From Chapter 8

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From Chapter 8
Action Graded Potentials (review Interactive
Physiology) the Synapse
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Outline

• Detailed look at an action potential
• Synapses
• Electrical versus chemical synapses
• Review of important neurotransmitter of PNS
• Note this chapter contains additional
  information on some CNS neurotransmitters which I
  have not emphasized

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A simple flow chart of electrical events

• Graded potentials
• Action potentials
• Neurotransmitter release

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Graded potentials decrease in strength as they
spread out from the point of origin
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The Action Potential
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Action Potential depolarizationstep-by-step
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Repolarization
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SUMMARY
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Refractory Periods

• Absolute
• Na channels are inactive
• K channels are open
• Relative
• Some Na channels reset
• Some K open

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Quiz Question

• What 2 factors contribute to the interruption of
  the positive feedback loop?

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Answers

• Closing of Na channels
• Opening of slow K channels

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What are two factors related to the neuron that
might contribute to the speed of an action
potential?
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Answers

• Diameter
• Myelination

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Blocking an Action Potential

• Local Anesthetics
• Procaine (Novocaine)
• Lidocaine (Xylocaine)

NO ACTION POTENTIAL NO SENSORY PERCEPTION
Blocks Na channels
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2. Types of Synapses
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Synapses

• Chemical via neurotransmitters
• Electrical via gap junctions

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Chemical Synapse
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Cholinergic Chemical Synapse

• Neurotransmittor
• Acetylcholine
• Receptors
• Nicotinic
• Muscarinic

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Cholinergic Receptors

• Nictotinic
• Only Excitatory
• Found neuromuscular junctions

• Muscarinic
• Excitatory or Inhibitory
• Found in CNS, heart

disorder
Myastenia Gravis
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Adrenergic Chemical Synapse

• Neurotransmitter
• Norepinephrine
• Receptors
• Alpha
• Beta
• How does Norepinephrine breakdown?

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ADRENERGIC

• Alpha-1
• Excitatory
• Found in Smooth muscle contracts blood vessels
• Found in CNS

• Beta 1
• Excitatory
• Found in the heart
• Increases heart rate
• Dilates blood vessels of skeletal muscle

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Monoamine OxidaseMAOmitochondrial enzyme
breaks down norepinephrine dopamine serotonin

• How does Norepinephrine breakdown?

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Note Synaptic Potentials may be classified as
depending upon the effect of the neurotransmitter

• Excitatory Postsynaptic Potential (EPSP)
• or
• Inhibitory Postsynaptic Potential (IPSP)

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SummaryPost synaptic cell varied response
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The end!