The dendrite carries impulses

How many of the following cells are excitable?
Neuroglia,Muscle fiber,Fibroblast,Mast cell,Neuron,Macrophage

Which of the following statements is correct about the nodes of Ranvier?

On nerve fibres,to prevent the leakage of an impulse,a layer of ...... is found.

In the following list,how many structures are included in grey matter?
Cell body,myelinated axon,unmyelinated axon,and dendron.

Choose the correct statements about Nissl's granules from the codes given below:
$I.$ There are regular masses of ribosomes
$II.$ There are irregular masses of ribosomes and $ER$
$III.$ There are granular bodies
$IV.$ They synthesise proteins in the cell