absolute refractory period in cardiac muscle?

Answer 11

It prevents wave summation and tetanus, allowing the heart to function properly.

Question 12

What is the primary mechanism that generates action potential in neurons?

Answer 12

The influx of sodium ions (Na+) due to the opening of voltage-gated Na+ channels.

Question 13

True or False: Astrocytes were previously thought to be non-excitable.

Answer 13

True.

Question 14

What does hyperpolarization refer to?

Answer 14

An increase in membrane potential making the inside of the cell more negative.

Question 15

What is the role of calcium ions in smooth muscle action potential?

Answer 15

Calcium ion diffusion via gap junctions is essential for generating action potential.

Question 16

What is the typical duration of action potential in smooth muscle?

Answer 16

10 ms.

Question 17

What is the function of secondary sensory receptors?

Answer 17

They have an additional receptor cell between the stimulus and sensory neuron.

Question 18

Define generator potential.

Answer 18

The potential resulting from the activation of voltage-gated channels leading to an influx of sodium or calcium ions.

Question 19

What is the role of potassium channels during repolarization?

Answer 19

They open to allow K+ ions to exit the cell, restoring the resting membrane potential.

Question 20

What is the effect of a stimulus acting on a cell?

Answer 20

It activates voltage-gated ion channels, allowing influx of sodium or calcium ions.

Question 21

What is the role of neurotransmitters in the generation of action potentials?

Answer 21

They mediate cellular signaling that results in depolarization of the postsynaptic membrane.

Question 22

What happens when the membrane potential reaches the threshold?

Answer 22

A rapid influx of sodium ions occurs, resulting in the action potential.

Question 23

What is the difference between continuous and saltatory conduction?

Answer 23

Continuous conduction occurs along unmyelinated fibers, while saltatory conduction occurs along myelinated fibers.

Question 24

Fill in the blank: The RMP for astrocytes averages ______.

Answer 24

-60 to -85 mV.

Question 25

What is the duration of action potential for skeletal muscle?

Answer 25

1-2 ms.

Question 26

What is the critical level of depolarization for skeletal muscle action potential?

Answer 26

50 mV.

Question 27

What is the primary ion responsible for the rapid depolarization phase of action potential?

Answer 27

Sodium ions (Na+).

Question 28

What is the role of hyperpolarization-activated channels during afterhyperpolarization?

Answer 28

They contribute to the K+ current as the membrane potential becomes more negative.

Question 29

What is accommodation in the context of action potentials?

Answer 29

The failure of a slowly rising current to fire the nerve due to adaptation.