Olfaction and the limbic system

Question 1

Recall the composition of the olfactory epithelium

Answer 1

Bipolar olfactory neurons
Sustentacular cells
Basal cells

Question 2

Recall the structure of the olfactory system

Answer 2

Made up of an olfactory bulb and tract, bilaterally

Question 3

What cells make up the olfactory bulb?

Answer 3

Mitral cells (second order neurons)

Question 4

Where in the olfactory system is pathology seen in Parkinson’s disease?

Answer 4

Olfactory bulb

Question 5

In which regions of the cerebrum does olfactory processing take place?

Answer 5

Piriform and orbitofrontal cortices

Question 6

Why does smelling something tasty lead to salivation?

Answer 6

Olfactory connections to the brainstem cause autonomic responses

Question 7

What is the clinical significance of the location of the brain regions involved in smell?

Answer 7

Piriform cortex is in temporal lobe
Temporal lobe often involved in epilepsy
Epileptics can often detect a prodromal aura

Question 8

What is the term given to an absence of a sense of smell?

Answer 8

Anosmia

Question 9

What does “limbus” mean and how does this describe the location of the limbic system?

Answer 9

Limbus = rim

= rim of cortex adjacent to corpus callosum and diancephalon

Question 10

What is the general function of the limbic system?

Answer 10

Aimed at survival of individual

Question 11

Recall 4 behaviours that are controlled by the limbic system

Answer 11

Homeostasis (nutrition)
Agonistic behaviour
Sexual behaviour
Memory

Question 12

What are the key structures that make up the Papez circuit and where are they located?

Answer 12

Hippocampus
Amygdala
= temporal lobe

Question 13

Recall the afferent and efferent pathways connected to the hippcampus

Answer 13

Afferent: Perforant pathway
Efferent: fornix

Question 14

What is the alternative name for the fornix?

Answer 14

Fimbria

Question 15

What are the functions of the hippocampus?

Answer 15

Short term memory and learning

Question 16

Recall 2 pathologies of the hippocampus

Answer 16

Alzheimer’s (severely shrinks hippocampus)

Epilepsy

Question 17

Describe the location and connections to the hippocampus of the amygdala

Answer 17

In white matter - has connecting fibres to hippocampus but no absolute connections

Question 18

Where are the mamillary bodies located?

Answer 18

Other end of fornix to hippocampus

Question 19

Recall the areas of the brain affected by Alzheimer’s as the disease progresses

Answer 19

Hippocampus –> parietal lobe –> frontal lobe

Question 20

Describe the connection of the mamillary bodies to the thalamus

Answer 20

Connected to arcuate nucleus

Connected via mamillo-thalamic tract

Question 21

Recall the main afferent anf efferent connections of the amygdala

Answer 21

Afferent: (BOTH SETS)
1. Olfactory cortex
2. Septum
3. Temporal neocortex
4. Hippocampus
5. Brainstem
Efferent: 
Stria terminalis

Question 22

What is the function of the amygdala?

Answer 22

Producing feelings of fear/ anxiety

Question 23

What pathology is associated with loss of amygdala function?

Answer 23

Kluver-Bucy syndrome:

bilateral lesions of anterior temporal lobe including amygdaloid nucleus

Question 24

Recall the symptoms of Kluver-Bucy syndrome

Answer 24

Hyperorality
Hypersexuality
Loss of fear
Visual agnosia

Question 25

Where is the septum pellucidum located?

Answer 25

Between the 2 lateral ventricles in the brain

Question 26

Recall the afferents and efferents of the septum pellucidum?

Answer 26

Afferent:
amygdala
olfactory tract
hippocampus
brainstem
Efferent:
Stria medularis thalami
hippocampus
hypothalamus

Question 27

Where are the septal nuclei located?

Answer 27

Base of the septal membrane

Question 28

What is the function of the septum?

Answer 28

Reinforcement and reward

Question 29

Which pathway mediates drug dependence?

Answer 29

Mesolimbic pathway (Dopaminergic)

Question 30

Where in the midbrain can dopaminergic neurons be found?

Answer 30

Ventral tegmental area

Question 31

Where is the ventral tegmental area of the brainstem?

Answer 31

Just medial to the substantia nigra in the midbrain

Question 32

Describe the projection of dopaminergic neurons that originate in the VTA

Answer 32

Project via medium-forebrain bundle to nucleus accumbens

Question 33

What effect do drugs of abuse have on dopamine

Answer 33

Increase DA release in the nucleus accumbens