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SYNAPSES

SYNAPSES. D. C. Mikulecky Professor of Physiology http://views.vcu.edu/~mikuleck/. TWO TYPES OF SYNAPSE. ELECTRICAL CHEMICAL. ELECTRICAL. GAP JUNCTION: PROVIDES PATH FOR IONS TO FLOW FROM ONE CELL TO ANOTHER. CELL 1 . CELL 2. CHEMICAL: THE SYNAPSE. INCOMING NERVE. POST SYNAPTIC

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SYNAPSES

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  1. SYNAPSES D. C. Mikulecky Professor of Physiology http://views.vcu.edu/~mikuleck/

  2. TWO TYPES OF SYNAPSE • ELECTRICAL • CHEMICAL

  3. ELECTRICAL GAP JUNCTION: PROVIDES PATH FOR IONS TO FLOW FROM ONE CELL TO ANOTHER CELL 1 CELL 2

  4. CHEMICAL: THE SYNAPSE INCOMING NERVE POST SYNAPTIC NERVE SPACE

  5. EVENTS IN CELLULAR COMMUNICATION INPUT SIGNAL (CHEMICAL,MECHANICAL, PHOTO, ELECTRICAL) RECEPTOR TRANSDUCER EFFECTOR ENZYMES,GENOME,CONTRACTILE FILAMENTS, SECRETORY GRANULES RESPONSE (OUTPUT) SECRETION CONTRACTION/RELAXATION DIVISION PHAGOCYTOSIS

  6. HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS AXON CELL BODY AXON TERMINALS AXON HILLOCK DENDRITES

  7. THE NATURE OF CHEMICAL TRANSMISSION BETWEEN NERVES • PRESYNAPTIC EVENTS • POSTSYNAPTIC EVENTS • IN THE SPACE

  8. PRESYNAPTIC EVENTS • THE ALL OR NONE ACTION POTENTIAL TRIGGERS THE RELEASE OF CHEMICAL TRANSMITTER

  9. INCOMING ACTION POTENTIAL • DEPOLARIZES • TRIGGERS CALCIUM CHANNELS • CALCIUM ENTERS THE CELL

  10. THE SYNAPSE INCOMING ACTION POTENTIAL CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ••• ENZYME

  11. THE SYNAPSE: INCOMING ACTION POTENTAL INCOMING ACTION POTENTIAL CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ••• ENZYME

  12. CALCIUM INFLUX • CAUSES VESSICLES TO BE RELEASED • VESSICLES MIGRATE TO MEMBRANE • EXOCYTOSIS • NEUROTRANSMITTER ENTERS SPACE

  13. THE SYNAPSE: CALCIUM CHANNELS OPEN INCOMING ACTION POTENTIAL CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ••• ENZYME

  14. THE SYNAPSE: NEUROTRANSMITTER ENTERS SPACE CALCIUM CHANNEL ••• RECEPTOR ••• SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ENZYME

  15. POST SYNAPTIC EVENTS • IONOTROPIC (LIGAND GATED) CHANNELS • VOLTAGE GATED CHANNELS • ELECTROPHYSIOLOGICAL PRINCIPLES

  16. IONOTROPIC CHANNELS • BIND NEUROTRANSMITTER • OPEN CHANNEL • HYPER OR DE-POLARIZATION

  17. THE SYNAPSE:NEUROTRANSMITTER BINDS TO POSTSYNAPTIC RECEPTOR CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ENZYME

  18. HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS AXON CELL BODY AXON TERMINALS AXON HILLOCK DENDRITES

  19. IPSP POSTSYNAPTIC POTENTIALS EPSP RESTING POTENTIAL TIME

  20. SPATIAL SUMMATION SIMULTANEOUS INPUT FROM TWO SYNAPSES: ABOVE THRESHOLD THRESHOLD TIME

  21. SPATIAL SUMMATION SIMULTANEOUS INPUT FROM TWO SYNAPSES: ABOVE THRESHOLD THRESHOLD TIME

  22. TEMPORAL SUMMATION TOO FAR APART IN TIME: NO SUMMATION TIME

  23. TEMPORAL SUMMATION CLOSER IN TIME: SUMMATION BUT BELOW THRESHOLD THRESHOLD TIME

  24. THE GOLDMAN-HODGKIN-KATZ (GHK) EQUATION [Ko] + [Nao] Vm = 60 LOG -------------------------- [Ki] + [Nai]  IS THE RATIO OF SODIUM TO POTASSIUM PERMEABILITY

  25. TEMPORAL SUMMATION STILL CLOSER IN TIME: ABOVE THRESHOLD THRESHOLD TIME

  26. EPSP-IPSP CANCELLATION

  27. HOW EXCITATION OCCURS-THE ROLE OF DEPOLARIZATION AND HYPERPOLARIZATION • SUMMATION CAN DEPOLARIZE THE CELL BEYOND THRESHOLD • HYPERPOLARIZATION BLOCKS

  28. ACETYL CHOLINE DOPAMINE NOREPINEPHRINE EPINEPHRINE SEROTONIN HISTAMINE GLYCINE GLUTAMINE GAMMA-AMINOBUTYRIC ACID (GABA) NEURO TRANSMITTERS

  29. IN THE SPACE • ENZYME “CHEWS UP” LIGAND • MASS ACTION CAUSES LIGAND TO DISSOCIATE FROM RECEPTOR

  30. THE SYNAPSE CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ION CHANNEL ••• ••• ••• ••• ENZYME

  31. THE SYNAPSE CALCIUM CHANNEL ••• RECEPTOR SYNAPTIC VESSICLES ••• ••• ••• ••• ••• ION CHANNEL ••• ••• ••• ENZYME

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