Limbic System Flashcards
what is the limbic system?
A collection of cortical and subcortical structures located in the medial and ventral regions of the cerebral hemispheres
What is defined as the limbic cortex/lobe?
The cingulate gyrus and parahippocampal gyrus
What are the four main functions of the limbic system?
Homeostasis, olfactory, memory, emotion (HOME)
List the many components of the limbic system
- Limbic cortex
- Hippocampal formation
- Amygdala
- Olfactory cortex
- Diencephalon
- Septal nuclei
- Brain stem
- Basal ganglia
- Basal forebrain
What are the functions of the limbic cortex?
Cingulate gyrus: memory, emotional processing, afferent nervous system
Parahippocampal gyrus: Memory processing
What are the three parts of the hippocampal formation and do they receive input or send output?
Located on the medial temporal lobe
1. Dentate gyrus: afferent input
2. Subiculum: efferent output
3. Hippocampus: efferent output
What is the amygdala responsible for and what nuclei are involved?
Functions: emotion, behavior, emotional response to smell
Nuclei: corticomedial nucleus (olfaction), central nuclei (autonomic control), basilar nuclei group (all other emotions)
What are the nuclei involved in the limbic system within the hypothalamus?
Mamillary bodies: main nuclei involved in limbic pathways
ANS nuclei: give rise to parasympathetic and sympathetic pathways
What are the nuclei involved in the limbic system within the thalamus?
Anterior nucleus of the thalamus: involved in the Papez Circuit and memory
Mediodorsal nucleus of the thalamus: emotions and behaviors
How is the septal area involved in the limbic system?
- It is connected to the Habenula which is part of of the epithalamus
- Part of the reward pathways and involved in dopamine and serotonin
What is the association cortex?
- Part of the cerebral cortex that is not directly involved with sensation or movements
- Found in prefrontal cortex and temporal cortex
- Helps associate motor and sensation to emotions
Match the limbic system function acronym HOME with the key structure responsible for the function
Homeostasis: hypothalamus
Olfaction: olfactory cortex
Memory: hippocampal formation
Emotion: amygdala
What vasculature supplies blood to the limbic system?
Anterior cerebral artery: medial surface of frontal and parietal lobe
Posterior cerebral artery: medial and inferior surface of the temporal lobe
Anterior choroidal artery: cingulate gyrus, parahippocampal formation, and amygdala
Branches of circle of willis: hypothalamus, anterior commissure
List the tracts involved in the limbic system
- Medial and lateral olfactory stria
- Fornix
- Stria terminalis
- Ventral amygdala fugal pathway
- Mammillothalamic tract
- Medial forebrain bundle
Describe the medial and lateral olfactory stria
- Involved in olfaction
- Receives input from olfactory tracts
- Sends output to the primary olfactory cortex, orbital frontal olfactory cortex, corticomedial nucleus of the amygdala (smell evoked emotion), parahippocampal gyrus (smell evokes memory)
Describe the fornix
- Involved in memory pathways
- Signals sent between septal areas in deep center of brain, hippocampal formation, and mamillary bodies of the hypothalamus
Describe the mammillothalamic tract
- Involved in memory pathways
- Sends input to the anterior nucleus of the hypothalamus
Describe the stria terminalis
- Involved in the amygdala pathway (long way to reach septal area because it travels along the wall of the lateral ventricle)
- Signals between the septal area, amygdala (fornix), and hypothalamus
Describe the ventral amygdalofugal pathway
- Involved in the amygdala pathway (short way to reach septal area)
- Signals between septal area, amygdala, hypothalamus, and mediodorsal nucleus of the thalamus
Describe the medial forebrain
- Involved in sending information about behaviors, emotions, and personality to the brainstem and back (two way connection)
- Signals sent from amygdala to hypothalamus, to brainstem and back
What is olfaction?
- Function: smell contributes to the sensation of odors and taste
- Single odor molecule activates olfactory receptors, this results in a infinite number of different odors
- The only sensation that bypasses the thalamus
How is smell detected?
Smell stimulus > activation of olfactory receptors > olfactory nerves > through cribiform plate of ethmoid bone > olfactory bulb > olfactory tract > medial and lateral olfactory stria
Which part of the brain is responsible for declarative memory specifically?
- Hippocampal formation
- Medial temporal lobes (parahippocampal gyrus, entorhinal cortex)
How can memory influence decision making?
There is an important connection between the hippocampal formation and the prefrontal association cortex that allows you to consult your memory during decision-making to ensure you are making the correct decision