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Cells of the Nervous System

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  1. Cells of the Nervous System

  2. Layout of the Nervous System Central Nervous System (CNS) Brain (in the skull) Spinal Cord (in the spine) Interprets sensory input, initiates movement, and mediates complex cognitive processes Peripheral Nervous System (PNS) Located outside of the skull and spine Serves to bring sensory information into the CNS and carry motor signals out of the CNS

  3. Functional Unit of the Nervous System The functional unit of the nervous system is the neuron. Neurons are specialized cells for the reception, conduction, and transmission of electro-chemical signals Many sizes and shapes ~100 billion neurons ~100 trillion connections

  4. Major External Features of a Neuron A typical neuron has a cell body, dendrites and an axon. Flow of information: • dendrites receive inputs from other neurons • the cell body (or soma) integrates (processes) information • the axon transmits the output of processing to other neurons

  5. Major Internal Features of a Neuron • Similarities with other cells: • Contains a nucleus that holds genetic information • Contains organelles that support the life of the cell, including mitochondria and ribosomes • Surrounded by a membrane that protects the cell • Differences with other cells: • Stop dividing (reproducing) after birth • Have dendrites and axons, specialized structures designed to receive and transmit information

  6. The Cell Membrane Lipid bilayer with embedded proteins • separates inside and outside of cell • selective permeability controls flow of substances into and out of the cell The particular composition of embedded proteins in the cell membrane is critical for proper neuron function

  7. Visualizing Neurons 1 The major problem in visualizing neurons is not their minuteness. Rather, the major problem is neurons are so tightly packed and their dendrites and axons intricately intertwined. Golgi stain: for as-yet unknown reasons, silver stains some neurons black in their entirety but stains others not at all. Allows for visualization of individual neurons

  8. Visualizing Neurons 2 Nissl stain: selectively stains cell bodies. Used to indicate the number of neurons in an area

  9. Visualizing Neurons 3 Electron microscopy: provides information about the details of neuronal structure

  10. Visualizing Neurons 4 Tract tracing techniques: used to trace the paths of axons Anterograde: to trace axons projecting away from cell bodies Retrograde: to trace axons projecting into an area of cell bodies www.seriousmadscience.com cmbn-approd01.uio.no

  11. Neuroanatomical Structures Two kinds of gross neural structures; those composed primarily of cell bodies and those composed primarily of axons.

  12. Anatomical Classes of Neurons Neurons do not all look alike. One way to classify them is based on the number of processes emanating from their cell bodies. Structure is related to function and location.

  13. Functional Classes of Neurons information from tissue/organs integrate intermediate information to effector cells www.studyblue.com

  14. CNS Neurons Are Usually Multipolar

  15. PNS Neurons are Unipolar or Multipolar

  16. Connections Between Neurons Direction: afferent (approaching) efferent (exiting) Type: axon-dendrite but also axon-soma, axon-axon, dendrite-dendrite Neuroscience: Exploring the Brain, 3rd ed

  17. Glia: The Forgotten Cells of the NS • Helper cells (glia = “glue”) • Outnumber neurons 5:1 • Provide structural/metabolic support to neurons • Recent evidence for glial communication and modulatory effects of glia on neuronal communication www.jaynejubb.com

  18. Classes of Glial Cells • Oligodendrocytes: extensions rich in myelin; create myelin sheaths in CNS • Schwann cells: similar to function of oligodendrocytes, but in PNS; can guide axonal regeneration • Microglia: involved in response to injury or disease • Astrocytes: largest glia; star-shaped; many functions blogs.scientificamerican.com

  19. Myelination of neurons

  20. Microglia respond to injury or disease ramified motile ucsf.edu

  21. Astrocytes perform a variety of duties • Control and communicate widely with many neurons: • form a barrier to unwanted substances entering the brain • maintain the proper chemical state outside of neurons • send nutrients (glucose) to neurons • control blood flow to neurons (activity allows functional imaging) • digest old neuronal parts • surround synapses and can modify neuronal signals • secrete neurotransmitters and glialtransmitters www.nature.com