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The Nervous System: Neurons & Neuroglial Cells, & Synapses

The Nervous System: Neurons & Neuroglial Cells, & Synapses. pp. 222-230. Central vs. Peripheral NS. General Pathway. Animation Sensory receptors – on dendrites of peripheral nerves (PNS), activated by stimuli Sensory/Afferent neurons – sensory input to CNS, cell bodies in PNS

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The Nervous System: Neurons & Neuroglial Cells, & Synapses

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  1. The Nervous System:Neurons & Neuroglial Cells, & Synapses pp. 222-230

  2. Central vs. Peripheral NS

  3. General Pathway • Animation • Sensory receptors – on dendrites of peripheral nerves (PNS), activated by stimuli • Sensory/Afferent neurons – sensory input to CNS, cell bodies in PNS • Interneurons – integration by CNS • Motor/Efferent neurons – motor output from CNS, cell bodies in CNS • Somatic – controls skeletal muscle (voluntary) • Autonomic – controls cardiac muscle, smooth muscle, & glands (involuntary) • Effectors – muscles & glands at the ends of peripheral nerves (PNS)

  4. General Pathway

  5. Neurons & Neuroglia • Neurons • Nerve cells • Respond to stimuli & transmit electrical impulses to communicate to other nerves, muscles, or glands • Cannot divide • Neuroglia • Support, insulate, & protect neurons • Can’t transmit electrical impulses • Can divide

  6. Myelin • A lipid that sometimes coats axons • White matter = myelinated axons in CNS • Gray matter = cell bodies & unmyelinated axons in CNS • Produced by some neuroglial cells • Insulates neurons & increases efficiency of nerve impulses • Multiple sclerosis

  7. PNS Neuroglial Cells Schwann cells – Wrap around axon, forming myelin sheath • Neurilemma – outer layer containing the cytoplasm & organelles • Nodes of Ranvier – gaps in the sheath Satellite cells –Protect & cushion neurons

  8. CNS Neuroglial Cells • Microglial cells • Phagocytosis • Oligodendrocytes • Form myelin sheath around axons • No neurilemma • Astrocytes • Connect to capillaries – living barrier • Control chemical environment of brain • Ependymal cells • Line cavities & circulate cerebrospinal fluid

  9. Neuron Parts: • Cell body • Dendrites • Axon • Axon terminals

  10. At the Synapse • Presynaptic neuron • Axon terminal • Vesicle • Neurotransmitters • Synaptic cleft • Receptors • Postsynaptic neuron

  11. Neurotransmitters • Action potential reaches axon terminal • Ca+2 ions rush into the presynaptic neuron • Vesicles fuse with cell membrane (exocytosis) • NT’s released into synaptic cleft

  12. Neurotransmitters, part 2 • NT’s bind to receptors on postsynaptic neuron • Na+ ions rush into postsynaptic neuron • A new nerve impulse begins • Animation

  13. Neuron Types

  14. Damage to Nerves • Neurons don’t divide, but neuroglial cells can divide! • Injury to cell body – kills the neuron • Injury to the axon • In PNS • Axons may regenerate – Schwann cells help • In CNS • Axons do not regenerate – no Schwann cells • Neural stem cells in the brain

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