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Neuronal Function

Neuronal Function. Goal: electrochemical communication Requirement: Electrochemical signal generation Electrochemical signal propagation Electrochemical signal transmission. Neuronal Function. Neuronal Function. Electrochemical Signal generation. Establishing Membrane Potential ( V m ).

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Neuronal Function

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  1. Neuronal Function Goal: electrochemical communication Requirement: • Electrochemical signal generation • Electrochemical signal propagation • Electrochemical signal transmission SPPA 2050 Speech Anatomy & Physiology

  2. Neuronal Function SPPA 2050 Speech Anatomy & Physiology

  3. Neuronal Function SPPA 2050 Speech Anatomy & Physiology

  4. ElectrochemicalSignal generation SPPA 2050 Speech Anatomy & Physiology

  5. Establishing Membrane Potential (Vm) • Intracellular space • Cell membrane • Extracellular space SPPA 2050 Speech Anatomy & Physiology

  6. Establishing Membrane Potential (Vm) • Na: Sodium • K: Potassium • Cl: Chloride • Ca: Calcium • +: positive ion • -: negative ion SPPA 2050 Speech Anatomy & Physiology

  7. Establishing Membrane Potential (Vm) Active Transport: Na-K pump • Transports 3 Na+ ions out of the cell • Transports 2 K+ ions into the cell • Net effect • Electrostatic gradient • Concentration gradient • Requires energy SPPA 2050 Speech Anatomy & Physiology

  8. Resting membrane potential (Vm) Vm = ~ -70 millivolts Vm more positive → depolarization Vm more negative → hyperpolarization SPPA 2050 Speech Anatomy & Physiology

  9. Changing Vm Receptor mediated SPPA 2050 Speech Anatomy & Physiology

  10. Changing Vm Voltage Gated Channels SPPA 2050 Speech Anatomy & Physiology

  11. Changing Vm Physical change in permeability SPPA 2050 Speech Anatomy & Physiology

  12. Postsynaptic Potentials (EPSP & IPSP) • Local • Passive • Graded SPPA 2050 Speech Anatomy & Physiology

  13. Summation of PSP SPPA 2050 Speech Anatomy & Physiology

  14. Temporal Summation Spatial Summation SPPA 2050 Speech Anatomy & Physiology

  15. Reaching a Threshold threshold depolarization epsp epsp ipsp epsp -70 mV epsp epsp hyperpolarization Time SPPA 2050 Speech Anatomy & Physiology

  16. Electrochemical Signal Propagation SPPA 2050 Speech Anatomy & Physiology

  17. Action Potential Time course • ↑ depolarization (~ +100 mV) • Brief (~ 1 msec) • Repolarization • Hyperpolarization • Return to Vm Other features • Active • All-or-none • Refractory period • Absolute • Relative SPPA 2050 Speech Anatomy & Physiology

  18. Action Potential: Propagation SPPA 2050 Speech Anatomy & Physiology

  19. Action Potential: Propagation SPPA 2050 Speech Anatomy & Physiology

  20. Action potential: Saltatory Conduction • Conduction velocity • Conduction velocity increased by presence of • Myelin - insulates the axon • nodes of Ranvier – AP “skips” from node to node SPPA 2050 Speech Anatomy & Physiology

  21. Clinical Note • Multiple Sclerosis – a demyelinating disease SPPA 2050 Speech Anatomy & Physiology

  22. Electrochemical Signal Transmission SPPA 2050 Speech Anatomy & Physiology

  23. The Synapse • Secretory potential • Pre synaptic neuron • Post synaptic neuron • Synaptic cleft • Synaptic Vesicles • Neurotransmitters • Receptors • Neuromuscular junction SPPA 2050 Speech Anatomy & Physiology

  24. Features Excitatory Inhibitory Direct 2nd Messenger Common NT Acetylcholine Dopamine Serotonin Glutamate GABA Glycine Neurotransmitters SPPA 2050 Speech Anatomy & Physiology

  25. Receptor Action SPPA 2050 Speech Anatomy & Physiology

  26. Synaptic Modulation: Glutamate SPPA 2050 Speech Anatomy & Physiology

  27. Clinical Note: Parkinson’s Disease • Loss of dopamine • Causes movement disorder • Can cause dysarthria SPPA 2050 Speech Anatomy & Physiology

  28. Clinical Note: Botulinum Toxin (BOTOX) SPPA 2050 Speech Anatomy & Physiology

  29. Clinical Note: Botulinum Toxin (BOTOX) • Spasmodic dysphonia • Excess contraction of laryngeal muscles • BOTOX temporarily paralyzes the muscles SPPA 2050 Speech Anatomy & Physiology

  30. Stretch Reflex: Simple Neuromuscular Circuit • Also known as • Patellar tendon reflex • Knee-jerk reflex SPPA 2050 Speech Anatomy & Physiology

  31. Stretch Reflex: Components • Sensory receptor (muscle spindle) • Afferent nerve fibers • CNS neurons (interneurons) • Efferent nerve fibers • Muscle SPPA 2050 Speech Anatomy & Physiology

  32. Stretch Reflex SPPA 2050 Speech Anatomy & Physiology

  33. SPPA 2050 Speech Anatomy & Physiology

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