Neuron Structure Quiz
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Questions and Answers

What best describes the primary function of axo-somatic synapses?

  • To provide significant synaptic plasticity for learning and memory.
  • To control whether a postsynaptic neuron will fire an action potential. (correct)
  • To enhance the frequency of action potentials through excitatory neurotransmitters.
  • To modulate the release of neurotransmitters at axon terminals.

    • How do axo-axonic synapses primarily affect neurotransmitter release?

  • By directly assisting in the synthesis of neurotransmitters.
  • By enhancing or inhibiting the release of neurotransmitters from the postsynaptic axon terminal. (correct)
  • By mediating changes in ion channel conductance at the postsynaptic membrane.
  • By changing the electrical potential across the cell body of the postsynaptic neuron.

    • What is a characteristic of the signal strength in axo-somatic synapses?

  • Signals degrade rapidly before reaching the axon hillock.
  • They can reach the axon hillock with less decrement than other types. (correct)
  • The signals are completely blocked before reaching the postsynaptic neuron.
  • They are less efficient compared to axo-dendritic synapses.

    • Which neurotransmitter is primarily associated with the inhibitory function of axo-somatic synapses?

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

    What role does spatial exclusion play in axo-axonic synapses?

    <p>It limits the number of axo-axonic inputs that can be available, usually leading to inhibition.</p> Signup and view all the answers

    What is the primary role of the axon hillock in a neuron?

    <p>To initiate action potentials</p> Signup and view all the answers

    Which of the following accurately describes axon collaterals?

    <p>They allow a single neuron to connect with multiple target cells</p> Signup and view all the answers

    What is the function of the myelin sheath?

    <p>To insulate the axon and increase signal transmission speed</p> Signup and view all the answers

    What is contained within axon terminals?

    <p>Synaptic vesicles filled with neurotransmitters</p> Signup and view all the answers

    How does an action potential propagate along an axon?

    <p>By rapid rise and fall in voltage across the membrane</p> Signup and view all the answers

    What constitutes a synapse?

    <p>The junction between two neurons or a neuron and a target cell</p> Signup and view all the answers

    What is axonal transport primarily responsible for?

    <p>Moving proteins, organelles, and materials along the axon</p> Signup and view all the answers

    What is the primary motor protein responsible for retrograde transport in neurons?

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

    What contributes to the nervous system's Total Metabolic Rate (TMR)?

    <p>The energy-requiring processes such as axonal transport</p> Signup and view all the answers

    Which of the following describes the mechanism used by Dynein for movement along microtubules?

    <p>It uses ATP hydrolysis to change shape and move.</p> Signup and view all the answers

    What is the effect of colchicine on microtubules?

    <p>It binds tubulin, making it unavailable for assembly.</p> Signup and view all the answers

    Which drug is known for aggregating tubulin and leading to depolymerization?

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

    What happens to alpha motor neurons as a result of tetanus toxin action?

    <p>They are disinhibited leading to continuous muscle contraction.</p> Signup and view all the answers

    What role does ATP play in the functioning of Dynein motor proteins?

    <p>It regulates the binding and release of motor domains.</p> Signup and view all the answers

    Which diseases are mentioned as being associated with impaired axonal transport?

    <p>Alzheimer’s disease and Parkinson's disease</p> Signup and view all the answers

    How do drugs that affect microtubule assembly typically affect the nervous system?

    <p>They can cause peripheral polyneuropathy.</p> Signup and view all the answers

    What does retrograde transport in neurons refer to?

    <p>Transport from the axon terminal back to the cell body.</p> Signup and view all the answers

    What is the directionality of Dynein movement along microtubules?

    <p>Toward the minus end of the microtubule.</p> Signup and view all the answers

    What is the primary direction of anterograde transport in neurons?

    <p>From the cell body to the axon terminal</p> Signup and view all the answers

    Which motor protein is primarily responsible for anterograde transport?

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

    What characteristic of kinesin's heavy chains allows it to move along microtubules?

    <p>They have ATPase activity.</p> Signup and view all the answers

    What happens to a kinesin motor domain when it binds ATP?

    <p>It undergoes a conformational change.</p> Signup and view all the answers

    Which type of cargo is typically transported retrogradely in neurons?

    <p>Endocytosed materials</p> Signup and view all the answers

    What role do the light chains of kinesin play?

    <p>They bind to the cargo for transport.</p> Signup and view all the answers

    How does kinesin 'walk' along the microtubules?

    <p>In a hand-over-hand manner.</p> Signup and view all the answers

    Which of the following is NOT involved in anterograde transport?

    <p>Signaling endosomes</p> Signup and view all the answers

    What initiates the movement of kinesin along the microtubule?

    <p>Binding of ATP</p> Signup and view all the answers

    What process is critical for the survival and function of neurons in terms of transport?

    <p>Fast axonal transport</p> Signup and view all the answers

    What is the primary role of dendritic arbors in neurons?

    <p>They increase the surface area for synaptic connections.</p> Signup and view all the answers

    Which type of neuron has a cell body located between dendritic arbors and axon terminals?

    <p>Bipolar neuron</p> Signup and view all the answers

    What distinguishes pseudounipolar neurons from other types of neurons?

    <p>They possess a single process that bifurcates.</p> Signup and view all the answers

    What function do projection neurons typically fulfill?

    <p>They have long axons and may be myelinated.</p> Signup and view all the answers

    Which of the following best describes interneurons?

    <p>They generally have shorter axons and may be either excitatory or inhibitory.</p> Signup and view all the answers

    Where are bipolar neurons commonly found?

    <p>In the retina of the eye and vestibulocochlear nerve.</p> Signup and view all the answers

    What is the role of neurites in neurons?

    <p>They facilitate signal transmission.</p> Signup and view all the answers

    How does the structure of multipolar neurons differ from that of bipolar neurons?

    <p>Multipolar neurons have multiple dendrites and one axon.</p> Signup and view all the answers

    What is true about the peripheral branch of pseudounipolar neurons?

    <p>It transmits signals to peripheral tissues.</p> Signup and view all the answers

    What is the primary function of vesicles in axon terminals?

    <p>To store neurotransmitters.</p> Signup and view all the answers

    Study Notes

    Neuron Structure

    • The axon hillock is the point where the axon originates from the cell body and is crucial for initiating action potentials.
    • Axon collaterals are secondary branches that extend from the main axon allowing one neuron to send signals to multiple target neurons/muscle cells.
    • The myelin sheath, formed by oligodendrocytes in the CNS and Schwann cells in the PNS, insulates the axon, increasing electrical signal transmission speed.
    • Nodes of Ranvier are gaps in the myelin sheath where ion channels are concentrated.
    • Axon terminals (synaptic buttons) are the distal endings of the axon responsible for releasing neurotransmitters into the synaptic cleft. They contain synaptic vesicles filled with neurotransmitters.
    • The synapse is the junction for information transfer between two neurons or between a neuron and a target cell (e.g., muscle or gland). It includes the pre-synaptic membrane, synaptic cleft, and postsynaptic membrane.

    Action Potentials

    • An action potential is a rapid change in voltage across a cell membrane, initiated at the axon hillock and propagated down the axon.
    • A single cell is a neuron.
    • A nerve is a bundle of axons from many neurons.
    • Axonal transport moves proteins, organelles, and materials along the axon for neuronal maintenance, function, and survival.

    Anterograde Transport

    • Anterograde transport moves cargo from the cell body (soma) to the axon terminal using kinesin as the motor protein.
    • Kinesin proteins consist of heavy chains with motor domains at the N-terminus and light chains associated with the heavy chains at the C-terminus.
    • Kinesin motor domains bind to microtubules and "walk" along them by hydrolyzing ATP to power movement.
    • Light chains bind to cargo, ensuring specific materials are transported.

    Retrograde Transport

    • Retrograde transport moves cargo from the axon terminal back to the cell body using dynein as the motor protein.
    • Dynein uses a similar mechanism to kinesin with heavy and light chains.

    Axonal Transport and Diseases

    • Drugs affecting microtubule assembly/disassembly (e.g., colchicine, vincristine, vinblastine, taxol) can cause peripheral polyneuropathy.
    • Toxins/pathogens can be endocytosed at the axon terminal and transported retrogradely to the soma. (e.g., Tetanus toxin)
    • Axonal transport impairment is implicated in degenerative diseases like Alzheimer's, Huntington's, motor neuron disease, amyotrophic lateral sclerosis, and Parkinson's.

    Neurotransmission

    • Neurons communicate with targets through chemical or chemo-electric neurotransmission using neurotransmitters stored in axon terminal vesicles.

    Neuron Types

    • Dendritic arbor refers to the branched dendrite structure of a neuron, increasing surface area for synaptic connections.
    • Neurites are projections from the cell body including axons and dendrites.
    • Bipolar neurons have the cell body between the dendrites and axon terminals, often serving as sensory receptors.
    • Multipolar neurons have one axon originating from the cell body and multiple dendritic projections.
    • Pseudounipolar neurons have a single process that bifurcates into a peripheral branch receiving sensory input and a central branch transmitting sensory information to the CNS.

    Neuron Functions

    • Projection neurons have long axons and are usually excitatory in the CNS.
    • Interneurons have shorter axons and can be excitatory or inhibitory (usually inhibitory) in the CNS.

    Synapse Types

    • Axo-somatic synapses are between axon terminals and the soma of the postsynaptic neuron, strongly influencing the postsynaptic neuron's ability to fire.
    • Axo-dendritic synapses are located on dendrites.
    • Axo-axonic synapses are between axon terminals of the presynaptic neuron and the axon terminal/hillock of the postsynaptic neuron, modulating the release of neurotransmitters.

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    Introduction To The Central Nervous System PDF

    Description

    Test your knowledge on the structure of neurons with this quiz. It covers key components such as axon hillock, myelin sheath, and synapse, along with their functions. Perfect for students studying neuroscience or biology.

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