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Neuro OBG > Olfaction and the Limbic System > Flashcards

Olfaction and the Limbic System Flashcards

1
Q

What the three types of cell that makes up the olfactory epithelium?

A

Bipolar Olfactory Neurones

Sustentacular Cells – support cells mainly providing metabolic support

Basal Cells – there is some regeneration in olfactory neurones

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2
Q

Where is the olfactory bulb found?

A

Sitting on top of the cribriform plate

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3
Q

Which cells synapse within the olfactory bulb?

A

The bipolar cells pass their axons through the cribriform plate to synapse with the second order neurones (olfactory bulb mitral cells) in the glomerulus within the olfactory bulb

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4
Q

What structure do the second order neurones form and what does this structure split into?

A

Olfactory tract

It splits to form the medial and lateral olfactory stria

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5
Q

Where does higher processing of smell take place?

A

Piriform Cortex

Orbitofrontal Cortex

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6
Q

What is a clinical deficit in the olfactory system called?

A

Anosmia- lack of smell

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7
Q

What is a common cause of anosmia?

A

Mid-face trauma

Impact with enough force could cause a fracture of the cribriform plate, shearing the neurones going from the olfactory epithelium to the olfactory bulb

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8
Q

The piriform cortex is found within the temporal lobe. Explain thesignificance of this with regards to epileptic patients.

A

Epilepsy is often focused in the temporal lobe

This means that some people with epilepsy will experience PRODROMAL AURA (they are made aware of an imminent seizure because they’ll smell something that’s not there)

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9
Q

Neurodegenerative disease is a relatively common cause of anosmia.

State two neurodegenerative diseases that could cause anosmia.

A

Alzheimer’s disease

Parkinson’s disease

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10
Q

What is the limbic system?/ what makes it up

A

A rim of cortex adjacent to the corpus callosum and diencephalon, responsible for general survival instinct

composed of olfactory bulbs, hypothalamus, amygdala, hippocampus, thalamus and frontal lobe

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11
Q

What are the roles of the limbic system?

A

general survival instinct:

  • Homeostasis (mainly hypothalamic functions such as regulation of food intake and pituitary hormone release)
  • Agonistic behaviour (fight or flight)
  • Sexual and reproductive behaviour
  • Memory
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12
Q

State two important parts of the limbic system that are found within the temporal lobes.

A

Hippocampus and Amygdala

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13
Q

What circuit are these structures (Hippocampus and Amygdala) a part of?

A

Papez Circuit

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14
Q

What is the cortical representation of the limbic system?

A

Cingulate Cortex

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15
Q

What is the function of the Papez circuit?

A

It is a neural circuit for the control of emotional expression

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16
Q

Describe/draw the papez circuit.

A

Hippocampus —via Fornix —> Mammillary Bodies of hypothalamus —via Mammillo-Thalamic Tract (MTT) —> Anterior Nucleus of the Thalamus –> Cingulate Cortex — via Cingulum Bundle —> Hippocampus

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17
Q

What conditions could damage the mammillary bodies leading to amnestic issues?

A

Chronic Alcoholism

Wernicke-Korsakoff Syndrome

18
Q

What is our emotional expression ‘coloured’ by?

A

Neocortex- ie contributes past experiences/ previous memory

19
Q

What form of imaging is used to study the limbic system?

A

Digital Tensor Imaging – shows co-instant activity in different parts of the brain thus showing which parts of the brain are working together

20
Q

Describe the afferent pathway of the hippocampus.

A

Afferent Pathway = Perforant Pathway

The entorhinal cortex is linked to the hippocampus via the afferent pathway (perforant pathway)
The entorhinal cortex receives input from all other parts of the neocortex

21
Q

What is the efferent pathway of the hippocampus called?

A

Fimbria/Fornix

22
Q

What are the functions of the hippocampus?

A

Memory and Learning

23
Q

What happens to the hippocampus in Alzheimer’s disease?

A

It shrinks severely

24
Q

Describe the spatial relations of the hippocampus and the fornix to other important brain structures.

A

The hippocampus is found on the floor of the lateral ventricles

The fornix comes out of the hippocampus and passes under the corpus callosum

It then dives inferior and anteriorly towards the mammillary bodies

25
Q

Describe the appearance of advanced Alzheimer’s disease on a CT head scan in the coronal plane.

A

There will be extensive cortical atrophy

The ventricles would appear enlarged

There will also be widening of sulci

26
Q

State two microscopic hallmarks of neurodegeneration.

A

Tau Immunostaining
 Intracellular pathology – the cytoskeleton has been compromised
 The tau proteins show up in the staining and allow the damaged neurones to be seen

Senile Plaques
 Extracellular pathology
 Lumps of protein (alpha-beta proteins) sitting in between cells in the neuropil

27
Q

Describe the anatomical progression of Alzheimer’s disease, including the symptoms experienced.

A

Early
 Hippocampus and entorhinal cortex affected
 Short-term memory problems

Moderate
 Parietal lobe affected (where you have your procedural memory)
 Example of effects: dressing apraxia

Late
 Frontal lobe
 Loss of executive skills

28
Q

Where is the amydala found?

A

In the white matter of anterior temporal lobe

29
Q

What are the afferent connections of the amygdala?

A

Olfactory Cortex

Septum (septal nuclei)

Temporal Neocortex

Hippocampus

Brainstem

30
Q

What is the main output pathway (efferent) of the amygdala?

A

Stria terminalis

31
Q

What is the function of the amygdala?

A

Fear and Anxiety

fight or flight

32
Q

In Alzheimer’s and Parkinson’s disease, the amygdala starts showing pathology early on. What are the possible outcomes of this?

A

Patients could either become terrified of everything or they could become totally disinhibited and become quite aggressive

33
Q

State and describe a syndrome affecting the amygdala.

A 
Kluver-Bucy Syndrome  
Bilateral lesions of the anterior temporal lobe (including amygdaloid nucleus) 
Symptoms :
 Hyperorality
 Hypersexuality
 Loss of Fear 
 Visual Agnosia
34
Q

State three structures associated with aggression.

A

Hypothalamus

Brainstem (periaqueductal grey matter)

Amygdala

35
Q

What are the main afferent connections of the septum?

A

Amygdala

Olfactory Tract

Hippocampus

Brainstem

36
Q

What are the functions of the septum?

A

Reinforcement and Reward

37
Q

Name another structure that is important in the reward system.

A

Nucleus Accumbens

38
Q

Name a structure that is important in drug dependence.

A

Nucleus Accumbens

39
Q

What effect do all drugs of abuse have on the nucleus accumbens?

A

They all increase dopamine release in the nucleus accumbens

40
Q

what is the mesolithic pathway

A

Ventral tegmental area (midbrain –> Nucleus accumbens

via MFB- median forebrain bundle

41
Q

which drugs increase dopamine in the nucleus accumbens

A 
opiods
nicotine
amphetamines
ethanol
cocaine

Neuro OBG (20 decks)

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