Neurons and Neuroglia: Lecture 2
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Questions and Answers

What is the purpose of the myelin sheath?

  • To store nutrients for the neuron
  • To enhance the speed of information transfer (correct)
  • To slow down the transmission of information
  • To protect the axon from damage

    • What is the function of the axon hillock?

  • Storing organelles
  • Receiving information
  • Transmitting information
  • Originate action potentials (correct)

    • What is the main functional unit of the nervous system?

  • Dendrites
  • Glial cells
  • Neuroglia
  • Neurons (correct)

    • What is the term for the gaps in the myelin sheath?

    <p>Nodes of Ranvier</p> Signup and view all the answers

    What is the term for the process of transmission of information between neurons?

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

    What is the function of the cell body of a neuron?

    <p>To contain organelles</p> Signup and view all the answers

    What is unique about the conduction velocity in myelinated fibers?

    <p>It is proportional to the diameter</p> Signup and view all the answers

    What is the function of the presynaptic terminal?

    <p>To transmit information</p> Signup and view all the answers

    What is the term for the action potential 'jumping' from node to node?

    <p>Saltatory conduction</p> Signup and view all the answers

    What type of cells are responsible for forming the myelin sheath in the CNS?

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

    What is the main function of myelin in neurons?

    <p>To facilitate conduction of nerve impulses</p> Signup and view all the answers

    Which type of neuron has a single stem process that bifurcates to form two processes?

    <p>Pseudo-unipolar neuron</p> Signup and view all the answers

    What is the main function of sensory neurons?

    <p>To send information from receptors in sensory organs to the brain/spinal cord</p> Signup and view all the answers

    What is the main function of astrocytes?

    <p>To provide structural and metabolic support for neurons</p> Signup and view all the answers

    What is the primary function of microglia cells?

    <p>To act as macrophages and clear debris</p> Signup and view all the answers

    What is the main function of oligodendrocytes?

    <p>To provide support to axons of neurons in the CNS</p> Signup and view all the answers

    What is the main function of ependymal cells?

    <p>To create cerebrospinal fluid (CSF)</p> Signup and view all the answers

    What is the main function of Schwann cells?

    <p>To provide support to axons of neurons in the PNS</p> Signup and view all the answers

    What is the process of axonal degeneration distal to the lesion?

    <p>Wallerian degeneration</p> Signup and view all the answers

    What is the main difference between glial cells and neurons?

    <p>Glial cells do not have axons and dendrites</p> Signup and view all the answers

    Larger axons have longer internodes and slower conduction velocities

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

    In unmyelinated fibers, conduction is proportional to the square root of the diameter

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

    What type of neuron is considered the most common type of neuron?

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

    This neuron has two processes: 1 axon and 1 dendrite

    <p>Bi-polar</p> Signup and view all the answers

    Neurons are only classified by structure, not by function

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

    Most sensory/afferent neurons are pseudo-unipolar

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

    These are usually multipolar or bipolar neurons

    <p>More than one</p> Signup and view all the answers

    Motor neurons and Efferent are the same neuron

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

    Which of the following is NOT true about Glial cells

    <p>Participate directly in synaptic interactions and electrical signaling</p> Signup and view all the answers

    Neuroglia (aka glial cells) don not produce action potential

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

    Regarding glial cell location in the CNS, which of the following glial cells is NOT located in the CNS

    <p>Schwann cells</p> Signup and view all the answers

    Which of the following neuronal cells act as macrophages?

    <p>Microglia cells</p> Signup and view all the answers

    Identify this cell

    <p>Ependymal Cells</p> Signup and view all the answers

    Identify this cell

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

    Identify this cell

    <p>Schwann cells</p> Signup and view all the answers

    Identify this cell

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

    Identify this cell

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

    What type of glial cells are found in the PNS?

    <p>Schwann cells</p> Signup and view all the answers

    What cells are involved in creating cerbrospinal fluid?

    <p>Ependymal cells</p> Signup and view all the answers

    Which of the following is not a function of Astrocytes?

    <p>Provide support to axons of neurons in the CNS</p> Signup and view all the answers

    Regeneration is efficient in the CNS, not in the PNS

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

    Neurons can be classified according to structure and function. What are the types of neurons?

    <p>The neurons are multipolor, bipolar, and pseudo-polar (also called unipolar) neurons.</p> Signup and view all the answers

    List the glial cells located in the CNS.

    <p>Microglial cells, astrocytes, oligodendrocytes and ependymal cells</p> Signup and view all the answers

    What are Schwann cells also called?

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

    Study Notes

    The Nervous System

    • The nervous system consists of two categories of cells: neurons and neuroglia.
    • Neurons are the major functional units of the nervous system and are specialized in information processing.

    Neuron Structure

    • A neuron consists of:
      • Dendrites: an information-receiving area of the cell membrane
      • Cell body (soma or pericaryon): contains organelles
      • Axon: an information-carrying extension of the cell membrane
      • Axon hillock or trigger zone: axon origin; originates action potential
      • Presynaptic terminal: end of axon; transmits information
      • Myelin sheath: enhances the speed of information transfer
      • Node of Ranvier: gaps in the insulating myelin sheath

    Neuron Function

    • Neurons communicate via synapses, specialized contact areas with other neurons, muscle fibers, or glands.
    • Action potentials travel along the axon at a speed that varies from 0.5 to 120 meters per second.
    • Larger axons are myelinated, while smaller ones (< 1 μm in diameter) are not.

    Myelin Sheath

    • The myelin sheath is a greatly modified plasma membrane wrapped around the axon in a spiral fashion.
    • It originates from and is part of the Schwann cells in the PNS and oligodendrocytes in the CNS.
    • The periodic interruptions are the nodes of Ranvier, critical to the functioning of myelin.

    Classification of Neurons

    • Neurons can be classified according to their structure:
      • Multipolar neurons (most common type)
      • Bipolar neurons
      • Pseudo-unipolar neurons (also called unipolar)
    • Neurons can also be classified according to their function:
      • Sensory or afferent neurons
      • Interneurons or association neurons
      • Motor neurons or efferent neurons

    Neuroglia or Glial Cells

    • Neuroglia or glial cells are smaller than neurons and do not have axons and dendrites.
    • They fill all the spaces in the nervous tissue not occupied by neurons or blood vessels.
    • Glial cells are more numerous than neurons in the nervous tissue and have the capacity to divide.
    • They do not produce action potentials and do not participate directly in synaptic interactions and electrical signaling.

    Types of Glial Cells

    • Microglial cells: the brain's immune cells, act as macrophages, and play a role in the developing brain.
    • Astrocytes: star-shaped cells with numerous long-cell processes, provide structural and metabolic support for neurons.
    • Oligodendrocytes: provide support to axons of neurons in the CNS, and myelinate most axons > 1 μm in diameter.
    • Ependymal cells: cover the ventricles of the brain, central canal of the CNS, and choroid plexus in the 4th ventricle of the medulla oblongata.
    • Schwann cells: provide support to axons of neurons in the PNS, similar to oligodendrocytes.

    Wallerian Degeneration

    • Axonal degeneration distal to the lesion.
    • Regeneration is efficient in the PNS, not in the CNS.
    • Regeneration is guided by Schwann cells.

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