Neuroscience Classification of Axons
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Questions and Answers

What are the three major groups of axons?

  • A fibers (correct)
  • B fibers (correct)
  • C fibers (correct)
  • D fibers

    • What are the classifications of nerve fibers based on?

    amount of myelination, diameter, propagation speeds

    What are the four characteristics of A fibers?

    largest diameter, myelinated, have a brief absolute refractory period, conduct nerve impulses at speeds of 12 to 130 m/sec

    What are some examples of A fibers?

    <p>sensory neuron axons for touch, pressure, position of joints, and some thermal and pain sensations; motor neuron axons to skeletal muscles</p> Signup and view all the answers

    What are the four characteristics of B fibers?

    <p>diameters of 2-3 mm, myelinated, longer absolute refractory period than A fibers, exhibit saltatory conduction at speeds up to 15 m/sec</p> Signup and view all the answers

    What do B fibers do?

    <p>conduct sensory nerve impulses from the viscera to the brain and spinal cord</p> Signup and view all the answers

    What do B fibers constitute?

    <p>all axons of the autonomic motor neurons that extend from the brain and spinal cord to autonomic ganglia</p> Signup and view all the answers

    What are the four characteristics of C fibers?

    <p>smallest diameter, unmyelinated, longest absolute refractory period, propagate nerve impulses from 0.5 to 2 m/sec</p> Signup and view all the answers

    What do the unmyelinated axons of C fibers do?

    <p>conduct some sensory impulses for pain, touch, pressure, heat, and cold from the skin; and pain impulses from the viscera</p> Signup and view all the answers

    What are some examples of C fibers?

    <p>autonomic motor fibers that extend from autonomic ganglia to stimulate the heart, smooth muscle, and glands</p> Signup and view all the answers

    What are some examples of motor functions of B and C fibers?

    <p>constricting and dilating pupils, increasing and decreasing heart rate, and contracting and relaxing the urinary bladder</p> Signup and view all the answers

    Study Notes

    Classification of Axons

    • Three major groups of axons: A fibers, B fibers, C fibers.

    Classification Criteria

    • Axons are classified based on myelination amount, diameter, and propagation speeds.

    Characteristics of A Fibers

    • Largest diameter among nerve fibers.
    • Myelinated, allowing for faster impulse conduction.
    • Brief absolute refractory period enhances rapid signal transmission.
    • Conduct nerve impulses at speeds ranging from 12 to 130 m/sec.

    Examples of A Fibers

    • Sensory neurons for touch, pressure, joint position, and some thermal/pain sensations.
    • Motor neurons transmitting impulses to skeletal muscles.

    Characteristics of B Fibers

    • Medium diameter around 2-3 mm.
    • Myelinated, but with a longer absolute refractory period compared to A fibers.
    • Exhibit saltatory conduction, enabling speeds up to 15 m/sec.

    Functions of B Fibers

    • Conduct sensory nerve impulses from visceral organs to the brain and spinal cord.

    Role of B Fibers in the Autonomic Nervous System

    • Make up axons of autonomic motor neurons connecting the brain and spinal cord to autonomic ganglia.

    Characteristics of C Fibers

    • Smallest diameter among the three fiber types.
    • Unmyelinated, resulting in slower impulse conduction.
    • Longest absolute refractory period, slowing down nerve response.
    • Propagate impulses at speeds between 0.5 to 2 m/sec.

    Functions of C Fiber Axons

    • Conduct sensory impulses for pain, touch, pressure, heat, and cold from the skin, as well as visceral pain signals.

    Examples of C Fibers

    • Autonomic motor fibers extending from autonomic ganglia, stimulating the heart, smooth muscle, and glands.

    Motor Functions of B and C Fibers

    • Regulate pupil constriction and dilation, heart rate changes, and urinary bladder contraction and relaxation.

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    Description

    This quiz explores the classification of axons, focusing on A, B, and C fibers. Learn about their characteristics, functions, and propagation speeds. Test your knowledge on how these fibers contribute to sensory and motor functions in the nervous system.

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