2-Minute Neuroscience: Olfactory Nerve (Cranial Nerve I)

The olfactory nerve is also referred to as the first cranial nerve; it's responsible for transmitting information about olfaction, or smell, to the brain. In this video, I discuss the anatomy and function of the olfactory nerve, as well as describe what can happen when the nerve is damaged.

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I explain neuroscience topics in 2 minutes or less. In this installment I will discuss the olfactory nerve.

The olfactory nerve is a sensory nerve responsible for transmitting information about olfaction, or smell, to the brain. The nerve begins in the olfactory epithelium, a specialized collection of cells that lines the nasal cavity in humans. The olfactory epithelium contains millions of olfactory receptor cells. The axons of the olfactory receptor cells form bundles called fila that travel up through a structure called the cribriform plate, which is part of the bone called the ethmoid bone that separates the nasal cavity from the brain. The cribriform plate has holes that allow the fila to pass through it. The fila make up the olfactory nerve.

The olfactory nerve travels to an adjacent structure called the olfactory bulb, where it forms synaptic connections with several types of olfactory bulb neurons, like cells called mitral cells. These olfactory bulb neurons carry information about smell to the olfactory cortex as part of the olfactory tract.

Damage to the olfactory nerve can happen in a number of ways, such as head trauma or tumors. When the olfactory nerve is damaged, the sense of smell is affected. The deficits can include anosmia, which is a complete loss of the sense of smell, or varying levels of impaired or distorted olfaction. Olfactory nerve damage is also linked to abnormalities in flavor perception due to the role of the olfactory system in flavor. The ability to smell can be assessed through tests where patients are exposed to a variety of odorants and asked to identify them. An impaired sense of smell alone, however, can be due to a number of causes and doesn’t necessarily indicate olfactory nerve damage, so more testing must be done to verify the cause of the deficit.

Reference:

Doty RL, Bromley SM. 2007. Cranial Nerve I: Olfactory Nerve. In: Goetz CG, ed. Textbook of Clinical Neurology, 3rd ed. Philadelphia: Elsevier.