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Neuroglial cells _neurons


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Neuroglial cells _neurons

  1. 1. Neurons & Neuroglial Cells Chapter 9: Nervous System Unit 3: Integration and Coordination
  2. 2. Neuroglial Cells <ul><li>Neuroglial Cells fill spaces, provide structural framework, produce myelin, and carry on phagocytosis. </li></ul><ul><li>Essentially, since neurons are such specialized cells, neuroglial cells perform support roles for the neurons to ensure their survival </li></ul>
  3. 3. Neuroglial Cells <ul><ul><li>In the CNS, these cells greatly outnumber neurons. </li></ul></ul><ul><ul><ul><li>There are four major types of CNS neuroglial cells: </li></ul></ul></ul><ul><ul><ul><ul><li>-Astrocytes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-Ependymal Cells </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-Microglial Cells (microglia) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-Oligodendrocytes </li></ul></ul></ul></ul>
  4. 4. Astrocytes <ul><li>Astrocytes get their name due to the fact that they look somewhat like a star </li></ul><ul><ul><li>They have a central cell body surrounded by several cytoplasmic projections </li></ul></ul><ul><li>Typically found in the brain </li></ul><ul><ul><li>The cell body usually sits between a blood capillary and a neuron of the brain </li></ul></ul><ul><li>Function as the blood brain barrier </li></ul><ul><ul><li>Regulate the flow of ions, sugars, oxygen, & carbon dioxide into and out of neurons </li></ul></ul><ul><ul><li>Prevent toxins and poisons from entering brain neurons </li></ul></ul>
  5. 5. Astrocyte
  6. 6. Ependymal Cells <ul><li>Usually cube-shaped </li></ul><ul><li>Form the lining of the brain’s ventricles and the spinal columns central canal. </li></ul><ul><li>Produce cerebrospinal fluid </li></ul><ul><ul><li>Clear liquid that fills internal cavities in the brain and spinal cord </li></ul></ul><ul><ul><li>Protects the brain and spinal cord both mechanically and immunologically </li></ul></ul><ul><li>Ependymal cells have cilia to help circulate CSF </li></ul>
  7. 7. Ependymal Cells
  8. 8. Brain Ventricles
  9. 9. Microglial Cells <ul><li>Smallest of the neuroglial cells </li></ul><ul><li>Able to migrate around the CNS </li></ul><ul><li>Support neurons by phagocytizing bacterial cells and dead cell debris </li></ul>
  10. 10. Oligodendrocytes <ul><li>Oligodendrocytes occur in rows along nerve fibers. </li></ul><ul><ul><li>They provide insulating layers of myelin around axons within the brain and spinal cord </li></ul></ul><ul><ul><li>Myelin helps to speed up the transmission of electrical signals in neurons </li></ul></ul>
  11. 11. Oligodendrocytes
  12. 12. Peripheral Nervous System <ul><li>The peripheral nervous system contains neuroglial cells as well. </li></ul><ul><ul><li>These cells are called Schwann Cells . </li></ul></ul><ul><ul><ul><li>Schwann cells form a covering called a Myelin Sheath around axons. </li></ul></ul></ul><ul><ul><ul><li>Basically they perform the same roll as the oligodendrocytes found in the CNS </li></ul></ul></ul>
  13. 14. Neuron Structure <ul><li>Neurons vary considerably in size and shape, but they all have common features. </li></ul><ul><ul><li>These include: </li></ul></ul><ul><ul><ul><li>A cell body </li></ul></ul></ul><ul><ul><ul><li>Tubular, cytoplasm-filled dendrites </li></ul></ul></ul><ul><ul><ul><li>Long, usually thin axons </li></ul></ul></ul>
  14. 15. Neuron Structure <ul><li>Neurons have very high metabolic rates, and require constant supplies of glucose and oxygen </li></ul><ul><li>Most neurons can live as long as you can </li></ul><ul><li>Neurons are typically nonmitotic </li></ul>
  15. 16. Neurons Continued <ul><li>Larger axons of peripheral neurons are enclosed in sheaths composed of many Schwann cells. </li></ul><ul><ul><li>Schwann Cells wind tightly around axons, coating them with many layers of cell membrane that have little or no cytoplasm between them. </li></ul></ul><ul><ul><ul><li>These membrane layers are composed largely of a lipoprotein called Myesin . </li></ul></ul></ul><ul><ul><ul><li>Narrow gaps in the myelin sheath between Schwann cells are celled Nodes of Ranvier . </li></ul></ul></ul>
  16. 18. Myelin <ul><li>Axons with myelin sheaths are called Myelinated and those that lack sheaths are called Unmyelinated . </li></ul><ul><ul><li>Myelin is also found in the CNS. </li></ul></ul><ul><ul><ul><li>Masses of myelinated axons form the White Matter in the CNS. </li></ul></ul></ul><ul><ul><ul><li>Unmyelinated axons and neurons bodies form Grey Matter within the CNS. </li></ul></ul></ul>
  17. 20. Classification of Neurons <ul><li>On of the basis of structural differences, neurons are classified into the following three major groups: </li></ul><ul><ul><li>1. Bipolar Neurons </li></ul></ul><ul><ul><li>2. Unipolar Neurons </li></ul></ul><ul><ul><li>3. Multipolar Neurons </li></ul></ul>
  18. 21. Bipolar Neurons <ul><li>The cell body of a bipolar neuron only has two processes, one arising from each end. </li></ul><ul><ul><li>One process is an axon, the other is a dendrite. </li></ul></ul><ul><ul><li>Typically, neurons within special sense organs, such as the eyes, nose, and ears, are bipolar. </li></ul></ul>
  19. 22. Bipolar Neuron
  20. 23. Unipolar Neurons <ul><li>Unipolar neurons have a single process extending from its cell body. </li></ul><ul><ul><li>The process divides into two branches, both called an axon. </li></ul></ul><ul><ul><ul><li>One branch (peripheral process) is associated with dendrites near a peripheral body part. </li></ul></ul></ul><ul><ul><ul><li>The other branch (central process) enters the brain or spinal cord. </li></ul></ul></ul><ul><ul><ul><ul><li>The cell bodies of some unipolar neurons aggregrate in specialized masses of nervous tissue called Ganglia . </li></ul></ul></ul></ul>
  21. 24. Unipolar Neuron
  22. 25. Multipolar Neurons <ul><li>Multipolar neurons have many processes arising from their cell bodies. </li></ul><ul><ul><li>Only one process of each neuron is an axon. </li></ul></ul><ul><ul><ul><li>Most neurons whose cell bodies lie within the brain or spinal cord are multipolar. </li></ul></ul></ul><ul><ul><ul><li>Most of these neurons are motor neurons </li></ul></ul></ul>
  23. 26. Multipolar Neuron
  24. 27. Classification of Neurons Continued <ul><li>On the basis of functional differences, neurons are grouped as follows: </li></ul><ul><ul><li>1. Sensory Function </li></ul></ul><ul><ul><li>2. Interneurons </li></ul></ul><ul><ul><li>3. Motor Neurons </li></ul></ul>
  25. 28. Sensory Neurons <ul><li>Sensory neurons carry nerve impulses from peripheral body parts into the brain or spinal cord. </li></ul><ul><ul><li>Sensory neurons either have specialized Receptor Ends at the tips of their dendrites, or they have dendrites that are closely associated with Receptor Cells in the skin or in sensory organs. </li></ul></ul><ul><ul><ul><li>Most sensory neurons are unipolar, although some are bipolar. </li></ul></ul></ul>
  26. 29. Interneurons <ul><li>Interneurons lie entirely within the brain or spinal cord. </li></ul><ul><ul><li>They are multipolar and link other neurons. </li></ul></ul><ul><ul><ul><li>Interneurons transmit impulses from one part of the brain or spinal cord to another. </li></ul></ul></ul>
  27. 30. Motor Neurons <ul><li>Motor neurons are multipolar and carry nerve impulses out of the brain or spinal cord to effectors. </li></ul><ul><ul><li>Motor impulses also stimulate muscles to contract. </li></ul></ul><ul><ul><li>Stimulate glands to release secretions. </li></ul></ul>