Neuroscience Chapter 5: Synaptic Transmission

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Questions and Answers

What is the primary role of synaptic integration in a postsynaptic neuron?

To combine multiple synaptic potentials (correct)

To isolate synaptic inputs for processing

To completely block synaptic signals

To amplify individual synaptic inputs

How do neurons typically evaluate synaptic inputs over time?

By prioritizing inputs from specific neurons

By using weighted voting of all recent inputs (correct)

By averaging all inputs equally

By focusing on the most recent input

What unit is generally released during synaptic transmission?

Action potential

Miniature postsynaptic potential

Neurotransmitter molecule

Synaptic vesicle (quantum) (correct)

What is the outcome when multiple miniature EPSPs accumulate?

They generate a full EPSP Signup and view all the answers

What does quantal analysis help determine during neurotransmission?

The number of vesicles released Signup and view all the answers

What initiates the exocytosis process for neurotransmitter release?

Stimulation by intracellular calcium [Ca2+]i Signup and view all the answers

Which category does glutamate belong to?

Amino acids Signup and view all the answers

What effect does a ligand-gated ion channel receptor elicit on the postsynaptic cell?

Either excitatory or inhibitory effects Signup and view all the answers

What is the outcome of an excitatory post-synaptic potential (EPSP)?

Transient depolarization of the postsynaptic membrane Signup and view all the answers

How do G protein-coupled receptors differ from ligand-gated ion channels?

G protein-coupled receptors can enact more complex, long-term changes Signup and view all the answers

What process retrieves vesicle membrane after neurotransmitter release?

Endocytosis Signup and view all the answers

Which of the following neurotransmitters is classified as a peptide?

Dynorphin Signup and view all the answers

What characterizes inhibitory post-synaptic potential (IPSP)?

Transient hyperpolarization of postsynaptic membrane Signup and view all the answers

Which of the following neurotransmitters is an amine?

Histamine Signup and view all the answers

How do neurotransmitter receptors affect synaptic transmission?

They have specific receptors that determine the postsynaptic effect Signup and view all the answers

What is the primary function of synapses in the nervous system?

Information transfer between neurons Signup and view all the answers

Which type of synapse is directly characterized by the flow of ions between cells?

Electrical synapse Signup and view all the answers

What separates the pre-synaptic and post-synaptic neurons in chemical synapses?

The synaptic cleft Signup and view all the answers

What does the term 'connexon' refer to in the context of electrical synapses?

A structure formed by connexins Signup and view all the answers

Which of the following categories of synapses is considered the most common in the nervous system?

Chemical synapse Signup and view all the answers

In chemical synapses, neurotransmitters are released from which part of the neuron?

Presynaptic neuron Signup and view all the answers

What type of synapse allows for bidirectional flow of ions?

Electrical synapse Signup and view all the answers

How did Otto Loewi contribute to our understanding of synaptic transmission?

By demonstrating chemical transmission through acetylcholine Signup and view all the answers

What occurs at the postsynaptic neuronal membrane after neurotransmitter release?

Conversion of chemical message into electrical message Signup and view all the answers

Which anatomical connection is characterized as axon to axon?

Axoaxonic Signup and view all the answers

What is the primary function of autoreceptors in the presynaptic axon terminal?

Inhibit neurotransmitter release Signup and view all the answers

What phenomenon describes the summation of postsynaptic potentials?

Synaptic integration Signup and view all the answers

Which mechanism involves the reentry of neurotransmitter molecules back into the presynaptic axon terminal?

Reuptake Signup and view all the answers

What effect do selective serotonin reuptake inhibitors (SSRIs) have on neurotransmitter activity?

Prolong serotonin signaling Signup and view all the answers

What is the general directionality of information flow at a synapse?

Presynaptic to postsynaptic Signup and view all the answers

What type of drug acts as a receptor antagonist?

Curare Signup and view all the answers

Studies on the neuromuscular junction primarily advanced our understanding of what?

Chemical synaptic transmission Signup and view all the answers

Which synaptic connection occurs from dendrite to dendrite?

Dendrodendritic Signup and view all the answers

What process involves the breakdown of neurotransmitters in the synaptic cleft or terminal cytosol?

Degradation Signup and view all the answers

What role do G protein-coupled receptors play in neuronal signaling?

They mediate complex, long-term changes in post-synaptic neurons. Signup and view all the answers

What is neuropharmacology primarily concerned with?

The effects of drugs on nervous system tissue Signup and view all the answers

What is a common consequence of neurotransmitter receptor desensitization?

Decreased receptor responsiveness Signup and view all the answers

What is the primary function of EPSP summation in neurons?

To generate significant postsynaptic depolarization Signup and view all the answers

What distinguishes spatial summation from temporal summation?

Spatial summation occurs from different sites, while temporal summation occurs at the same site. Signup and view all the answers

How do dendrites function in synaptic integration?

They can amplify postsynaptic potentials. Signup and view all the answers

What effect do inhibitory synapses have on membrane potential?

They move the membrane potential away from the action potential threshold. Signup and view all the answers

What is a key feature of dendritic structure regarding signal transmission?

The membrane depolarization falls off exponentially with distance. Signup and view all the answers

What type of channels can many dendrites possess to modulate postsynaptic potentials?

Voltage-gated sodium, calcium, and potassium channels Signup and view all the answers

Which of the following correctly describes the role of dendrites in synaptic integration?

They can act as amplifiers and have active elements like ion channels. Signup and view all the answers

Which statement about inhibitory synapses is true?

They exert powerful control over neuronal output. Signup and view all the answers

Study Notes

Synaptic Transmission Overview

Synaptic transmission facilitates information transfer between neurons at a synapse, resembling a service network for message delivery.
Coined "synapse" by Charles Sherrington in 1897, crucial for nervous system functions.
Chemical synapses were first demonstrated by Otto Loewi in 1921, while electrical synapses were identified in the late 1950s by Furshpan and Potter.

Types of Synapses

Chemical Synapses: Most prevalent, requiring neurotransmitter release across the synaptic cleft, converting chemical signals to electrical ones.
Electrical Synapses: Fast and bidirectional, formed by gap junctions allowing direct ion flow between connected neurons.

Anatomical Connections

Types of synaptic connections include:
- Axodendritic: From axon to dendrite
- Axosomatic: From axon to cell body
- Axoaxonic: From axon to axon
- Axospinous: From axon to dendritic spine
- Dendrodendritic: From dendrite to dendrite

Neurotransmitter Release

Triggered by intracellular calcium levels, leading to exocytosis where neurotransmitters are released into the synaptic cleft.
Vesicle membranes are then recovered through endocytosis.

Categories of Neurotransmitters

Amino Acids: e.g., glutamate, glycine, GABA
Amines: e.g., dopamine, acetylcholine, histamine
Peptides: Short amino acid chains like dynorphin and enkephalins

Effects of Neurotransmitters

Specific receptors on postsynaptic membranes determine the effects:
- Ligand-Gated Ion Channels: Can produce excitatory (EPSP) or inhibitory (IPSP) postsynaptic potentials.
  - EPSP results in membrane depolarization.
  - IPSP results in membrane hyperpolarization.
- G Protein-Coupled Receptors: Involved in more complex, long-term changes related to neuroplasticity.

Autoreceptors and Neurotransmitter Clearance

Autoreceptors: Located on presynaptic membranes, sensitive to the released neurotransmitter, often inhibiting further release.
Neurotransmitter removal methods:
- Diffusion away from the synapse
- Reuptake into the presynaptic terminal
- Enzymatic destruction (e.g., AChE cleaves acetylcholine)
- Desensitization can occur, affecting response duration.

Neuropharmacology

Focuses on drug impacts on the nervous system, including:
- Antagonists: Inhibit neurotransmitter receptors (e.g., curare).
- Agonists: Mimic effects of neurotransmitters (e.g., nicotine).
Defective neurotransmission linked to various neurological and psychiatric disorders.

Synaptic Integration

Involves the summation of multiple synaptic potentials within a postsynaptic neuron, determining the cumulative effect over time.
Neurons receive thousands of inputs, using a "weighted voting" system for decision-making.
Quantal Release: Release of a fixed number of vesicles results in measurable changes in postsynaptic potential (minis to full EPSPs).

Summation Techniques

Spatial Summation: Simultaneous activation of multiple synapses.
Temporal Summation: Rapid succession activation at the same synapse.

Dendritic Involvement

Dendrites are critical in synaptic integration, acting as conduits for postsynaptic potentials.
Depolarization diminishes with distance along dendrites; however, structural complexity enhances processing capabilities.
Dendrites may contain voltage-gated channels, allowing active signal amplification.

Inhibitory Synapses

Play a vital role in controlling neuronal output, moving the membrane potential away from action potential thresholds, critical for overall neural balance.

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Description

This quiz explores the anatomy and function of synapses, focusing on both electrical and chemical types. Delve into the steps of neurotransmitter release, the various categories of neurotransmitters, and the integration of post-synaptic potentials. Test your knowledge on essential concepts in synaptic transmission.