31 - Chapter 28 Nervous System 3/31/08 28.5 28.6 - Are...

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Chapter 28 Nervous System 3/31/08 28.5 - Are all-or-none events - Are not weak or strong - Reach the threshold-signal is sent down axon - Does not matter if stimulus is strong or weak o Tap the domino or smack the domino - Intensity of stimulus can change frequency of action potentials - Action potential-wave of depolarization - Due to influx of Na+ ions 28.6 - Synapse-junction between synaptic terminal and the next cell o Two types Electrical synapse Electrical currents passes directly from one neuron to the next Found in heart and digestive tract. - Chemical synapse - Action potential induces exocytosis of vesicle containing neurotransmitters - Neurotransmitter is released into synaptic cleft. - Neurotransmitter binds to receptor on receiving cell. - What happens to receiving cell? o If it’s a neuron? Triggers an action potential (+++ ions flood into cell) o If it’s a muscle cell? Trigger contraction (Ch. 30) - Neurotransmitter release requires Ca++ (remember blood regulation?) - After signaling, neurotransmitter are reloaded into vesicles (reuptake)
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This note was uploaded on 04/17/2008 for the course BIO 152 taught by Professor Grandy/holloway during the Spring '08 term at MCPHS.

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31 - Chapter 28 Nervous System 3/31/08 28.5 28.6 - Are...

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