Limbic System Flashcards
What is the limbic system involved in?
Emotion, memory and learning
Where is the limbic system found medial to?
Aspects of frontal, pariental and temporal lobes
What is limbic system made of?
Orbito-frontal cortex and cingulate cortex
The parahippocampal cortex is which part of the limbic cortex?
3rd
What mainly supplies the limbic system?
Anterior cerebral artery which supplies medial structures
What also supplies limbic system?
Posterior cerebral artery
What is activated during pain and depression?
Anterior cingulate gyrus
What is anterior cingulate cortex split into?
Caudal and rostral parts
What does caudal anterior cingulate do?
Registers quality of pain (how bad it is)
What proves the function of caudal anterior cingulate?
Cingulotomy
What is a cingulotomy?
Involves cutting cingulate gyrus to disrupt fibres which reduces emotional distress of pain
What does rostral anterior cingulate do?
Decides upon action in response to the pain
What does rostral anterior cingulate merge into?
Orbitofrontal cortex
What may people do if they cannot decide what action to take?
Freeze
What disorder may excessive activity in rostral anterior cingulate cause?
OCD
What happens in loss of function of posterior cingulate gyrus?
Correlates with disorientation seen in Alzheimers patients
Where are parahippocampal gyrus located?
Medial and inferior in the temporal lobe
What do parahippocamapl gyrus involved in?
Learning and memory
What are the parahippocampal gyrus closely related to?
subcortical regions of the limbic system; hippocampus and amygdala
What does hippocampus do?
Registers place and time information to help form new memories
What does loss of hippocampus do?
Failure to create experiences into memories
What is anterograde amnesia?
Loss of ability to store new experiences
Where does hippocampus lie?
Medial wall of the inferior horn of the lateral ventricle
What do the hippocampus’ outfit fibres form?
Fornix
What route does the fornic take?
Curves upwards and over the top of the 3rd ventricle
Where do hippocampus fibres lie?
Under midline of corpus callosum, ending in the mammillary body of the hypothalamus
What are the fornices attached to?
Septum pellucidum
What is the septum pellucidum?
Thin sheet separating the anterior horns of the lateral ventricles
Where does the septum pellucidum attach between?
Fornix and corpus callosum
What are at the anterior pole of the hypothalamus?
Septal nuclei
In the Papez circuit, information goes from cingulate cortex to where?
Parahippocampal gyrus
Info from parahippocampal gyrus goes where in papez circuit?
hippocampus
Info from hippocampus travels where in papez circuit
Along the fornix to mammillary bodies of hypothalamus
Info from hypothalamus goes where in papez circuit?
Anterior thalamus
Where does info from anterior thalamus go in papez circuit?
Cingulate cortex
What is Wernicke-Korsakoff syndrome?
Thiamine (B1 vitamin) deficiency
Where is thiamine deficiency mostly seen in?
Alcoholics
What does thiamine deficiency lead to?
Atrophy of mammillary body, hippocampus and fornix
Symptoms of wernicke-korsakoff syndrome?
Anterograde and retrograde amnesia Confabulation Opthalmoplegia Confusion Ataxia
What is Kluver-Bucy syndrome?
When subjects lose all sense of fear
What are the categories in Kluver-Bucy syndrome?
Psychic blindness Oral tendencies Hypermetamorphism Altered sexual behaviour Emotional changes
Why does Kluver-Bucy syndrome occur?
Bilateral removal of the temporal lobe tips (amygdala)
Where is the amygdala located?
Enterhinal (olfactory) cortex in Anterior-medial temporal lobe
What does stimulation of amygdala do?
Produces panic
fear
terror responses
What does amygdala activate?
Fight or flight response of sympathetic NS
What compliments the amygdala?
Hippocampus
What does septal nuclei connect with?
Reticular formation
What mechanism is the septal nuclei?
Sensory mechanism
Where does reticular formation forward signals to?
Ventral striatum (nucleus accumbens)
How are reticulospinal tracts activated?
Signals is sent from RF from hypothalamus
Where does septal nucleus lie?
Bottom of septum pallucidum
What do the septal nucleus merge to form?
Basal nucleus
Accumbens nucleus and septal nucleus form the what?
Ventral striatum
What fibres does the accumbens nucleus receive?
Dopaminergic fibres
What pathway is accumbens nucleus part of?
Mesolimbic
What is mesolimbic pathway?
Set of dopamine neurones that project from the brainstem to the accumbens nucleus
What is the ventral striatum involved in?
Initiation of termination of behaviours that trigger reward pathways e.g. chewing food
What sends axons down brainstem to activate dopaminergic neurones
Septal nuclei
What forms dorsal striatum
caudate and putamen
What does dorsal striatum do?
Decide what actions to take next based on frontal lobe plans
What does ventral striatum do?
Decide what actions to take place based on reward systems or impending threats
What does hypothalamus do?
Command signals can be sent down axons to nuclei via the brainstem reticular formation
