Olfaction Flashcards
The olfactory bulb containes 4 types of cells
Output cells - Mitral Tufted Cells
Inhibitory interneurons - Periglomerular cells Granule Cells
Where do the Olfactory Neurons synapse on thedendrites of mitral and tufted cells (olfactory bulb)?
glomeruli
The fibers of the lateral olfactory tract terminates in 5 areas
What are they?
1) The anterior olfactory nucleus (AON)
2) anterior and posterior cortical nuclei of the amygdala,
3) the olfactory tubercle,
4) a portion of the entorhinal cortex
5) piriform cortex.
What sends axions to the ipsalateral olfactory bulb?
The anterior olfactory nucleus (AON)
What is considered the primary olfactory cortex and receaves the most olfactory inputs
Piriform cortex
Hyposmia
reduced ability to detect odors.
Anosmia
complete inability to detect odors
Parosmia
change in the normal perception of odors
Phantosmia
the sensation of an odor that isn’t there
What can cause hyposmia or absence of smell (anosmia)
A blow to the head
can shear or sever receptor axons passing through the cribiform plate. If axons are severed, there is often permanent anosmia, but if axons are slightly sheared there can be recovery due to receptor cell regeneration.
Olfactory hallucinations (phantosmia) can result from
lesions of the parahippocampal gyrus
produce hallucinations of repugnant odors
Focal seizures in the parahippocampal gyrus (uncinate seizures)
Diseases associated with olfactory deficits
Alzheimer’s
Parkinson’s
MS
Schizophrenia
Three types of taste bud papillae on the tongue
Fungiform
Circumvallate
Foliate
5 basic types of tastes
Sweet
sour
salty
umami
bitter
Three nerves that inneravate the taste sensation of the tongue
VII - chorda tympani (Facial Nerve) - anterior 2/3 of tongue
IX - Glossopharangeal - posterior 1/3 of tongue
X- Vagas nerve - pharnex
Where do all the taste nerve synapse?
Nucleus of the solitary tract
Where does the solitary tract synapse
Ipsalaterally on the ventroposterior medial of the Thalamus
Then on to the insular and frontal taste cortices
Hypogeusia –
reduced ability to taste
Ageusia –
complete loss of taste.
Dysgeusia –
a foul or metallic taste in the mouth
Glossopharyngeal Neuralgia
Damage to nerve IX occasionally produces attacks of severe pain in the throat that radiates to the neck and jaw.
Loss of Gag Reflex:
A somatosensory component relays touch, pain, temperature from the posterior tongue and pharynx, skin of the external ear and tympamic membrane. Absence of a gag reflex is an indicator of damage to nerve IX
Causes of taste disorders:
Genetics
Upper respiratory and middle ear infections (damage to nerve VII).
Chemotherapy/radiation therapy for cancers of the head and neck (destroys olfactory and gustatory receptor cells)
Surgeries – (i.e. middle ear surgery)
Chemical exposure or medications
Poor oral hygiene and dental problems
