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Year 2 - LCRS - Neuroscience and Mental Health > Limbic System > Flashcards

Limbic System Flashcards

1
Q

Anosmia

A
  • Loss of smell

- can be an early sign of neuroegeneration

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2
Q

What is the loss of smell sensation called?

A

Anosmia

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3
Q

How many smells can humans detect?

A

2000 - 4000 odours

-> molecular mechanisms of smelling are largely unknown

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4
Q

What are the components of the olfactory epithelium?

A
  • bipolar olfactory neurons (from epithelium to olfactory bulb)
  • sustentacular cells (support cells)
  • basal cells (-> potential for production of new cells)
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5
Q

Does smell stay the same throughout life?

A

No, there is progressive loss of smell with age.

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6
Q

How do smells get transmitted to the brain?

A
  • bipolar neurones from olfactory epithelium travel through cribriform in ethmoid bone
  • synapse in the olfactory bulb with 2nd order neurones that make up the olfactory tract
  • the olfactory tracts split into stria, one connecting to the piriform complex the other connecting to the orbitofrontal cortex
  • there are also some connections to the brainstem -> salivation
  • molecular mechanisms of small are not known.
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7
Q

What are some causes of anosmia?

A
  • midface trauma

- it is an early sign of neurodegenerative disease, e.g. PD

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8
Q

How do some people detect that they will have a seizure?

A
  • some poeple sense a certain smell hat they associate with having a seizure
  • a lot of epilepsy is associated with the temporal lobe = prodromal aura
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9
Q

piriform cortex

A
  • in the temporal lobe

- its function relates to smell

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10
Q

What is the limbic system?

A

structurally and functionally interrelated areas concidered as a single functional complex

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11
Q

What are the functions of the limbic system?

A

System responsible for processes aimed at survival of the individual:

  • maintenance of homeostasis via activation of visceral effector mechanisms, modulation of pituitary hormone release and initiation of feeding and drinking
  • agonistic (defence & attack) behaviour (-> fight or flight)
  • sexual & reproductive behaviour
  • memory (memory is a huge part of emotional processing)
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12
Q

What are the components of the limbic system?

A
  • frontal lobe
  • thalamus
  • hippocampus
  • amygdala
  • hypothalamus
  • olfactory bulb
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13
Q

LIMBUS in latin

A

= border

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14
Q

What is the fornix?

A
  • c-shaped bundle fo nerve fibres that go from the hippocampus to the mammilary bodies of the hypothalamus and from there to the thalamus
  • also connects Hippocampus to the septal nuclei and nucleus accumbens
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15
Q

How does the paper circuit work?

A
  • There are projections from the hippocampus to the mammillary bodies of the thalamus called the fornix)
  • the hypothalamus is the main component of emotional expression / reaction
  • through he MTT (mamillo-thalamic-tract) signals go from the hypothalamus to the anterior nucleus of the thalamus
  • the anterior nucleus of the thalamus sends ifs to the consulate cortex.
  • the cingulate cortex has input from the neocortex (emotional colouring based on experiences). The neocortex feeds into the circuit.
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16
Q

What changes occur in the brain in depression?

A
  • there are no anatomical changes, post-mortems do not reveal anything
  • there are functional changes that can be seen in e.g. diffusion tensor imaging
17
Q

What are the main functions of the hippocampus?

A
  • memory and learning
18
Q

What are the main connections of the hippocampus?

A
  • Afferent: Perforant pathway

- Efferent/output: Fimbria/ fornix

19
Q

What are some clinical problems associated with the hippocampus?

A

Alzheimer’s disease, epilepsy

20
Q

What is the difference between fimrbria and fornix?

A

It is the same pathway. When it is physically attached to the hippocampus its the fimbria, as soon as it detaches it is called the fornix.

21
Q

Where is the hippocampus?

A

on the medial temporal lobe

22
Q

Where is the amygdala?

A
  • in the white matter of the temporal lobe
  • lying in front of the hippocampus
  • it is a grey matter nucleus embedded in the white matter of the temporal lobe.
  • different parts of the amygdala are more susceptible to neurodegeneration
23
Q

What are some structural changes in the brain that occur in Alzheimers?

A
  • enlargement of the ventricles
  • atrophy of the cortex -> brain shrinks
  • atrophy of the hippocampus
  • Tao – normal scaffolding within neurons is disturbed – tangles.
24
Q

What are the 2 microscopic components of AD?

A
  • tangles (in cell bodies of neurones?)

- plaques (protein pathology)

25
Q

Anatomical preogression of AD

A

Early

  • Hippocampus and entorhinal cortex
  • Short-term memory problems

Moderate

  • disease spreading to parietal lobe
  • Dressing apraxia

Late

  • Frontal lobe
  • Loss of executive skills, personality change

=> there is a fairly predictable course

26
Q

What are the main connections of the amygdala?

A
  • Afferent: Olfactory cortex, septum, temporal neocortex, hippocampus, brainstem
  • Efferent: Stria terminalis (= main output pathway, goes to more anterior parts of the hypothalamus)
27
Q

What are the main functions fo the amygdala?

A
  • fear and anxiety

- fight or flight

28
Q

What are some clinical problems associated with the amygdala?

A
  • Kluver-Bucy syndrome: has a number of features including a more basic view of the world, hyperorality, heightened fear, oral tendencies, memory loss, emotional changes, extreme sexual behavior
  • can be caused by lesions (e.g. trauma or infections) in the temporal lobe.
29
Q

Degeneration of the amygdala?

A

Different parts of the amygdala appear to have a different susceptibility to neurodegeneration.

30
Q

Kluver-bucy-syndrome?

A

Syndrome originally described in monkeys with bilateral temporal lobectomy

  • Hyperorality
  • Loss of fear
  • Visual agnosia
  • Hypersexuality
31
Q

Which structures in the brain are experimentally associated with aggression?

A
  • Hypothalamus
  • Brainstem (periaqueductal grey)
  • Amygdala

5-HT in raphe nuclei (serotonin) is the main NT here

32
Q

What are the main connections of the septal nuclei?

A
  • Afferent: Amygdala, olfactory tract, hippocampus, brainstem
  • Efferent: Stria medularis thalami, hippocampus, hypothalamus
33
Q

What are the main functions of the septal nuclei?

A

Reward and reinforcement

34
Q

Where are the septal nuclei?

A
  • by the septum (membrane lying between lateral ventricles)
35
Q

What is the mesolimbic pathway?

A
  • it is a dopaminergic pathway
  • reward pathway
  • originates in the midbrain (VTA)
  • travels to NAcc, cortex and amygdala via MFB (median forebrain bundle)
  • different than the nigrostriatal dopaminergic pathway that is affected in PD.
36
Q

What is the problem in PD?

A
  • problem in the dopaminergic projections from substantia nigra to basal ganglia
37
Q

What is the pathway in drug dependance?

A
  • projectionstions from ventral tegmental area to cortex, amygdala and nucleus accumbens
  • Opioids, nicotine, amphetamines, ethanol and cocaine all increase DA release in nucleus accumbens
  • Stimulate midbrain neurons, promote DA release or inhibit DA reuptake
  • Other neurotransmitters also modify this system
  • thought to be the basis of addiction - constant DOPAMINE release

=> mesolimbic pathway - reward pathway

38
Q

What is the entorhinal cortex?

A
  • area of the brain in the medial temporal lobe
  • Functions: memory, navigation, perception of time
  • main interface between the neocortex and the hippocampus
  • important for declarative memories (e.g. autobiography, semantic, episodic memories) and particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep
39
Q

Stria terminalis

A
  • Efferent pathway of the amygdala
  • goes to more anterior parts of the hypothalamus
  • Durch die Stria terminalis verlaufen Projektionen zum Hirnstamm, insbesondere zum Kreislauf-, Atem- und Brechzentrum in der Formatio reticularis. Sie wird aktiviert bei Anspannung, Stress und Sexualität.

Year 2 - LCRS - Neuroscience and Mental Health (21 decks)

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