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Transmission of Impulse to the Next Cell

28 Oct. 2011. Synapses.ppt. 2. Synapses. Electrical synapsesGap junctions," tiny holes connect cytoplasm of adjacent cellsA.P. continuous from cell to cellChemical synapsesAxon (

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Transmission of Impulse to the Next Cell

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    1. 28 Oct. 2011 Synapses.ppt 1 Transmission of Impulse to the Next Cell Synapses

    2. 28 Oct. 2011 Synapses.ppt 2 Synapses Electrical synapses “Gap junctions,” tiny holes connect cytoplasm of adjacent cells A.P. continuous from cell to cell Chemical synapses Axon (& A.P.) ends short of next cell, Synaptic knob (axon end) releases chemical transmitter

    3. 28 Oct. 2011 Synapses.ppt 3 Synapse Presynaptic axon end (synaptic knob) Gap = synaptic cleft Postsynaptic membrane

    4. 28 Oct. 2011 Synapses.ppt 4 Locations of synapses Neuromuscular junction = axon to muscle fiber Axon to dendrite Axon to cell body Axon to axon

    5. 28 Oct. 2011 Synapses.ppt 5 Synapse When Action Potential reaches synaptic knob, Synaptic vesicles unite with membrane, Release neurotransmitter, Neurotransmitter diffuses across synaptic cleft, Neurotransmitter binds to receptors in postsynaptic membrane, Chemically gated channels open.

    6. 28 Oct. 2011 Synapses.ppt 6 Synapse Neurotransmitter can't remain in cleft (would continue to stimulate uncontrollably) ACh removed by acetylcholinesterase (AChE) Acetate & choline reabsorbed by axon end, resynthesized to ACh Other neurotransmitters taken back by axon or diffuse away

    7. 28 Oct. 2011 Synapses.ppt 7 Neurotransmitters may be … Excitatory depolarize postsynaptic membrane Excitatory Postsynaptic Potential (EPSP) Inhibitory hyperpolarize postsynaptic membrane Inhibitory Postsynaptic Potential (IPSP)

    8. 28 Oct. 2011 Synapses.ppt 8 Neurotransmitters Excitation (EPSP) must be post-synaptic Inhibition (IPSP) may be Post-synaptic (inhibitory neuron synapses with post-synaptic cell) Pre-synaptic (inhibitory neuron synapses with pre-synaptic axon end) blocks presynaptic A.P.

    9. 28 Oct. 2011 Synapses.ppt 9 SUMMATION Several to many to very many axons synapse with one neuron Whether Action Potential occurs in postsynaptic neuron depends on number of excitatory inputs (doses of transmitter) number of inhibitory " If sum EPSP - IPSP > threshold, then yields Action Potential

    10. 28 Oct. 2011 Synapses.ppt 10 Temporal summation: Add effects of neurotransmitters over short times at one synapse at 2+ synapses

    11. 28 Oct. 2011 Synapses.ppt 11 Spatial summation: Add effects of neurotransmitters adjacent in space (one post-synaptic neuron) at 2+ synapses at same time

    12. 28 Oct. 2011 Synapses.ppt 12 NEUROTRANSMITTERS: Six classes Acetylcholine Widespread in body; most studied, best understood.

    13. 28 Oct. 2011 Synapses.ppt 13 NEUROTRANSMITTERS: Six classes Biogenic amines

    14. 28 Oct. 2011 Synapses.ppt 14 NEUROTRANSMITTERS: Six classes Amino acids

    15. 28 Oct. 2011 Synapses.ppt 15 NEUROTRANSMITTERS: Six classes Peptides (small proteins)

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