CN I: Olfactory nerve

Authors

Affiliations

Nate Yomogida, PT, DPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, PT, DPT

Doctor of Physical Therapy

B.A. in Neuroscience

• Type: Sensory
• Function: Sense of smell
• Dysfunction: Anosmia (loss of smell)

flowchart TD
  A[Nose] -- smell --> B["Cribriform plate"]
  B --> C["Olfactory Sulci"]
  C -- Skips Thalamus --> D["Olfactory Tract"]
  D --> E[Olfactory Bulb]
  
  E --> F[Insula gustation but i wrote that this was wrong]
  E --> G[Piriform Cortex]
  E --> H[Amygdala]
  E --> I[Entorhinal Cortex]

  F --> J{Gustation}
  G --> K{Olfaction processing}
  H --> L{Emotion of Fear}
  I --> M{Formation of Memory}

Central Olfactory Structures

Pathway:

First order neurons:

1. Smell is detected by specialized chemoreceptors on bipolar primary sensory neurons found in the olfactory neuroepithelium¹
2. Olfactory nerve (made up of axons combined with other receptor cell axons)¹
3. Pass through Cribriform plate of Ethmoid bone¹
4. Terminate on the olfactory bulb (main relay station of olfactory pathway)¹

Second order neurons:

1. Olfactory tract
2. Split: Medial & Lateral striae
   1. Medial Stria: Projects to subcallosal gyrus
   2. Lateral Stria: continues on to Parahippocampal gyrus

Relevant Structures

The olfactory nerve does not have peripheral ganglia

Olfactory cortex: no single structure - Piriform cortex: - Located: Below lateral olfactory stria - Function: Olfactory processing - Amygdala: - Located: Anterior to Temporal/Inferior horn of Lateral Ventricle - Function: Emotion & Fear - Entorhinal cortex: - Location: Anterior part of Parahippocampal gyrus - Function: Formation of Memory

Pupillary light reflex

CN2 is involved in the pupillary light reflex

Dysfunction

• Anosmia

References

1.

Blumenfeld H. Neuroanatomy Through Clinical Cases. 3rd ed. Oxford university press; 2022.