DSA Hypothalamic And Limbic System Flashcards
Where does the hypothalamus come from embyrologically?
Diencephalon
What info does the hypothalamus integrate?
Info from
Forebrain Brainstem Spinal cord ANS Hormones from blood (etc.)
What is the role of the hypothalamus?
Maintenance of homeostasis
What is homeostasis require control over?
Water and electrolyte balance Food intake Temperature BP Circadian rhythm Stress response Body metabolism
Where is the location of hypothalamus?
Surround 3rd ventricle - forms the floor and wall of it
Anterior to optic chiasm
Posterior hypothalamus merges onto tegmentum and PAG (midbrain)
What is the hypothalamus continuous through?
Continuous through infundibulum stalk w/ posterior pituitary
What are the structures of the hypothalamsu?
Mammillary bodies
Tuber cinereum
Median eminence
What part of the hypothalamus do the mammillary bodies form?
Posterior part
Adj. to cerebral peduncles
What is the Tuber Cinereum
Section b/w mammillary bodies and optic chiasm/tract
What does the median eminence come from?
What will is narrow into?
From tuber cinereum
Narrows into infundibulum
How are hypothalamic nuclei divided?
Longitudinally into anterior, tuberal, and mammillary region
Medially and laterally by the fornix
What does the tuberal region of the hypothalamic nuclei contain?
Tuber cinereum
What does the posterior or mammillary region of the Hypothalamic Nuclei include?
Includes the mammillary bodies
What is in the Periventricular zone of the hypothalamic nuclei?
PAG thru the third ventricle
What does the fornix do in terms of divisions?
Divides remainder of hypothalamus into medial and lateral zones
How are neurons arranged in the lateral zone of the hypothalamus?
What does it contain?
Diffusely arranged
Medial forebrain bundle
What will a lesion to the lateral zone of the hypothalamus cause?
Decrease in feeding behavior
—> weight loss
What other regions are contained in the medial zone of the hypothalamus?
Anterior, tuberal and posterior regions
How are the neurons arranged int he medial zone of the hypothalamus?
Into distinct nuclei
What is the blood supply to the hypothalamus?
Perforating arteries form Circle of Willis
What serves the anteromedial group of the hypothalamus?
Branches from ACA (A1)
Anterior communicating a.
What is the anteromedial group of the hypothalamus?
Preoptic area
Supraoptic region
Septal nuclei
Rostral portions of the lateral hypothalamic areas
What is the blood supply to the posteromedial group of the hypothalamus?
PCA -P1
Posterior communicating a.
What is included in the Posteromedial group of the hypothalamus?
Tuberal region (Rostral post. Comm. a.)
Mammillary region (caudal post. Comm. a.)
What nuclei are found in the supraoptic region?
Supraoptic = anterior
Supraoptic/paraventricular nucleus
Suprachiasmatic nucleus
Anterior nucleus
What nuclei are found int he posteiror/mammillary region?
Medial mammillary nucleus
What nuclei are found in the tuberal region?
Ventromedial nucleus
Dorsomedial nucleus
What does the Supraoptic/Paraventricular nucleus contain?
What will it release to?
Oxytocin (SO)
ADH (PVN) -vasopressin
—> posterior pituitary
What will a lesion to the supraoptic/paraventricular nucleus cause?
Diabetes insipidis (DI)
Increased H20
Increased urination
What does the suprachiasmatic nucleus receive input from?
What does it help regulate?
Input from retina
Involved w/ circadian rhythms
What will a lesion to the suprachiasmatic nucleus cause?
Modification or abolishment of circadian rhythms
What is the function of the anterior nucleus?
Visceral/somatic function
Temperature regulation
What does the medial mammillary nucleus receive and send info from/to?
Afferents from hippocampus via fornix
Efferents to thalamus and Brainstem
What will a lesion to the medial mammillary nucleus cause?
Inability to process short term events
Into long term memory
What is the role of the Ventromedial nucleus of the tuberal region?
Satiety center
What will a lesion of the ventromedial nucleus cause?
Excessive eating —> abnormal weight gain
What is the role of the Dorsomedial nucleus of the Tuberal Region?
Subserves functions of emotional behavior
What will stimulation of the Dorsomedial nucleus of the Tuberal region cause?
Sham rage
What will a lesion to the Dorsomedial Nucleus of the Tuberal region cause?
Decreased aggression and feeding
What is the largest single input to the hypothalamus?
Subiculum and hippocampus thru Fornix
What does the Medial Forebrain bundle (MFB) interconnect?
What will it go thru?
Septal nuclei
Hypothalamus
Midbrain tegmentum
Thru lateral hypothalamic zone
What goes thru amygdalohypothalamic fibers?
What is the target?
Stria terminalis and Ventral Amygdalofugal pathways
Targets:
Septal nuclei
Preoptic area
Medial hypothalamic zone of hypothalamus
What are the 2 efferent routes coming from the Hypothalamus?
Mammillary Fasciculus
Hypothalamothalamic fibers
Where does the mammillary fasciculus come from?
Medial mammillary nucleus
What will the mammillary fasciculus bifurcate into?
Mammillothalamic tract
Mammillotegmental tract
What is the path of the efferent Mammillothalamic tract?
What circuit is this an important part of?
—> Anterior nucleus
Circuit of papez
Where does the Mammillotegmental Tract go to?
Brainstem nuclei in tegmental areas
What is the origin and destination of the efferent Hypothalamothalamic fibers?
Origin: lateral preoptic area
Destination: Dorsomedial nucleus (Thalamus) Amygdaloid nucleus (via stria terminalis and ventral amygdalofugal pathway)
How is the hypothalamus connected to the Pituitary gland?
Posterior lobe via Supraoptic Hypophyseal tract
Anterior lobe via Tuberoinfundibular Tract
What is the supraoptic hypophyseal tract made of?
axons of neurons in Supraoptic Nucleus (SON) & Paraventricular Nucleus (PVN)
What will the supraoptic hypophyseal tract produce?
Oxytocin(SO)
ADH (PVN)
What does the Supraoptic hypophyseal tract store oxytocin and ADH in ?
Herring bodies
How is oxytocin and ADH released by the Supraoptic hypophyseal tract to the posterior pituitary?
Released in capillary plexus of posterior pituitary
What does the tuberoinfundibular tract receive input from?
neurons in periventricular zone, PVN and others (“Hypothalamic neurosecretory neurons”)
What will the Tuberoinfundibular tract release to the Anterior Pituitary?
Releasing hormone to
Median eminence & Infundibulum
What are circadian rhythms?
Hormonal fluctuations secondary to light-dark cycles
What does the SCN do re: Circadian rhythms?
Opposes drive for sleep
Essential for timing of rest vs. activity
How does the SCN influence the circadian rhythm?
Cells maintain 24 hour day time frame via transcription/translation control of the CIRCADIAN GENES
Gene products indirectly CONTROL MELATONIN (pineal gland)
When will gene products increase melatonin secretion?
Just prior to normal sleep slight
What does the melatonin secretion do re: SCN?
Acts as internal indicator of circadian time
Feedbacks to SCN
What are the Hypothalamus’ 2 direct links to the ANS?
Hypothalamomedullary fibers
Hypothalmospinal fibers
Where will hypothalamomedullary fibers go?
Solitary nucleus
Dorsal Vaal motor nucleus
Nucleus Ambiguus
Where will hypothalamospinal fibers go?
Intermediolateral cell column of GVE preganglionics
What happens if there is a lesion in the anterolateral medulla?
Hypothalamomedullary fibers
Hypothalamospinal fibers
Are disrupted
Sympathetic outflow disrupted to face and head or body
(Horner’s Syndrome)
What is the indirect link of the Hypothalamus to the ANS?
Posterior longitudinal fasciculus
Mammillotegmental tract
Where will the indirect links of the hypothalamus to the ANS go?
To PAG and then to visceral areas of brainstem
Solitary and dorsal motor vagal nuclei
What are the characteristics of the Hypothalamus’ indirect links to the ANS?
Short tracts that influence autonomic nuclei in brainstem
What does the Limbic system consist of?
Subcallosal area Cingulate gyrus Parahippocampal gyrus Uncus Hippocampal formation Subcortical nuclei
What do connections of the Limbic system influence?
Behavior
Memory
Pain perception
What will happen to the Limbic system with age?
Will actually change
One of the few gray areas to do so
What is the Papez circuit ?
An anatomicophysiologic mechanism for emotion
What gyrus is crucial in the Papez circuit?
Cingulate gyrus
What is the role of the hippocampal formation?
Learning and memory
What does the hippocampal formation contain?
Hippocampus
Subiculum
Entorhinal cortex
Dentate gyrus
What is the subiculum?
Transitional area b/w hippocampus and entorhinal cortex
What are the sub fields of the hippocampus ?
CA1
Ca2
CA3
CA4
What is the afferent pathway of the hippocampus?
Dentate gyrus —> CA3 —> CA1 —> subiculum
C2, c4 = modulators
What is the efferent pathway of the hippocampus?
Subiculum —> fornix —> nuclei
Medial mammillary nucleus
Ventromedial nucleus
Anterior nucleus
(Also to septal nuclei, frontal cortex, preoptic, and anterior nuclei, nucleus accumbens)
What does the cingulate gyrus receive info from and send info to?
Receive afferents from thalamus and cortex
Send efferents to entorhinal cortex via cingulum
Where is the septal region?
What does it control?
Small area above anterior commissure
Controls rage behavior
What is the medial Forebrain bundle?
What is the role of the MFB?
A group of DA fibers that go from anterior to posterior thru lateral hypothalamic area
Conduit for septal nuclei and hypothalamus to communicate with brainstem
Where is the nucleus accumbens located?
In rostral and ventral forebrain;
Where head of caudate nucleus and putamen are continuous
What does the Nucleus accumbens receive input from?
Send efferents to?
Afferents from
Amygdala and Hippocampus
Efferents to
Hypothalamus
Brainstem
Globus pallidus
What is the role of the nucleus accumbens?
Regulates behaviors related to addiction and chronic pain
What is the role of the papez circuit?
Modulates feelings (fear, anxiety, sadness, happiness, etc. )
What is the path of the Papez circuit?
Cingulate gyrus
—> hippocampal formation (Subiculum&entorhinal cortex)
—> fornix
—> medial mammillary nuclei
—> anterior nucleus via mammillothalamic tract
—> cingulate gyrus
What is the role of the amygdala?
Encoded the motivation and emotional connotations of experiences
Where is the amygdala?
Deep and medially within the temporal lobe
What does the amygdala receive afferent info from?
‣ Inferior temporal association cortex ‣ Thalamus ‣ Septum ‣ Olfacotry tract ‣ Brainstem
What does the amygdala project to?
Hypothalamus and basal ganglia (via stria terminalis)
Hypothalamus, septal nuclei, frontal/prefrontal/cingulate/insular cortices
&
Brainstem to end of visceral nuclei and raphe nuclei (via ventral amygdalofugal pathway)
Where is the ventral tegmental area?
Medial to substantia nigra
What nuerons does the VTA contain?
Lots of Dopaminergic neurons
What does the VTA form connections with?
Ventral striatum
Amygdala
Etc.
What does the VTA send efferent to?
What will this play a role in?
Nucleus Accumbens
Role in reward & motivation, contribution to addition
What is anosmia?
Loss of smell
What can cause anosmia?
What is the outcome typically?
Viral infection of olfactory mucosa Obstruction of nasal passages Congenital defects Lesion of CN1 Tumors in floor of anterior cranial fossa
Will not recover sense of smell
What is Phantosmia or Olfactory hallucinations?
Distortion in smell experience, or perception of smell when there is no odor present
What causes Phantosmia?
Abnormal sequence of neuron activity
Possibly from LESION at... anterior/medial temporal lobe, hippocampus, amygdala, medial dorsal Thalamic nuclei
What is hippocampal amnesia?
Deficit in anterograde episodic memory
What causes hippocampal amnesia?
Bilateral lesions of hippocampi
What are the outcomes of Hippocampal amnesia?
Cannot learn new material
Procedural and working memory still ok
IQ and formal reasoning ~Normal
What is Korsakoff’s syndrome caused by?
Thiamine deficiency from chronic alcoholism or poor diet
What happens to brain anatomy in Korsakoff’s syndrome?
Degeneration of mammillary bodies, hippocampal complex & dorsomedial Thalamic nucleus
how does Korsakoff’s syndrome manifest?
Cannot retain newly acquire memory (short term doesn’t go to long term)
Difficulty learning new tasks and transforming into long memory
Difficulty understanding written material and conducting meaningful conversation
Confabulation by patient
What is confabulation?
What syndrome is this seen in?
Korsakoff’s syndrome
Combine fragmented memories into a memory of an event that never occurred
What does Kluver Bucy syndrome result from?
Bilateral lesions of temporal lobe that destroy amygdaloid complex
What behavioral changes are associated with Kluver Bucy Syndrome?
Hyperorality
Hypermetamorphosis
Hypersexuality
(Also, visual agnosia, placidity, hyperphagia)
What is hyperorality?
Tendency to examine objects by mouth
What is hypermetamorphosis?
Tendency to intensely explore immediate environment or overreact to visual stimuli
What is hypersexuality?
Suggestive behavior and talk, attempts at sexual contact
What is visual agnosia?
Cannot recognize objects by sight
Wha this Placidity?
No fear or anger where it would be appropriate
What is hyperphagia?
Eating in excess even when not hungry or when objects are not food
What is an Uncal Herniation?
Caused by?
When the uncus and parahippocampal gyrus extrudes over edge of tentorium cerebelli
Hemorrhagic lesion or tumor in hemisphere
What can an uncal herniation do to surrounding anatomy?
Compress midbrain
And if untreated, damage could extend into lower brainstem levels
What are the symptoms of an Uncal Herniation?
CN3 palsy IPSILATERAL to herniation
(Dilated pupil, down and out eye, double vision)
CST Contralateral to herniation
(Weakness in extremities)
Could progress and hit respiratory centers, cause abnormal reflexes, and a rapid decline
