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Y3S1 NEURO > Limbic System > Flashcards

Limbic System Flashcards

1
Q

what body responses are involved in the fight or flight response

A
  • heart rate increases
  • sweating
  • resp. rate etc.
  • defecation
  • micturition
  • fascial expression
  • evacuation
  • muscle blood blood to prepare to fight
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2
Q

what are the two main parts of the limbic cortex

A

cingulate gyrus

insula

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3
Q

what does the limbic system process

A

emotion and related brain activity, memories, environmental cues and state of the individual and acts on this information to maximise survival strategies

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4
Q

what does the amygdala focus on

A

emotion

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5
Q

what does the hippocampus focus on

A

memory

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6
Q

what are the two structures which allow output from this area of processing

A

hypothalamus and brainstem structures

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7
Q

where is the amygdala located

A

in the anterior temporal lobe at the tail of the caudate nucleus and rostral to the hippocampus

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8
Q

what are the four nuclei of the amygdala

A

central nucleus, corticomedial nuclei and the basal and lateral nuclei

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9
Q

what is Klüver-Bucy syndrome

A

associated with damage to the anterior temporal lobes
• Hyperorality
• Placidity (lack of fear)

can be caused by:

  • herpes encephalitis
  • trauma
  • tumours
  • hypoxia
  • picks disease
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10
Q

if one experiences fear what nuclei in the amygdala is activated

A

the central nucleus and the bed nucleus of the stria terminalis (BST)

it is this area in which the centres are enhanced in anxiety disorders

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11
Q

where does input enter the amygdala

A

lateral nuclei

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12
Q

where does output exit the amygdala

A

the central nucleus

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13
Q

there are three types of fear pathway, all related to different aspects of the fear

A
  • stimulus
  • concept
  • context
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14
Q

stimulus pathway

A

this takes a fast tracked pathway to the thalamus - doesn’t reach our actual consciousness (subliminal short route)
(view of a snake or hiss of a snake)

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15
Q

the concept pathway

A

this is via the cerebral cortex

this is the idea of a snake or a previous memory you may have

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16
Q

the context pathway

A

this is via the hippocampus and insinuates the snake is in the room with you

17
Q

how can the amygdala learn - stimulus pairing

A

this is noise or scene associated with a fear stimulus can itself elicit fear
this extends to context as well such as a place or a person

the lateral nucleus responds to the stimulus pairing

then the central nucleus droves the response via two main centres:

  • the hypothalamus (this is via the stria terminalis
  • the brainstem
18
Q

what is the stria terminalis

A

a c shaped structure that ends in the hypothalamus and the BST (basal nucleus of the stria terminalis)

19
Q

if the central nucleus of the amygdala outputs via the brainstem, where does this take place

A
  • periaqueductal grey matter (PAG)
  • locus coeruleus (LC)
  • parasympathetics (solitary nucleus, dorsal vagal nucleus)
  • ventral tagmental area
20
Q

what is valency

A

determining if something you are experiencing is good or bad

21
Q

there are three areas of the cingulate gyrus, what are these known as?

A
  • ACC
  • MCC
  • PCC

anterior/middle/posterior Cingulate gyrus

22
Q

what makes up the limbic cortex - this processes emotion

A

the ACC and anterior portion of the MCC

also as a side note remember that the insulation is also considered to be part of the limbic cortex

23
Q

ACC connects to where when thinking about effectors

A

the amygdala and to effectors in the brainstem

this encodes basic emotions such as happiness, sadness and fear, also focuses on emotional memory of fear

24
Q

MCC connects to where when thinking about effectors

A

to the motor Cortex so primarily movement and behaviour

25
Q

what is the top down influence of the anterior cingulate

A
  • Computes relevance/outcomes - drives appropriate behaviour
  • Provides conflict resolution (dorsal ACC e.g. self vs non self in threat)
  • Part of pain network - thalamus, primary somatosensory area and insula
26
Q

ACC + some of the MCC are considered to be called what

A

the primary limbic cortex

thesis a higher level of processing emotion and is combined with the top down functions of the amygdala

deals with emotional conflict “friend tied to a chair”

determines motivators

27
Q

what is the main role of the insula

A

empathy

this is closely connected to the ACC and works with it

it gets input from the visceral information including pain

limbic sensory cortex and it encodes for emotional awareness

28
Q

what happens to the limbic system in PTSD

A

part of the ACC becomes hypo-responsive and there is a reduction in the size of the ACC

so ACC works less so is unable to perform top down conditioning

Amygdala becomes hyper-responsive to trauma and related stimuli

the top down control of the amygdala by the ACC is therefore missing in PTSD

29
Q

locus coeruleus - effector and regulator

A

this is a midbrain nucleus that is involved in the physiological response to panic and stress

there are noradrenaline fibres that project from the nucleus to the widespread brains structures

promotes alertness and wakefulness

can also promote anxiety + formation and retrieval of emotional memories from the amygdala via dense projections

30
Q

Periaqueductal grey (PAG) - fight/flight/freeze responses

A

inputs from the cingulate gyrus and the amygdala

projects to the nucleus of the solitary tract, dorsal nucleus of the vagus, intermediolateral column

projects from the PAG to LC selects the fight to flight response

31
Q

what is the PAG freeze pathway

A

ventrolateral (vl) PAG -> vagal paths (parasympathetic in freezing)

32
Q

what is the PAG fight or flight pathway

A

dorsolateral (dl) PAG -> LC and BStem (fight-or-flight switching)

33
Q

why is traumatic pain often not felt till mins/hours after an incident

A

Pain regulation ->encephalin -> raphe nuclei -> 5HT dorsal horn -> interneuron block pain paths

34
Q

Dorsal raphe nucleus (DRN)

A

Midbrain nucleus projects an ascending system
• Projects to and receives from amygdala and ACC
• 5HT (serotonin) neurons
• Determines tonic limbic activity and dynamic mood state
• Also processes descending pain paths from PAG to DRN to spinal cord

35
Q

In established depression what are the effects on the limbic system

A
  • Reduced metabolism in ACC
  • Reduced size of ACC
  • Amygdala reduced size and hyperactive
36
Q

HIPPOCAMPAL FORMATION and function of the hippocampus

A

Hippocampus AND associated cortex

  • Hippocampal formation structures in temporal lobe floor of the lateral ventricle
  • Combines spatio-temporal information with emotional, sensory and cognitive information
  • Explicit episodic memory
  • Damaged in Alzheimers disease, genetic syndromes and chronic alchohol use
37
Q

fornix

A

major output role for memory from the hippocampus

38
Q

Wernicke-Korsakoff syndrome

A

thiamine deficient alcohol related hippocampal damage and decrease in hippocampal learning

39
Q

ATROPHY OF THE HIPPOCAMPUS FOUND IN

A
  • Alzheimer’s disease
  • Hypertension
  • Depression
  • Epilepsy
  • Cushing’s disease
  • Stress (PTSD)
  • Genetic disorders
  • Chronic alcohol use

Y3S1 NEURO (44 decks)

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