Anat 401 > Limbic system > Flashcards

Limbic system Flashcards

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1
Q

What is the limbic system?

A

The cortical representation of feeling - Who we are (our memories, unique personalities, thoughts, emotions and feelings) - mediated by distinct neuronal circuits within the brain

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2
Q

What are the major players pf the limbic system?

A

The hippocampal formation (hippocampus, fornix, dentate gyrus), amygdala, hypothalamus (and mammillary bodies), cingulate gyrus, nuclei of thalamus (anterior, lateral dorsal & medial dorsal) and the limbic association cortices

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3
Q

What does the dysfunction of one or more of these structures lead to?

A

Psychiatric disorders

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4
Q

Where is the amygdala found?

A

Near the hippocampus in the frontal portion of the temporal lobes - just in front of the hippocampus

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5
Q

What are the functions of the amygdala?

A

Involved in the formation/storage of info related to emotional events
Facilitates long-term memory formation (convert/retain learning from pleasure responses)
Helps us recognize when we are in danger or fearful of something

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6
Q

What can an injury to the amygdala affect?

A

Memory formation, emotional sensitivity, learning and retention, depression and anxiety

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7
Q

What is the fornix?

A

The connection between the hippocampus and the hypothalamus

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8
Q

What type of fibers is the fornix?

A

Long association fibers

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9
Q

What is the stria terminalis?

A

The connection between the amygdala and the hypothalamus

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10
Q

What are the 3 parts of the fornix?

A

The crus, the body and the column

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11
Q

What is the mammillary body?

A

Where the axons of the hippocampus synapse

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12
Q

Where does the hippocampus sit?

A

In the CSF fluid-filled space of the inferior horn of the lateral ventricle

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13
Q

What is the connection between the left and right crus of fornix?

A

The commissure of fornix

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14
Q

What are the fimbriae?

A

The axons that extend from the hippocampus to create the collection of axons at the crus of fornix

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15
Q

What is the alveus?

A

A thin layer of white matter that covers the ventricular surface of the hippocampus

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16
Q

What is the entorhinal cortex?

A

A part of the hippocampal formation situated at the temporal pole (adjacent to hippocampus and amygdala) that transmits input coming from the neocortex/limbic cortex and amygdala to the hippocampus

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17
Q

Where do the axons from the entorhinal cortex synapse on the hippocampus?

A

On the granule cells of the dentate gyrus

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18
Q

Which region do the granule cells of the dentate gyrus connect to?

A

pyramidal neurons in the CA3 region

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19
Q

Where do the neurons of the CA3 region project to?

A

CA1 pyramidal cells

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20
Q

What do the CA1 pyramidal cells become?

A

The axons that leaves the fimbriae and make up the fornix

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21
Q

When looking at the brain, what can you see in patients with Alzheimer’s?

A

Lots of CSF around the brain, cell death, an abnormal 3rd ventricle and more space in the lateral ventricle

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22
Q

Where is the limbic association cortex located?

A

On the medial surface of the frontal, parietal and temporal lobes

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23
Q

What is the limbic association cortex made up of?

A

The temporal pole (periamygdaloid cortex and entorhinal cortex), parahippocampal gyrus, cingulate gyrus, subcallosal gyrus (gyrus below corpus callosum), paraterminal gyrus and the orbitofrontal gyrus

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24
Q

Who suggested the ‘limbic lobe’ forms a neural circuit?

A

James Papez

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25
What 4 structures did Papez use to demonstrate that emotion is not a function of a specific brain center but of a circuit?
Hypothalamus + mammillary bodies, anterior thalamic nucleus, cingulate gyrus, hippocampus
26
What is the cingulum?
The axon tract that relays back to the hippocampus from the cingulate gyrus
27
Why did Papez argue that the hypothalamus must communicate reciprocally with higher cortical centers?
Because emotions reach levels of consciousness and thought and higher cognitive functions affect emotions
28
How did Papez propose the cortex influences the hypothalamus?
Through connections of the cingulate gyrus to the hippocampal formation
29
What is the pathway for the limbic circuit of Papez?
The circuit starts at the hippocampal formation Axons are relayed through the fornix to the mammillary bodies of the hypothalamus The mammillary-thalamic tract sends the axons to the anterior thalamic nucleus The info is then relayed to the cingulate gyrus The cingulate gyrus communicates bilaterally with the cortex Information is sent back to the hippocampal formation by the cingulum
30
What did Paul Maclean add to the limbic circuit of Papez?
The importance of the amygdala in the circuit
31
What are the parts of the real limbic circuit (a possible pathway) ?
1. Entorhinal cortex 2. Hippocampus 3. Fimbriae 4. Fornix 5. Mammillary body 6. Anterior nucleus of the thalamus 7. Cingulate gyrus 8. Prefrontal cortex 9. Limbic association cortex 10. Cingulate gyrus 11. Parahippocampal gyrus 12. Temporal pole/amygdala
32
What kind of emotions are involved with the amygdala?
Love, anger, fear, sexual desire/arousal, preference in food and in sexual partners
33
What do the amygdala and hippocampus work together to do?
To store memories with emotional links
34
If the left hippocampus is damaged, what does this cause?
Auditory/vocal memory loss
35
What happens if both hippocampus are removed?
You can't form new memories
36
What is the name for the disease when you can't form new memories?
Anterograde amnesia
37
Which 2 major limbic system functions do the hippocampal formation and the amygdala mediate?
Learning and memory and emotions
38
What is the amygdala mostly involved with?
Emotional experiences and behavioral expression
39
What is the hippocampal formations role in emotion?
Only indirect
40
What is the hippocampal formation mostly involved with?
Memories - explicit memory, memory consolidation and learning from emotional experiences
41
What is the anterior commissure?
The connection between the 2 amygdala
42
What are the 2 amygdala?
The lateral amygdala and the medial amygdala
43
What is the lateral amygdala linked to?
The neocortex
44
What is the medial amygdala linked to?
The striatum
45
What does the stimulation of the lateral amygdala cause?
The stimulation of anxiety and fear
46
What does the medial amygdala do?
Connects to motor and brainstem
47
What is the lateral hypothalamus?
The pleasure center (studies show rates preferred this over food, sleep, etc.)
48
What is the ventromedial hypothalamus?
The aversion center
49
What are the septal nuclei and nucleus accumbens?
The reward centers of the brain
50
Where do the septal nuclei and nucleus accumbens connect with?
Projects heavily throughout the hypothalamus and maintains connections with the amygdala, hippocampus, cingulum and reticular formation
51
Where are the septal nuclei found?
At the very front of the frontal pole
52
Where is the nucleus accumbens found?
Below the putamen and head of the caudate nucleus
53
What are the septal nuclei and nucleus accumbens responsible for?
Reward, motivation and addiction
54
What does a bilateral lesion of the frontal gyri cause?
Difficulties concentrating, loss of initiative, apathy and you cannot decide
55
What does a bilateral lesion to the orbital cortex cause?
Unstable emotional behavior, loss of inhibition and inappropriate social behavior
56
What does the bilateral removal of the amygdala cause?
Fearlessness (stimulation = anxiety/fear)
57
What does a bilateral lesion to the parahippocampal gyrus cause?
No new memories
58
What is the overall pathway for emotion and memory?
The limbic association cortex receives info from higher order sensory areas (prefrontal cortex/parieto-temporal-occipital association cortex) Limbic association cortex conveys the info to the amygdala and hippocampus Amygdala uses the sensory info to link particular stimuli with particular emotions Hippocampus receives more integrated sensory info thought to reflect more complex features of the environment (spatial relationships)
59
In the example of seeing a snake, what do the amygdala and hippocampus do?
The amygdala uses the visual info of the snake to organize an initial emotional response to the threat The hippocampus uses the environmental setting and context (to help change the emotional response)
60
What are the principal afferents of the hippocampus?
Prefrontal and orbital limbic association cortex Amygdala Temporal association cortex Lateral cortex: temporal and posterior parietal Cingulate gyrus (+ other association areas) Entorhinal and parahippocampal cortex
61
What are the principal efferents of the hippocampus?
Fornix Mammillary bodies Mammillothalamic tract Anterior nuclei of the thalamus Cingulate gyrus Diverse cortical association areas Septal nuclei Amygdala Entorhinal cortex
62
What are the principal afferents of the amygdala?
Higher order sensory areas in temporal and insular cortex Association cortex Olfactory bulb Thalamus Brainstem autonomic nuclei (NTS) Hippocampal formation
63
What are the 2 pathways of the principal efferents of the amygdala?
Stria terminalis and the ventral amygdalofugal pathway
64
What are the principal efferents in the stria terminalis pathway?
Hypothalamus and nucleus accumbens
65
What sensation is associated to the efferents of the stria terminalis?
A euphoria sensation
66
What are the principal efferents of the ventral amygdalofugal pathway?
Thalamus Hypothalamus Rostral cingulate gyrus and orbitofrontal cortex
67
What are disorders of the amygdala?
Mood disorders - including depression, anxiety and substance abuse Stimulation = feelings of fear and apprehension Bilateral temporal lobectomies = Kluver-Bucy syndrome = docile, tame and fearless, flattened affect, psychic blindness
68
What are disorders of the hippocampus?
Severe anterograde amnesia Alzheimer's disease - loss of neurons in hippocampi, mammillary bodies, cortex Korsakoff's psychosis - damage to hippocampi, mammillary bodies and medial-dorsal nucleus of thalamus Hippocampus implicated in the pathogenesis of schizophrenia
69
What is Korsakoffs's psychosis?
Amnesic syndrome - lose new memories
70
What 4 neurotransmitters are delivered to limbic areas?
Dopamine, serotonin, norepinephrine and acetylcholine
71
Why is the innervation of the limbic system by the neurotransmitter regulatory systems important?
Important for normal thoughts, moods and behaviors
72
What neurotransmitter receptor is blocked from drugs for schizophrenia?
Dopamine receptors
73
Where are dopaminergic projections going to and from in the limbic system?
From the midbrain ventral tegmental area and substantia nigra compacta To the limbic areas, amygdala and hippocampal formation
74
What center also releases dopamine?
The reward center - Nucleus accumbens
75
How do dopaminergic projections go from the midbrain to the limbic areas?
Via the medial forebrain bundle
76
What do drugs that increase dopamine mimic?
Schizophrenia
77
Where do ascending serotonergic projections go to and from?
To the amygdala, hippocampus, striatum and cerebral cortex From the reticular formation (raphe nuclei)
78
How do ascending serotonergic projections travel?
Vie the medial forebrain bundle
79
What are drugs blocking serotonin reuptake (SSRI) used for?
Treating depression, anxiety and obsessive compulsive disorders
80
What nucleus also secretes serotonin?
The nucleus accumbens
81
Where do noradrenergic projections go to and from?
To the entire cerebral cortex including limbic association areas and limbic structures From the locus coeruleus (norepinephrine)
82
How do noradrenergic projections travel?
Via the medial forbrain bundle and ascending pathways
83
What does cell death of noradrenergic neurons lead to?
Alzheimers disease, PD, depression and stress responses/anxiety
84
Where do basal forebrain Cholinergic projections go to and from?
To the entire cerebral cortex, limbic association cortex, amygdala and hippocampal formation From the basal forebrain Cholinergic neurons (septal nuclei)
85
How do basal forebrain Cholinergic projections travel?
Via diverse pathways
86
What can the loss of Cholinergic neurons lead to?
The beginning of Alzheimers disease
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