Forebrain and Limbic System Flashcards
What is does the Diencephalon consist of?
The 4 thalamic structures!
- Epithalamus =
- Thalamus
- Hypothalamus
- Subthalamus
What two stuctures make up the Epithalamus and what do they do?
- Pineal gland = Secretes melatonin, released during darkness, regulates sleep-wake cycles.
- Habenula = paired near base of pineal gland.
What is the major input and output for the Habenula?
Input = Stria medullaris, limbic input Output = Habenulointerpeduncular tract (Fasciculus retrofelxus) to midbrain RF.
_____ is the gateway to the cortex.
The thalamus
What pathways does the thalamus act as a relay for?
- All sensory except olfaction
- The cerebellum. basal ganglia, limbic system.
- These systems use different parts with some overlap so thalamus is composed of distinct nuclei.
What are the 6 subdivisons of thalamic nuclei?
- Anterior divison: Anterior Nucleus
- Medial division: Dorsomedial nucleus
- Lateral Divison:
- Dorsal tier = lateral dorsal, lateral posterior & pulvinar nuclei
- Ventral tier = ventral Anterior, Ventral Lateral, ventral Posterior, and medial & Lateral geniculates nuclei. - Intralaminar: Centromedian, parafasciular, and other nuclei.
- Reticular nucleus
- Midline nucleus
Which subdivision of the thalamus is the largest?
The Lateral subdivision
Subdivisions of the Thalamus are defined by ___________.
Internal medullary lamina (IML) “kinda like a membrane that separates divisions)
_______ sits in a split in the IML.
Anterior subdivision
All thalamic nuclei (except the reticular nucleus) are based on the same general theme…all consist of what?
- Projection neurons: provide output form thalamus
- Interneurons = small inhibitory.
- Projections vary from nucleus to nucleus.
What are the two types of thalamic inputs?
- Specific inputs
- Regulatory inputs
What is the function of the Specific inputs of the thalamus?
Conveys info a thalamic nucleus passes on nearly directly to the cortex (ex. medial leminisus to VPL or pic tract to LGN)
What is the function of the Regulatory Input of the thalamus?
Thalamic nucleus contributes to the info it receives before it is passed on to cortex.
Describe the function of the relay Nuclei…
Relay nuclei = receive well defined specific input from a subcortical source (Such as medial lemniscus) and projects to a well defined area of cortex (Such as spomatosensory cortex)
Describe the function of the Association Nuclei….
Receives specific inputs from association cortex (Like prefrontal cortex) and projects back.
Describe the function of the Intralaminar and midline Nuclei….
Receive distinct set of specific inputs (Basal ganglia, limbic structures)
*Project to cortex, basal ganglia and limbic system
What are the 3 specific types of thalamic nuclei?
Specific
Association
Intralaminar & midline
How is the reticular nucleus different from the other nuclei?
Its different because it has no projections to the cortex!
Its nucleus is a sheet of neurons that covers the thalamus. Axons must traverse nucleus to enter/leave thalamus and send collaterals to it.
What does the reticular nucleus do?
Important source of regulatory input to thalamus.
What are the main inputs and outputs of the Reticular nucleus?
Input = cortex & Thalamus Output = Inhibitory axons to thalamus
______, ________ & ______ have relay nuclei.
Sensory, Motor and Limbic systems
Motor system has what kind of relay nuclei?
VA & VL
Sensory system has what kind of relay nuclei?
VPL & VPM
Limbic system has what kind of relay nuclei?
Anterior & Lateral division
______ & _______ are main association Nuclei?
Dorsomedial & Pulvinar
*2 huge areas of association cortex.
DM is the association nuclei for _______ .
Prefrontal cortex (Foresight & affect)
Pulivinar-LP Complex is the association nuclei for ______, ______ & _______.
Parietal, occipital & temporal lobes of cortex.
Function unknown maybe visual?
Almost all fibers going to or from the cortex pass through the _______.
Internal capsule
What is the Internal Capsule?
Area kind of surrounding the Putamen & globus pallidus (Together = lenticular nucleus) thats collects and forms cerebral peduncle down. *Corticopontine, corticobulbar and corticospinal fibers all descend through the IC.
What are the 5 parts of the Internal capsule?
- Based on relationship to lenticular nucleus….
1. Anterior limb = Lenticular nucleus, caudate
2. Posterior Limb = Lenticular nucleus, thalamus
3. Genu = between A & P Limbs
4. Retrolenticular
5. Sublenticular
What does the Anterior limb of the IC contain?
Ant. nucleus -> Cingulate gyrus
DM -> Prefrontal cortex
What does the Post. Limb go the IC contain?
VA/VL -> motor areas -> brainstem/spinal cord
VPL/VPM -> somatosensory cortex
What does the Retrolenticular limb of the IC contain?
MGN -> Auditory complex
Pulvinar/LP -> parietal, occipital, temporal cortex
What does the Sublenticular limb of the IC contain?
LGN -> Visual cortex
* Fact check?
What does the Limbic system do?
Generates feelings/ emoting from sensory inputs, evolved to promote survival so variable depending on physiological needs.
What parts of the brain are included in the limbic system? (3)
- cingulate & parahippocampal gyrus
- amygdala
- hippocampus
_________ bridges autonomic/voluntary responses to environmental changes.
Limbic system
What is the function of the hypothalamus?
Critical in autonomic, endocrine, emotional and somatic functions; maintains physiological range or homeostasis.
What are the 3 main connections of the Hypothalamus?
- Interconnected with limbic system.
- Output to pituitary
- Interconnects visceral/somatic nuclei
What is the Longitundal organization of the hypothalamus?
Ant. region
Tuberal Region
Post. region
What is the Medial lateral organization of the Hypothalamus?
Lateral = rostral continuation of RF Perivent = Rostral continuation of periaqueductal gray Medial = nuclei
What are the 2 important inputs of the Hypothalamus?
- Parts of forebrain, especially limbic system (Convey info needed fro the hypothalamus to mediate autonomic/somatic aspects of emotional states)
- Brainstem & Spinal cord (conveys viceral & Sensory info)
What parts of the forebrain/limbic system play a part in hypothalamic input?
- Septal nuclei
- Ventral striatum
- Insula, orbitofrontal cortex
- All above from MFB
- Hippocampus
- Via fornix
- Amygdala
- Via stria terminalis, Ventral amygdalogugal pathway (VAP)
What parts of the Spinalcord/brainstem play a part in hypothalamic input?
Many inputs use medial forebrain bundle, dorsal longitudinal fasciulus (DLF)
*Other pathways as well. (STT Collaterals)
Describe the Outputs of the hypothalamus…
Same pathways used by inputs.
*Cortical outputs end diffusely.
_______ controls both pituitary lobes.
Hypothalamus
Antiduretic hormone or vasopressin does what?
Increases water reabsorption & Decreases urine output
Oxytocin does what?
Contraction of uterine and other smooth muscles
______ carries adeno releasing or inhibiting hormones.
Adenohypophysis of pituitary gland
______ caries antiduretic hormone and oxytocin.
Neurohypophysis of pituitary gland
What structure of the limbic system is MORE involved with emotional response?
Amygdala
What structure of the limbic system is involved with learning and memory?
Hippocampus (Cause hippos never forget……oh wait…no thats elephants.)
What structures of the limbic system are associated with the Amygdala?
Ventromedial prefrontal, anterior temporal and insular cortex as a liasion to neocortex *Dorsomedial thalamic nucleus
What structures of the limbic system are associated with the Hippocampus?
Posterior cingulate and parahippocampal cortex as a liaison to neocortex
*Ant. Nucleus of thalamus and mammillary bodies
Describe the structure and location of the Amygdala….
In the anterior, medial temporal lobe.
Merges with periamygdaloid cortex; part of uncle surface.
*Has 3 nuclear groups
What are the 3 Nuclear groups of the Amygdala?
- Has 3 nuclear groups
- medial = olfaction
- Central = hypothal, PAG, (emotional responses)
- Basolateral = cortex; central nuclei (emotional response)
Amygdala inputs take 4 routes, what are they?
- Stria terminalis: from hypothalamus & septal Nuclei
- Ventral Amygdalofugal pathway: from thalamus, hypothalamu, orbital and anterior cingulate cortex.
- Lateral olfactory tract: olfactory build & olfactory cortex
- Directly from temporal lobe cortex and hippocampus
Fibers leave amygdala through ______ & _______.
Stria teminalis & VAG
Amygdala output to Ventral striatum is believed to be a means fro what?
a means for drive related info to influence decisions about movement.
Tell me about the Limbic loop in basal ganglia…
Allows drive related info to influence movement
- associates stimuli with rewards
- pleasure results in increase VS dopamine release.
_____ line the perception of an object/ situation with the correct emotional response (especially with danger)
Amygdala
Inputs to amygdala include what?
- Thalamus & Cortex = inform amygdala about situations or object in the environment
- Hypothalamus & limbic system = inform amygdala about current physiologic and emotional state.
The outputs from the amygdala include what?
- Ventral striatum, hypothalamus and brainstem = initiate emotional responses.
- Cortex = increases awareness
- Limbic system = contributes to emotional experience.
Describe Kluver-Bucy Syndrome…
- Bilateral temporal lobe injury, involves amygdala, parahippocampal gyrus.
- fearless, placid, no emotions.
- Males hypersexual
- inordiante attetion to all stimuli (Sniff and eat everything)
Where is the fornix of the hippocampus and what is its function?
- has a long course under the corpus also and it is an important hippocampal output pathway.
The ______ and the ____ are 2 interlocking c’s.
Dentate and Hippocampus
What are the 3 distinct zones of the Hippocampus?
- Dentate gyrus
- Hippocampus proper (Cornu ammonia)
- Subiculum =Transition between hippocampus proper and adjacent parahippocampal cortex.
Describe the 8 Hippocampal output-inputs….Look at slides fro this too.
- Afferent fibers from sensory cortex input to Entorhinal cortex.
- Entorhinal Cortex projects to dentate gyrus
- Dentate neuron projects to CA3
- CA3 Neuron projects into fimbria & CA1
- CA1 neuron projects to subiculum
- Subiculum projects to fimbria (alvear pathway)
- Subicular neuron projects to entorhinal cortex
- Entorhinal neuron projects to sensory cortex.
Where does the main source of afferent fibers enter the hippocampus?
Entorhinal cortex (gets info from olfactory and other areas)
Where do the majority of Efferents leave the hippocampus and where do they go?
Leave via the subiculum; some go to entorhinal cortex, but MOST go thru fornix.
Describe the Papez circuit, What structures are involved?
Interactions among limbic structures, cortex and Hypothalamus.
