Olfactory System

Question 1

the olfactory system is the only sensory system that doesn’t ..?

Answer 1

make connections through the thalamus

it is a direct system to the cortex

Question 2

what is the olfactory system responsible for?

Answer 2

smelling

highly related to emotion; smells can triggue memory system (connection with the hippocampus)

elicits autonomic NS responses (salivation)–> hypothalamic connection

Question 3

what are olfactory receptor cells?

where are they located?

Answer 3

=chemoreceptors

located in the olfactory epithelium- in the walls and roof of the nasal cavity

axons of the receptors collect into the olfactory file
end in the olfactory bulb (lateral to optic chiasma)

axons are unmyelinated-very slow conduction

Question 4

what do projections from the olfactory bulb form?

what do these fibers also travel as?

Answer 4

the olfactory tract

many olfactory tract fibers travel as the “lateral olfactory tract” – the principal central projection pathway for the olfactory system

Question 5

fibers of the lateral OT go to what?

where is the olfactory info then projected to?

Answer 5

1- primary olfactory cortex (an area of cortex covering part of the amygdala, and a small, anterior region of the parahippocampual gyrus)
2- amygdala, anterior part of parahippocampal gyrus

then, the olfactory info is projected to:

• hypothalamus (connection b/w smell & ANS)
• limbic structures (hippocampus & the rest of the amygdala)
• thalamus

OT crosses at the anterior commissure; goes to anterior aspect of temporal lobe (uncus) and straight to temporal lobe

Question 6

what is the orbital cortex? what is it important for?

Answer 6

neocortex related to olfaction

important for discrimination and identification of odors

this area also important in taste and perceiving flavor of foods

Question 7

what is anosmia?

Answer 7

loss of the ability to smell

diagnostically useful in case of tumors growing on the base of the skull

pt is likely to complain less of a loss of smell than of a taste disorder

sensorineural olfactory deficits- caused by head injuries or neurodegenerative disease

Question 8

what is parosmia?

Answer 8

distortion of the usual sense of smell

odors perceived by usually with an unpleasant quality

Question 9

what are uncinate seizures?

Answer 9

seizures originating in the vicinity of the uncus

• may begin with an olfactory hallucination
• seizure may include chewing movements and feelings of deja vu

Question 10

what is ageusia?

Answer 10

loss of taste sensations

Question 11

what are the 2 general processes that disrupt the sense of smell?

Answer 11

1- Conductive olfactory deficit- processes that prevent odorants from reaching the olfactory epithelium (nasal polyps, septal deviations, inflammations)

2- Sensorineural olfactory deficit- processes that damage olfactory receptor neurons or parts of the olfactory CNS (head injuries, parkinson’s, alzheimer’s)

Question 12

what innervates the anterior 2/3 of the tongue?

posterior 1/3?

what nucleus in the BS? Functional component?

Answer 12

anterior 2/3= CN 7

posterior 1/3= CN 9

rostral part of the nucleus solitarius – GVA

Question 13

what are the 2 routes taste takes from the solitary nucleus ?

Answer 13

1- VPM nucleus of the thalamus
Relays to:
-S1- localization of tastes and tongue (primary somatosensory cortex)
-insula- primary taste (gustatory) cortex

2- Lateral hypothalamus & amygdala
-feeding role (homeostasis)

Question 14

in particular, the human OFC is thought to regulate what?

Answer 14

planning behavior associated with sensitivity to reward and punishment