Action Potential Quiz: Test Your Knowledge of Neuron Structure

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Questions and Answers

What is the function of dendrites in a neuron?

Transmit signals to other cells

Increase conduction velocity

Receive signals from other neurons (correct)

Initiate action potentials

Where are action potentials initiated in a neuron?

Axon hillock (correct)

Cell body

Dendrites

Synaptic terminals

What do myelin sheaths do for the axon?

Initiate action potentials

Increase conduction velocity of action potentials (correct)

Transmit signals to other cells

Receive signals from other neurons

Which organelle in a neuron contains most of the cell's organelles?

Cell body Signup and view all the answers

What type of cells improve the efficiency of axon conduction velocity?

Astrocytes Signup and view all the answers

What is the resting membrane potential of a neurone?

-70mV Signup and view all the answers

Which ion is most permeable through the neuronal membrane under resting conditions?

Potassium (K+) Signup and view all the answers

What is the main function of Sodium-Potassium ATPase pumps in neuronal cells?

Maintain both K+ and Na+ gradients Signup and view all the answers

What happens when an artificial membrane model separates two chambers with high KCl concentration in one chamber and low KCl in the other chamber?

Negative charge (Cl-) accumulates in the inner chamber Signup and view all the answers

What is the primary effect of open potassium channels in the neuronal membrane?

Enable K+ ions to move out of the cell Signup and view all the answers

Why do K+ ions diffuse out of the cell in neurons?

To balance their concentration gradient Signup and view all the answers

What is the role of the resting membrane potential (RMP) in neurons?

Required for normal function such as muscle contraction and synaptic transmission Signup and view all the answers

Which cells are responsible for insulating and nourishing most neurons?

Glial cells Signup and view all the answers

What is the basis for electrical excitability in the nervous system?

Ion pumps and ion channels establishing the resting potential Signup and view all the answers

What is the distribution of ions like in the extracellular environment of neurons?

Mainly Sodium and Chloride ions Signup and view all the answers

Which of the following describes the resting potential of a neuron?

Membrane potential when no signals are being transmitted Signup and view all the answers

What is the fundamental role of ions in the neuronal membrane?

Establishing membrane potential Signup and view all the answers

What is the approximate resting membrane potential of a neuron?

-70mV Signup and view all the answers

During the action potential, what happens at the peak of depolarization?

Na+ inactivation gate closes Signup and view all the answers

What initiates repolarization of the neuron during the action potential?

K+ channels opening Signup and view all the answers

What causes after hyperpolarization in a neuron?

K+ channels opening Signup and view all the answers

What is responsible for defining the equilibrium potential for one ion only?

Nernst equation Signup and view all the answers

What is responsible for stopping Na+ from entering the neuron during an action potential?

Na+ activation gate closing Signup and view all the answers

What is the equilibrium potential for K+ ions?

-90mV Signup and view all the answers

What does the Nernst equation calculate?

Equilibrium potential for a specific ion Signup and view all the answers

What would be the hypothetical membrane potential if the cell were ONLY permeable to Na+ ions?

+62mV Signup and view all the answers

What is the equilibrium potential for Na+ ions?

+62mV Signup and view all the answers

What contributes to the resting membrane potential being closer to the equilibrium potential for K+ ions?

High permeability to K+ and some to Na+ and Cl- Signup and view all the answers

What is the main factor contributing to the membrane potential according to the information provided?

Balance of electrical and chemical driving forces Signup and view all the answers

Study Notes

Neuronal Membrane Potential

Under resting conditions, the neuronal membrane is highly permeable to K+ ions and has a small permeability to Na+ ions.
The resting membrane potential of a neuron is approximately -65 to -70mV.

Formation of the Resting Potential

The concentration of K+ is highest inside the cell, while the concentration of Na+ is highest outside the cell.
Large negatively charged proteins are also trapped inside the cell.
Sodium-potassium ATPase pumps use the energy of ATP to maintain the K+ and Na+ gradients across the plasma membrane, producing approximately -5mV of the membrane potential.
Open potassium channels in the neuronal membrane allow K+ ions to freely move out of the cell, down its concentration gradient.

Modeling the Resting Potential

The resting potential can be modeled by an artificial membrane that separates two chambers with different concentrations of KCl.
K+ diffuses down its gradient to the outer chamber, building up a negative charge (Cl-) in the inner chamber.
At equilibrium, both the electrical and chemical gradients are balanced.

Neuronal Structure and Function

Neurons form networks, transmitting information from a presynaptic cell to a postsynaptic cell.
Most neurons are nourished or insulated by cells called glia.
The resting membrane potential is the basis for electrical excitability in the nervous system.
Ion pumps and ion channels establish the resting potential of a neuron.
Changes in membrane potential act as signals, transmitting and processing information.

Ion Distribution and Membrane Potential

The distribution of ions is fundamental to the membrane potential.
Extracellular fluid mainly contains sodium and chloride ions, while intracellular fluid contains potassium and non-diffusible molecules (e.g., proteins with negatively charged side chains and phosphate compounds).
The thin shell of ions on the inside and outside of the neuronal membrane determines the membrane potential.

Action Potential Initiation

The axon hillock, also known as the initial segment, is where action potentials are initiated.
The action potential is an all-or-none response, traveling along the axon to the synaptic terminal.