SYNAPSES

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SYNAPSES

• A. INTRODUCTION
• 1) A synapse is a junction between 2 nerve
  cells or a nerve cell and a muscle cell.

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• B) ANATOMY OF A SYNAPSE
• 1) Synaptic knob with transmitter vesicles
  and presynaptic membrane.
• 2) Synaptic cleft.
• 3) Postsynaptic membrane with receptors for
  transmitters.

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• C) FUNCTION OF THE SYNAPSE
• 1) Electrical impulse in knob causes influx of
  Ca, vesicles rupture, release transmitters.
• 2) Transmitters diffuse across,cleft attach to
  receptors.

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• 3) Receptors open gates for ions.
• a) Can be direct
• b) May be indirect via G-proteins (which
  diffuse from receptor to ion channel.)
• 4) Transmitters can be broken down, taken
  up by presynaptic membrane or diffuse
  away.

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• D) TRANSMITTERS
• 1) Acetylcholine was first discovered,
  there are many others.
• 2) Monoamines
• a) The catacholamines dopamine,
  norepinephrine, epinephrine?
• b) Serotonin

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• 3) Amino acids
• a) glutamate
• b) GABA and glycine - inhibitory
• 4) Amines such as acetylcholine and
  histamine.
• 5) Polypeptides such as enkephalins and
  endorphins.
• 6) Gases such as nitric oxide and CO.

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• E) ONE-WAY CONDUCTION
• 1) Synapses make nervous system a one- way
  system - dendrites do not have neurotransmitter
  vesicles.
• 2) Synaptic delay

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• F) TYPES OF SYNAPSES
• 1) Synapses can be excitatory or inhibitory.
  a) If an excitatory transmitter is released,
  then an excitatory postsynaptic potential
  (EPSP)will be created.
• b) If an inhibitory transmitter is released,
  then an inhibitory postsynaptic potential
  (IPSP)will be created.

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• G) SYNAPTIC INTEGRATION
• 1) Most synapses involve many neurons.
• 2) Whether or not postsynaptic membrane has
  an action potential is dependent upon algebraic
  sum of EPSPs and IPSPs.

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• 3) Spatial summation occurs when numerous
  synaptic knobs release their transmitters.
• 4) Temporal summation can occur if neuron
  releases transmitter rapidly.

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• H) CHEMICALS WHICH AFFECT THE SYNAPSE
• 1) Many chemicals that affect nervous system
  do so by affecting synapse.
• a) Clostridium botulinum toxin.
• b) Clostridium tetanii toxin.
• c) Caffeine
• d) Anesthetics
• e) Strychnine
• f) Psychotropic drugs

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