OLFACTORY (I) NERVE

OLFACTORY NERVE: Ist CRANIAL NERVE

• Special visceral afferent nerve 

• Mediates sense of smell (olfaction).

• Pure sensory nerve.

Olfactory nerve has following unique features:-

• The primary olfactory neurons lie at the body surface in the epithelium lining the roof of nasal cavity (olfactory epithelium).

• The primary olfactory neurons undergo continuous turnover being replaced from stem cells in the olfactory epithelium.

• It is the only cranial nerve that projects directly to forebrain (telencephalon).

• The olfactory neurons enter the allocortex directly without relaying through thalamus.

• The olfactory pathway to highest cortical center is ipsilateral.

Termination– Glomerulus of the olfactory bulb.

Olfactory Pathway:

                        First order neuron

                (Present in olfactory epithelium)

                          Olfactory nerve

                                  ↓

                       Second order neuron

                    (Present in olfactory bulb)

                                  ↓

                         Olfactory tract

                                  ↓

                 Ends in Pre-piriform & piriform cortex

                     (Primary olfactory cortex)

                      Receives smell sense

                                  ↓

                    Uncus & para hippocampus

                   (Secondary olfactory cortex)

                                  ↓

                     Receives smell sense

APPLIED ANATOMY:

• During fracture of anterior cranial fossa- olfactory nerves may separate from olfactory bulb and cerebrospinal fluid (C.S.F) leaks through nose-Rhinorrhoea.

• Anosmia- loss of smell sensation-eg. in Rhinitis.

• Parosmia– Preverted sense of smell.

• Caprosmia-unpleasent odour due to decomposition of the tissue of the individiual- bad smell is felt during expiration.

Don’t Forget to Solve all the previous Year Question asked on OLFACTORY (I) NERVE
Click Here to Start Quiz