Neuroscience Chapter on Membrane Potential

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What function do pumps serve in cellular processes?

They create energy without the need for ATP.

They actively push ions against their chemical gradient. (correct)

They facilitate passive transport of ions along their gradient.

They are responsible for the resting membrane potential without energy.

How much of the neuronal energy is consumed by the sodium-potassium pump?

It does not consume any energy.

1/3 of all neuronal energy.

50% of all neuronal energy.

2/3 of all neuronal energy. (correct)

What is the major consequence of the sodium-potassium pump's activity?

It pushes 3 Na+ ions out and 2 K+ ions in. (correct)

It causes the cell to reach equilibrium.

It allows ions to move freely across the membrane without energy.

It maintains a net positive charge inside the cell.

What would happen to a cell without any channels or pumps?

Nothing would move into or out of the cell. Signup and view all the answers

What is the resting membrane potential typically represented as?

0mV Signup and view all the answers

What primarily causes hyperpolarization during the action potential process?

Slow closing of voltage-gated K+ channels Signup and view all the answers

What effect does suprathreshold stimulation have on an axon?

It generates an action potential that propagates without diminishing. Signup and view all the answers

In unmyelinated axons, where are Na+ channels located?

All along the length of the axon Signup and view all the answers

What contributes to the faster conduction of action potentials in myelinated axons, compared to unmyelinated axons?

Action potentials only occur at the Nodes of Ranvier. Signup and view all the answers

How does the Na+/K+ pump influence the action potential process?

It helps restore ion balance after the action potential. Signup and view all the answers

What is the result of hyperpolarizing the membrane in a postsynaptic neuron?

Decreases the likelihood of firing an action potential Signup and view all the answers

What occurs when the sum of EPSPs and IPSPs reaches the axon initial segment and exceeds the threshold?

An action potential is generated Signup and view all the answers

How does the action potential differ from postsynaptic potentials?

It is all-or-none and consistent in size Signup and view all the answers

What is the primary effect of depolarizing the membrane at the postsynaptic neuron?

Increases the likelihood of firing an action potential Signup and view all the answers

What value represents the threshold of excitation for generating an action potential?

-55 mV Signup and view all the answers

What characteristic of an action potential allows for consistent communication within the brain?

All-or-none and uniform in size Signup and view all the answers

What primarily causes the generation and conduction of an action potential?

Voltage-activated ion channels Signup and view all the answers

What happens to the membrane potential during an action potential?

It reverses from negative to positive Signup and view all the answers

What primarily determines the resting membrane potential in neurons?

Chemical gradients of sodium and potassium ions Signup and view all the answers

How do ions behave in relation to resting membrane potential?

Ions move according to both electrical and chemical gradients Signup and view all the answers

What is necessary for an intracellular electrode used in measuring membrane potential?

It must have a very fine tip Signup and view all the answers

What happens when the electrical and chemical gradients are opposed?

Equilibrium is achieved at a non-zero potential Signup and view all the answers

What role does the lipid bilayer of the cell membrane play?

It acts as a selective barrier keeping out harmful substances Signup and view all the answers

What characterizes the channels in the neuron membrane?

They allow only certain molecules to pass through Signup and view all the answers

Why is the resting membrane potential variable from cell to cell?

Membrane composition can vary across different cell types Signup and view all the answers

What is the charge characteristic of sodium (Na+) and potassium (K+) ions?

Na+ and K+ are both positively charged ions Signup and view all the answers

What triggers the opening of voltage-gated Ca++ channels in the terminal bouton?

Depolarization of the bouton Signup and view all the answers

What role does the SNARE complex play in neurotransmission?

It fuses vesicles with the membrane Signup and view all the answers

Which type of neurotransmitter is glutamate classified as?

Most common excitatory neurotransmitter Signup and view all the answers

Which characteristic distinguishes action potentials from graded potentials?

They are rapid Signup and view all the answers

What occurs when neurotransmitters bind to the receptors on the dendrite membrane?

Ligand-gated ion channels open Signup and view all the answers

What can be said about the strength of graded potentials compared to action potentials?

Graded potentials can vary in strength Signup and view all the answers

What is located at the ends of axons in the process of neurotransmission?

Terminal boutons Signup and view all the answers

What type of channels are typically opened by the binding of neurotransmitters to their receptors?

Ligand-gated ion channels Signup and view all the answers

Study Notes

Resting Membrane Potential

The resting membrane potential is initially measured using intracellular and extracellular electrodes.
It can be measured in invertebrates because their neurons are larger and easier to access.
Different cells and regions of the cell have slightly different resting membrane potentials due to variations in ion concentrations and permeability.

Neuronal Communication

Neuronal communication is driven by the movement of ions, primarily sodium (Na+) and potassium (K+).
These ions move into and out of the cell through channels and pumps, changing the electrical potential across the membrane.

Chemical and Electrical Gradients

Ions move from areas of high concentration to low concentration (chemical gradient).
Charged particles move from areas of high potential to low potential (electrical gradient).
These gradients can be opposing forces, creating an equilibrium that may not be equal to 0mV.

Cell Membrane and Ion Movement

The cell membrane is a lipid bilayer that acts as a barrier, keeping out molecules and ions.
Channels provide passive diffusion of ions along the concentration gradient.
Pumps actively transport ions against their concentration gradient using energy (ATP).

The Sodium-Potassium Pump

The pump is embedded in the cell membrane and is important for maintaining the resting membrane potential.
It pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, creating a chemical gradient.
It results in an electrical gradient with the inside of the cell being more negative than the outside.

Postsynaptic Potentials

Neurotransmitters bind to receptors on the postsynaptic membrane.
These receptors can trigger depolarization (EPSP) or hyperpolarization (IPSP) of the postsynaptic neuron.
The transmission of PSPs is graded, rapid, and decremental, travelling like an electrical signal.
EPSPs and IPSPs sum together spatially and temporally, influencing the likelihood of an action potential.

Action Potential

An action potential (AP) is a rapid and brief reversal of the membrane potential.
It occurs when the sum of EPSPs and IPSPs reaches the threshold of excitation at the axon initial segment.
It is an all-or-none event, always the same size and shape in a given neuron.
It is the main method of communication within the nervous system.
It is generated by voltage-gated ion channels, especially sodium (Na+) channels.

Conduction

Action potential is a self-propagating event that travels down the axon.
In unmyelinated axons, Na+ channels are distributed along the axon, allowing the signal to move continuously.
In myelinated axons, Na+ channels are concentrated at the Nodes of Ranvier, allowing for faster conduction via saltatory conduction.
Myelination increases conduction speed by reducing membrane capacitance and preventing ion leak.
Action potentials are unidirectional because of the refractory period of Na+ channels.

Neurotransmission

Axons end in terminal boutons, containing vesicles filled with neurotransmitters.
The arrival of an action potential causes Ca++ channels to open, triggering the release of neurotransmitters.
Neurotransmitters bind to receptors on the postsynaptic membrane, either directly opening ion channels or activating signaling pathways.

Types of Potentials

Postsynaptic potentials (PSPs) are graded, while action potentials (APs) are not.
PSPs are rapid and decremental, while APs are less rapid and non-decremental.
PSPs use amplitude modulation (AM), while APs use frequency modulation (FM) to convey information.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key concepts related to resting membrane potential, neuronal communication, and ion movement across cell membranes. Understand how different ions and their gradients influence the electrical properties of neurons. Test your knowledge on the mechanisms behind neuronal signaling and the factors affecting membrane potential.