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MD4001 Physiology > The limbic system, emotion, the hypothalamus, appetites > Flashcards

The limbic system, emotion, the hypothalamus, appetites Flashcards

1
Q

What does the limbic system process?

A

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

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2
Q

What are the core componenets and effectors of the limbic system?

A

Core components:
- Amygdala - emotion
- Hippocampus )+cortex) (H. formation) - memory
- Limbic cortex - cingulate gyrus/insula
Effectors (output)
- Hypothalamus
- Brain stem structures

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3
Q

What make up the limbic cortex?

A

Cingulate gyrus + insula

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4
Q

Where is the amygdala located?

A
  • Anterior temporal lobe at the tail of caudate nucleus and rostal to hippocampus
  • Not a basal ganglia structure
  • Close to lateral ventricle
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5
Q

What syndrome can give an insight into amygdala function?

A

Kluver-Bucy syndrome (rare syndrome in humans which produces behavioural impairment)

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6
Q

What are some of the symptoms of Kluver-Bucy syndrome?

A
  • Placidity (lack of fear)
  • Hyperorlaity
  • Hypersexuality
  • Angnosia
  • Memory loss
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7
Q

What are some pf the causes of Kluver-Bucy syndrome?

A
  • Herpes encephalitis
  • Trauma
  • Tumours
  • Hypoxia
  • Pick’s disease (type of FTD tau-opathy)
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8
Q

What disease is a rare genetic recessive disorder which induces calcification in both temporal lobes?

A

Urbach-Wiethe disease

- Lacks fear

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9
Q

What does fear activate in the brain?

A
  • Amygdala generates and is activated by fear
  • Fear activates central nucleus (and bed nucleus of the stria terminalis (BST))
  • Centres are enhanced in anxiety disorders
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10
Q

What are the 3 types of inputs into the amygdala which cause a fear response?

A
  • Stimulus (e.g view of a snake)
  • Concept (e.g idea of a snake/ memory)
  • Context (e.g snake in the room)
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11
Q

What are the 2 pathways fear stimulus can take to reach the amygdala and therefore cause a response?

A
  • Take a fast track pathway via the thalamus - doesn’t reach consciousness (e.g. subliminal short route)
  • Longer route via cerebral cortex (long route e.g. visual cortex)
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12
Q

The concept of a fear (e.g idea of a snake) reaches the lateral amygdala via what?

A

Cerebral cortex

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13
Q

The contex of the fear (e.g snake in the room) reaches the amygdala via what?

A

Hippocampus

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14
Q

Where do inputs of fear go to?

A

Lateral nucleus of amygdala

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15
Q

Where do outputs of fear come from?

A

Central nucleus of amygdala

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16
Q

How can the amygdala learn a modified fear response (emotional memory)?

A

Synapse strengthening

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17
Q

What does the output to the hypothalamus from the amygdala travel via?

A

Stria terminalis (another C shaped structure)

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18
Q

What does the amygdala output to in the brainstem?

A
  • Periaqueductal grey matter (PAG)
  • Locus Coeruleus (LC)
  • Parasympathetics (solitary nucleus, dorsal vagal nucleus)
  • Ventral tegmental area
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19
Q

What is the function of the amygdala?

A

Controls emotional reactions (particularly threat/fear) via effectors (hypothalamus, brain stem through to the autonomic nervous system, endocrine and motor system)

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20
Q

What are the 3 areas the cingulate gyrus can be broken up into?

A
  • Anterior cingulate cortex
  • Midde cingulate cortex
  • Posterior cingulate cortex
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21
Q

What part of the cingulate gyrus is involved in emotion and what is it called?

A

Anterior Cingulate cortex and anterior portion of middle involved in emotion make up what is called:
- Limbic Cortex

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22
Q

What does the anterior cingulate encode?

A

Basic emotions, happiness, sadness and fear and emotional memory (so more than just fear)

23
Q

What are the functions of the anterior cingulate?

A
  • Top down influence - works to recode the amygdala
  • Computes relevance/outcomes - drives appropriate behaviour
  • Provides conflict resolution (dorsal ACC e.g. self vs non-se;f in threat)
  • Part of pain network - thalamus, primary somatosensory area and insula
24
Q

What are the ways in which the limbic cortex can affect the motor control?

A
  • Motor reactions complex and context dependant
  • Specific zone for driving face muscles
  • Direct outputs from ACC to autonomic system
25
Q

What is considered to be the primary limbic cortex?

A

The anterior cingulate cortex (can influence the amygdala)

26
Q

What is the function of the insula?

A
  • Works with ACC in evaluating emotional contexts - role in empathy
  • Encodes emotional awareness
  • Classified as limbic “sensory” cortex
27
Q

How does PTSD affect the limbic system?

A
  • Part of ACC is hypo-responsive in PTSD
  • Reduction in size of ACC
  • Amygdala becomes hyper-responsivene to trauma related stimuli
  • Top down control of amygdala by ACC is therefore missing in PTSD
28
Q

What are the main functions of the cingulate gyrus?

A
  • Emotion response regulation coordinated via connections with the amygdala
  • Make prediction about negative consequences resolves conflicts
  • Top down regulation “recodes” the amygdala processing/responses
  • Drives conscious responses to unpleasant experiences
  • Drives avoidance behaviours and motor such as facial expression (from MCC to motor cortex)
  • Also direct influence on limbic effectors (ANS) by-passing amygdala
  • Works with insula which provides wider context of awarenwss to unpleasant especially visceral stimuli (empathy; pain)
29
Q

What are the 4 main functions of the Hypothalamus?

A
  • Autonomic - CV, resp, piloerection sweating etc.
  • Endocrine - e.g stress response
  • Behavioural - General level of activity up to and including rage for pursuit of food, water, sex etc; ingestion/disinterest in food; fear behaviour; increased sexual drive
  • Basic homeosasis - Fluid electrolyte, feeding energy, thermoregulation, reproduction, sleep wake
30
Q

What part of the limbic system promotes alertness and wakefulness?

A

Locus coeruleus

31
Q

What is the locus coruleus and what is its function?

A
  • Midbrain nucleus involved in physiological responses to panic and stress
  • Input from CG, amygdala, PAG and hypothalamus
  • NA fibres projecting from nucleus to widespread brain structures
  • Promotes alertness and wakefulness (widespread connections)
  • Promotes anxiety + formation and retrieval of emotional memories (amygdala) - dense projections from LC to amygdala
  • Projections to hypothalamus from LC maintains arousal and also effect ANS output
  • Projections FROM PAG selects fight or flight mode
32
Q

What is the function of the PAG?

A
  • Part of the pathway that mediates LIMBIC autonomic reactions (fear, pain, analgesia) inputs from cingulate gyrus and amygdala
  • Projects to nucleus of solitary tract, dorsal nucleus of vagus, intermediolateral column. Projections from PAG to LC selects fight or flight mode
33
Q

What are the 2 defensive fear network paths the PAG fibres can take?

A
  • Amygdala -> ventrolateral (vl) PAG -> vagal paths (parasympathetic in freezing)
  • Amygdala/CG -> dorsolateral (dl) PAG -> LC and Bstem (flightorflight switching)
34
Q

How is fear processed in the brain if the stimulus is far away?

A

Cingulate gyrus processes response through basolateral amygdala to striatum (PAG independantly)

35
Q

How is fear processed in the brain if the stimulus is close by?

A

Central amygdaala drives PAG and other brainstem centres to panic mode (AS)

36
Q

Describe the function of the Dorsal Raphe Nucleus (DRN)

A
  • Midbrain nucleus projects an asceding system
  • Projectd 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
37
Q

What is the theory of 5HT and depression/mood?

A
  • High levels of 5HT = Mainia

- Low levels of 5HT = Depression

38
Q

What disease are variant polymorphisms in 5HT transporter gene thought to predispose for?

A

Depression

39
Q

What happens to the limbic system in established depression?

A
  • Reduced metabolism in ACC
  • Reduced size of ACC
  • Amygdala reduced size and hyperactive
40
Q

What are the functions of the hippocampus in terms of memory?

A
  • Combines spatio temporal information with emotional, sensory and cognitive information to establsih new episodic memory
  • Including memories for locations and events that take place at those locations
41
Q

Where is the hippocampus and what does it look like?

A
  • Deep in temporal lobes
  • Elongate structure in the floor of the lateral ventricle
  • Name reflects similarity to a seahorse
  • Rolled appearence
  • Evolutionarilly old cortex
42
Q

What makes up the hippocampal formation?

A
  • Hippocampus and associated cortex (parahippocampal gyrus) together
43
Q

What structure is thought to creat new memories?

A

Hippocampus

44
Q

What are the 2 types of declerative memory?

A
  • Episodic memory (recollection about a specific event in one’s past tied to a specific time and place)
  • Semantic memory (general knowledge about the world)
45
Q

What is the function of the hippocampus in terms of memory?

A

Plays a critical role in memory formation by providing the brain with a spatiotemporal framework within which the various sensory, emotional, and cognitive components of an experience are bound together
- This framework allows the experience to be stored in such a way that it can be later retriebed as a conscious recollection of that experience

46
Q

Where in the parahippocampal gyrus is associated with scenes?

A

Parahippocampal cortex

47
Q

Where in the parahippocampal gyrus is associated with objects?

A

Perirhinal cortex

48
Q

Where in the parahippocampal gyrus is associated with faces?

A

Entorhinal cortex

49
Q

What are diseases in the hippocampus associated with?

A
  • Sensitive to stress (glucocorticoids)
  • Cushing’s disease and glucocorticoid administration
  • Ischaemia sensitive
  • Alzheimer’s (lead to atrophy)
  • Hypertension
  • Depresion
  • Epilepsy
  • Stress (PTSD)
  • Genetic disorders
  • Chronic alcohol use (all lead to atrophy)
50
Q

What is one of the first regions to be affected by Alzheimer’s?

A

Hippocampus

51
Q

What is the fornix?

A

A major output tract of the hippocampus involved in memory
- Fornix projects to the mammillary bodies which are connected to the anterior nucleus of the thalamus (damage to the fornix and these 2 structures cause memory problems)

52
Q

How is language and visiospatial output divided in the fornix?

A

Left/Right segregation

L - Language

53
Q

How is emotional/motivational learning divided from scene learning in the fornix?

A

Output sgregated according to hippocampus processing (rostral/caudal)

MD4001 Physiology (22 decks)

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