what is saltation conduction of nerve impulse . describe condction o nerve impulse at synapse?

 Ans1) The conduction in which nerve impulse jumps along the myelinated axons from one node of Ranvier to the next node, then it is called saltatory conduction.During development of neurons, the schwann cells in PNS and oligodendrocytes in CNS wrap around the axon of nerve cells, forming an insulation cover on axon. At some points along the length of axon, there are gaps in insulation. These gaps are called nodes of Ranvier. Voltage gated sodium ion channels are restricted only to these nodes. As a result, nerve impulse jumps node to node instead of travelling along the entire length of axon. This speeds up the conduction.





Ans2) The nerve impulse is transmitted from the pre-synaptic neuron to the post-synaptic neuron crossing the synaptic cleft with the help of chemicals called neurotransmitters.
Here is given  flow diagram, mentioning the steps of conduction of nerve impulse across a chemical synapse
An action potential arrives the pre- synaptic membrane and depolarises it.
                                             ↓
The wave of depolarisation causes the voltage- gated calcium ion and sodium ion channels opening in synaptic knob.
                                                ↓
Calcium ions enter the synpatic knob and induces the fusion of synaptic vesicles with the pre- synaptic membrane.
                                      ↓
Synaptic vesicles release the neurotransmitter in the synaptic cleft by exocytosis.
                                     ↓
Neurotransmitters are recieved by receptors on post synaptic membrane.
                                    ↓
Binding of neurotransmitters causes the voltage gated sodium ion channels to open
and allow the influx of sodium ions in post- synaptic neuron.
                                        ↓
Sodium ions generate action potential in post synaptic neuron.
                                       ↓
To avoid the continous stimulation of neuron, enzyme acetylcholinesterase, in synaptic cleft, breaks the acetylcholine into choline and acetate and the choline molecules are then returned back to synaptic knob.

 

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