Nervous System Physiology Essentials 3
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Questions and Answers

What triggers the voltage-gated Ca+2 channels to open in the presynaptic neuron?

  • Accumulation of acetylcholine (Ach)
  • Depolarization of the presynaptic neuron (correct)
  • An increase in neurotransmitter concentration
  • Opening of sodium channels

What is released into the synaptic cleft following the fusion of the vesicle with the presynaptic membrane?

  • GABA
  • Calcium ions
  • Sodium ions
  • Acetylcholine (Ach) (correct)

Which type of channel does the postsynaptic nicotinic Ach receptor (nAcHR) represent?

  • Voltage-gated ion channel
  • Leak channel
  • Mechanically gated ion channel
  • Ligand-gated ion channel (correct)

What primarily determines the number of vesicles discharged into the synaptic cleft?

<p>The amount of Ca+2 in the presynaptic terminal (B)</p> Signup and view all the answers

What occurs after Ach binds to postsynaptic nicotinic receptors?

<p>A miniature motor end plate potential forms (C)</p> Signup and view all the answers

What type of potential is generated following the accumulation of excitatory postsynaptic potentials (EPP)?

<p>Action potential (D)</p> Signup and view all the answers

Which neurotransmitter is known as the most common excitatory neurotransmitter in the CNS?

<p>Glutamate (B)</p> Signup and view all the answers

What is the primary role of GABA in the central nervous system?

<p>Balancing excitatory signals (C)</p> Signup and view all the answers

What type of synapse is formed between a neuron and a muscle cell?

<p>Neuromuscular junction (C)</p> Signup and view all the answers

What is a distinguishing feature of electrical synapses compared to chemical synapses?

<p>They allow ions to flow freely between cells. (D)</p> Signup and view all the answers

What provides the gap for ion flow in electrical synapses?

<p>Gap junctions (A)</p> Signup and view all the answers

Which of the following accurately describes the synaptic cleft in chemical synapses?

<p>20-40 nanometers wide (D)</p> Signup and view all the answers

What initiates the release of neurotransmitters in chemical synapses?

<p>Calcium ions entering the presynaptic cell (B)</p> Signup and view all the answers

Which type of synapse is characterized by almost no physical distance between connected cells?

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

What is formed when cells communicate through electrical synapses?

<p>Syncytium (C)</p> Signup and view all the answers

In which part of the nervous system are gap junctions predominantly found?

<p>In peripheral nervous system and muscle cells (A)</p> Signup and view all the answers

What role does acetylcholine play in the central nervous system (CNS)?

<p>Initiating muscle contractions (A), Storing memories (C)</p> Signup and view all the answers

Which characteristic distinguishes chemical synapses from electrical synapses?

<p>Chemical synapses are slower in transmission. (D)</p> Signup and view all the answers

What is the primary function of V-SNARE proteins?

<p>To assist in the process of exocytosis (D)</p> Signup and view all the answers

Which of the following conditions affects the neuromuscular junction?

<p>Myasthenia Gravis (D)</p> Signup and view all the answers

What is the role of synaptotagmin in the SNARE complex?

<p>To enhance the assembly of the SNARE complex (C)</p> Signup and view all the answers

How does botulinum toxin affect muscle movement?

<p>By inhibiting neurotransmitter release from synaptic vesicles (C)</p> Signup and view all the answers

What primarily mediates the transmission in electrical synapses?

<p>Ion currents (B)</p> Signup and view all the answers

Which proteins form the SNARE complex during exocytosis?

<p>Synaptobrevin, syntaxin, and SNAP-25 (B)</p> Signup and view all the answers

What is the mechanism of action of botulinum toxin on neurotransmitter release?

<p>It blocks the release of acetylcholine by destroying SNARE proteins. (B)</p> Signup and view all the answers

Which of the following is a clinical use of botulinum toxin?

<p>Treatment of muscle spasms. (C)</p> Signup and view all the answers

Which food source poses a risk for botulism due to the presence of botulinum spores?

<p>Canned low-acid foods. (A)</p> Signup and view all the answers

How does tetanus toxin affect neurotransmitter release in the body?

<p>It destroys synaptobrevin, leading to reduced inhibitory signaling. (C)</p> Signup and view all the answers

What autoimmune response does Lambert-Eaton Syndrome trigger?

<p>Production of antibodies against voltage-gated Ca2+ channels. (B)</p> Signup and view all the answers

Which mechanism contributes to the muscle weakness observed in Myasthenia Gravis?

<p>Autoantibody formation against nicotinic acetylcholine receptors. (D)</p> Signup and view all the answers

What is the primary source of botulinum toxin?

<p>Clostridium botulinum. (C)</p> Signup and view all the answers

What is the effect of the compound curare in the body?

<p>It has muscle relaxant properties. (D)</p> Signup and view all the answers

What is the primary action of curare on the neuromuscular junction?

<p>Blocks acetylcholine receptors (B)</p> Signup and view all the answers

What happens to acetylcholine levels when curare is applied?

<p>They become abundantly present in the synaptic cleft. (A)</p> Signup and view all the answers

Which neurotransmitter is primarily involved in producing an EPSP?

<p>Glutamate (C)</p> Signup and view all the answers

What is the effect of inhibitory neurotransmitters on the postsynaptic neuron?

<p>They make the membrane potential more negative. (A)</p> Signup and view all the answers

What is convergence in the context of neuron signaling?

<p>Multiple presynaptic neurons send signals to a single postsynaptic neuron. (B)</p> Signup and view all the answers

What primarily determines whether a postsynaptic neuron will fire an action potential?

<p>The sum of EPSP and IPSP in the postsynaptic neuron. (C)</p> Signup and view all the answers

What effect does hyperpolarization have on a neuron?

<p>Decreases the likelihood of an action potential. (C)</p> Signup and view all the answers

How does the opening of Na channels impact a postsynaptic potential?

<p>Results in depolarization. (C)</p> Signup and view all the answers

Flashcards

Synapse Definition

The connection between two cells, especially neurons, in the nervous system. In the CNS, both cells are neurons; in the PNS, the second cell can be a neuron, muscle, or gland.

Neuromuscular Junction

A specialized synapse between a neuron and a muscle cell.

Presynaptic Cell

The cell before the synapse that releases neurotransmitters.

Postsynaptic Cell

The cell after the synapse that receives and responds to the signal.

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Electrical Synapse

Direct connection between neurons, allowing ions to flow directly for rapid signal transmission.

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Chemical Synapse

Uses neurotransmitters to transmit signals across a small gap (synaptic cleft).

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Synaptic Cleft

The small gap between the presynaptic and postsynaptic cells in a chemical synapse.

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Gap Junctions

Protein channels that connect cells in electrical synapses, allowing for the direct movement of ions.

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Neurotransmitter Release

The process by which neurotransmitters are released from a presynaptic neuron into the synaptic cleft.

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Synaptic Vesicle

Small sacs that store neurotransmitters within the presynaptic neuron, ready for release.

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Exocytosis

The process of releasing neurotransmitters from synaptic vesicles into the synaptic cleft.

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Action Potential

A brief electrical signal that travels down the axon of a neuron.

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Voltage-Gated Calcium Channels

Channels in the presynaptic membrane that open in response to a change in voltage.

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Acetylcholine (ACh)

A neurotransmitter that plays a crucial role in the nervous system, particularly muscle contractions.

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Miniature Motor End Plate Potential (MEPP)

A small graded potential generated when a single vesicle releases its neurotransmitters.

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Excitatory Postsynaptic Potential (EPP)

A graded potential that can trigger an action potential if it reaches threshold.

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Acetylcholine's role

A neurotransmitter that triggers muscle contractions and is essential for learning/memory in the central nervous system (CNS).

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Electrical Synapse vs. Chemical Synapse

Electrical synapses transmit signals faster by directly passing ions, while chemical synapses use neurotransmitters for slower, unidirectional transmission.

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SNARE proteins

Proteins (V-SNAREs and T-SNAREs) that facilitate the fusion of synaptic vesicles with the presynaptic membrane, releasing neurotransmitters.

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V-SNARE

Vesicle-associated SNARE proteins found on the surface of synaptic vesicles.

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T-SNARE

Target-associated SNARE proteins located on the presynaptic membrane.

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Botulinum toxin's effect

A neurotoxin that blocks neurotransmitter release, causing muscle paralysis.

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Neuromuscular Junction Conditions

Conditions affecting the interaction between nerves and muscles, like Lambert-Eaton Syndrome, Botulism, Tetanus, Myasthenia Gravis, and Curare Effect.

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Botulinum Toxin Action

Botulinum toxin blocks the release of neurotransmitters at nerve endings, preventing muscle contraction.

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Botulinum Toxin Targets

Botulinum toxin targets SNARE proteins (SNAP-25, synaptobrevin, and syntaxin), crucial for neurotransmitter release.

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Botulism Infection

Botulism is a food poisoning caused by botulinum toxin produced by Clostridium botulinum bacteria, often found in improperly canned foods or honey.

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Tetanus Toxin Action

Tetanus toxin specifically destroys synaptobrevin in inhibitory interneurons, leading to overactive motor neurons and muscle spasms.

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Lambert-Eaton Syndrome

An autoimmune disease where the body attacks voltage-gated calcium channels, disrupting acetylcholine release at nerve endings and causing muscle weakness.

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Myasthenia Gravis

Myasthenia Gravis is an autoimmune disease in which the body produces antibodies that attack acetylcholine receptors, causing delayed neurotransmission.

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Curare Effect

Curare, a natural compound, acts as a muscle relaxant by blocking acetylcholine receptors, preventing muscle contraction.

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Synaptic Vesicle Release

Neurotransmitters are released from synaptic vesicles into the synaptic cleft, the space between nerve cells, initiating a signal or response.

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Curare's Action

Curare blocks acetylcholine receptors at the neuromuscular junction, preventing muscle contraction. This leads to muscle relaxation and paralysis.

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What is a Postsynaptic Potential?

A temporary change in the electrical potential of a postsynaptic neuron caused by neurotransmitters released from the presynaptic neuron.

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EPSP (Excitatory Postsynaptic Potential)

A depolarization of the postsynaptic membrane, making it more likely to fire an action potential. This occurs when excitatory neurotransmitters, like glutamate, bind to receptors.

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IPSP (Inhibitory Postsynaptic Potential)

A hyperpolarization of the postsynaptic membrane, making it less likely to fire an action potential. This occurs when inhibitory neurotransmitters, like GABA, bind to receptors.

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What is Convergence?

Multiple presynaptic neurons sending signals to a single postsynaptic neuron.

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What is Divergence?

A single presynaptic neuron sending signals to multiple postsynaptic neurons.

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How does Curare affect AchE receptors?

Curare blocks acetylcholine receptors, preventing acetylcholine from binding. This leads to an accumulation of acetylcholine in the synaptic cleft, causing an increase in AchE receptors.

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What does the 'Summation' of EPSPs and IPSPs determine?

The sum of EPSPs and IPSPs determines whether the postsynaptic neuron will fire an action potential or not.

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Study Notes

Nervous System Physiology Essentials 3

  • The nervous system is composed of neurons and other cells
  • The connection between a neuron and another cell is a synapse
  • In the central nervous system (CNS), both connected cells are neurons
  • In the peripheral nervous system, the second cell can be a neuron, a muscle, or a gland cell.
  • The synapse between a neuron and a muscle cell is called a neuromuscular junction
  • The cell before the synapse is presynaptic
  • The cell after the synapse is postsynaptic

Synapse Types

  • Synapses are connections that allow the transmission of information between neurons.
  • They are categorized according to structure and function
  • Synapses can be electrical or chemical
  • Electrical synapses allow ions to flow directly between cells through gap junctions
  • Chemical synapses involve the release of neurotransmitters into a synaptic cleft
  • Electrical synapses have a much faster transmission speed than chemical synapses

Electrical Synapse

  • Electrical synapses utilize gap junctions to transmit signals.
  • These junctions create a very short distance between the cells
  • Gap junctions connect the presynaptic and postsynaptic cells
  • The distance between the cells is 2-4nm
  • The transmission occurs very quickly, approximately 6 times faster than in a chemical synapse
  • They are ion-based
  • In electrical communication, nerve conduction is based on an ion balance
  • They are present in smooth muscle and heart muscle

Chemical Synapse

  • Chemical synapses are more common than electrical synapses.
  • A physical space called a synaptic cleft exists between neuron endings.
  • The synaptic cleft is 20-40 nanometers wide
  • Signals are transmitted via neurotransmitters
  • Neurotransmitters are released from presynaptic terminals into the synaptic cleft

Neurotransmitters

  • Neurotransmitters are signaling molecules
  • They transmit signals between nerve cells and other cells.
  • They're stored in synaptic vesicles
  • The action potential results in the release of neurotransmitters at the presynaptic membrane
  • Important Neurotransmitters: Glutamate, GABA, acetylcholine, and others

T-SNARE and V-SNARE proteins

  • V-SNARE and T-SNARE proteins are critical for the fusion of synaptic vesicles with the presynaptic membrane
  • These proteins allow the fusion of vesicles and release of neurotransmitters

Conditions Affecting the Neuromuscular Junction

  • Lambert-Eaton Syndrome: Autoimmune disease affecting calcium channels, hindering neurotransmitter release.
  • Botulism: A neurotoxin that blocks the release of acetylcholine, causing muscle weakness or paralysis
  • Tetanus: A neurotoxin that interferes with inhibitory neurotransmitters, causing muscle spasms
  • Myasthenia Gravis: Autoimmune disease affecting acetylcholine receptors, hindering neuromuscular transmission
  • Curare effect: Substance that blocks acetylcholine receptors, leading to muscle paralysis.

EPSPs and IPSPs

  • EPSPs (excitatory postsynaptic potentials) are a brief depolarization of a postsynaptic membrane caused by excitatory neurotransmitters from the presynaptic neuron
  • IPSPs (inhibitory postsynaptic potentials) are a brief hyperpolarization of the membrane
  • These changes are small electrical signals called postsynaptic potentials
  • Summation of various EPSPs and IPSPs determines whether the postsynaptic neuron will reach the action potential threshold

Convergence and Divergence

  • Convergence: A single postsynaptic neuron receives input from multiple presynaptic neurons.
  • Divergence: A single presynaptic neuron sends signals to multiple postsynaptic neurons.
  • Facilitated: Temporary increase in the excitability of a neuron following repeated stimulation with additional inputs or signals.

Summation

  • Summation is the process by which multiple graded potentials combine to affect a postsynaptic neuron.
  • Temporal summation involves repeated stimulation from a single presynaptic neuron in a short period
  • Spatial summation involves simultaneous stimulation of a postsynaptic neuron from multiple presynaptic neurons.

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Description

Explore the fundamentals of nervous system physiology including neuron structure, synapse types, and their functionalities. Understand the differences between electrical and chemical synapses and their roles in neurotransmission. This quiz will test your knowledge on the essential concepts of how neurons communicate within the nervous system.

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