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BB2 > Structure & Function of the Limbic System > Flashcards

Structure & Function of the Limbic System Flashcards

1
Q

What is the limbic system?

A

Anatomical concept
Group of cortical and subcortical nuclei on medial aspect of frontal/parietal/temporal lobes
All interconnected by cortico-cortical pathways

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2
Q

What is the blood supply to the limbic cortex in the frontal and parietal lobes?

A

Anterior cerebral artery

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3
Q

What is the blood supply to the limbic cortex in the temporal lobe?

A

Posterior Cerebral artery

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4
Q

What part of the limbic cortex does the middle cerebral artery supply?

A

Tip of the temporal lobe and orbital cortex

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5
Q

What cortices make up the limbic cortex in the frontal and parietal lobes?

A

Orbito-frontal cortex

Cingulate cortex

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6
Q

What cortex makes up the third part of the limbic cortex?

A

Parahippocampal cortex in the medial temporal lobe

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7
Q

What does the limbic system do?

A
  • mediates sense of reward which you get from promoting survival (eating/drinking/sex)
  • mediates sense of unhappiness/misery when decrease chance of survival (pain when injured/depressed when you fail)
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8
Q

What is the limbic system fundamentally involved in?

A

Memory processes

- to be rewarded/punished for something, it comes after the act so you have to remember the experience

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9
Q

What else is the limbic system involved in?

A

Learning - when an act is rewarded you tend to do it again vs. if it is punished you avoid doing it again

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10
Q

What are motivational processes?

A

Processes which link reward or punishment to changes in behaviour

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11
Q

What are emotional processes?

A

Subjective experience of motivational processes

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12
Q

Why do some smells make you feel hungry/nauseous?

A

Limbic system is intimately connected to the olfactory system

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13
Q

What is the association of the limbic system with the olfactory system?

A

Some smells are hard wired to pleasure/unpleasant emotions and don’t have to learn

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14
Q

What are reward circuits?

A

Neuronal circuits that are active when you have sensation of pleasure/joy/happiness

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15
Q

What are negative reinforcement circuits?

A

Essentially punishment circuits but cannot call them this

- neuronal circuits which are active when you are unhappy/depressed/in pain

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16
Q

When is the anterior cingulate cortex active?

A

During experience of pain/feelings of misery or depression

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17
Q

What is the pathway of pain/

A

Nociceptive pain info travels up lateral SPT

  • goes to parabrachial nucleus to amygdala
  • via anterior thalamic nucleus to anterior cingulate cortex and insula
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18
Q

What is the function of the anterior cingulate cortex?

A

Cortical area responsible for unpleasantness of pain and its depressing emotional consequences

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19
Q

What is the function of the prefrontal cortex?

A

Activated to do something about the pain you experience

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20
Q

What is cingulotomy?

A

cutting into anterior cingulate gyrus to disrupt fibres which pass rosro-caudally though it
- reduces emotional distress of pain

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21
Q

What is the function of the orbitofrontal cortex?

A
  • anterior part of cingulate merges into it
  • associated with behaviour when a threat is anticipated
  • fits in with frontal love role as involved in planning future actions
  • eg. actions to avoid pain
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22
Q

What happens if making a decision when a threat is anticipated is very difficult?

A
  • no win situation
  • unable to chosoe between actions so freezes
  • prolonged pressure to make impossible choices = extreme stress
  • release of stress hormones (cortisol and adrenaline)
  • leads to sense of hopelessness and clinical depression
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23
Q

What is different about the orbito-frontal limbic cortex in patients with OCD?

A

MRI shows excessive activity in orbito-frontal limbic cortex

24
Q

What is the posterior cingulate cortex involved in/

A

Emotional significance of memories

25
Q

Where does the parahippocampal gyrus lie?

A

Medially and inferiorly in temporal lobe

26
Q

What is the role of the parahippocampal gyrus?

A

Primary involve with acquisition of new memories

Closely connected to subcortical parts of limbic system inside temporal lobe

27
Q

What are the subcortical parts of the limbic system?

A
  • hippocampus and amygdala

- around walls of inferior horn of lateral ventricles in temporal lobe

28
Q

Where does the hippocampus lie?

A

Along medial wall of inferior horn of lateral ventricle

- output fibres form fornix

29
Q

Where is fornix?

A

Curves upwards and round over the top of the 3rd ventricle

  • fibre tract leaving hippocampus
  • underneath corpus collosum
  • dives down into hypothalamus
30
Q

When the fornices converge what do they attach to?

A

Septum pellucidum

31
Q

Where do the fornix axons end?

A

In the septal nuceli and the mammillary body of the hypothalamus

32
Q

How does information flow between the hippocampus and the limbic cortex?

A
  • from cingulate cortex to parahippocampal gyrus and entorhinal cortex
  • to hippocampus
  • along fornix to mamillary bodies of hypothalamus
  • to anterior thalamus
  • back to cingulate cortex

IN A LOOP

33
Q

What is the entorhinal cortex?

A

Tail of parahippocampal cortex

34
Q

What is the name given to the series of connections in the limbic system forming a closed loop?

A

Papez’s circuit

35
Q

How does severe anterograde amnesia present?

A

When someone can no longer store new experiences/memories
As soon as they stop concentrating on it they forget it
Can retrieve stuff from memory before condition arised but cannot put new stuff in it

36
Q

What is the role of the hippocampus?

A

Has a mechanism for storage memory

Not where memory is stored

37
Q

How does the hippocampus provide labels?

A

Has a spatial map as well as a time of day enabling you to retrieve memories from these labels/possibly other parameters such as who you were with/what the weather was like
Essentially gives new experiences a context meaning they are properly stored

38
Q

What is declarative memory?

A

When you ask someone what they remember and they tell you

39
Q

What is procedural memory?

A

When someone learns to ride a bicycle/drive a car
This bypasses the hippocampus and so if you have severe anterograde amnesia you may still have limited motor ability
Depends on cerebellum and other brain regions instead

40
Q

What does loss of hippocampal function cause?

A

Failure to transfer new experiences into long term memories
Anterograde amnesia
Does not affect ability to learn new motor skills

41
Q

What is anterograde amnesia?

A

Loss of ability to store new experiences

42
Q

What is the Kluver-Bucy syndrome?

A

Bilateral removal of amygdala and adjacent temporal cortex:

  • psychic blindness
  • oral tendencies
  • altered sexual behaviour
  • emotional changes
43
Q

What does the Kluver-Bucy syndrome suggest?

A
  • electrical stimulation to amygdala = panic/fear/terror responses
  • amygdala is a fear centre in the brain
  • Made up of subnuclei with different connections and functions
44
Q

Where is the amygdala?

A

Embedded in entorhinal cortex in anterior medial temporal lobe

45
Q

What is the function of the amygdala?

A
  • continuously analyses sensory input to brain
  • activates fight or flight response of SNS
  • activates behavioural responses (running away/fighting)
  • aids ability to recognise emotion in others and therefore empathise/conduct normal social relationships
  • complements the hippocampus in labelling new experiences telling you whether they were painful/pleasant etc.
46
Q

How does the amygdala activate the SNS?

A
  • sends commands to hypothalamus -> reticular formation -> activates reticulospinal tracts -> activates SNS
47
Q

Where are the septal nuclei?

A

Lie at the base of the septum pellucidum

merge into basal nucelus of Meynert

48
Q

What is the ventral striatum

A

Septal nuclei + basal nucleus of meynert + accumbens nucleus

49
Q

What is the accumbens nucleus?

A

Anatomically part of basal ganglia
Functionally part of limbic system
Receives dopaminergic fibres as part of mesolimbic dopaminergic pathway

50
Q

What is the mesolimibic pathway?

A

Set of dopamine neurons which project from brainstem next to substantia nigra to accumbens nucleus

51
Q

What is the function of the accumbens?

A

Part of ventral striatum

  • involved in initiation and termination of behaviours (motor actions) which activate reward pathways
  • dopamine input to accumbens is necessary for pleasurable behaviour
52
Q

What happens if you block dopamine receptors in accumbens?

A

May help stop motor actions involved in addictive behaviours

53
Q

What is the dorsal striatum?

A
  • caudate and putamen
  • involved in selection of actions based on cognitive plans created in dorsal frontal cortex
  • feed into motor cortex via globus pallidus and motor thalamus
54
Q

What is the ventral striatum?

A
  • nucelus accumbens
  • involved in selection of actions based on rewards/threats
  • feeds into motor system via ventral pallidum and globus pallidus
55
Q

What are the similarities between the dorsal and ventral striatum?

A
  • require activity in dopamine axons from midbrain work

BB2 (31 decks)

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