Hypothalamus and Limbic System Flashcards
What are the nuclear GROUPS of the medial region of the hypothalamus?
Preoptic
Suprachiasmatic
Tuberal
Mamillary bodies
What hormone is release in the medial preoptic nucleus?
Gonadotropic releasing hormone
The nucleus is also known as the sexually dimorphic nucleus. It is twice as large in males than in females.
What is secreted in the supraoptic and paraventricular nuclei?
PVN: Oxytocin
SON: ADH
What increases ADH secretion as monitored by the supraoptic nucleus?
DEHYDRATION and increaes in serum osmolarity, Pain, stress, opiates, barbiturates
Decrease is due to alcohol intake resulting in urination during beer drinking!
- The Ventro medial nucleus in the tuberal region is for?
2. Combined with obesity and hypogonadism due to involvement of the adjacent infundibulum this can result to?
- Satiety center– bilateral lesions result in a voracious appetite, obesity and savage behaviour– also RAGE!!
The feeding center on the other hand is in the lateral hypothalamus
FAT MONSTER! LIKE THE BLOB in X-Men! - Frohlich syndrome
What nucleus in the tuberal region secretes dopamine for prolactin and GH control?
Arcuate nucleus– also with ACTH and beta endorphins
Target for leptin because it has food promoting and inhibiting properties
Destruction of the orexin/hypocretin neurons int he lateral region of the hypothalamus is responsible for?
narcolepsy
NB: Hypocretin/Orexin inhibits anorexinergic and excites orexinergic neurons in the arcuate nucleus
Which extrensic hypothalamic connection is responsible?
- Light for circadian rhythm
- Link to the periaqueductal gray matter to effect autonomic responses
- Light for circadian rhythm: Retino-hypothalamic
- Link to the periaqueductal gray matter: Dorsal Longitudinal Fasciculus of Schutz
NB: Mamilotegmental tract also plays a vita role for autonomic effects of the hypothalamus
What is also known as:
- Prolactin inhibiting factor
- Somatic inhibiting releasing factor
What controls the release of ACTH?
- Domapine
- Somatostatin
Cotropin releasing factor
In relation to temperature control– what regions of the hypothalamus are involved? What happens with damage to these regions?
How about in sleep?
Temp
Anterior: Sensitive to high temperature– hyperthermia– for cooling! AC! DC
Posterior: Sensitive to low temp– poikilothermia (body temperature fluctuates with environmental temp)– for heating!
Sleep
Anterior sleep
Posterior wake up
Lateral with hypocretin system is the major neuromodulatory system that controls monoamines and cholinergic systems that control vigilance states
What areas of the hypothalamus are concerned with PS and Symphathetic systems?
Lateral and caudal for symptathetic
Medial and rostral for PS
What nucleus of the hypothalamus is responsible for the circadian rhythm?
Suprachiasmatic nucleus– regulates the melatonin secretion by the pineal gland based on retinal inputs
Which part of the H plays role in memory?
Mamillary bodies
Mamillary for memory!
What is the treatment of diabetes insipidus?
How does SIADH result from hypothalamic injury?
desmopressin
Damage to the hypothalamic osmoreceptors
What is the Shapiro syndrome?
Episodic hypothermia with
polydipsia,
hyponatremia
and autonomic paroxysms
The diencephalic syndrome of infancy (Russel Syndrome) is usually due to?
Anterior hypothalamus tumor
What is the Kleine-Levin syndrome?
Episodic compulsive eating, hypersomnolence, hypersexuality in adolescent males
Seen in hypothalamic and medial thalamic lesions
CONTRAST WITH KLUVER BLUCY syndrome!
What kind of memory problems are brought about by hypothalamic damage?
Inability to encode NEW . memories for personally experienced time specific events– EPISODIC MEMORY!
Mamillary bodies connect to the hippocampus by the fornix and to the anterior thalamic nucleus by the mamillothalamic tract
What are the 5 members of the rhinencephalon?
Olfactory nerve rootlets Olfactory bulb Olfactory tract Olfactory striae Primary olfactory cortex
What are the layers of the olfactory bulb?
- Olfactory nerve layers
- Glomerular layer: synapse
- Plexiform layer: Tufted neuron
- Mitral cell layer:Mitral cell neuron
- Granule layer: Granule neuron and short axon neuron
Axons of which neurons are found in the olfactory tract?
Mitral from the mitral cell layer and tufted neurons from the plexiform layer
What are the 3 olfactory striae and where do they go?
Lateral OS: Projects to the primary olfactory cortex
Intermediate OS: Blends with the anterior perforated substance
Medial OS: Projects to the medial olfactory area AKA septa area in the medial surface of the frontal lobe ventral to the genu and rostrum of the CC anterior to the lamina terminalis– mainly for emotional responses elicited by the smell
What are the three components of the primary olfactory cortex?
- Pyriform cortex
- Periamygdaloid area
- Uncus
These are both anterior to the uncus
The three areas of the olfactory cortex are interconnected by?
Diagonal band of Broca
What are the components of the limbic lobe?
- Subcallosal gyrus
- Cingulate gyrus
- Isthmus of the cingulate gyrus
- Parahippocampal gyrus
- Uncus
What is the flow of signals in the Papez circuit (James Papex 1937)?
Hippocampus»_space; fornix»_space; mamillary bodies»
- mamillothalamic tract» anterior thalamic nucleus
- thalamocortical system» cingluate gyrus» entorhinal area»_space; hippocampus
What parts of the following are part of the limbic system?
- Hypothalamus
- Thalamus
- Brianstem
- Neocortex
- Hypothalamus: mamillary bodies
- Thalamus: anterior and medial thalamic nuclei
- Brianstem: Reticular formation
- Neocortex: Basal frontotemporal
What is the hippocampal formation?
What are the 3 components of the hippocampal formation?
It is an infolding of the parahippocampal gyrus into the inferior temporal horn of the lateral ventricle consisting of:
Starting from the parahippocampal gyrus going inwards:
- Subiculum
- Hippocampus
- Dentate
What are the 3 major layers of the hippocampus?
- Molecular
- Pyramidal cell layer
- Striatum oriens (Polymorphic layer)– most superficial adjacent to the ventricle
What part of the hippocampus is most sensitive to hypoxia and serve as the trigger zone for some forms of temporal lobe epilepsy?
Medium vulnerability
Least vulnerable
CA1 Sommer’s sector
CA 4
CA 2 and 3
What neurons in the hippocampus contribute to the outflow of signals?
Principal neurons (Pyramidal cells)
What structure carries the outflow tract of the hippocampus?
Axons of the pyramidal tract are oriented towards the ventricular surface where they gather to form the alveus and fibria and finally join the FORNIX as the outflow tract
What are instrinsic neurons of the hippocampus and where are they located?
What do they do?
Basket cells and polymorphic cells are located in the stratum oriens– they are inibihitory to pyramidal cell activity
One basket cell to 200-500 pyramidal cells– similar to the cerebellum!
Which among the three parts of the hippocampal formation DOES not contribute to the output of the structure?
Dentate gyrus– mostly granular cells that form the mossy fiber system that connects to the pyramidal cells in the hippocampus
The bulk of extrinsic input to the hippocampal formation is mainly from?
Entorhinal area of the PH gyrus (From the thalamic output as part of the Papez circuit!!)
and the septal area (aka medial olfactory area) where the medial olfactory striae go to form the olfactory tract!
What part of the cortex of the cortex is most damaged by AD and the site where the disease begins?
Entorhinal cortex
What brodmann areas comprise the entorhinal cortex?
28– entorhinal cortex
34– Dorsal entorhinal area
In the mesial termporal lobe acting as the interface of the hippocampus with the neocortex
Trace the parts of the fornix starting from the hippocampus all the way to the mamillary bodies.
Hippocampus** Fimbra»_space; Crus fornix»_space; Comissure of the fornix»_space; body of fornix (attached to the inferior surface of the septum pellucidum)» 2 anterior columns of the fornix ** Mamillary bodies
Where do fibers of the post commisural fornix go? Where are the fibers from?
From the subiculum
Going to the Mammillary body and anterior nucleus of the thalamus (Part of the Papez circuit!!)
Bilaterall ablation of the hippocampus results in what kind of memory loss?
- Loss of recent (60s) memory
- Inability to store newly learned facts (anterograde amnesia)
Remote and long term memories remain intact
T or F: The hippocampus has a low threshold for seizures but the spread of such epileptic activity all over the cortex is NOT usual.
T
Where is the amygdala?
At the tip of the temporal lobe beneath the cortex of the uncus and rostral to the hippocampus and inferior horn of the lateral ventricle
What is the major outflow tract of the amygadal?
Stria terminalis
Other: Ventral amygdalofugal pathway
Re: Food intake
- Lesions in the corticomedial group will result in? Stimulation will result in?
- Lesions in the basolateral group will result in? Stimulation will result in?
- L: Aphagia, decreased emotional tone
S: Defensive aggressive action - Hyperphagia, happiness and pleasure
S: Fear and flight
Corticomedial group is similar to a ghoul! Stimulation will likely give you an aggressive hungry person
What is the main effect of the amygdala on arousal?
Facilitatory– mainly from the basolateral nuclear group
Bilateral lesions of the amygdala results in what sexual activity?
Hypersexuality
What are the two components of the septal area?
Septum pellucidum Septum verum ventral to the SP contains: 1. Septal nuclei 2. Diagongal band of broca 3. Bed nucleus of the stria terminalis 4. Nucleus accumbens septi
The major connections of the septal area are with? traveling through?
Hippocampus via fornix
What characterizes the septal syndrome?
Destruction of the septal nuclei gives rise to behavioral overreaction to most environment stimuli.
What part of the limbic system is primarily responsible for the ff:
- Memory
- Emotion and sexuality
- Motivation
- Social behavior
- Memory: Hippocampus
- Emotion and sexuality: Amygdala
- Motivation: Anterior cingulate gyrus
- Orbitofrontal cortex: Social behaviour
What 2 types of memory are NOT affected by mesial temporal damage?
Procedural skill learning memory and
Retrograde memory
There is severe declarative (explicit) memory loss and anterograde memory loss
What are the two types of implicity memory?
- Procedural
- Priming: short lived enhancement of perceptually based performance following recent exposure to a visually similar material
What is the most common type of memory loss (amnesia)?
Anterograde
What is the etiology of wernicke korsakoff syndrome?
B1 deficiency
What are the two main classifications of memory?
Explicit: Semantic and Episodic (Long term (Anterograde and retrograde) and Short term)
Implicit: Procedural and Priming
What syndrome results from bilateral lesions of the temporal lobe that involve the amygdala, hippocampal formation and adjacent neural structures?
Characterized by: hyperorality, hypersexuality, visual agnosia/ psychic blindness, docility, lack of emotional response, increased appetite, memory deficity
Klüver-Bucy syndrome
What autonomic effects result from stimulation of the right and left insular cortex?
Right: sympathetic– tachycardia
Left: parasympathetic– bradycardia
Cowdry type A inclusions occur in what type of encephalitis?
HSV
