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NEURONS

NEURONS. THE BASIC HARDWARE. It all Starts with the Neuron. Neurons are SO diverse in shape and size that it is impossible to have a drawing that adequately represents them…. They all have similar features though….

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NEURONS

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  1. NEURONS THE BASIC HARDWARE

  2. It all Starts with the Neuron Neurons are SO diverse in shape and size that it is impossible to have a drawing that adequately represents them…. They all have similar features though…

  3. On a piece of computer paper, draw this outline, label as indicated in following slide, color as you like Your name here

  4. Neuron Structure SOMA

  5. The cell body • Contains the cell’s Nucleus Soma- Greek for BODY • Round, centrally located structure • Also called “soma” • Contains DNA • Controls protein manufacturing • Directs metabolism • No role in neural signaling

  6. Dendrites Greek for TREE • Information collectors • Receive inputs from neighboring neurons • Inputs may number in thousands • If enough inputs the cell’s AXON may generate an output

  7. Dendritic Growth • Mature neurons generally can’t divide • But new dendrites can grow • Provides room for more connections to other neurons • New connections are basis for learning

  8. Axon • The cell’s output structure • LONG….One axon per cell, 2 distinct parts • tubelike structure & the branches at end that connect to dendrites of other cells Greek for AXLE

  9. Terminal Buttons • At the Axon end • Small knobs that secrete chemicals called.. NEUROTRANSMITTERS Chemicals are messengers to activate neighbors

  10. Synapse Greek for JUNCTION A synapse is a place where information is transmitted from one neuron to another

  11. Myelin Sheath Myelin sheath • White fatty casing on axon • Acts as an electrical insulator • Not present on all cells • When present increases the speed of neural signals down the axon. With Multiple Sclerosis the Myelin Sheath deteriorates  - muscle control loss

  12. How neurons communicate • Hodgkin and Huxley ’52, studied neural impulses of SQUID to understand the ‘mystery’ • The neuron is like a battery (store of potential energy) • Inside and outside the neuron are electrically charged atoms and molecules = IONS

  13. Outside of Cell K+ Na+ Cl- Cell Membrane in resting state K+ Na+ Cl- A- Inside of Cell Ion concentrations

  14. Resting Potential When the neuron is stable When the cell is inactive At rest the inside of the cell is at -70 millivolts

  15. K+ Na+ Cl- Outside of Cell Cell Membrane at rest Na+ - 70 mv A- K+ Cl- Inside of Cell Potassium (K+) can pass through to equalize its concentration Sodium and Chlorine cannot pass through Result - inside is negative relative to outside The Cell Membrane is Semi-Permeable

  16. Action Potential When neuron is stimulated, channels in membrane OPEN, allowing positively charged sodium ions to rush in. This electrical signal is called the Action Potential Action Potentials are based on movements of ions between the outside and inside of the cell (electrical)

  17. Absolute Refactory Period After firing of an action potential the channels close up. The time between when they can fire again is called the ABSOLUTE REFACTORY PERIOD 1-2 milliseconds

  18. The All-or None Law • The idea that either the neuron fires or it does not- no part way firing. • Like a gun

  19. See it another way… http://learner.org/discoveringpsychology/03/e03expand.html?pop=yes&pid=1525

  20. How Neurons Communicate

  21. Messages • 2 types of messages can be sent • Excitatory PSP (postsynaptic potential) • + voltage shift that increases the likelihood that the PS neuron will fire action potentials • Inhibitory PSP • - voltage shift that decreases the likelihood that the PS neuron will fire action potentials Most are reabsorbed in the presynaptic neuron - REUPTAKE

  22. Neurotransmitters 9 well established, classic transmitters 40 additional part-time transmitters Handful of ‘novel’ transmitters You need to know the following 4…for sure

  23. Acetylcholine Lack of ACH has been linked to Alzheimer’s disease. ACh Only transmitter between neurons and voluntary muscles Nicotine can work as an Agonist of ACh (mimics the ACh action) Curare can work as an Antagonist (opposes the ACh action) causes muscles unable to move.

  24. Agonists and Antagonists

  25. Dopamine • Its function is motor movement and alertness. Lack of dopamine is associated with Parkinson’s disease. Overabundance is associated with schizophrenia.

  26. Serotonin • Function deals with mood control. Lack of serotonin has been linked to depression.

  27. Endorphins • Function deals with pain control. We become addicted to endorphin causing feelings.

  28. Drugs & Their Effects

  29. Divisions of the Nervous System

  30. Nervous System Explain how your part of the nervous system functions How does it connect to the other parts of the nervous system? Create something to help remember your part (drawing, acronym, alliteration)

  31. Central Nervous System • Sensory neurons send info from.. • Body tissues & sensory organs to… • Brain and spinal cord With the help of INTERNEURONS (billions and billions) The CNS then sends info to body tissues via MOTOR NEURONS

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