Biological Psychology: Cells of the Nervous System

Anatomy of Neurons

• External Features of Neuron
  • Cell Membrane: the semipermeable membrane that encloses the neuron
  • Cell Body: the metabolic center of the neuron; aka soma
  • Dendrites: the short processes emanating from the cell body, which receive most of the synaptic contacts from other neurons
  • Axon Hillock: the cone-shaped region at the junction between the axon and cell body
  • always singular
  • Axon: the long, narrow process that projects from the cell body
  • an axon always starts at the axon hillock
  • Myelin: the fatty insulation around many axons
  • insulation, protection; speeds up transmission or transfer of impulses (most important feature)
  • Nodes of Ranvier: gaps between sections of myelin
  • Terminal Buttons or Buttons: the buttonlike endings of the axon branches, which release chemicals into synapses
  • Synapses or Synaptic Gap or Cleft: the gaps between adjacent neurons across which chemical signals are transmitted
• Internal Features of a Neuron
  • Mitochondria: sites of aerobic (oxygen-consuming) energy release; powerhouse
  • Nucleus: the spherical DNA-containing structure of the cell body
  • Endoplasmic Reticulum: a system of folded membranes in the cell body; rough portions (those with ribosomes) play a role in the synthesis of proteins; smooth portions (those without ribosomes) playa a role in the synthesis of fats
  • Cytoplasm: the clear internal fluid of the cell
  • Ribosomes: internal cellular structures on which proteins are synthesized; they are located on the endoplasmic reticulum
  • Golgi Complex: a connected system of membranes that packages molecules in vesicles
  • Endoplasmic Reticulum vs Golgi Complex:
    • Endoplasmic Reticulum: synthesize protein
    • Golgi Complex: smooth; packaging
  • Microtubules: tubules responsible for the rapid transport of material throughout neurons
  • transport of substances and nutrients happen
  • Synaptic Vesicles: spherical membrane packages that store neurotransmitter molecules ready for release near synapses
  • Neurotransmitters: molecules that are released from active neurons and influence the activity of other cells
• Cell Membrane
  • The ^^cell membrane^^ is a lipid bilayer with signal proteins and channel proteins embedded in it
  • Lipid Bilayer: 2 layers of fat molecules
  • embedded are numerous protein molecules that are the basis of many of the cell membranes functional properties
  • Channel Proteins: through which certain molecules can pass
  • Signal Proteins: transfer a signal to the inside of the neuron when particular molecules bind to them on the outside of the membrane
• Classes of Neurons
  • Unipolar Neuron: a neuron with one process extending from its cell body
  • cell body is smooth
  • Bipolar Neuron: a neuron with 2 processes extending from its cell body
  • Multipolar Neuron: a neuron with more than 2 processes extending from its cell body
  • one axon multiple dendrites; can receive or send out efferent axon away; away from axon (going out the neuron); motor or afferent to the neuron; sensory = accept; sensory
  • Multipolar Interneuron: neurons with a short axon or no axon at all
  • function is to integrate neural activity within a single brain structure, not to conduct signals from one structure to another
  • in between 2 other neurons; serves to conduct impulses through another neuron without the use of axon
  • Neurons and Neuroanatomical Structure
  • Nuclei (singular = nucleus): clusters of cell bodies in the central nervous system
  • Ganglia (singular = ganglion): clusters of cell bodies in the peripheral nervous system
  • Tracts: bundles of axons in the central nervous system
  • Nerves: bundles of axons in the peripheral nervous system

Glia: The Forgotten Cells

• Glia: most common type of cells in the nervous system
• Major Types of Glia
  • Oligodendrocytes: glial cells with extensions that around the axons of some neurons of the central nervous system
  • extensions are rich in myelin, a fatty insulating substance, and the myelin sheaths they form increase the speed and efficiency of axonal conduction
  • “cake roll”
  • Schwann Cells: similar function as oligodendrocytes in the peripheral nervous system
  • only Schwann cells can guide axonal regeneration (regrowth) after damage
  • “sandwich”
• Major Types of Glia
  • Microglia: smaller than other glial cells
  • respond to injury or disease by multiplying, engulfing cellular debris or even entire cells, and triggering inflammatory responses
  • have immune system-like responsibilities in the brain, and they play a role in the regulating of cell death, synapse formation, and synapse elimination
  • rehabs the cell until cells are fully functional
  • Astroglia: largest of the glial cells; support and provide nourishment for neurons and form part of the blood-brain barrier
  • have the ability to contract or relax blood vessels throughout the brain
  • establish and maintain connections between neurons

\