Histology Nervous Tissue

• Nervous System


  Group of organs brought together for the purpose of making us react to the environment
• Nervous System


  Formed by nerve cells (Neurons) and supporting cells (Glial cells)
• Nervous System compromises of CNS and PNS
• Nervous System


  • Three major functions: Sensory - monitors internal & external environment through presence of receptors
  • Integration - interpretation of sensory information
  • Motor - response to information processed through stimulation of effectors
• 2 Anatomical Divisions of Nervous System

  • Central nervous system (CNS)
  • Peripheral nervous system (PNS)
• Central nervous system (CNS)


  Consists of Brain and Spinal chord
• Peripheral nervous system (PNS)


  Consists all the neural tissue outside CNS (cranial, spinal and peripheral nerves)
• Ganglia


  Small group of nerve cells outside CNS
• Types of nerve cells in nervous system

  • Neurons or Nerve cell
  • Neuroglia or Glial cell
• Neurons or nerve cells


  Processing, transfer, and storage of information
• Neuroglia or Glial Cells


  Support, regulation & protection of neurons
• Types of CNS Neuroglia

  • Astrocytes
  • Oligodendrocytes
  • Microglia
  • Ependymal cells
• Astrocytes


  • Form barrier between capillaries and neurons (Blood-Brain Barrier)
  • Control chemical environment of CNS
  • Create supportive framework for neurons
• Oligodendrocytes


  • Create myelin sheath in the CNS
  • Most common glial cells in the white matter
  • Myelinated axons transmit impulses faster than unmyelinated axons
• Microglia/Mesoglia


  • Small phagocytic type, mesodermal in origin
  • "brain macrophages", phagocytize cellular wastes & pathogens together with neutrophils
  • Increased in injury and infection
• Ependymal cells


  • Line ventricles of brain & central canal of spinal cord
  • Produce, monitor & help circulate CSF (cerebrospinal fluid)
• Types of PNS Neuroglia


  • Schwann cells or Neurolemmocytes
  • Satellite cells
• Schwann cells or Neurolemmocytes


  • Produce myelin in jelly-roll like fashion
  • Allows for potential regeneration of damaged axons
  • Creates myelin sheath around most axons of PNS
• Satellite cells


  • Serve as covering for the large neuronal cell bodies in the ganglia of PNS
  • Support groups of cell bodies of neurons w/in ganglia of PNS with insulation, nutrition and regulation of their environment
• Is skin afferent or efferent?

  • Afferent
• is muscle afferent or efferent?

  • Efferent
• Receptors

  • are sensory structures that detect changes in the internal and external environment
• Effectors

  • target organs whose activities change in response to neural commands
• Cell body or Soma or Perikaryon

  • contains nucleus, mitochondria, ribosomes, and other organelles
• Axon

  • conducts nerve impulse away from the cell body and towards the synaptic terminal
• Synaptic Terminal

  • affect other neuron or effector or organ
• 4 parts of neuron

  1. Dendrites
  2. Cell Body or Soma or Perikaryon
  3. Axon
  4. Synaptic Terminals
• • Cell Body

  Primarily a tropic center/ nutritive center and genetic center of a neuron
• Shape of the nucleolus of Cell body

  • Spherical or Oval
• Chromatin pattern of Cell Body

  • finely dispersed or uncoiled (euchromatic)
• Neuron Cell Body

  • Cytoplasm - contains Nissl’s

  granules/substance/bodies (basophilic granule)
• Neuron Dendrites

  • Elongated processes extending from soma
  • Specialized in receiving stimuli from the environment, from the sensory epithelial or from other neurons at unique sites called synapses
• Neuron Axon

  • Specialized in generating and conducting nerve impulses to other cells (nerve, muscle or glands)

  • Starts as short pyramid-shaped initial segment called AXON HILLOCK.
• Axons with myelin sheath

  • myelinated axons
• What does the presence of myelin do to the transmission of action potentials along the axon?

  speeds up
• Unmyelinated gaps left when myelin laid down in segments (internodes) along the axon?

  Nodes of Ranvier
• Unique sites in the neuron that send stimuli?

  Synaptic Terminal
• What is the area where neuron communicates with another cell, muscle cell, another neuron attached or close to it?

  Synapse
• Pre synaptic cell - Neuron that sends message
• Post synaptic cell– Neuron that receives message