CN 1: Olfactory Nerve (Scheme, Pathway, Clinical Relevance) | Neuroanatomy
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Content:
0:00 Introduction
00:49 Olfactory Nerve Scheme
02:43 Olfactory Nerve and Epithelium
04:11 How Do We Detect Smells?
06:14 Mechanism of Odorant Signal Transduction
07:20 Olfactory Nerve
08:00 Olfactory Bulb
09:27 Olfactory Pathway
10:12 Lateral Olfactory Stria
14:13 Medial Olfactory Stria
14:40 Intermediate Olfactory Stria
15:15 Anosmia and Dysosmia
18:29 Recap
Olfactory Scheme / Overview:
Smell - Olfactory Nerves - Olfactory Bulb - Olfactory Tract - Olfactory Trigone - Lateral Stria, Medial Stria and Intermediate stria
Olfactory Epithelium:
Pseudostratified Columnar epithelium (supporting cells)
Consists of: Basal Cells, Sustentacular Cells, Olfactory gland cells (Bowmans glands), Olfactory receptor neurons
Olfactory neurons are bipolar neurons
How we detect smell:
Odorants enters nasal cavity through either nasal opening or nasopharynx.
Olfactory Neuron:
Dendrites detect smell through a g-protein couples membrane receptor.
Signals pass through the cell body and axon
Axons form nerve bundles (fila olfactoria)
Olfactory Bulb (bulbus olfactorius):
Mitral Cells
Olfactory Glomerulus (glomeruli)
Tufted Cells
Amacrine Granular Cells
Periglomerular Cells
Olfactory Pathway:
Olfactory Bulb to the Olfactory Tract
When the tract gets closer to the olfactory tract, it widens as the Olfactory Trigone (trigonum olfactorium) and divides into Lateral olfactory stria, Medial olfactory stria and intermediate olfactory stria.
Lateral Olfactory Stria (stria olfactoria lateralis)
Towards Primary Olfactory Cortex, which sends information to secondary olfactory cortex
Medial Olfactory Stria (stria olfactoria medialis):
Go towards the subcallosal gyrus (part of limbic system)
Intermediate Olfactory Stria (stria olfactoria intemedialis):
Goes towards the olfactory Tubercle (part of the limbic system and the rewards system)
Clinical Relevance:
Anosmia: Temporary or permanent loss of the sense of smell
Dysosmia: Distortion of the perception of smell
Parosmia: Normal smell smell and taste unpleasant/disgusting
Phantosmia: Detect smells that aren't really there in your envirnoment
Sources:
Singh, I. (2017). Human neuroanatomy (10th ed.).
Olfaction: The Sense of Smell (biology-pages.info)
Physiology, Olfactory - StatPearls - NCBI Bookshelf (nih.gov)
Olfactory Nerve | Radiology Key
Frontiers | Effects of odor on emotion, with implications (frontiersin.org)
Other sources used;
Helwany M, Bordoni B. Neuroanatomy, Cranial Nerve 1 (Olfactory) [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NB...
Kozlowski, T. (2017). Memorix Anatomy: The Complete Study Guide. 2nd ed. Thieme Medical Publishers.