Notes on Limbic System from Nonexpert

I provide these notes freely a reminder my degree is in Computer Engineering and I am not a Doctor or Expert in Anatomy, I am trying to Learn

Limbic System

Hippo with a HAT – Hypothalumus, Amygdala, Thalamus, and Hippocampus

Not a doctor or specialist in anatomy. For me personally Acronyms are useful for encoding memory thus I have provided several that I am using to help me remember better. Acronyms increase surface area of matchable patterns. Pattern matching factors into memory. Also increases number of reiterations, fast reiterations that have potential to increase memory. They also require you to encode and decode information which I think works the short term and longer term memory.

via – by the way of

Limbic System – Gray Matter and White Matter Structures involed in Olfaction (Smell), Emotional Responses, Behavioral Activities, and Memories (LmbSys-GM&WM-OlfSml-EmResp-BhActv-Mem)

Gray Matter

GMDn – Gray Matter Dendrites (generally associated with receiving and processing signals)

Nucleus – in the CNS Central Nervous System a nucleus is a group of neurons associated with a specific function that is Gray Matter

Limbic Lobe

1. Cingulate Gyrus (GMDn-CG) – Memory, Emotional Processing, and ANS Autonomic Nervous System MemEm&ANS (GMDn-CG – MemEm&ANS)
2. Parahippocampal Gyrus (GMDn-PHG) – Memory Processing in the Temporal Lobe MemPnTL (GMDn-PHG – MemPnTL)

Hippocampal Formation – Memory

1. Dentate Gyrus (GMDn-DGHpc-AIn) – Afferent (Incoming) Information, Input
2. Subiculum (GMDn-SubcHpc-EOut) – Efferent (Outgoing) Information, Output
3. Hippocampus Proper (Cornu Amonus-EOut) (GMDn-HpcPrpCA) – Efferent (Outgoing) Information, Output

Amygdala (Amg-EmBhOlfSml) – Emotions, Behaviors, and Smell

1. Corticomedial Nuclear Group GMDn-CMNucG (olfaction, smell)
2. Besolateral Nuclear Group GMDn-BLNucG (emotions and behavoirs not related to smell)

Hypothalamus (GMDn-Hptha)

1. Mamimmilary Bodies (GMDn-MBHptha)
2. ANS Autonomic Nervous System Nuclei (GMDn-ANSNuc)

Thalamus (GMDn-Tha)

1. Anterior Nucleus (GMDn-AntThaNuc)
2. Mediodorsal Nucleus (GMDn-MDThaNuc)

Septal Area GMDn-SptA – found in Septum (connected via Striae Medularis Thalimi WMAx-SMTha), Reward Pathway and Emotional Responses RwPth&EmRsp (GMDn-SptA-RwPth&EmRsp)

Habinula GMDn-HabEptha – part of Epithalamus (connected via Striae Medularis Thalimi WMAx-SMTha), Reward Pathway and Emotional Responses RwPth&EmRsp (GMDn-HabEptha-RwPth&EmRsp)

GMDn-SptA connects via WMAx-SMTha to GMDn-HabEptha

Gray Matter Dendrite Septal Area connects via White Matter Axon Striae Medularis Thalami to Gray Matter Dendrite Habinula in Epithalamus

White Matter – to connect limbic nuclei with one another

WMAx – White Matter Axons (generally associated with sending information)

Fornix (WMAx-Fnx) – Hippocampus (GMDn-Hpc) → Septal Area (GMDn-SeptA) and Mammilary Bodies in Hippothalamus (GMDn-MBHptha)

GMDn-Hpc → viaWMAx-Fnx → GMDn-SeptA
GMDn-Hpc → viaWMAx-Fnx → GMDn-MBHptha

Amygdala – 2 pathways

1. Striae Terminalis – Amygdala → under corpus callosum → Septal Area GMDn-SptA and Hypothalamus GMDn-Hptha (viaWMAx-ST – Amg → under corpus callosum → SptA and GMDn-Hptha)
2. Ventral Amygdalo Fugal Pathway WMAx-VAFP – Amygdala → MDNuc Mediodoral Nucleus of Thalamus, Septal Area GMDn-SptA, Hypothalamus GMDn-Hptha (viaWMAx-VAFP – Amg -> GMDn-MDNuc of Tha, GMDn-SptA, GMDn-Hptha)

Striae Medularis Thalimi SMT is Septal Area SptA (Septum) to Habinula (Epithalamus) HabEptha

GMDn-SptA connects via WMAx-SMTha to GMDn-HabEptha

Mammillo Thalamic Tract MThaT – Mammillary Bodies (Hypothalamus) MBHptha → Anterior Nucleus of Thalamus AntNucTha (viaWMAx-MThaT – GMDn-MBHptha → GMDn-AntNucTha)

Medial Forbrain Bundle MFB – Prefrontal Cortex → Hypothalamus Hptha → Reticular Formation of the Brain Stem RetFoBS

viaWMAx-MFB – FL-GMDn-PFC → GMDn-Hptha → RetFoBS

Mammillo Techmental Tract (MTegT) – Mammillary Bodies (Hypothalamus) → Ventrial Tegmental Area VTA (Dopamenergic) (viaWMAx-MTegT – GMDn-MBHptha → VTA)

Mammillary Peduncles – Ventrial Tegmental Area VTADopa (Dopamenergic) → Mammillary Bodies MBHptha (VTADopa → viaWMAx-MPdn → GMDn-MBHptha)

Functions of Limbic System

1. Olfaction OlfSml

Epitheylial cells in Nose

Smell Olfactory Bulb → Olfactory Tract → bifercate → lateral L.O.S Lateral Olfactory Striae to Parhippocampal Gyrus PHG and Amygdala

biferates in other way (not laterally) → Orbital Frontal Cortex OFC

2. Memory

Papez Circuit

GMDn-SubcHpc Subiculum (Hippocampus) → WMAx-Fnx Fornix→ GMDn-MBHptha Mammillary Bodies (Hypothalamus) → WMAx-MThaT Mammillo Thalamic Tract → GMDn-AntNucTha Anterior Nucelus of Thalamus → GMDn-CG Cingulate Gyrus → GMDn-PHG Parahippocampal Gyrus → ERC Entorhinal Cortex → GMDn-DGHpc Dentate Gyrus (Hippocampus) → GMDn-SubcHpc Subiculum (Hippocampus)

GMDn-SubcHpc → viaWMAx-Fnx → GMDn-MBHptha → viaWMAx-MThaT → GMDn-AntNucTha → GMDn-CG → GMDn-PHG → viaERC → GMDn-DGHpc → GMDn-SubcHpc

GMDn-SubcHpc Subiculum (Hippocampus) → WMAx-Fnx Fornix → GMDn-MBHptha Mammillary Bodies (Hypothalamus) → MThaT Mammillo Thalamic Tract → AntNucTha Anterior Nucelus of Thalamus → CG Cingulate Gyrus → FL-GMDn-PFC Prefrontal Cortex (Frontal Lobe)

GMDn-SubcHpc → viaWMAx-Fnx → GMDn-MBHptha → viaWMAx-MThaT → GMDn-AntNucTha → GMDn-CG → FL-GMDn-PFC

3. Emotion and Behaviors

Emotional Responses – Fear, Anger, Rage, Sadness EmResp-FARS

Behaviors – Feeding, Sexual, Motivation Bh-FSM

Limbic System is in communication with Cerebral Cortex

Prefrontal Cortex (Frontal Lobe) (FL-GMDn-PFC) – thought process, reasoning, decision making, personality, and behaviors

Temporal Lobe (TL-GMDn) – smell, taste, insula involed in visceral sensation, auditory associations

PAA – Posterior Association Area – SSC Somatosensory Association Cortex, VAC Visual Association Cortex, AAC Auditory Association Cortex and communicates it to Amygdala

Amygdala (Amg) via Striae Terminalis (WMAx-ST) to Septal Area (GMDn-SptA) and Hypothalamus (GMDn-Hptha) (Amg → viaWMAx-ST → GMDn-SptA and GMDn-Hptha)

See a Bear and Fear → PFC (FL-GMDn-PFC) communicates it to Amygdala (Amg) (FL-GMDn-PFC → Amg)

Feeding Behavior (Feed-GMDn-VMNuc&GMDn-LHpthaNuc)

1. Ventromedial Nucleus VMN – Satiety (GMDn-VMNuc-Stty)
2. Lateral Hippothamlic Nucleus LHN – Hunger (GMDn-LHpthaNuc-Hngr)

Sexual Behavior (SexBh-GMDn-PVNuc&GMDn-MPONuc)

1. paraventricular nucleus PVN (GMDn-PVNuc-Oxyt) – releases oxytocin, can increase sex drive and blood flow
2. medial preoptic nucleus MPON (GMDn-MPONuc-GnRHTest) → GnRH → releases Testosterone, increases sex drive

Motivational Behavior (drug abuse, substance abuse, euphoria) MtvBh-DrgAb-SubAb-Euph-VTADopa

Amygdala via Striae Terminalis Septal Area

Ventral Tegmental Area VTA – Brain Stem, Lots of Dopamine, Dopaminergic Neurons

1. Nucleus Accumbens – VTA to Nucleus Accumbens Mesolimbic Pathway (Since of Reward from Dopamine)
2. Prefrontal Cortrex – VTA to PFC Meso-cortical Pathway (Since of Reward from Dopamine)

Pathway commonly involved in Substance Abuse

See a Bear and Fear → Amygdala via Striae Terminalis to Hypothalamus (Amg → WMAx-ST → Hptha)

Posterior Hypothalimic Nucleus PHNuc – associated with Fear

Hypothalamo Spinal Tract WMAx-HpthaST

invervates the Preganglionic Neurons (PGnNeur) located within Thoracal Lumbar (wnThorLmbSpnC) region of Spinal Cord to Sympathetic Nerves will go out to ANS-SympN-LHBpR

Amg → viaWMAx-ST or viaWMAx-VAFP → GMDn-Hptha → PHNuc(Fear) → viaWMAx-HpthaST → PgnNeur-wnThorLmbSpnC → Sympathetic Nerves ANS-SympN-LHBpR

ANS Autonomic Nervous System Response – Sympathetic Nerves out to Liver (increase Glucose for Increased Energy), Heart needs to start pumping, Increase d Blood Pressure, Increased Respiratory Rate

Another Neuron (not PHNuc) in Hypothalamus releases CRH – Cortico Releasing Hormone CRH → Pituitary → ACTH → Adernal Gland → Cortisol (Stress)

Conditions

Kluver-Bucy – bilateral loss of Amydalas, mellownrdd, placcidity, less ability to control eating (hyperphagia) and sexual drive (hypersexual), damage to hippocampus (Amnesia – memory loss)

Wernickes – vitamin B1 deficiency, damages mammillary bodies,

1. confabulation – missing memories leads to reconstructed memories (potentially not real)
2. middle cerebella peduncles – leads to ataxia
3. opthalmoplegia

Terms

Superior – Top

Inferior – Bottom

Anterior – front of body or brain

Posterior – back of body or brain

Dorsally – Back of Spinal Cord, Top Superior Part of Brain (like fin on a Dolphin)

Ventrally – Front Anterior Part of Spinal Cord, Bottom Inferior Part of Brain

Rostral – towards the nose, Spinal cord points toward head, in Brain Rostral points to Anterior

Caudal – towards the tail, Spinal cord points toward feet, in Brain Caudal points to Posterior

Sagittal Section – brain view cut from top of head to chin showing a side view

Horizontal Section – transverse section, cut perpendicular to long axis of body, as if cut through both sides of temples so the inside of brain could be viewed from top of head

Coronal/Front Section – section cut as if from central sulcus, potentially removing Frontal Lobe or PFC to allow ability to see what is beneath, parallel to long axis of body

Medial – closer to midline of brain, close to longitudinal fissure

Lateral – closer to sides of brain

Visceral – “of or relating to the viscera. affecting the viscera. of the nature of or resembling viscera. characterized by or proceeding from instinct rather than intellect: a visceral reaction. characterized by or dealing with coarse or base emotions; earthy; crude:” – Dictionary.com

Viscera – “Anatomy, Zoology. the organs in the cavities of the body, especially those in the abdominal cavity. (not used scientifically) the intestines; bowels.” – Dictionary.com