Limbic system Flashcards
What is the limbic system?
- A sub-cortical area going from the corpus calossum to the diencephalon
- Different areas that are structurally and functionally related
What is the function of the limbic system?
- Homeostasis
- pituitary hormone controll
- feeding + drinking initiation
- visceral effector mechanisms
- Fight and flight response –> defence and attack
- Sexual and reproductive behaviour
- Memory
What are the parts of the limbic system?
- Hippocampus
- Amygdulla
- Hypothalamus
- Thalamus
- but also part of the frontal cortex
What are the different parts in empotional response?
Which parts of the brain correlate with each?
Emotional response has three layers
- Emotional experience –> laying down new memory
- cingulate cortex
- hippocampus
- anterior nucleus of thalamus
- Emotional colouring –> consolidation of previous memories to experience
- neocortex
- Emotional expression
- emotion reaction
Explain the Papez circuit in the limbic system
- From Hippocampus Fornix runs to Mamillary bodies in hypothalamus)
- There the mamillo-thalamic tract (MTT) runs to the anterior nucleus of the thalamus
- Which is connected to the cingulate cortex
- The cingulate cortex
- also recieves input from neocortex
- Goes to the hippocampus via the Cingulum bundle
What is the funciton of the Hippocampus?
Mainly involved in memory and learning
Which conditions might affect function of the hippocampus?
vAlzheimer’s disease, epilepsy
What are the main afferent and efferent pathways of the hippocampus
Main input: recived from perforant pathway (memory, perception of time)
Main output: Fornix (fimbria)
Hippocampus
Where is the hippocampus located?
In the medial temporal lobe
Explain the pathology of alzheimiers disease
Neuronal cytoskeleton distubed –> pathology progesses
- Atrophy of hippocampus
- Cortical atrophy
- enlargement of ventricles
Wher is the site of pathology in early alzheimers disease?
Which symptoms does it lead to?
Located in Hippocampus and entorhinal cortex
–> Short-term memory problems
Where does the pathology of Alzheimers spread in moderate diseae?
Which symptoms does it lead to?
It spreads from hippocampus to the Parietal lobe
causing
- disorientation
- Dressing apraxia
Where does the pathology of Alzheimers spread to in late stages?
What does this lead to?
Spreads from hippocampus over parietal lobe to Frontal lobe
- Loss of executive skills
What is the functio of the amygdulla?
Involved in Fear and Anxiety
and Fight or Flight response
What are the efferent and afferent connections of the Amygdulla?
Afferent
- septum (membrane between hemispheres)
- temporal neocortex
- olfactory cortex
- brainstem
- hippocampus
Efferent
- Stria terminalis to hypothalamus
Where is the amygdala located?
It is a grey matter nucleus in the frontal temporal lobe
What happens in damage to the Amygdala?
Might lead to Kluver-Bucy syndrome
- Hyperorality
- Loss of fear
- Visual agnosia
- Hypersexuality
Which neuronal structures are associated with agression?
- Hypothalamus
- Brainstem (periaqueductal grey)
- Amygdala
–> often mediated by serotonin
Where are the septal nuclei located?
In the midline between the two hemispheres
What are the funciton of the septal nuclei?
Associated with Reinforcement & reward
What are the connections of the septal nuclei?
Afferent: v: Amygdala, olfactory tract, hippocampus, brainstem
Efferent: Stria medularis thalami, hippocampus, hypothalamus
What is the dopaminergic pathway associated with drug dependance?
•Mesolimbic pathway
- Originates in the Midbrain
- Via the Median Forebrain bundle into
- Cortex
- Amygdala
- Nucleus accumbence –> involved in addiction
Explain the very basic principle of drug addiction
Drugs such as cocaoi, ethanol, nicotine, opioids, amphetamines all increase Dopamine in the Nucleus accumbence
- Via: Stimulate midbrain neurons that promote DA release or inhibit DA reuptake
- Leading to a: stimmulation of the reward system
- adaptation to high dopamine levels
