KATHOPNISHADA - CHAPTER 6 SHLOKA 16

                                                           शतं चैका च हृदयस्य नाड्य

                                                         -स्तासां मूर्धानमभिनिःसृतैका । 

                                                            तयोर्ध्वमायन्नमृतत्वमेति 

                                                        विष्वङ्ङन्या उत्क्रमणेभवन्ति ॥ १6

                                    SHATAN  CHA EKA CHA RHUDAYASYSA  NADYAS 

                                        TAASAM  MURDHANAM  ABHINISSRTA EKA |

                                      TAYA  URDHVAM  AAYAN  AMRUTAVAM  ETI 

                                        VISHVAM  ANYA UTKRAMNE BHAVATI  ||16

HUNDRED AND ONE ARE THE NERVES OF THE HEART OF THEM ONE PENETRATES

 CROWN OF THE HEAD -GOING UPWARD THROUGH IT ONE ATTAINS IMMORTALITY -

                             OTHERS LEAD  DIFFERENTLY (WORLDLY STATE) ||16

    This Shloka is interesting as it mentions something that has not been mentioned in entire Upanishad until now. The NASIS that are mentioned here are the nerves  and the one that pierces the crown is the SUSHUMNA nadi . We have spine  and inside the bony spine we have spinal cord  and the nerves come out of it . The spinal cord had 3 coverings. This is the GROSS body or STHULA SHARIR . The replica of this is in ASTRAL BODY or the SUKSHMA SHARIR  The coiled up energy is in lowest part of the spinal cord - in Astral or Sukshma or subtle body  and when one does meditation, the coiled up energy - called KUNDALINI rises up going through the CHAKRAS  and then finally reaches SAHASTAHAR  CHAKRA - one with has thousands of petals. There are 2 other channels -namely IDA and PINGALA. I think they may be parasympathetic and sympathetic chains.

     Normally the sensation is carried by nerves from the peripheral receptor via nerves through spinal cord to brain. Then the brain sends the command - via spinal cord through nerve to muscles or other areas . This is physical brain . But when we  send impulse from Kundalini up the SUSHUMNA NADI to the highest Chakra , then that is the final goal . Once we have done that at command then there is no cycle of birth and death. But if we continue to operate at the level of hundreds of nerves carrying impulses OUTWARDS from the Brain , then we continue have cycles of birth and death.

  In the previous Shlokas they have mentioned that the ATMA - BRAHMAN resides in the CAVE OF THE HEART  and that is why they are talking about the NADI from the Heart. Hundred means MANY and ONE is for the SUSHUMNA . So mention of hundred  and one.