Membrane and Action Potential Flashcards
What is the definition of resting membrane potential (RMP)?
The electrical potential of the cell at rest, mainly due to the asymmetrical distribution of ions across the plasma membrane.
What is the typical RMP for a neuron?
-50 to -80 mV (commonly around -70 mV).
What is the primary ion responsible for establishing RMP?
K+ (potassium) ions.
What is the role of Na+/K+ ATPase in RMP?
It contributes about 20% to the resting membrane potential.
What is an action potential?
A rapid change in membrane potential that occurs when a neuron or muscle cell is stimulated.
What is the threshold for action potential generation in neurons?
-40 to -55 mV.
What does the term ‘all-or-none law’ refer to?
Once a stimulus reaches the threshold, further increasing the stimulus amplitude will not result in a bigger response.
What are the two types of refractory periods?
- Absolute refractory period
- Relative refractory period
What is the duration of action potential in cardiac muscle?
~300 ms (ranging from 200-400 ms).
Fill in the blank: The RMP for skeletal muscle is ______.
-90 to -80 mV.
What is the significance of the absolute refractory period in cardiac muscle?
It prevents wave summation and tetanus, allowing the heart to function properly.
What is the primary mechanism that generates action potential in neurons?
The influx of sodium ions (Na+) due to the opening of voltage-gated Na+ channels.
True or False: Astrocytes were previously thought to be non-excitable.
True.
What does hyperpolarization refer to?
An increase in membrane potential making the inside of the cell more negative.
What is the role of calcium ions in smooth muscle action potential?
Calcium ion diffusion via gap junctions is essential for generating action potential.
What is the typical duration of action potential in smooth muscle?
10 ms.
What is the function of secondary sensory receptors?
They have an additional receptor cell between the stimulus and sensory neuron.
Define generator potential.
The potential resulting from the activation of voltage-gated channels leading to an influx of sodium or calcium ions.
What is the role of potassium channels during repolarization?
They open to allow K+ ions to exit the cell, restoring the resting membrane potential.
What is the effect of a stimulus acting on a cell?
It activates voltage-gated ion channels, allowing influx of sodium or calcium ions.
What is the role of neurotransmitters in the generation of action potentials?
They mediate cellular signaling that results in depolarization of the postsynaptic membrane.
What happens when the membrane potential reaches the threshold?
A rapid influx of sodium ions occurs, resulting in the action potential.
What is the difference between continuous and saltatory conduction?
Continuous conduction occurs along unmyelinated fibers, while saltatory conduction occurs along myelinated fibers.
Fill in the blank: The RMP for astrocytes averages ______.
-60 to -85 mV.
What is the duration of action potential for skeletal muscle?
1-2 ms.
What is the critical level of depolarization for skeletal muscle action potential?
50 mV.
What is the primary ion responsible for the rapid depolarization phase of action potential?
Sodium ions (Na+).
What is the role of hyperpolarization-activated channels during afterhyperpolarization?
They contribute to the K+ current as the membrane potential becomes more negative.
What is accommodation in the context of action potentials?
The failure of a slowly rising current to fire the nerve due to adaptation.
