QS Study

Synapse is a functional connection between two neurons where one neuron ends and another neuron begins. It is a particular junction at which a neuron cell communicates with a target cell. At a synapse, one neuron sends a message to a target neuron – another cell. There is no anatomical continuity between two neurons involved in the formation of the synapse.

Properties of Synapse

  1. One way conduction,
  2. Synaptic delay,
  3. Fatigue,
  4. Synaptic response.
  5. Inhibition,
  6. Summation – (Spatial and Temporal)
  7. Occlusion,
  8. Convergence and divergence,
  9. Synaptic block.

One way conduction: In the chemical synapse, since neurotransmitter is present only in the presynaptic region, impulse gets conducted from pre- to postsynaptic region only and not vice versa.

Synaptic delay

It is the interval required for crossing a synapse for an impulse. It is about 0.5 m/sec., the cause of the delay, is –

  • The release of neurotransmitters.
  • Passing through synaptic cleft.
  • The combination of postsynaptic receptors.
  • Set up an action potential.

Importance: Measure of a number of synapse and neuron.


When a synapse is rapidly and repeatedly stimulated, the power of conduction of impulse will progressively become less, called fatigue of synapse.

Occurs due to –

  • Reduction/Exhaustion of neurotransmitters.
  • Progressive inactivation of a postsynaptic receptor.
  • Gradually abnormal ion accumulation in post synaptic membrane.

Inhibition – The impulse conduction across a synapse may either stimulate or inhibit an activity of the postsynaptic region.

Summation: When a stimulus of subthreshold strength is applied, there will not be a development of action potential in the postsynaptic region

Convergence and divergence – Impulses from one pre­synaptic nerve fiber may end on the postsynaptic region of large number neurons and this is called as divergence. When nerve fibers of different pre­synaptic neurons end on a common postsynaptic neuron, this is known as convergence.

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