Neuroscience Chapter 5: Synaptic Transmission
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Questions and Answers

What is the first step in the process of chemical synaptic transmission?

  • Neurotransmitter synthesis (correct)
  • Removal of neurotransmitter from synaptic cleft
  • Vesicles fuse to presynaptic terminal due to Ca2+
  • Binds to postsynaptic receptors

    • Which step directly involves the neurotransmitter interacting with the postsynaptic neuron?

  • Vesicles fuse to presynaptic terminal due to Ca2+
  • Load neurotransmitter into synaptic vesicles
  • Biochemical/electrical response elicited in postsynaptic cell
  • Neurotransmitter spills into synaptic cleft (correct)

    • What role does Ca2+ play in the process of chemical synaptic transmission?

  • It facilitates the removal of neurotransmitter from synaptic cleft
  • It binds to postsynaptic receptors
  • It triggers vesicles to fuse to the presynaptic terminal (correct)
  • It initiates neurotransmitter synthesis

    • What happens after the neurotransmitter binds to postsynaptic receptors?

    <p>Biochemical/electrical response is elicited in postsynaptic cell</p> Signup and view all the answers

    What is the final step in the chemical synaptic transmission process?

    <p>Removal of neurotransmitter from synaptic cleft</p> Signup and view all the answers

    What is the primary process through which neurons consider multiple synaptic potentials?

    <p>Weighted voting</p> Signup and view all the answers

    Which factor influences the strength of synaptic integration in postsynaptic neurons?

    <p>The accumulation of recent inputs</p> Signup and view all the answers

    What does quantal analysis measure in synaptic transmission?

    <p>The number of vesicles released</p> Signup and view all the answers

    What is the outcome of releasing one synaptic vesicle?

    <p>One miniature postsynaptic potential (mini)</p> Signup and view all the answers

    How many vesicles typically release at the neuromuscular junction to achieve a significant EPSP?

    <p>200 vesicles</p> Signup and view all the answers

    What is a common effect of activating autoreceptors in presynaptic terminals?

    <p>Inhibition of neurotransmitter release</p> Signup and view all the answers

    How do G protein-coupled receptors influence post-synaptic neurons?

    <p>They enact complex, long-term changes.</p> Signup and view all the answers

    What does reuptake refer to in the context of neurotransmitter clearance?

    <p>Neurotransmitters reenter the presynaptic terminal.</p> Signup and view all the answers

    What class of drugs are selective serotonin reuptake inhibitors (SSRIs) considered?

    <p>Reuptake inhibitors</p> Signup and view all the answers

    Which of the following is an example of a receptor antagonist?

    <p>Curare</p> Signup and view all the answers

    What role do autoreceptors primarily serve in the nervous system?

    <p>Act as a feedback mechanism</p> Signup and view all the answers

    Which of the following processes leads to the inactivation of acetylcholine?

    <p>Desensitization via AChE</p> Signup and view all the answers

    What aspect of neuropharmacology involves drugs that mimic neurotransmitter actions?

    <p>Receptor agonism</p> Signup and view all the answers

    What is the primary role of synaptic integration in neurons?

    <p>To allow neurons to perform complex computations</p> Signup and view all the answers

    What differentiates spatial summation from temporal summation?

    <p>Spatial summation combines signals from different sites, while temporal summation involves signals at the same synapse in rapid succession</p> Signup and view all the answers

    How do dendrites contribute to synaptic integration?

    <p>They have voltage-gated channels that can enhance postsynaptic potentials</p> Signup and view all the answers

    What happens to membrane depolarization as it travels along a dendrite?

    <p>It falls off exponentially with increasing distance</p> Signup and view all the answers

    What is the primary function of inhibitory synapses?

    <p>To decrease the likelihood of reaching action potential threshold</p> Signup and view all the answers

    How do dendritic sodium channels behave in certain cells?

    <p>They can transmit electrical signals in both directions</p> Signup and view all the answers

    What is the significance of the dendritic length constant (l)?

    <p>It measures how far depolarization can travel before it diminishes significantly</p> Signup and view all the answers

    Which of the following is true regarding the relationship between excitatory and inhibitory synapses?

    <p>Both excitatory and inhibitory synapses are important for proper neural function</p> Signup and view all the answers

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

    <p>Transmitting information between neurons</p> Signup and view all the answers

    Which type of synapse is characterized by fast and often bidirectional communication?

    <p>Electrical synapse</p> Signup and view all the answers

    What anatomical feature separates the pre and post-synaptic neurons at a chemical synapse?

    <p>Synaptic cleft</p> Signup and view all the answers

    What term is used to describe the connections between the cytoplasm of one neuron and another in an electrical synapse?

    <p>Connexons</p> Signup and view all the answers

    What aspect of neurotransmitter release at a chemical synapse is crucial for converting chemical messages to electrical messages?

    <p>Binding to receptors on the postsynaptic membrane</p> Signup and view all the answers

    What type of synaptic connection involves the axon terminating on the cell body of another neuron?

    <p>Axosomatic</p> Signup and view all the answers

    Charles Sherrington is known for coining which term related to neuron communication?

    <p>Synapse</p> Signup and view all the answers

    What was the significant finding of Otto Loewi in 1921 regarding synaptic transmission?

    <p>It involves chemical mediation</p> Signup and view all the answers

    Which type of synaptic connection is made between axons and axons?

    <p>Axoaxonic</p> Signup and view all the answers

    What role do postsynaptic potentials (PSPs) play in synaptic transmission?

    <p>They summate to influence neuronal firing</p> Signup and view all the answers

    Which of the following is a defining characteristic of chemical synapses?

    <p>They use neurotransmitter release across a synaptic cleft</p> Signup and view all the answers

    What experimental model contributed significantly to our understanding of chemical synaptic transmission?

    <p>Crawfish neuromuscular junction</p> Signup and view all the answers

    What is the general direction of information flow in synapses?

    <p>From presynaptic to postsynaptic neurons</p> Signup and view all the answers

    What is the main functional difference between electrical and chemical synapses?

    <p>Electrical synapses directly connect cells, while chemical synapses do not</p> Signup and view all the answers

    Study Notes

    Synaptic Transmission Overview

    • Synapses serve as crucial points for information transfer between neurons, resembling a service network for communication.
    • Charles Sherrington named "synapse" in 1897, illustrating its foundational importance in nervous system operations.

    Types of Synapses

    • Chemical Synapses: Most prevalent type, involves neurotransmitter release across the synaptic cleft, converting chemical messages into electrical signals.
    • Electrical Synapses: Fast and often bidirectional, facilitated by gap junctions that connect neuronal cell membranes, allowing direct ion flow.

    Synapse Directionality

    • Signal flow generally occurs in one direction: from presynaptic neuron (sender) to postsynaptic neuron (receiver).
    • Anatomical connections include axodendritic, axosomatic, axoaxonic, axospinous, and dendrodendritic synapses.

    Steps of Chemical Synaptic Transmission

    • Neurotransmitter synthesis occurs within the presynaptic neuron.
    • Neurotransmitters are loaded into synaptic vesicles which fuse with the presynaptic membrane in response to calcium influx.
    • Neurotransmitters are released into the synaptic cleft and bind to postsynaptic receptors, triggering a biochemical or electrical response.
    • Final steps involve neurotransmitter clearance via diffusion, reuptake, enzymatic degradation, or desensitization.

    Neurotransmitter Effects and Autoreceptors

    • G protein-coupled receptors in postsynaptic cells can elicit complex changes associated with learning and memory (neuroplasticity).
    • Autoreceptors on presynaptic terminals regulate neurotransmitter release, often functioning as inhibitory feedback mechanisms.

    Neurotransmitter Reuptake and Clearance

    • Reuptake involves the neurotransmitter re-entering the presynaptic terminal, while enzymatic destruction (e.g., acetylcholinesterase) renders it inactive.
    • Pharmacological manipulation of timing for neurotransmitter reuptake plays a role in treating various medical conditions (e.g., SSRIs).

    Synaptic Integration

    • Summation of multiple synaptic potentials occurs within postsynaptic neurons, allowing cumulative input effects to be considered.
    • Most CNS neurons receive thousands of inputs, employing a "weighted voting" system for decision-making based on recent synaptic inputs.

    Quantitative Aspects of Synaptic Integration

    • The amount of neurotransmitter vesicles released defines the mathematical framework of synaptic integration, where multiple small potentials can lead to significant postsynaptic depolarization.
    • Quantal release of vesicles correlates with the magnitude of postsynaptic potential (EPSP).

    EPSP Summation Techniques

    • Spatial Summation: Simultaneous EPSPs from different synaptic inputs.
    • Temporal Summation: Rapid successive EPSPs from a single synapse.

    Dendrites and Synaptic Integration

    • Dendrites facilitate communication of synaptic integration, acting as conduits for electrical signals.
    • They exhibit complex structures with channels that can amplify postsynaptic potentials rather than passively transmit them.

    Inhibitory Synapses

    • Critical to neuronal output regulation, inhibitory synapses drive membrane potential away from the action potential threshold.
    • Not all synapses amplify signals; inhibitory ones are vital for maintaining balanced neuronal activity.

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    Description

    This quiz covers the essential concepts of synaptic transmission as outlined in Chapter 5. Participants will learn about the anatomy and function of synapses, the two types (electrical and chemical), and the process of neurotransmitter release. Additionally, the quiz will discuss post-synaptic potentials and synaptic integration.

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