Olfactory Nerve Flashcards
Where is the olfactory epithelium
It lies above the superior conchae in the nasal passages
How do olfactory receptor neurons work
Within the epithelium they send their axons through the cribriform plate of the ethmoid bone into the olfactory bulb
What does each olfactory neuron contain
G protein coupled receptors (GPCRs) that bind only one type of odour molecule
Where does the sensory pathway reach
The cerebral cortex NOT passing through thalamus
What is the olfactory pathway
Olfactory receptor cells - olfactory nerves - olfactory bulb - olfactory tract - olfactory striae - olfactory cortex
What are olfactory receptors
Specialised ciliated bipolar nerve cells that lie in olfactory epithelium
What are groups of 15-40 olfactory receptors ensheathed with at basement membrane level
Glial cells
How is a stimuli received and passed on through an axon
At its dendrite from apical pole and conducts them to axon from basal pole
How are fila olfactoria created
Once axon penetrates through basement membrane it joins other non myelinated processes to form this
What is fila olfactoria
Bundles of olfactory axons
What do olfactory receptor cells have
Microvilli which extend into the aqueous and mucous fluid of the nasal epithelium
What is the purpose of the microvilli in the olfactory receptors
They form a mat on surfaces of the nasal epithelium so lipid and water soluble odour molecules must dissolve in the fluid to reach the receptor membrane
What do mitral cells do
Project along the olfactory bulbs to higher brain centres
What do olfactory receptor cells contact with
The dense dendrites of the second order mitral cells in spherical glomeruli
Where does the olfactory bulb lie
In olfactory groove within anterior cranial fossa above ethmoid bone and below frontal lobe
What is the synaptic glomeruli
Where olfactory nerve fibres synapse with mitral cells forming the collections known as this
What happens from the glomeruli
Second order nerves pass posteriorly into olfactory tract
Where does the olfactory tract run
Posteriorly to inferior surface of frontal lobe
What does the olfactory tract spilt into
Medial and lateral olfactory striae
What does the medial stria (root) do
Carries axons and crosses midline
Connects olfactory centres of 2 cerebral hemispheres
What does the lateral stria (root) do
Carries olfactory fibres to end in cortex of uncus and adjacent hippocampal gyrus
What does the primary olfactory cortex do
Sends nerve fibres to many other areas of brain
Receives and process sensory input and is involved in memory and appreciation of olfactory sensations
How is special sensory smells detected
By olfactory mucosa located in roof of nasal cavity composed of pseudostratified columnar epithelium
What 4 types of cells does the olfactory mucosa contain
Basal cells
Sustentacular cells
Olfactory receptor cells
Bowman’s glands
What do basal cells do
Form new stem cells which new olfactory cells can develop
What do sustentacular cells do
Tall cells for structural support
Analogous to glial cells located in CNS
What are the 2 process in olfactory receptor cells
Dendritic process
Central process
What is the dendritic process
Projects to surface of epithelium where they project a number of short cilia into mucous membrane
React to odours in air and stimulate olfactory cells
What is the central process
Axon - projects in opposite direction through basement membrane
What does the bowman’s glands do
Secrete mucus
