Hypothalamus and limbic system Flashcards
Limbic system
a collection of cortical and subcortical structures that regulate learning, memory, emotion, and executiev function
- involve hippocampus, entorhinal cortex, and frontal lobes, etc
Regulate emotion est understood by its results
- experience/feelings of emotional state
- expression of behaviours
- involve: amygdala, hypothalamus, frontal lobes
Limbic lobe anatomy
ring of cortex on medial surface of the brain, spanning aspects of frontal, parietal, and temporal lobes
Hippocampus anatomy
deep within temporal lobe
floor of inferior horn of lateral ventricle
curved sheet of cortex folded in on itself
Amygdala anatomy
rostal/anterior and medial to hippocampus
deep to the uncus
Hippocampus fxn
learning
memory function & retrieval
site of adult neurogenesis
Amygdala function
emotional learning & memory
fear
reward
Memory classifications
Short Term
Long term
Declarative: episodic/semantic
Nondeclarative
Hippocampus ascending output
entorhinal cortex association areas (temporal, insular)
Hippocampus descending output
Fimbria-fornix
Mamillary body: anterior thalamus (mamillo-thalamic tract), Raphe (mammillo-tegmental tract)
Hypothalamus: behaviour, autonomic, endocrine function
Send information back up to areas of cortex to further modulate memory storage and behavioural output
Hippocampus input
Amygdala: basolateral (BLA), sensory part)
Sensory association areas: temporal lobe, insular cortex
Entorhinal area (via the cingulum): anterior thalamus, medial prefrontal/orbital cortex
Allowing to-down cortical control of emotional responses
Amygdala nuclei
Medial (MeA)
Basolateral (BLA)
Central (CeA)
Medial nucleus of amygdala
output to hypothalamus
regulates social behaviour
Basolateral nucleus of amygdala
BLA
Outputs to cortex, hippocampus, hypothalamus
Integrates sensory information
Central nucleus of amygdala
CeA
Outputs to hypothalamus (PVN = cortisol), frontal cortex, brainstem (adrenaline)
- mediate fight/flight, including subjective, physiological changes in emotional state
- can also regulate cortisol and reticular, medullary, and brainstem responses
Hypothalamus cell groups
Medial Preoptic Suprachiastmatic Supraoptic Dorsomedial Ventromedial Arcuate Nucleus Mammillary bodies Paraventricular nucleus
Paraventricular nucleus fxn
PVN
Regulates release of cortisol from adrenal gland
Mediated by HPA axis
Cortisol (lipophilic) is highly catabolic, and can access almost every cell in the body, including limbic system (largest # of GC receptors in the body)
Acute consequences of cortisol elevation
adaptive mobilize energy increased vascular tone suppress digestion suppress reproduction immune suppression sharpen cognition
Chronic consequences of cortisol elevation
Maladaptive myopathy, diabetes hypertension ulceration amennorhea, impotence increased disease risk neuron death
First response (emotional)
Thalamus –> Amygdala activated and induces arousal, adrenaline, HR, and BP
Also stimulates PVN to increase cortisol in circulation
Higher reasoning (emotional)
careful appraisal by sensory and frontal cortices dampen amygdala’s reaction
Logic prevails
Panic is removed, cortisol levels return to normal
Misguided fear
IF logic fails:
amygdala continues to arouse, cause fear/ panic
Chronic elevation in cortisol can lead to a myriad of disorders
