nerve impulse 2

• Synapse between neurons


  • Buttons (Synaptic knobs)
  • Synaptic (Nervous) vesicles
  • Synaptic cleft
• Buttons (Synaptic knobs)


  Swellings at the end of terminal arborizations of a nerve cell axon, located very close to the dendrites (or cell body) of the next neuron
• Synaptic (Nervous) vesicles


  Small sacs present inside the buttons, filled with chemical transmitters (neurotransmitters) such as acetylcholine and noradrenalin
• Synaptic cleft


  Narrow space between the buttons and dendrites of the next neuron, separating the presynaptic membrane (axon) from the postsynaptic membrane (dendrite)
• Mechanism of transmitting the nerve impulse across a synapse

  1. Arrival of nerve impulse to the buttons (synaptic knobs)

  2. Entry of calcium ions inside the cell

  3. Rupture of synaptic vesicles and release of chemical transmitters

  4. Chemical transmitters cross the synaptic cleft and reach the membrane of dendrites of the next neuron

  5. Chemical transmitters bind to receptors on dendrite membrane, leading to depolarization and action potential propagation
• After performing its function, acetylcholine (chemical transmitter) is destroyed under the effect of choline-esterase enzyme, and the membrane returns to its resting potential