Nervous System Physiology Essentials 3
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Questions and Answers

What is the mechanism by which botulinum toxin inhibits muscle contraction?

  • It increases the production of acetylcholine, leading to muscle fatigue and paralysis.
  • It blocks the release of acetylcholine, preventing muscle contraction. (correct)
  • It directly binds to muscle fibers, disrupting their ability to contract.
  • It stimulates the release of acetylcholine, causing prolonged muscle contraction.

    • Which of the following is NOT a common way that people can be infected with botulinum toxin?

  • Homemade canned foods
  • Consuming raw eggs (correct)
  • Honey
  • Commercial canned foods

    • How does tetanus toxin differ from botulinum toxin in its mode of action?

  • Tetanus toxin is a bacterial toxin, while botulinum toxin is a viral toxin.
  • Tetanus toxin blocks the release of excitatory neurotransmitters, while botulinum toxin blocks the release of inhibitory neurotransmitters.
  • Tetanus toxin blocks the release of inhibitory neurotransmitters, while botulinum toxin blocks the release of excitatory neurotransmitters. (correct)
  • Tetanus toxin directly binds to muscle fibers, while botulinum toxin acts on nerve endings.

    • What is the primary cause of muscle weakness in Lambert-Eaton syndrome?

    <p>Reduced acetylcholine release due to destruction of voltage-gated Ca2+ channels. (D)</p> Signup and view all the answers

    Which of the following describes the mechanism of action of curare?

    <p>It directly binds to acetylcholine receptors, preventing their activation. (A)</p> Signup and view all the answers

    What is the primary difference between botulinum toxin A-E and botulinum toxin C?

    <p>Botulinum toxin C acts on different SNARE proteins than botulinum toxin A-E. (D)</p> Signup and view all the answers

    Which of these has the DIRECT effect on acetylcholine production and release?

    <p>Lambert-Eaton syndrome (A)</p> Signup and view all the answers

    Which of these is a risk factor associated with botulinum toxin poisoning?

    <p>Consuming commercially canned foods (A), Eating honey (B), Eating raw meat (C)</p> Signup and view all the answers

    What is the role of acetylcholine in the central nervous system (CNS)?

    <p>Initiates muscle contractions (A)</p> Signup and view all the answers

    Which characteristic is unique to electrical synapses compared to chemical synapses?

    <p>Narrow synaptic gap (A)</p> Signup and view all the answers

    What is the primary function of V-SNARE proteins?

    <p>Assist in the exocytosis of neurotransmitters (C)</p> Signup and view all the answers

    Which statements best describes the merging process involving SNARE proteins?

    <p>The process requires calcium ions and includes all SNARE proteins (A)</p> Signup and view all the answers

    Which of the following conditions or diseases specifically affects the neuromuscular junction?

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

    What is the primary effect of botulinum toxin on the nervous system?

    <p>Stops muscle movements by blocking neurotransmitter release (B)</p> Signup and view all the answers

    In which scenario would synaptic transmission occur the fastest?

    <p>In an electrical synapse (A)</p> Signup and view all the answers

    Which protein is responsible for binding to calcium ions to enhance the SNARE assembly?

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

    What is the primary effect of curare at the neuromuscular junction?

    <p>It blocks acetylcholine receptors. (B)</p> Signup and view all the answers

    What happens when the total result of EPSP is significantly higher than IPSP in a postsynaptic neuron?

    <p>The postsynaptic neuron is stimulated. (C)</p> Signup and view all the answers

    Which neurotransmitter is primarily responsible for producing an EPSP?

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

    What is the result of opening potassium (K) and chloride (Cl) channels in a postsynaptic neuron?

    <p>Hyperpolarization occurs, leading to IPSP. (D)</p> Signup and view all the answers

    What defines convergence in neuronal signaling?

    <p>The sending of signals from many presynaptic neurons to a single postsynaptic neuron. (B)</p> Signup and view all the answers

    How does an excitatory neurotransmitter affect the membrane potential of a postsynaptic neuron?

    <p>It makes the membrane potential less negative. (B)</p> Signup and view all the answers

    What is the consequence of acetylcholine accumulation at the synaptic cleft when curare blocks the nicotinic acetylcholine receptors?

    <p>It results in prolonged paralysis. (A)</p> Signup and view all the answers

    Which of the following describes IPSP?

    <p>It reduces the likelihood of an action potential. (B)</p> Signup and view all the answers

    What initiates the opening of voltage-gated Ca+2 channels in the presynaptic neuron?

    <p>Depolarization of the presynaptic membrane (C)</p> Signup and view all the answers

    Which neurotransmitter is released into the synaptic cleft when an action potential reaches the presynaptic neuron?

    <p>Acetylcholine (ACh) (D)</p> Signup and view all the answers

    What is the role of V-SNAREs and T-SNAREs in neurotransmitter release?

    <p>They form a complex that aids in vesicle fusion with the membrane. (C)</p> Signup and view all the answers

    What happens when Acetylcholine binds to nicotinic ACh receptors?

    <p>Na+ enters and K+ exits the postsynaptic cell. (B)</p> Signup and view all the answers

    What type of potential is formed at the motor end plate upon ACh binding?

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

    What influences the number of vesicles discharged into the synaptic cleft?

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

    What is the primary role of the excitatory neurotransmitter glutamate in the CNS?

    <p>To transmit excitatory signals related to learning and memory (A)</p> Signup and view all the answers

    Which statement about inhibitory neurotransmitter GABA is correct?

    <p>It has a calming effect by preventing nerve cell overstimulation. (B)</p> Signup and view all the answers

    What is the name of the connection between a neuron and another functional cell in the nervous system?

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

    What is the name of the synapse between a neuron and a muscle cell?

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

    What type of synapse provides a direct connection between neurons, allowing ions to flow freely?

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

    Which of the following is NOT true about gap junctions in electrical synapses?

    <p>They are responsible for the release of neurotransmitters. (A)</p> Signup and view all the answers

    What is the name of the structure that forms when cells are stimulated simultaneously in a synchronized wave-like pattern?

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

    Which of the following is NOT a structural feature of chemical synapses?

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

    Which of these events occurs FIRST when an action potential (AP) arrives at the axon terminal of a presynaptic neuron in a chemical synapse?

    <p>Calcium ions enter the presynaptic neuron. (A)</p> Signup and view all the answers

    What is the name of the entire postsynaptic structure in a chemical synapse?

    <p>Motor end plate (B)</p> Signup and view all the answers

    Study Notes

    Nervous System Physiology Essentials 3

    • The connection between a neuron and another cell is a synapse.
    • In the central nervous system (CNS), both cells are neurons.
    • In the peripheral nervous system (PNS), the second cell can be a neuron, muscle, or gland.
    • A synapse between a neuron and muscle is a neuromuscular junction.
    • The cell before the synapse is the presynaptic cell.
    • The cell after the synapse is the postsynaptic cell.
    • Synapses are connections that allow information to be transmitted between neurons.

    Synapse Types

    • Synapses are divided into types based on function or structure.
    • Main types include electrical and chemical synapses.
    • Structural features include axodendritic, axosomatic, and axoaxonic synapses.
    • Functional features include excitatory and inhibitory synapses.

    Electrical Synapse

    • Electrical synapses form a direct connection between neurons.
    • Ions flow freely between cells via gap junctions.
    • Stimulus transmission is very quick and direct.
    • The distance between cells is 2-4 nm (6 times shorter than a chemical synapse).
    • These connections are present in smooth muscle and heart muscle.
    • Syncytium is formed between cells (cells are stimulated simultaneously).
    • No chemical is needed for conduction; ion balance is the key.

    Chemical Synapse

    • Chemical synapses are more common than electrical synapses.
    • They are separated by a synaptic cleft (20-40 nm).
    • Neurotransmitters are stored in vesicles in the presynaptic terminal
    • Calcium ions trigger the release of neurotransmitters into the synaptic cleft.
    • Neurotransmitters bind to receptors on the postsynaptic membrane.
    • Neurotransmitters in response cause a postsynaptic response (EPSP or IPSP).

    Neurotransmitters

    • Neurotransmitters are chemicals that nerve cells use to transmit signals to each other.
    • They are stored in synaptic vesicles and released upon arrival of an action potential.
    • Neurotransmitters bind to receptors on the postsynaptic cell.

    Examples of Neurotransmitters and their roles

    • Glutamate: The most common excitatory neurotransmitter in the CNS; important for learning and memory.
    • GABA: A main inhibitory neurotransmitter. Reduces nerve cell activity; playing a role in anxiety control.
    • Acetylcholine: Plays a role in muscle contraction and learning and memory.

    Conditions or diseases Affecting Neuromuscular Junction

    • Lambert-Eaton Syndrome: A rare autoimmune disease where autoantibodies destroy the calcium-dependent neurotransmitters in the neuromuscular junction. Causing muscle weakness.
    • Botulism: A powerful neurotoxin produced by Clostridium botulinum that prevents the release of acetylcholine.
    • Tetanus: A disease caused by Clostridium tetani. It results in overactivity of motor neurons, leading to severe muscle contraction.
    • Myasthenia Gravis: An autoimmune disease where the body's immune system attacks acetylcholine receptors in muscle cells resulting in delayed neuromuscular transmission and muscle weakness.
    • Curare Effect: A natural compound used traditionally to paralyze animals, prevents muscle contraction by blocking acetylcholine receptors.

    Synaptic Potentials

    • EPSP (Excitatory Postsynaptic Potential): Neurotransmitters cause a more positive membrane potential in a postsynaptic cell making an action potential more likely to occur.
    • IPSP (Inhibitory Postsynaptic Potential): Neurotransmitters cause a more negative membrane potential in a postsynaptic cell making an action potential less likely to occur.
    • These are temporary changes in the postsynaptic cell's membrane potential.

    Summation

    • Temporal summation: Successive stimuli from the same presynaptic neuron that arrive close together in time summate their effect on a postsynaptic cell.
    • Spatial summation: Simultaneous stimuli from multiple presynaptic neurons summate their effect on a postsynaptic cell.

    Convergence and Divergence

    • Convergence: Many presynaptic neurons can synapse with a single postsynaptic neuron.
    • Divergence: A single presynaptic neuron can synapse with many postsynaptic neurons.
    • Facilitation: Repeated stimulation of a presynaptic neuron can increase the excitability of a postsynaptic neuron.

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    Nervous System Physiology Essentials 3 PDF 2024-2025

    Description

    Test your understanding of synapse types and their functions in the nervous system. This quiz covers key concepts, including electrical and chemical synapses, the structure and function of neurons, and the differences between presynaptic and postsynaptic cells. Dive into the essentials of neural connections!

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