PSYU2236 W3 | The Synapse and Action Potentials

Questions and Answers

What is the effect of an Excitatory Post Synaptic Potential (EPSP)?

It leads to hyperpolarization.

It decreases the likelihood of an action potential.

It causes a small depolarization. (correct)

It always produces an action potential.

What happens at the axon hillock when sufficient EPSPs are reached?

EPSPs are converted into IPSPs.

IPSPs increase the threshold.

Na+ channels open and lead to an action potential. (correct)

The cell becomes hyperpolarized permanently.

What is the primary outcome when multiple EPSPs and IPSPs are present?

Both will always lead to an action potential.

They can cancel each other out. (correct)

The EPSPs always dominate leading to action potentials.

IPSPs always inhibit action potentials.

How do Inhibitory Post Synaptic Potentials (IPSPs) affect the generation of action potentials?

They inhibit action potentials by pushing the potential down. Signup and view all the answers

What initiates the generation of an action potential at the axon hillock?

Reaching a threshold of positive charge. Signup and view all the answers

What type of communication occurs through gap junctions in the brain?

Electrical communication via direct ion transfer Signup and view all the answers

What is the typical distance between cells in a gap junction?

3.5 nm Signup and view all the answers

Which of the following is a function of gap junctions in neural communication?

Synchronization between neurons Signup and view all the answers

Which scenario exemplifies the use of gap junctions for fast communication?

Coordination of breathing between brain hemispheres Signup and view all the answers

What role do connexons play in gap junctions?

Facilitating the transfer of ions between neurites Signup and view all the answers

What initiates the process of neurotransmitter release in chemical synapses?

Increase in calcium in the axon terminal Signup and view all the answers

Which of the following accurately describes the role of vesicles in chemical synapses?

Vesicles contain neurotransmitters that are released during exocytosis. Signup and view all the answers

What occurs after the vesicle content is emptied into the synaptic cleft?

Neurotransmitters bind to receptors on the postsynaptic neuron. Signup and view all the answers

Which step occurs first when an action potential reaches the presynaptic bouton?

Movement of vesicles towards the membrane Signup and view all the answers

What is the primary function of neurotransmitters in chemical synapses?

To convey messages across the synaptic cleft Signup and view all the answers

What role do neurotransmitters play in neuron communication?

They bind to receptors on postsynaptic dendrites. Signup and view all the answers

Which of the following accurately describes exocytosis at the terminal bouton?

It occurs after vesicle contents are moved to the membrane by trafficking proteins. Signup and view all the answers

What initiates exocytosis in the terminal boutons during neurotransmitter release?

Action potential raising calcium ion concentration. Signup and view all the answers

In axosomatic synapses, where do the axons form connections?

With the soma of other neurons. Signup and view all the answers

What is the purpose of endocytosis in neuron communication?

To recycle neurotransmitters after they have bound to receptors. Signup and view all the answers

What is the function of SNARE proteins during neurotransmitter release?

To dock vesicles to the presynaptic membrane. Signup and view all the answers

Which arrangement describes a synapse between two axons?

Axoaxonic Signup and view all the answers

Where does neurotransmitter metabolism occur?

After neurotransmitters bind to receptors. Signup and view all the answers

Which of the following best describes the synaptic cleft?

A narrow gap between the presynaptic and postsynaptic neurons. Signup and view all the answers

What is the primary role of agonists in relation to receptors?

They mimic the effect of the neurotransmitter. Signup and view all the answers

How do antagonists affect neurotransmitter action?

They block the receptor, preventing neurotransmitter action. Signup and view all the answers

What might be a consequence of removing components involved in synaptic transmission?

Inhibition of neurotransmitter release. Signup and view all the answers

Which of the following accurately describes a characteristic of synaptic receptors?

They interact specifically with either agonists or antagonists. Signup and view all the answers

What effect does an agonist typically have on a postsynaptic neuron?

It increases the likelihood of an action potential. Signup and view all the answers

What is a potential effect of using an antagonist at a synapse?

It reduces the overall effectiveness of neurotransmitter communication. Signup and view all the answers

Which statement about neurotransmitter activity is true?

Agonists and neurotransmitters bind in a similar manner. Signup and view all the answers

Which of these would most likely impair synaptic transmission?

The presence of an antagonist. Signup and view all the answers

Study Notes

Synaptic Transmission Overview

Action potentials result from the summed potential change and depolarization of a neuron.
Postsynaptic potentials involve two types: Excitatory Post Synaptic Potential (EPSP) and Inhibitory Post Synaptic Potential (IPSP).

Excitatory Post Synaptic Potential (EPSP)

EPSPs occur when positive ions enter the neuron, causing a slight depolarization.
Individual EPSPs are insufficient to trigger an action potential on their own.

Inhibitory Post Synaptic Potential (IPSP)

IPSPs arise when negative ions enter the neuron, leading to hyperpolarization.
IPSPs inhibit action potentials by pushing the potential downward and counteracting EPSPs.

Integration of Postsynaptic Inputs

Neurons receive multiple inputs that can balance or cancel each other out, particularly EPSPs and IPSPs.
A sufficient number of EPSPs can lead to an action potential if the threshold at the axon hillock is reached.

Action Potential Generation

When depolarization at the axon hillock reaches a critical threshold, Na+ channels open, leading to a rapid influx of sodium ions.
This influx creates the action potential, while significant IPSP activity can prevent action potential firing.

Types of Synapses

Electrical synapses (gap junctions) allow direct ion transfer between neurons for faster communication.
Chemical synapses involve neurotransmitter release across a synaptic cleft for communication.

Electrical Synapses

A gap of approximately 3.5 nm allows for rapid signaling and synchronous neuron activity.
Examples include coordination between brain hemispheres during breathing and reflex responses.

Chemical Synapses

Formed between axon terminals and dendritic spines, relying on neurotransmitters to convey signals.
Action potentials at the presynaptic bouton trigger calcium influx, leading to neurotransmitter exocytosis from vesicles.

Synaptic Transmission Process

Vesicles containing neurotransmitters migrate to the presynaptic membrane following action potential arrival.
Exocytosis occurs, releasing neurotransmitters into the synaptic cleft, where they bind to postsynaptic receptors.

Synaptic Receptors and Neurotransmitter Dynamics

Neurotransmitter binding can activate post-synaptic receptors, leading to either excitatory or inhibitory effects.
Some neurotransmitters are recycled through reuptake mechanisms, while others are metabolized.

Summary of Synaptic Arrangements

Common arrangements include axodendritic (axon to dendrite), axosomatic (axon to soma), and axoaxonic (axon to axon) connections.

Revision Tips

Visual aids of pre-synaptic and post-synaptic components, and action potential mechanics are beneficial for mastering the content.
Modulating components could illustrate impacts on neuronal communication.

Next Topics

Upcoming lectures will cover neuroanatomy, with specific readings suggested for deeper understanding.

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Description

Explore the concepts of depolarization and Action Potentials in the nervous system. This quiz delves into the role of Excitatory Post Synaptic Potentials (EPSPs) in neuronal communication and how they contribute to the overall potential change in neurons.