Neuroscience Week 6: Limbic System Flashcards
Limbic System Functions
has a role in basic emotions such as anger and fear and is the part of the brain that regulates basic “fight or flight” behaviors
- Homeostasis
- Olfaction
- Memories
- Emotions
- Reward pathway
Limbic system Mnemonics
HOMER
- Homeostasis
- Olfaction
- Memories
- Emotions
- Reward Pathway
5Fs
- Feeling
- Feeding
- Fleeing
- Fighting
- Fucking
Limbic system was first described by?
Paul Broca in 1870’s
Identify Limbic System
limbus definition
medial border of the brain between the upper border of the cortex and the brainstem
Describe Limbic circuitry
Emotions have what components?
Emotions have significant visceral and autonomic components
Which cortical areas have direct connection with the hypothalamus?
- Most cortical areas have no direct connections with the hypothalamus.
- Limbic-cortical areas and limbic areas connect directly to the hypothalamus
Hypothalamus Nuclei
7 listed
- Lateral Nucleus
- Ventromedial Nucleus
- Anterior Nucleus
- Posterior Nucleus
- Suprachiasmatic Nucleus
- Supraoptic/Paraventricular Nucleus
- Preoptic Nucleus
Hypothalamus: Lateral nucleus function
Feeding behavior
Hypothalamus: Lateral nucleus stimulated by?
Stimulated by Ghrelin
Hypothalamus: Lateral nucleus inhibited by?
Inhibited by Leptin
Hypothalamus: Lateral nucleus Damage leads to?
failure to thrive/anorexia
Hypothalamus: Ventromedial nucleus function
Satiety
Hypothalamus: Ventromedial nucleus Stimulated by?
Leptin
Hypothalamus: Ventromedial nucleus Damage leads to?
Hyperphagia
Hypothalamus: Anterior nucleus function
Cooling
Hypothalamus: Anterior nucleus Controlled by?
Parasympathetic/Sympathetic Control
Hypothalamus: Posterior nucleus function
heating
Hypothalamus: Posterior nucleus controlled by?
Sympathetic control
Hypothalamus: Suprachiasmatic nucleus function
Circadian rhythm
Hypothalamus: Suprachiasmatic nucleus regulation
control of sleep and wake cycles
Hypothalamus: Supraoptic/Paraventricular nucleus function
Synthesize ADH and oxytocin
Hypothalamus: Supraoptic/Paraventricular nucleus Regulation
ADH and Oxytocin are carried to posterior pituitary for storage and release
Hypothalamus: Preoptic nucleus Function
Thermoregulation & sexual behavior (Release GnRH)
Hypothalamus: Preoptic nucleus malfunction
Failure of GnRH neurons to migrate leads to Kallmann Syndrome
Hypothalamus homeostatic regulatory functions
7 listed
TAN HATS
- Thirst and water balance
- Adenohypophosis (anterior pituitary)
- Neurohypophosis (posterior pituitary)
- Hunger
- Autonomic nervous system
- Temperature
- Sexual urges
Identify Limbic system and which are components of each pathway
- Medial Limbic Circuit (Papez) yellow
- Limbic Loop (Reward Pathway) Red
Papez circuit AKA
Medial Limbic Circuit
Medial Limbic Circuit AKA
Papez Circuit
Medial Limbic Circuit primarily involved in?
Memory formation and propagation of epileptic seizures
Medial Limbic Circuit path from the hippocampus
hippocampus→(up through fornix)→Mamillary bodies→(project up)→anterior nucleus of the thalamus→(thalamic projections up)→cingulate gyrus←input from mid-orbitofrontal cortex and lateral prefrontal cortex
Cingulate gyrus→(project down through entorhinal cortex to the temporal lobe back to the)→hippocampus
Components of the Medial Limbic Circuit
4 listed
- Hippocampus
- Mammillary bodies
- anterior thalamic nuclei
- Cingulate gyrus
Medial Limbic Circuit Pathway from the Hippocampus
- hippocampus→(up through fornix)→
- Mamillary bodies→(project up)→
- anterior nucleus of the thalamus→(thalamic projections up)→
- cingulate gyrus
- ←input from mid-orbitofrontal cortex and lateral prefrontal cortex
- Cingulate gyrus→(project down through entorhinal cortex to the temporal lobe back to the)→
- hippocampus
The Medial Limbic Circuit is important in?
The MLC is important in learning, memory and mesial temporal epilepsy
Limbic circuit related to mesial temporal epilepsy?
Medial Limbic Circuit
Medial Limbic Circuit Mnemonic
He-Man Ate a Cat
He = Hippocampus (limbic system)
Man = Mammillary body (hypothalamus)
Ate -= Anterior thalamic Nuclei (thalamus)
Cat = Cingulate gyrus (limbic system)
Hippocampus location
the hippocampal formation is easily seen on the ventro-medial aspect of the temporal lobe and comprises the floor and medial wall of the inferior horn of the lateral ventrical
Entorhinal cortex is the _______ pathway
Input pathway
Identify components
Dentate gyrus receives input from
Entorhinal cortex
Dentate gyrus projects to?
mossy fibers (axons of neurons from the dentate gyrus) project to CA3
CA3 Projects to?
CA2
CA2 projects to
CA1
CA1 projects to
back to the subiculum
synapses on CA2, CA1 AKA
Schaeffer Collaterals
Where are new neurons made?
Neurogenesis occurs in the Dentate gyrus and nowhere else
Specific neurons from the subiculum form the
Fornix
Some subiculum neurons also project directly back to the?
Entorhinal cortex not just to the fornix
Fornix is comprised of?
axons from pyramidal neurons in the hippocampus and subiculum
The majority of axons in the fornix project to
the mammillary bodies of the hypothalamus
Damage to the mamillary bodies will lead to
memory impairments
Identify
fornix
hippocampal commissure and importance
- connects both hemispheres of the hippocampus
- need bilateral damage to have anterograde amnesia (inability to form new memories)
Anterograde amnesia Definition
inability to form new memories
Anterograde amnesia causes
bilateral damage to the hippocampus because of the hippocampal commissure
Hippocampus connection to cortical areas
- memories are not formed in isolation, they have sights, smells, sounds and what’s going on
- constant frontal monitoring attention appropriately
The limbic loop AKA ________ pathway
Motivation pathway
or
reward pathway
The limbic loop uses this(ese) neurotransmitters? from?
dopamine from the ventral tegmental area
The limbic loop: nucleus accumbens gets input from
2 listed
- Medial PFC
- Limbic prefrontal cortex
Nucleus accumbens projects to?
ventral pallidum
Nucleus accumbens is located in the?
Ventral Striatum
All drugs of abuse and stress affect the activity of this nucleus
Nucleus Accumbens
Cortico-striatal loops and behavior
Limbic loop distinguished from the motor loop by?
4 listed
- the source and nature of the cortical input (orbital and medial prefrontal)
- The division of the striatum and pallidum that process the input (both are in the ventral areas)
- The source of dopaminergic neurons from the midbrain (VTA)
- the thalamic target of the pallidal output (MDT)
Amygdala location
the amygdala is the other major limbic structure of the temporal lobes, lying directly in front of the hippocampus
The amygdala and the prefrontal cortex are involved in?
The formation of fears and phobias
CNS components involved in the formation of fears and phobias
amygdala and prefrontal cortex
Lesions of the amygdala result in?
5 listed
- decreased aggression “tameness”
- hypersexuality
- hyperorality
- visual agnosia
- lack of fear
Limbic components: Amygdala
most important Nuclei of the amygdala
- basal nucleus
- lateral nucleus
- or basolateral nucleus of the amygdala
Amygdala pathway
Damage to the bilateral amygdala leads to?
Inability to experience fear
However, greater than average fear and panic attacks in response to novel physiological fearful experiences such as feelings of suffocation
Kluver-Bucy Syndrome
Kluver-Bucy Syndrome
- The absence of emotional responses (fear, rage, aggression) (amygdala)
- Over-attention to sensory stimuli (amygdala)
- Hypersexuality (amygdala)
- Visual Agnosia (inability to recognize objects visually) (temporal cortex)
Visual Agnosia definition
Inability to recognize objects visually
(temporal cortex)
Nucleus Accumbens Location
one of the septal nuclei in the ventral striatum
besides from the VTA the ________________ is a convergent site for input from the amygdala, hippocampus, entorhinal cortex and anterior cingulate gyrus
Nucleus Accumbens
The ________ has reciprocal connections to many of these areas but also projects to ____________.
- Nucleus Accumbens
- The frontal cortex
_________, _________, ________, _______, and __________receive a significant dopaminergic innervation from the Ventral tegmental area (VTA) of the midbrain
5 listed
- Limbic cortical areas
- amygdala
- hippocampus
- septal nuclei
- Nucleus accumbens
_________ neurons in the septal and basal nuclei are important components of the _________
- Cholinergic neurons
- limbic system
Diagonal band of Broca
+
Nucleus Basalis of Meynert
location
Nucelus basalis of Meynert
Identify
Identify
Diagonal band of Broca
+
Nucleus Basalis of Meynert
and the limbic system
- cholinergic neurons in the septum and the basal forebrain project to the cortex and hippocampus and play an important role in modulating learning and memory systems
- these neurons degenerate at early stages of Alzheimer’s Disease
Identify
The limbic loop and motivation
Association with depression
The limbic and olfactory systems
Prirform and pre-piriform cortex location
located in the uncus
The primary olfactory cortex is located in?
the uncus in the piriform and pre-piriform cortex
Identify
Identify
Seizure activity is common in the _______________.
Ventromedial temporal lobe (parahippocampal gyrus and uncus)
It is frequently associated with olfactory hallucinations (rotten-egg smell)
- seizure activity anventromedial temporal lobe (parahippocampal gyrus and uncus) (mesio temporal lobe epilepsy)
- it is thought that sense they are adjacent to the primary olfactory cortex it is stimulated
mesio temporal lobe epilepsy is associated with?
It is frequently associated with olfactory hallucinations (rotten-egg smell)
&
the medial Limbic circuit
Lying just deep to the uncus is the?
Amygdala
the primary olfactory cortex projects to the?
Entorhinal cortex and then to the orbitofrontal cortex for discriminating olfactory input
The ____________ projects to the Entorhinal cortex and then to the orbitofrontal cortex for discriminating olfactory input
Primary olfactory cortex
Summary
Nucleus Accumbens receives input from
4 listed
- hippocampus
- amygdala
- VTA (DA)
- Dorsal Raphe (5-HT)
Kallman Syndrome
Kallmann syndrome is a condition characterized by delayed or absent puberty and an impaired sense of smell. This disorder is a form of hypogonadotropic hypogonadism, which is a condition resulting from a lack of production of certain hormones that direct sexual development.
Damage to which area produces Kallman Syndrome
Preoptic nucleus of the hypothalamus
