Nervous System Cells Overview
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Nervous System Cells Overview

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Questions and Answers

Which type of cells line the fluid-filled ventricles of the brain and central canal of the spinal cord?

  • Ependymal cells (correct)
  • Astrocytes
  • Microglia
  • Oligodendrocytes

    • What is a primary function of astrocytes in the brain?

  • Insulating axons
  • Producing myelin
  • Regulating extracellular fluid ionic concentration (correct)
  • Generating action potentials

    • What feature distinguishes fibrous astrocytes from protoplasmic astrocytes?

  • Fibrous astrocytes have shorter processes.
  • Fibrous astrocytes are abundant in gray matter.
  • Protoplasmic astrocytes are more numerous. (correct)
  • Protoplasmic astrocytes have long radiating processes.

    • What role do the cilia at the apical ends of ependymal cells serve?

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

    Which cell type has the unique marker GFAP (glial fibrillary acid protein)?

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

    Where within a neuron is the Golgi apparatus located?

    <p>In the cell body only</p> Signup and view all the answers

    What initiates the action potential in a neuron?

    <p>Axon hillock depolarization</p> Signup and view all the answers

    What occurs when sodium channels open during action potential?

    <p>Na+ influx</p> Signup and view all the answers

    At what membrane potential is a neuron typically considered to be at rest?

    <p>-65 mV</p> Signup and view all the answers

    What is the primary role of dendrites in a neuron?

    <p>Signal reception and processing</p> Signup and view all the answers

    What occurs during the repolarization phase of an action potential?

    <p>K+ channels open and K+ exits the cell</p> Signup and view all the answers

    What effect do local anesthetics have on action potentials?

    <p>Inhibit Na+ influx</p> Signup and view all the answers

    What is the result of depolarizing a neuron to +30 mV?

    <p>Action potential is reached</p> Signup and view all the answers

    What type of neurons receive stimuli from receptors?

    <p>Sensory neurons</p> Signup and view all the answers

    What is the primary function of autonomic motor nerves?

    <p>Involuntary control of glands and smooth muscles</p> Signup and view all the answers

    Which of the following best describes the morphology of the cell body in neurons?

    <p>Depends on actin filaments</p> Signup and view all the answers

    Which treatment is typically used to address the loss of dopamine-producing neurons?

    <p>L-dopa</p> Signup and view all the answers

    What are interneurons primarily responsible for?

    <p>Forming complex functional networks in the CNS</p> Signup and view all the answers

    What is the primary characteristic of anaxonic neurons?

    <p>Lack a distinct axon</p> Signup and view all the answers

    What type of staining is used to visualize the nucleus of a typical neuron?

    <p>Nissl stain</p> Signup and view all the answers

    What term describes the trophic center of a neuron?

    <p>Cell body</p> Signup and view all the answers

    Where are the cell bodies of the preganglionic sympathetic nerves located?

    <p>Thoracic and lumbar segments of spinal cord</p> Signup and view all the answers

    What neurotransmitter is commonly associated with preganglionic sympathetic nerves?

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

    Where are the second neurons of the parasympathetic nervous system primarily located?

    <p>Small ganglia near the effector organ</p> Signup and view all the answers

    What condition describes the changes in a neuron when it undergoes chromatolysis?

    <p>Cell body swells and Nissl is diminished</p> Signup and view all the answers

    Which cells are known to proliferate at injured sites in the nervous system?

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

    What is the role of astrocytes in the central nervous system?

    <p>Modulate blood flow and support neuron movement</p> Signup and view all the answers

    Which cell type originates from neural progenitor cells?

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

    What distinguishes Schwann cells from oligodendrocytes?

    <p>Schwann cells are found only in the PNS</p> Signup and view all the answers

    What feature characterizes the cerebral cortex?

    <p>It has six distinct layers</p> Signup and view all the answers

    What is the primary function of microglia in the CNS?

    <p>Act as immune defenders by secreting cytokines</p> Signup and view all the answers

    How do astrocytes communicate with one another?

    <p>Via gap junctions</p> Signup and view all the answers

    Which staining technique visualizes nuclei in tissue samples?

    <p>H&amp;E Stain</p> Signup and view all the answers

    What happens to microglial cells when activated by damage or microorganisms?

    <p>They retracted their processes</p> Signup and view all the answers

    Study Notes

    Nervous System Cells

    • Neurons
      • Specialized cells that transmit nerve impulses
      • Types:
        • Anaxonic
          • No apparent axon or dendrites
          • Found in brain and retina
        • Multipolar
          • Multiple dendrites
          • Single axon
          • Most common type of neuron
        • Bipolar
          • One dendrite and one axon
          • Found in sensory organs
      • Function: Receive, process, and transmit information
      • Difficult to classify under a microscope

    Neuron Structure

    • Cell Body (Perikaryon or Soma)
      • Contains the nucleus
      • Trophic center: produces most of the cytoplasm
      • Has a large, euchromatic nucleus with a prominent nucleolus
      • Cytoplasm:
        • Many free ribosomes
        • Highly developed RER
          • Basophilic
          • Chromatophilic or Nissl substance/bodies
      • Golgi apparatus is only in the cell body
      • Mitochondria is throughout the cell (abundant in axon terminals)
      • Actin and intermediate filaments
        • Neurofilaments: Neurofibrils when stained with silver stains and viewed under a light microscope
      • Lipofuscin: pigment inclusion made up of residual bodies from lysosomal digestion.

    Neuron Structure (cont)

    • Dendrites
      • Site of signal reception and processing in neurons
      • Short, small processes
      • Covered by synapses
      • Thin as they branch
      • Dendrite spine synapses on dendrites in the CNS
    • Axon
      • Responsible for transmitting information
      • True axon: single, long process extending from the cell body
      • Contains action potential
        • Initiated at the axon hillock
        • Propagated along the axon as a "wave" of membrane depolarization
          • Produced by voltage-gated Na+ and K+ channels
        • Resting potential: -65 mV
          • Na is increased outside the cell
          • K is increased inside the cell
        • Depolarization (+30 mV): influx of Na+
      • Myelin: multiple compacted layers of cell membrane
        • Formed from moving out of the cytoplasm during wrapping of the axon
        • Insulates axons and facilitates rapid transmission of nerve impulses

    Nervous System Cells (cont)

    • Glial Cells - Supportive cells of the nervous system:
      • Astrocytes
        • "astro" = star
        • Most numerous glial cells in the brain
        • Functions:
          • Cover synapses
          • Regulates ECF ionic concentration (buffers K+ levels)
          • Guide and support movement of neurons during CNS development
          • Form the glial limiting membrane that lines meninges at the external CNS
          • Form astrocytic scar that fills tissue defects after CNS injury
        • Large number of long, radiating, branching processes
        • Proximal regions: glial fibrillary acid protein (GFAP)
          • Unique marker
        • Distal region: + GFAP
        • Types:
          • Fibrous astrocytes: abundant in white matter
          • Protoplasmic astrocytes: shorter processes in gray matter
      • Oligodendrocytes (myelin-forming cells of CNS)
        • Form myelin sheaths for axons
        • Can myelinate multiple axons
        • Functions:
          • Insulate axons and speed up nerve impulse transmission
          • Support and organize axons
      • Schwann Cells
        • "neurolemmocytes"
        • Functions:
          • Provide myelin sheaths around one axon only
          • Trophic interactions
      • Microglia
        • Small cells with actively mobile processes that are evenly distributed
        • Migrate throughout gray and white matter
        • Functions:
          • Removes damaged or effete synapses
          • Major mechanism of immune defense in the CNS
          • Secretes cytokines
        • Originate from monocytes (macrophage, antigen-presenting cell)
      • Ependymal cells
        • Line the fluid-filled ventricles of the brain and the central canal of the spinal cord
        • Functions:
          • Apical ends have cilia that move CSF
          • Long microvilli for absorption
        • Joined apically by apical junctional complexes
        • Elongated basal ends that extend to adjacent neuropil

    CNS Structure

    • Major structures:
      • Cerebrum:
        • Cerebral nuclei: localized darker areas containing a large number of aggregated cell bodies
        • Cerebral cortex:
          • Has 6 layers
          • Contains pyramidal neurons: most conspicuous
    • Different types of neurons and their functions:
      • Sensory:
        • Afferent
        • Receive stimuli from receptors
      • Motor:
        • Efferent
        • Send impulses to effector organs
        • Somatic motor: voluntary control of skeletal muscles
        • Autonomic motor: involuntary control of glands, heart, and smooth muscles
    • Interneurons:
      • Form complex functional networks (circuits) in the CNS
      • Can be either multipolar or anaxonic

    Autonomic Nervous System

    • Divisions:
      • Sympathetic (fight-or-flight response)
        • Preganglionic sympathetic nerve cell bodies are in the thoracic and lumbar segments of the spinal cord
        • Sympathetic 2nd neurons are in small ganglia of the vertebral column
      • Parasympathetic (rest-and-digest response)
        • Preganglionic parasympathetic nerves are in the medulla, midbrain, and sacral portion of the spinal cord
        • Parasympathetic 2nd neurons are in small ganglia near the effector organ
    • Intramural ganglia: in the walls of the GI tract
    • Two circuits:
      • Preganglionic fiber (in CNS): Its axon synapses with a postganglionic peripheral ganglion system
      • Postganglionic fiber (in peripheral ganglion system)
    • Acetylcholine: neurotransmitter in preganglionic fibers of the autonomic nervous system

    Neural Plasticity & Regeneration

    • Controlled by neurotrophins:
      • Promote anabolic events of axon regeneration
    • Neuronal stem cells:
      • Located in the ependyma
    • Astrocytes:
      • Can proliferate at injured sites
    • Chromatolysis:
      • Cell body swells
      • Nissl substance diminishes
      • Nucleus migrates to a peripheral position in the perikaryon
      • New Schwann cells align, guiding regrowing axons

    Local Anesthetics

    • Low molecular weight compounds
    • Bind to voltage-gated Na+ channels
    • Interfere with Na+ influx
    • Inhibits action potential:
      • By interfering with the influx of Na+
      • Prevents depolarization of the membrane
    • Resting potential (-65 mV)
    • Na+ channel opens: Na+ influx
    • Depolarization (+30 mV)
    • Na+ channel closes
    • K+ Channel opens: K+ influx
    • Membrane returns to resting potential

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    Description

    Explore the fascinating world of nervous system cells, focusing on neurons and their various types. Learn about their structure, functions, and the complexities involved in classifying them under a microscope. This quiz will test your understanding of the key components of the nervous system.

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