Q1..) Describe the conduction of nerve impulse through a neuron

Q2..) Describe the conduction of impulse through a synapse

(1) POLARISED MEMBRANE /  RESTING  POTENTIAL
     In resting phase when neuron is not conducting an impulse , the axonal  membrane is called polarised. this is due to concentration of ions across the axonal membrane .
      AT REST 
  • Axoplasm inside  the axon contain high conc. of K+ and low conc. ofNa+.
  • the fluid outside the axon contain low conc. of K + and high conc. of Na+ .
As a result the outer  surface of axonal membrane is positively charged and inner surface is negatively charged .the electric potential difference across the resting plasma membrane is called resting potential .
    Action potential : when a nerve fibre is stimulated the permeability of membrane to Na+ is greatly increased at the point of stimulus (rapid infiux of Na+ ) and hence polarity of membrane is reversed and now membrane is said to be depolarised . The electric potential difference across the plasma membrane at that site is called action potential , which infact termed as nerve impulse.
depolarisation is very rapid , so that conduction of nerve impulse along the entire length of axon occures in fractions of second.

(2). TRANSMISSION OF IMPULSES AT SYNAPSE
  • ​​At electrical synapses: here the membrane of pre and post -syneptic neuronare invery close proximity. Electric current can flow directly from one neuron  into other across these synapses, like impulse conduction along a single axon.
  • AT CHEMICAL SYNAPSES:Here the membrane of pre and post -synaptic neuron are separated by fluid filled space called synaptic cleft. Neurotransmitter are involved  here .
when an  impulse arrives at the axon terminal,it stimulates the movement of the synaptic vesicles towards membrane and they fuse with the plsama membrane and release their neurotransmitter in the syneptic cleft . these chemicals blind tospecific receptor, present on the post -syneptic membrane . Their binbing opens ion channels and allow the entry of ion which generate new potential in post synaptic neuron.
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