OPTM4106: Action Potential Quiz

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Questions and Answers

What is the primary function of an action potential in neurons?

To maintain resting membrane potential

To facilitate the movement of nutrients into the neuron

To propagate electrical signals along the axon (correct)

To enhance cellular metabolism

What typically characterizes the resting membrane potential of neurons?

It is constantly neutral at 0mV

It is positive due to ion movement

It is negatively charged at around -70mV (correct)

It fluctuates frequently throughout the day

Which ion is predominantly found outside the neuron during resting potential?

N+ (correct)

K+

Cl-

-ve charged protein molecules

What happens to the membrane potential when a neuron is stimulated?

It depolarizes towards a positive charge Signup and view all the answers

During the action potential process, which ion is primarily responsible for repolarization?

K+ Signup and view all the answers

What occurs at -45mV in photoreceptors during the process of an action potential?

The photoreceptor is fully depolarized Signup and view all the answers

Why do neurons maintain a resting membrane potential of -70mV?

To allow for action potentials to occur when needed Signup and view all the answers

Which type of ion is most associated with creating a net negative charge inside the neuron?

-ve charged protein molecules Signup and view all the answers

What is the ratio of sodium (Na$^+$) pumped out to potassium (K$^+$) pumped in according to the given content?

3 Na$^+$ out for every 2 K$^+$ in Signup and view all the answers

Which ion influx is primarily responsible for initiating the threshold potential?

Sodium (Na$^+$) Signup and view all the answers

What triggers the opening of sodium channels in neurons?

The binding of neurotransmitters to dendrites Signup and view all the answers

Where do neurotransmitters bind to initiate action potential in the next neuron?

Dendrites of the next neuron Signup and view all the answers

What is the primary consequence of Na$^+$ influx during the action potential process?

Depolarization of the neuron Signup and view all the answers

The action potential is primarily initiated when which of the following events occurs?

Sufficient Na$^+$ influx surpasses threshold potential Signup and view all the answers

What is required for a neuron to fire?

Threshold potential to be reached Signup and view all the answers

What occurs when a neuron reaches threshold potential?

Depolarization of the neuron Signup and view all the answers

What is true about the interval after a neuron fires an action potential?

No action potential can occur during this interval Signup and view all the answers

How does the propagation of an action potential act in terms of direction?

Unidirectional only Signup and view all the answers

What must happen to initiate a second action potential after one has occurred?

A greater stimulus than usual must be applied Signup and view all the answers

What causes the refractory period in neurons?

Inactivation gate of sodium channels Signup and view all the answers

Which of the following describes the effect of reaching threshold potential on the neuron's state?

Activation of axonal transmission Signup and view all the answers

What happens to sodium channels after they are inactivated?

They remain inactive until depolarization occurs Signup and view all the answers

What characterizes the action potential in terms of interval and response?

There is a refractory period after firing Signup and view all the answers

What effect does depolarization have on the likelihood of firing in a neuron?

It makes the potential closer to the threshold Signup and view all the answers

How does hyperpolarization affect a neuron's ability to fire?

It decreases the likelihood of firing Signup and view all the answers

Which factor does NOT influence whether a neuron will fire an action potential?

Group of neurotransmitters present Signup and view all the answers

Which statement is true regarding action potentials and the refractory period?

Sodium channels reset during the refractory period Signup and view all the answers

Which ion's channels play a critical role in the generation of action potentials?

Sodium Signup and view all the answers

What role do neurotransmitters play in neuronal signaling?

They modulate the postsynaptic potentials Signup and view all the answers

What is the primary function of the inactivation gate of sodium channels?

To prevent the response to subsequent stimuli Signup and view all the answers

What effect does stimulation have on photoreceptors?

It hyperpolarizes the membrane Signup and view all the answers

What is the nature of the hyperpolarization in photoreceptors?

It is graded based on the intensity of the stimulus Signup and view all the answers

What is the role of excitatory postsynaptic potentials (EPSP)?

They increase the likelihood of a postsynaptic action potential Signup and view all the answers

What is the effect of inhibitory postsynaptic potentials (IPSP)?

They decrease the likelihood of an action potential occurring Signup and view all the answers

Which factors determine the action of neurotransmitters on subsynaptic membranes?

Size and electric charge of hydrated ions Signup and view all the answers

What happens during the inhibitory action of IPSP on a target cell?

It causes no current flow of ions Signup and view all the answers

Study Notes

Acknowledgement

The University of Western Australia is located on Noongar land, recognizing the cultural custodianship of Noongar people.

Objectives

Understand mechanisms of action potential.

Action Potential Overview

An action potential involves the propagation of electrical signals along the axon.
Key ionic players include sodium (Na+), potassium (K+), chloride (Cl-), and negatively charged protein molecules.

Resting Membrane Potential

Neurons have a resting membrane potential of approximately -70mV.
Photoreceptors exhibit a resting potential of around -45mV.
More Na+ ions are outside the neuron than inside, contributing to a net negative charge.
Sodium-potassium pump functions by expelling 3 Na+ ions for every 2 K+ ions imported.

Steps Involved in Action Potential

Initiation occurs when neurotransmitters from one neuron interact with receptors on another neuron's dendrites, generating a threshold potential.
A significant influx of Na+ ions leads to depolarization, triggering the action potential.
Neurons fire only if the threshold potential is reached; otherwise, no action potential occurs.

Propagation of Action Potential

Action potentials travel in a unidirectional manner along the axon.
The refractory period prevents the initiation of another action potential immediately after the first.
Sodium channels become inactivated and unresponsive to stimuli during this period.

Graded and Hyperpolarized Potentials

Graded potentials influence the likelihood of an action potential, with hyperpolarization moving the membrane potential away from the threshold.
In photoreceptors, stimulation leads to hyperpolarization and decreased glutamate release.

Neurotransmitters and Ion Flow

Excitatory postsynaptic potential (EPSP) increases the chance of an action potential in the next neuron.
Inhibitory postsynaptic potential (IPSP) decreases the likelihood of an action potential occurring.
Subsynaptic currents from neurotransmitter actions can either add or remove charge from the postsynaptic membrane.
The effectiveness of neurotransmitters depends on hydrated ion sizes and electric charge, not their chemical nature.

Summary

Neuronal structure is critical for information propagation both along and between neurons.
Glial cells play a supportive role in the retina, alongside major neurotransmitters influencing visual processing.

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Description

Test your understanding of the mechanisms of action potentials in this OPTM4106 quiz. Designed for students at The University of Western Australia, this quiz will assess your knowledge on the key principles of electrophysiology. Prepare to dive into the exciting world of neuronal signaling!