Cranial Nerves + The Eye (2nd copy) PDF - Olfactory Nerve

CN I: Olfactory Nerve Function: Special visceral sensory only → Smell Course: Shortest cranial nerve Olfactory receptors in the nasal epithelium detect smell These assemble into olfactory fascicles (nerve bundles) which penetrate the cribriform plate to enter the cranial cavity These bun...

CN I: Olfactory Nerve Function: Special visceral sensory only → Smell Course: Shortest cranial nerve Olfactory receptors in the nasal epithelium detect smell These assemble into olfactory fascicles (nerve bundles) which penetrate the cribriform plate to enter the cranial cavity These bundles then enter the olfactory bulb (an ovoid structure) where they synapse with mitral cells at the olfactory glomeruli 2nd order neurons pass into the olfactory tract which divides into medial and lateral stria to reach to primary olfactory cortex The Olfactory Mucosa Responsible for detecting smell and some aspects of taste Located in the roof of the nasal cavity Pseudostratified columnar epithelium with: ○ Basal cells - form new stem cells from which new olfactory cells develop ○ Sustentacular cells - structural support ○ Olfactory receptor cells -bipolar neurons consisting of two processes Dendritic process: Projects to the surface of the epithelium where it projects short cilia (olfactory hair) into the mucous membrane to react with odors in the air Central process (axon): Projects through the basement membrane CN I Pathology - Anosmia Absence of the sense of smell It is caused by damage or disruption to CN I. There are 4 types: Temporary ○ Infection (e.g. meningitis) ○ Local disorders of the nose (e.g. common cold, COVID-19!) Permanent ○ Head injury ○ Tumours in the olfactory groove (e.g. meningioma) Progressive ○ Parkinson’s ○ Alzheimer’s ○ In neurodegenerative conditions it is progressive and often precedes motor symptoms but may not be noticed by the patient Congenital ○ Kallmann syndrome (failure to start or finish puberty) ○ Primary Ciliary Dyskinesia (defective, immobile cilia)