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year 2 - neuroscience > Olfaction & The Limbic System > Flashcards

Olfaction & The Limbic System Flashcards

1
Q

What is the olfactory system?

A

Sense of smell!

Can smell between 2000-4000 different odours

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2
Q

Anatomy of the olfactory system?

A

The epithelium contains:
o bipolar olfactory neurones
o sustentacular cells
o basal cells

There is progressive loss of olfactory epithelium with age

The olfactory bulb projects neurones through fenestrations in the ethmoid bone

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3
Q

What is the olfactory pathway?

A
  1. Olfactory bulb (mitral cells)
  2. Olfactory tract
  3. Olfactory stria (medial & lateral)
  4. Piriform cortex (lateral stria) and orbitofrontal cortex (medial stria)
  5. Connections to brainstem - promote autonomic responses
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4
Q

What is the clinical defect in smell known as?

A

Anosmia

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5
Q

Relationship between epilepsy and smell?

A

In SOME patients, prior to seizures they begin to smell something that isn’t there - knows as

PRODROMAL AURAS

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6
Q

What is an early target for many pathologies in the olfactory pathway?

A

Olfactory bulbs

i.e. in people with Parkinson;s

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7
Q

Locations of the Olfactory pathway?

A

ONENOTE!!

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8
Q

Why is the Limbic System named ‘limbic’?

A

Due to close adherence to the limb of the corpus callosum (Ludleys!!)

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9
Q

Functions of the Limbic System

A

Responsible for processes aimed at survival of the individual

o Homeostasis
- activation of visceral effector mechanisms, modulation of pituitary hormone release, initiation of feeding & drinking

o Agonistic behaviour - defence & attack

o Sexual & reproductive behaviour

o Memory

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10
Q

What is the Limbic System compsoed of?

A

o Olfactory bulbs

o Hypothalamus

o Amygdala

o Hippocampus

o Thalamus

o Frontal lobe

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11
Q

Describe the Papez Circuit

ONENOTE!!

A

Hippocampus –> hypothalamus –> Anterior nucleus of thalamus –> cingulate cortex (neocortex inputs here)

o Neocortex - contributes things such as previous memory (emotional colouring)
o Cingulate cortex (emotional experience)
o Hypothalamus (emotional expression)

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12
Q

Tracts that take neural information to different parts of the Papez Circuit (output tract)?

A

o Cingulate cortex –> hippocampus
via. Cingulum bundle

o Hippocampus –> Hypothalamus
via. Fornix

o Hypothalamus –> anterior nucleus of thalamus
via. MTT (mammilla-thalamic tract)

o ANofT –> CC
via. thalamo-cortical projections

Fornix = specifically projects to the mammillary bodies of the hypothalamus

Cingulum bundles run along the midline of the corpus callosum

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13
Q

Function of Papez Circuit?

A

Neural circuit for the control of emotional expression

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14
Q

DTI?

A

Diffusion Tensor Imaging

Used to theorise the pathways/networks in the brain
o to highlight parts of the brain that are interconnected when performing certain actions/functions (e.g. crying)

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15
Q

Main connections of the Hippocampus?

A

Afferent = Preforant pathway
o Entorhinal cortex receives input from all other part of the brain for the hippocampus

Efferent = Fimbria –> fornix
o known as the fimbria
o while the path is attached to the hippocampus, when it leaves, becomes the fornix

ONENOTE!!

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16
Q

Function of the Hippocampus?

A

Memory & learning

17
Q

Clinical importance of Hippocampus?

A

Alzheimer’s & epilepsy

18
Q

Where is the Hippocampus?

A

Medial temporal lobe

19
Q

How does Alzheimer’s Disease present

A

Presents with severe CORTICAL ATROPHY with a particularly affected hippocampus

20
Q

Tau immunostaining?

A

In Alzheimer’s
o Sporadic tau proteins in the brain become hyper-phosphorylated
o HENCE this stops the proteins from functioning so they die

21
Q

Senile plaques?

A

Alpha-beta proteins build up in Alzheimer’s
o when there is too much, the cells excrete it
AND
o the proteins form toxic plaques

22
Q

Anatomical progression of Alzheimer’s?

A

Early:
o Affected - hippocampus & entorhinal cortex
o Symptoms - short-term memory loss

Moderate:
o Affected - Parieral lobe
o Symptoms - dressing apraxia (inability to perform purposive actions)

Late:
o Affected - Frontal lobe
o Symptoms - loss of executive skills (e.g. recognition)

23
Q

Main connections of the Amygdala?

A 
Afferent
 o Olfactory cortex
 o Septum
 o Temporal neocortex
 o Hippocampus
 o Brainstem

Efferent
o Stria terminalis

24
Q

Function of the Amygdala?

A

Fear and anxiety (and opposite)

Fight or flight

25
Q

Location of the Amygdala?

A

This is buried in the white matter of the anterior temporal lobe

26
Q

Clinical importance of the Amygdala?

A

Kluver-Bucy Syndrome
o post-trauma, temporal lobes are sheared off middle cranial fossa & amygdala is damaged

Symptoms
 o hyperorality
 o loss of fear
 o visual agnosia
 o hypersexuality
27
Q

What is an issue brought by the Amygdala when seeing sections of the brain?

A

Can NOT see the horns of the ventricles in coronal sections of the brain with the amygdala

28
Q

What are the structures associated with aggression?

A

o Hypothalamus
o Brainstem - specifically, periaqueductal grey
o Amygdala

29
Q

What can aggression be stimulated by?

A

5-HT and serotonin release from the Raphe nuclei

30
Q

Main connections of the Septum?

A 
Afferent:
 o Amygdala
 o Olfactory tract
 o Hippocampus
 o Brainstem

Efferent:
o Stria medularis thalami
o Hippocampus
o Hypothalamus

31
Q

Functions of the Septum?

A

Reinforcement & reward (from the nucleus accumbens)

ONENOTE!!

32
Q

Main pathway that can be affected by drug dependence?

A

Mesolimbic pathway (using dopamine)

o MFB - Median Forebrain Bundle
o Midbrain projects dopaminergic neurons into the cortex, nucleus accumbens & amygdala

33
Q

Where does the Mesolimbic pathway project to?

A

Shows the VTN (ventral tegmental nucleus)
o projects neurons into the nucleus accumbens

ONENOTE!!

34
Q

What is the other dopaminergic pathway?

A

Dopaminergic neurons from the substantia nigra (in the midbrain) project to the basal ganglia

35
Q

Drugs that increase DA in the nucleus accumbens?

A 
o Opioids
o Nicotine
o Amphetamines
o Ethanol
o Cocaine
36
Q

What are the different ways that the drugs can increase DA?

A

o Stimulating midbrain neurons to release DA

OR

o Inhibiting DA re-uptake (e.g. cocaine)

Other NTs can also modify the system

year 2 - neuroscience (18 decks)

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