NERVOUS SYS

• Functions of the Nervous System


  • Sensory Input
  • Integration
  • Homeostasis
  • Mental Activity
  • Control of Muscles and Glands
• Central Nervous System (CNS)


  Brain and spinal cord
• Peripheral Nervous System (PNS)


  Nerves and ganglia

  
• Divisions of the Peripheral Nervous System


  • Sensory or Afferent Division
  • Motor or Efferent Division
• Sensory or Afferent Division


  Conducts action potentials from sensory receptors to CNS via sensory neurons
• Motor or Efferent Division


  Conducts action potentials from the CNS to effector organs like muscles and glands via motor neurons
• Subdivisions of the Motor or Efferent Division


  • Somatic Motor Nervous System
  • Autonomic Nervous System (ANS)

  
• Somatic Motor Nervous System


  Transmits action potentials from CNS to skeletal muscles
• Autonomic Nervous System (ANS)


  Transmits action potentials from CNS to cardiac muscle, smooth muscle and glands
• Subdivisions of the Autonomic Nervous System


  • Sympathetic Division
  • Parasympathetic Division
  • Enteric Nervous System (ENS)

  
• Sympathetic Division


  "Fight-or-flight" division; prepares the body for physical activity; prepares the person to face a threat or leave as quickly as possible
• Parasympathetic Division


  "Rest or repose" division; Stimulates vegetative activities such as digestion, defecation, urination
• Enteric Nervous System


  Capable of monitoring & controlling the digestive tract independently of the CNS
• Neuron


  Nerve cell

  
• Parts of a Neuron


  • Cell body
  • Dendrites
  • Axon

  
• Cell body


  • Mononucleated; rough ER, Golgi apparatus, mitochondria, neurofilaments, microtubules, Nissl bodies (rough ER concentrated areas)
• Dendrites


  Short, branching cytoplasmic extensions; receive information from other neurons & transmit info toward the cell body

  
• Types of Neurons


  • Multipolar
  • Bipolar
  • Unipolar
• Multipolar Neuron


  Several dendrites, one axon (CNS, motor neurons)

  
• Bipolar Neuron


  One dendrite, one axon (some sensory neurons like retina & nasal cavity)
• Unipolar Neuron


  With a single axon (most sensory neurons)
• Types of Neuroglia/Glial Cells


  • Astrocytes
  • Ependymal
  • Microglia
  • Oligodendrocytes
  • Schwann Cells/Neurolemmocytes/Neurolemma

  
• Astrocytes


  Major supporting tissue of CNS; form a layer around blood vessels, contribute to blood-brain barrier

  
• Ependymal


  Line ventricles of brain, produce & circulate CSF
• Microglia


  Help remove bacteria & cell debris from CNS
• Oligodendrocytes


  Form myelin sheaths around axons, or enclose unmyelinated axons in the CNS

  
• Schwann Cells/Neurolemmocytes/Neurolemma


  Form myelin sheaths around axons in the PNS

  
• Types of Axons


  • Unmyelinated
  • Myelinated

  
• Unmyelinated Axon


  Rests in indentations of the oligodendrocytes in the CNS and the Schwann cells in the PNS

  
• Myelinated Axon


  With specialized sheaths called myelin sheaths wrapped around it and is an excellent insulator that prevents almost all electric current flow thru cell membrane; Nodes of Ranvier – gaps in the myelin sheath where current flows easily bet. extracellular fluid & axon

  
• Organization of Nervous Tissue in the CNS


  • Gray Matter
  • White Matter

  
• Gray Matter


  Groups of cell bodies w/ their dendrites
• Cortex


  Gray matter on brain surface
• Nuclei


  Gray matter deep w/n the brain
• White Matter


  Bundles of parallel axons w/ myelin sheaths

  
• Conduction pathways & Nerve Tracts

  Formed by white matter
• Organization of Nervous Tissue in the PNS


  • Ganglion
  • Nerves

  
• Ganglion


  Groups of cell bodies
• Nerves


  Bundles of axons and their connective tissue sheaths
• Synapse


  A junction where the axon of one neuron interacts w/ another neuron or an effector organ such as a muscle or gland