Olfaction & The Limbic System Flashcards

1
Q

What is the olfactory system?

A

Sense of smell!

Can smell between 2000-4000 different odours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the clinical defect in smell known as?

A

Anosmia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

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

A

Olfactory bulbs

i.e. in people with Parkinson;s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Locations of the Olfactory pathway?

A

ONENOTE!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is the Limbic System named ‘limbic’?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the Limbic System compsoed of?

A

o Olfactory bulbs

o Hypothalamus

o Amygdala

o Hippocampus

o Thalamus

o Frontal lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Function of Papez Circuit?

A

Neural circuit for the control of emotional expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
Location of the Amygdala?
This is buried in the white matter of the anterior temporal lobe
26
Clinical importance of the Amygdala?
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
What is an issue brought by the Amygdala when seeing sections of the brain?
Can NOT see the horns of the ventricles in coronal sections of the brain with the amygdala
28
What are the structures associated with aggression?
o Hypothalamus o Brainstem - specifically, periaqueductal grey o Amygdala
29
What can aggression be stimulated by?
5-HT and serotonin release from the Raphe nuclei
30
Main connections of the Septum?
``` Afferent: o Amygdala o Olfactory tract o Hippocampus o Brainstem ``` Efferent: o Stria medularis thalami o Hippocampus o Hypothalamus
31
Functions of the Septum?
Reinforcement & reward (from the nucleus accumbens) ONENOTE!!
32
Main pathway that can be affected by drug dependence?
Mesolimbic pathway (using dopamine) o MFB - Median Forebrain Bundle o Midbrain projects dopaminergic neurons into the cortex, nucleus accumbens & amygdala
33
Where does the Mesolimbic pathway project to?
Shows the VTN (ventral tegmental nucleus) o projects neurons into the nucleus accumbens ONENOTE!!
34
What is the other dopaminergic pathway?
Dopaminergic neurons from the substantia nigra (in the midbrain) project to the basal ganglia
35
Drugs that increase DA in the nucleus accumbens?
``` o Opioids o Nicotine o Amphetamines o Ethanol o Cocaine ```
36
What are the different ways that the drugs can increase DA?
o Stimulating midbrain neurons to release DA OR o Inhibiting DA re-uptake (e.g. cocaine) Other NTs can also modify the system