Nerve Impulse and Synaptic Transmission Flashcards
Resting Membrane Potential (18 cards)
Describe the factors that generate a resting membrane potential.
The resting membrane potential is generated by differences in ion concentrations inside and outside the cell, as well as differences in the permeability of the plasma membrane to these ions.
Explain the role of potassium ions (K+) in resting membrane potential.
Potassium ions (K+) play the most important role in establishing the resting membrane potential, as the intracellular fluid (ICF) has a higher concentration of K+ compared to the extracellular fluid (ECF).
Define resting membrane potential (RMP).
Resting membrane potential (RMP) is the electrical potential difference across the plasma membrane of a cell when it is not actively sending signals, and it varies depending on the cell type.
How do voltage-gated channels function in neurons?
Voltage-gated channels in neurons open and close in response to local currents (graded potentials), allowing for the generation of action potentials.
Explain the state of voltage-gated channels at rest in neurons.
At rest, all voltage-gated channels in neurons are closed, while only leakage channels are open to maintain the resting membrane potential.
Describe the difference between graded potentials and action potentials in neurons.
Graded potentials decay in amplitude with distance traveled, while action potentials do not decay and occur only in cells with excitable membranes, such as neurons and muscle cells.
What is the significance of chloride ions in resting membrane potential?
Chloride ions help balance the ionic composition of the extracellular fluid, contributing to the overall maintenance of the resting membrane potential.
How does depolarization affect voltage-gated channels in neurons?
During depolarization, voltage-gated channels open slowly, allowing ions to flow and contribute to the generation of an action potential.
Explain the concept of polarization in cells.
All cells are polarized, meaning there is a difference in charge across their plasma membranes, which is essential for processes like signal transmission in neurons.
Describe the role of negatively charged proteins in intracellular fluid.
Negatively charged proteins in the intracellular fluid help balance the higher concentration of potassium ions (K+) and contribute to the overall resting membrane potential.
Describe the process that occurs during depolarization in neurons.
During depolarization, the membrane potential becomes less negative, typically due to the influx of sodium ions through voltage-gated channels.
Explain the role of inactivation gates in action potentials.
Inactivation gates are open at rest and block the channel once it is open, preventing further ion flow and contributing to the repolarization phase.
Define the term ‘threshold voltage’ in the context of action potentials.
Threshold voltage is the critical level of depolarization that must be reached for an action potential to be triggered.
How does the all-or-none phenomenon relate to action potentials?
The all-or-none phenomenon means that an action potential either occurs fully or not at all, with no partial action potentials.
What happens at threshold during an action potential?
At threshold, the membrane is depolarized by 15 to 20 mV, initiating a positive feedback cycle that leads to the rapid rise of the action potential.
Explain the significance of hyperpolarization in neuronal activity.
Hyperpolarization is a phase where the membrane potential becomes more negative than the resting potential, which can inhibit the generation of subsequent action potentials.
Do all depolarization events lead to action potentials?
No, not all depolarization events produce action potentials; only those that reach the threshold voltage can trigger one.
Describe the feedback mechanism that occurs during the action potential.
A positive feedback cycle begins at threshold, where the opening of sodium channels leads to further depolarization and more sodium influx.
