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Neuroscience and Mental Health > 16. Olfactory and limbic system > Flashcards

16. Olfactory and limbic system Flashcards

1
Q

Where are the 2 olfactory bulbs located?

A

Inferior surface of the frontal lobes

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2
Q

Describe the olfactory epithelium

A 
• Upper part of the nose
• Bipolar primary olfactory neurones
- sustentacular cells support these
• Basal cells exist - produce new olfactory cells
- lost with age
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3
Q

What projects through the cribriform plate?

A

Bipolar olfactory receptor cells project through it, into the olfactory bulb

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4
Q

What are the cells in the olfactory bulb called?

A
  • Mitral cells

* Glomerular like structures int their interactions with the first order olfactory neurones

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5
Q

Where do the second order olfactory neurones project to?

A

(mitral cells)
• Olfactory tract lies on the inferior surface of the frontal lobe
• Split into medial and lateral olfactory stria

• Project to the olfactory processing centres

  • piriform cortex of the temporal lobe
  • orbitofrontal cortex

(promotes autonomic responses)

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6
Q

What is a prodromal aura?

A
  • A smell that gives an indication of the onset of a disease
  • e.g. a seizure in temporal lobe epilepsy
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7
Q

What is a common cause of anosmia?

A

Mid-face trauma

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8
Q

What are the theories for an environmental trigger of Parkinson’s?

A
  • Stimulation through the gut
  • Up the vagus nerve to the brainstem
  • Diarrhoea is a presenting symptom
  • Through the nose
  • Anosmia is a presenting symptom
  • Pathology in the olfactory bulb is an early aspect of the disease
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9
Q

What is the limbic system?

A
  • Rim of the cortex adjacent to the corpus callosum and diencephalon
  • Consists of structurally and functionally interrelated areas considered as a single functional complex
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10
Q

The limbic system is responsible for which processes aimed at the survival of an individual?

A
  • Maintenance of homeostasis (hypothalamic function), modulation of pituitary hormone release and feeding + drinking
  • Agonistic behaviour (fight or flight)
  • Sexual and reproductive behaviour
  • Memory - vital in terms of emotional response to stimuli
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11
Q

Describe the Papez circuit

A

Neural circuit for the control of emotional expression
• Fornix is the main output pathway of the hippocampus - comes out of the inferior horn of the lateral ventricle
• Fibres go under the corpus callosum and synapse in the mammillary bodies (in the hypothalamus)
• Mammillo-thalamic tract (MTT) projects to the anterior nucleus of the thalamus
• Thalamo-cortical projections go to the cingulate cortex - emotional experience
• Loop completed by fibres projected back to the hippocampus via the cingulate bundle
• Neocortex has input - emotional colouring based on previous experience

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12
Q

Describe the afferent connections of the hippocampus

A
  • Called the perforant pathway
  • Main connections from the adjacent (entorhinal) cortex, which receives input from every other neocortical area itself
  • Part of memory encoding process
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13
Q

Describe the efferent connections of the hippocampus

A
  • Called the fimbria/fornix

* Part of the Papez circuit

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14
Q

What are the functions of the hippocampus?

A
  • Memory

* Learning

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15
Q

Where is the amygdala located?

A
  • Nucleus buried in the white matter

* In the anterior part of the temporal lobe

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16
Q

Where are the inter-locking cells of the dentate gyrus and the pyramidal cells located?

A

In the hippocampus

17
Q

Where is the hippocampus located?

A

Medial temporal lobe

18
Q

What happens to the hippocampus structure in Alzheimer’s disease?

A

Severe shrinking (atrophy)

19
Q

Describe the pathology of Alzheimer’s disease at a cellular leve?

A
  • Tangles - abnormal cytoskeleton proteins
  • Cytoskeleton breaks down and neuronal cell function breaks down
  • Different susceptibilities - some cells not affected
  • Senile plaques - protein disturbs memory function
20
Q

Describe the progression of Alzheimer’s disease?

A
  • Early on - spreads to hippocampus/entorhinal cortex => short term memory problems
  • Moderate - spreads to parietal lobe => dressing apraxia
  • Late - spreads to frontal lobe => loss of executive skills
21
Q

Where does the efferent of the amygdala go to?

A

Hypothalamus (Stria terminalis pathway)

22
Q

What are the functions of the amygdala and what can damage lead to?

A
  • Fear and anxiety
  • Fight or flight
  • Damage => Kluver-Bucy syndrome
23
Q

What is Kluver-Bucy syndrome?

A
  • Reversion to the basis survival instincts and exploration of the environment
  • Become completely fearless
  • Hyperorality (putting things in mouth), visual agnosia, hypersexuality, compulsive eating
24
Q

Where is the septum/septal nuclei and what is its function?

A
  • Septum is the membrane between the two lateral ventricles anteriorly
  • Septal nuclei are at the base of the septum
  • Function - reinforcement and reward
25
Q

What are retrograde fibres

A

Fornix (hippocampus => mammillary bodies)

This pathway also picks up some reverse fibres going from the septum to the hippocampus

26
Q

If you implant an electrode in the septal nuclei in a rodent and stimulate it, how will its mood change, and why is this clinically significant in humans?

A

• Rodent becomes happy
• Humans have an analogous areas
- potential area for deep brain stimulation
- used to reduce tremor in Parkinson’s

27
Q

Which structures have been shown to experimentally associated with aggression?

A

• Hypothalamus
• Brainstem (periaqueductal grey matter)
• Amygdala
(• Serotonin in the raphe nuclei of the brainstem)

28
Q

Describe the mesolimbic pathway (dopamine)

A

• A second dopaminergic pathway
• Comes from the ventral tegmental area (VTA) - also in the midbrain
• Projections go via medial forebrain bundle (MFB) to:
- cortex
- amygdala
- nucleus accumbens (important in drug dependece)

29
Q

Where is the ventral tegmental area located compared to the substantia nigra?

A

VTN is more medial

30
Q

Where do the dopaminergic neurones of the substantia nigra project to?

A

Basal ganglia

31
Q

How do all drugs of abuse affect the nucleus accumbens?

A

Increase dopamine release in the nucleus accumbens
• Stimulate midbrain neurones
• Promote DA release
• Inhibit DA reuptake e.g. cocaine

Neuroscience and Mental Health (17 decks)

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