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Neurons and Neurotransmitters

Neurons and Neurotransmitters. Nervous System. Central nervous system (CNS): Brain Spinal cord Peripheral nervous system (PNS): Sensory neurons Motor neurons. The Nervous System. A physical organ system like any other 2 main kinds of cells Neurons Glia. Neurons.

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Neurons and Neurotransmitters

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  1. Neurons and Neurotransmitters

  2. Nervous System • Central nervous system (CNS): • Brain • Spinal cord • Peripheral nervous system (PNS): • Sensory neurons • Motor neurons

  3. The Nervous System • A physical organ system like any other • 2 main kinds of cells • Neurons • Glia

  4. Neurons • Basic units of the nervous system • Receive, integrate, and transmit information • Operate through electrical impulses • Communicate with other neurons through chemical signals

  5. Glial cells • 100 billion neurons • 10x more glial cells • Glial cells • Support neurons (literally, provide physical support, as well as nutrients) • Cover neurons with myelin • Clean up debris • “Housewives”

  6. Three main types of neurons • Motor Neurons • Aka Efferent Neurons • Sensory Neurons • Aka Sensory Neurons • Interneurons • In the brain & spinal cord • Facilitates communication between afferent & efferent neurons

  7. Motor (Efferent) vs. Sensory (Afferent) motor (efferent) neurons CNS Neurons that transmit commands from the CNS to the muscles, glands, and organs e.g., muscle sensory (afferent) neurons CNS e.g., skin Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS

  8. The Withdrawal Reflex

  9. Neuron Anatomy and Neural Communication

  10. Soma Dendrites MyelinSheath Axon Neurons Dendrites of another neuron Axon of anotherneuron

  11. Neural Anatomy • Dendrite • the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body • Soma (Cell body) • Center of the neuron • Contains the nucleus and produces energy for the neuron

  12. Neural Anatomy • Axon • the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands • Myelin Sheath • Insulating layer of fat cells surrounding the axon

  13. Neural Anatomy • Terminal Buttons • Small knoblike structures at the end of an axon • Contains neurotransmitters

  14. All-or-None Principle • Neurotransmitters from other neurons produce changes (post-synaptic potentials) in the membrane of the post-synaptic neuron • For a neuron to fire, a minimum level or threshold must be met. • If the threshold is met, neuron fires 100%. • Produces an electrical charge = action potential • If its not met, neuron does not fire.

  15. Neural Impulse • Action potential is created in the cell body, then travels down the axon, to the terminal buttons where neurotransmitters are released

  16. Action Potential When dendrites stimulated, the delicate balance is altered Membrane breaks down Positively charged ions rush in (depolarization) Charge = less negative Causes release of chemicals from terminal buttons

  17. W. W. Norton

  18. Relay Race • Action Potential starts at dendrite • Through cell body • Down Axon • Axon Terminals • How does it get to the next cell’s dendrites? • Neurons don’t touch • Synapse = millionth inch gap • In synapse = vesicles w/ neurotransmitters • Chemical messengers that transmit info

  19. Neural Anatomy and communication • Synapse • junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron • tiny gap at this junction is called the synaptic gap or cleft

  20. Communication • Impulse releases neurotransmitter from vesicles • Neurotransmitter enters synaptic gap • Neurotransmitter binds to receptors on the receiving neuron

  21. Myelin Sheath • Fatty material made by glial cells • Insulates the axon • Allows for rapid movement of electrical impulses along axon • Nodes of Ranvier: gaps in myelin sheath where action potentials are transmitted • Multiple sclerosis is a breakdown of myelin sheath • Speed of neural impulse Ranges from 2 – 200+ mph

  22. Myelinization clip Myelin conduction clip

  23. Neurotransmitters • chemical messengers that traverse the synaptic gaps between neurons • when released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse

  24. Neurotransmitters (>60) • Acetylcholine (ACh) • 1st substance identified as NT • Links motor neurons and muscles (contract or relax) • e.g. curare vs black widow spider • Also involved in memory, learning, sleep, dreaming (acetylcholine movie) • Endorphins (the brain’s own morphine) • 1973 injected rats with morphine • Bound like NTs • Brain had receptors for exogenous substance? • Brain must produce its own morphine • Released during pain and discomfort

  25. More neurotransmitters Receptor binding movie

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