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84 Cards in this Set

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What is the hypothalamus a division of?
The diencephalon
What is the function of the hypothalamus?
To maintain homeostasis by controlling three important systems
What are the 3 systems controlled by the Hypothalamus?
1. ANS
2. Endocrine system
3. Limbic system
How is the hypothalamus related to the 3rd ventricle?
It forms the walls and floor of the third ventricle.
What separates the hypothalamus from the overlying thalamus?
The hypothalamic sulcus
What is situated anterior to the hypothalamus?
The optic chiasm and lamina terminalis
What is situated posterior to the hypothalamus?
The mamillary bodies
What makes the lateral borders of the hypothalamus?
The optic tracts
What makes the medial order of the hypothalamus?
The third ventricle
Where is the hypothalamus visible from?
Only from a ventral view
What 4 structures can be seen from a ventral view?
-optic chiasm
-Infundibulum
-Tuber cinereum
-Mammillary bodies
What is the infundibulum?
The stalk of the pituitary
What is contained in the infundibulum?
-Portal vessels
-Important tracts connecting the hypothal to posterior pituitary
What is another name for the posterior pituitary?
Neurohypophysis
What is the anterior portion of the infundibulum called?
The median eminence - it slightly protrudes
What is housed within the median eminence?
It houses hypothalamic peptidergic neurons which release regulatory factors carried by portal vessels to the anterior pituitary.
What is another name for the anterior pituitary?
Adenohypophysis
What is the Tuber Cinereum?
A bulge between the optic chiasm and mammillary bodies.
What are the mammillary bodies part of?
The limbic system (Papez circuit)
What gives the highly vascularized supply to the hypothalamus?
The circle of willis
3 divisions of the hypothalamus:
-Lateral
-Medial
-Periventricular
What 2 structures separate the medial from lateral zones?
1. Mammillothalamic tracts
2. Fornix
Is there a distinct division between the thin periventricular zone and medial areas?
No
What does the periventricular zone surround?
The third ventricle
What are the lateral zones comprised of?
Loosely arranged neuronal cell groups
What traverses the lateral zones?
Fibers of the medial forebrain bundle
What are the 3 major nuclei in the lateral zones?
1. Lateral Preoptic nucleus
2. Lateral Hypothalamic Area
3. Lateral Tuberal Nucleus
What is the lateral preoptic nucleus derived from?
The telencephalon
What is the function of the Lateral Hypothalamic Area?
It induces eating when stimulated - so you GROW LATERALLY
What is the result of ablation of the lateral hypothalamic area?
Anorexia and starvation
What do neurons in the Lateral Tuberal Nucleus release? To where?
Histamine - to widespread portions of the forebrain.
What is the release of histamine by the Lateral Tuberal Nucleus a function of?
Attention and arousal processes
What do these lateral nuclei look like in general? Why?
Speckled - because they're loosely arranged and are traversed by the medial forebrain bundle.
What are the 4 anatomic regions of the Medial Hypothalamic Zone (from front to back)?
1. Preoptic area
2. Supraoptic area
3. Tuberal area
4. Mammillary area
What is the preoptic area?
The anterior telencephalic portion of the hypothalamus
What nucleus is in the preoptic area? What type of neurons does it house?
The Medial Preoptic Nucleus - contains parvocellular neuron cell bodies that send hormones to the anterior pituitary!
What is INAH1-4?
Interstitial cells housed in the anterior preoptic area that are sexually dimorphic.
What regulates the development of INAH1-4 Interstitial cells?
Testosterone - so this area is bigger in men.
What exact hormones are sent from the Medial Preoptic Nucleus to stimulate the ant pituitary?
GnRH - gonadotropin releasing hormones!!
4 nuclei in the Supraoptic Area of the Medial Zone:
1. Suprachiasmatic nucleus
2. Anterior Hypothalamic nucleus
3. Paraventricular nucleus
4. Supraoptic nucleus
Where is the Suprachiasmatic nucleus located?
Just dorsal to the optic chiasm
What gives direct input to the Suprachiasmatic nucleus?
The retina
What does the Suprachiasmatic nucleus play a critical role in?
Control of Circadian Rhythmicity
Where does the Anterior Hypothalamic nucleus lie?
Just above the suprachiasmatic nucleus, and just below the PVN
What is the Anterior Hypothalamic nucleus involved in?
-Temperature regulation - it dissipates heat - COOLING
-Stimulatory drive of the ParaNS
Bilateral lesions of the Anterior hypothalamic nuclei result in:
Hyperthermia
What lies overtop the anterior hypothalamic nucleus?
The PVN - paraventricular nucleus
Why is the PVN important?
Because it houses Magnocellular cell bodies of neurons that make and release oxytocin and ADH in the posterior pituitary
What hormone other than ADH and Oxytocin is made in the PVN?
CRH - corticotropin releasing hormone
Where do non-pituitary related neurons in the PVN project?
To the intermediolateral cell column of the SC from T1-L2
What do the non-pituitary related neurons in the PVN do?
Excite the sympathetic preganglionic neurons.
Where is the Supraoptic Nucleus found?
Just behind the suprachiasmatic nucleus (under the anterior)
What do the neurons in the supraoptic nucleus do?
Make/release Oxytocin and ADH
What are the 3 important nuclei in the Tuberal (middle) area of the medial hypothalamic zone?
-Dorsomedial nucleus
-Ventromedial nucleus
-Arcuate nucleus
What happens when the Dorsomedial nucleus is stimulated?
Agression and savage behavior
What happens when the Ventromedial nucleus is stimulated?
It inhibits the urge to eat
So what is the Lateral Hypothalamic nucleus? What is the Ventromedial nucleus?
Lateral = hunger center
Ventromedial = satiety
What does bilateral destruction of the Ventromedial nuclei cause?
Hyperphagia and savage behavior
Where is the arcuate nucleus located?
In the tuber cinereum
What is the Arcuate nucleus involved in controlling?
The release of various anterior pituitary hormones
What does the Arcuate nucleus play a prominent role in?
Feeding behavior
2 important nuclei in the Mammillary area of the medial hypothalamic zone:
-Posterior nucleus
-Mammillary bodies
What is the Posterior nucleus important for?
Thermoregulation - heat conservation and production.
What does a bilateral lesion of the posterior hypothalamic nucleus result in? Why?
Inability to thermoregulate at all - NOT hypothermia; because the anterior hypothalamic nucleus projects through here too.
What is the inability to thermoregulate called?
Poikilothermia
What is the mammillary nucleus a component of?
The limbic papez circuit
What do neurons in the Mammillary nuclei recieve input from?
The hippocampus via the fornix
Where do the mammillary nuclei project to?
The anterior thalamus via the mammillothalamic tract
What will damage to the mammillary nuclei cause?
Learning and memory deficits
What nucleus is in the periventricular zone?
The periventricular nucleus
What is the periventricular one really?
Just the layer of cells lining the wall of the third ventricle
How many major fiber tracts run through the hypothalamus?
Seven
What are the major fiber tracts in the hypothalamus?
1. Fornix
2. Mammillothalamic tracts
3. Stria terminalis
4. Medial forebrain bundle
5. Supraopticohypophyseal tract
6. Tuberoinfundibular tract
7. Hypothalamospinal tract
What is the fornix?
The tract that carries input from the hippocampus to the mammillary bodies
What is the Mammillothalamic tract?
The projection from the mammillary bodies to the anterior thalamus - Key in the Papez circuit
What is the Stria terminalis?
The pathway that connects the amygdala to the medial zone of the hypothalamus
What is the Medial forebrain Bundle?
The MOST COMPLEX FIBER PATHWAY IN THE ENTIRE CNS!!!
How many distinct constituent parts are within the medial forebrain bundle?
At least 50
Where does the Medial Forebrain Bundle pass thru the hypothalamus?
Thru the lateral zone
What does the medial forebrain bundle connect (rostral->caudal)
The septal area nuclei to the brainstem.
What is the Supraopticohypophyseal tract?
The fibers that pass from the supraoptic SON and PVN to the posterior pituitary.
What is the Tuberoinfundibular tract?
The fibers that go from the arcuate nucleus to the portal system in the medial eminence (to go to anterior pituitary)
What is the Hypothalamospinal tract?
The axons that go from the hypothalamus to the spinal cord to drive both the SNS and PNS
finish
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