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An Introduction to:

An Introduction to:. Neurons. Neurons. The two classes of cells in the nervous system are: Neurons (nerve cells) Glia ( glial cells) The brain contains billions of neurons The interactions between neurons enables people to: t hink, move and feel emotions

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An Introduction to:

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  1. An Introduction to: Neurons

  2. Neurons • The two classes of cells in the nervous system are: • Neurons (nerve cells) • Glia (glial cells) • The brain contains billions of neurons • The interactions between neurons enables people to: • think, move and feel emotions • Neurons have specialized parts with specialized functions

  3. cell body Anatomy of a Neuron axon axon terminals dendrites nucleus OUTPUT INPUT

  4. Cell body (soma) • is the metabolic center of the neuron • contains the nucleus • most proteins are made here

  5. Dendrites • these are branched processed specialized to receive input and carry information towardsthe cell body

  6. Axon • is larger in diameter than dendrites • is specialized to carry information away from the cell body • may be very long, up to 1 m • Some large axons are surrounded by a fatty insulating material called myelin which enables electrical signals to travel down the axon at higher speeds

  7. Axon terminals • Fine branches of the axon which end in close proximity to the dendrites of another neuron • Called presynaptic terminals

  8. Synapses • The connection between two neurons is called a synapse • Neurons interact with other neurons through synapses the axon terminals of one neuron will end near the dendrites of another neuron • the Presynaptic neuron: sends out information • the Postsynpatic neuron: receives information • note: There is no physical connection between the two neurons • The intercellular space between the presynaptic and postsynaptic neurons is called the synaptic space or synaptic cleft

  9. Synapses (con’t) • an average neuron form aprox. 1000 synapses with other neurons • There are more synapses in the human brain than stars in our galaxy! • Synaptic connections are not static, meaning there are not permanent • Neurons form new synapses or strengthen synaptic connections in response to life experiences • This dynamic change in neuronal connections is the basis of learning

  10. Glial Cells • There are 10-50 times more glial cells than neurons in the CNS (central nervous system) • Glial cells can be categorized as either: • Microglia: phagocytic cells that are mobilized after injury, infection or disease • Macroglia: • oligodendrocytes, astrocytes, Schwann cells • Oligodendrocytes and schwann cells form the myelin sheath that insulates axons

  11. Gliall Cells (con’t) • Glial cells fulfill a variety of functions: • Act as supporting elements in the nervous system to provide support and to separate and insulate groups of neurons • Act as scavengers that remove debris after injury or neuronal death • Direct the outgrowth of axons during development • Remove neurotransmitters from the extracellular space after neurotransmission

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