hypothalamus Flashcards
how does the brain start developing ?
it starts as a tube then 2 constriction occur then it divides the brain into 3 parts
what are the 3 parts of the brain that form from the 2 constriction?
forebrain
midbrain
hindbrain
which ones grow slowly compared to the others?
the hindbrain and midbrain grow much slower than the FOREBRAIN
Forebrain is faster
what are the components of the forebrain?
Telencephalon
diencephalon
what does the telencephalon consist of?
cerebral cortex
Basal ganglia
also forms the lateral ventricles
what does diencephalon consist of?
thalamos
hypothalamus
which part of the forebrain grows faster?
the telencephalon grows much faster than the diencephalon and it covers it like a mushroom
what is the function of the hindbrain?
vital autonomic functions
what is the function of the midbrain?
relay for visual and auditory signals
what is the function of the thalamus?
sensory relay ( receives all signals b4 reaching the cortex except the signals from olfactory )
what is the function of hypothalamus?
autonomic and endocrine function control
wheres the diencephalon located?
sandwiched between the cerebral cortex and it includes both thalamus and hypothalamus
what does the diencephalon serve as?
station between the brainstem and cortex
describe the lateral ventricles of the brain?
c shaped cavities located deep within each cerebral hemisphere –> expand in the hemisphere forming cavities
sits on top of the 2 thalamus
what forms the 3rd ventricle?
the 2 lateral ventricles join together and form the 3rd ventricle
what is the diencephalon divided into to?
Posterior diencephalon
anterior diencephalon
what does the dorsal ( posterior ) diencephalon consist of?
Epithalamus
Thalamus
Metathalamus
what does the ventral ( anterior ) diencephalon consist of?
hypothalamus
what is optic chiasm ?
area between the 2 superior optic canals where both optic nerves cross each others
it is anterior
what is found between the 2 thalamus?
3rd ventricle coming from lateral ventricles
where do descending tracts and ascending tracts has to go through?
the diencephalon because it a station between the brainstem and cerebral cortex and the thalamus receives signals from everywhere
what connects the 2 thalamus together?
interthalamic connection
where is the hypothalamus located?
anterior inferior
below the third ventricle and the thalamus
base of the brain
above the optic chiasm and the pituitary stalk ( infundibulum )
what forms the base of the brain?
the inter peduncular fossa ( area between the 2 peduncles of the brain ( stems )
what is anterior to the inter peduncular fossa?
optic chiasm
describe the relations of the interpedunclar fossa?
it is between the 2 peduncles
above the pons –> pons are above the medulla oblangata
posterior to the optic chiasm
what are the relations of the hypothalamus?
Superiorly : continuous with the thalamus at the hypothalamic sulcus
inferiorly : Continuous with the midbrain
what are the functions of the hypothalamus?
coordinate hunger / satiety
coordinate thirst
coordinate sexual behaviors
temperature regulations
coordinate sleep and circadian rhythms
what is the blood supply of the hypothalamus ?
circle of willis coming from the internal carotid artery
what is hypothalamic sulcus ?
groove that separates the thalamus and hypothalamus
where is the midbrain located compared to the hypothalamus?
posteriorinferior to the hypothalamus but they are continuous
what are neuroendocrine cells?
nerves system cells that act as endocrine cells -produce hormones and secrete into blood stream
Found in GIT, Lung, Hypothalamus
what are the 4 regions of the hypothalamus?
Preoptic area –> in front of the optic chiasm
Supraoptic region –> between optic chiasm and the infundibulum
Tuberal region –> behind infundibulum
mammillary region —> most posterior
what nuclei is found in the preoptic area?
preoptic nucleus –> in front of optic chiasm
what are the nucleis found in the supraoptic region?
Periventricular nucleus —> surrounding the third ventricle
paraventricular nucleus –> more lateral to the periventricular
Lateral hypothalamic nucleus –> most lateral one and extends posteriorly to the tuberal region
Supraoptic nucleus –> ABOVE the optic chiasm
what are the nucleus found in the tuberal region ?
Periventricular –> surrounding the third ventricle ( same in the supraoptic area )
Lateral hypothalamic nucleus –> most lateral ( same in the supraoptic region )
Arcuate nucleus –> on top of the optic tract
what is the function of preoptic nucleus?
regulate the release of gonadotropic hormones ( LH, FSH ) from adenohypohpysis —-> the anterior pituitary gland
it secretes gonado releasing hormone and gonado inhibiting
it was in the preoptic region
where do the axons of the preoptic nucleus go?
they go to the capillaries in the anterior pituitary gland ( adenohypophysis )
what is the median eminence?
the area where the axons start emptying into capillary bed —> for example the preoptic nucleus axons empty into it
which nucleus doesnt empty in the median eminence or the capillaries ?
Paraventricular –> ( Oxytocin ) –> found in supraoptic region
Supraoptic —> ( ADH ) –> found in supraoptic region
these hormones will go directly to posterior pituitary
what is the function of lateral hypothalamic nucleus ?
induce eating
if it is damaged it will cause anorexia and starvation
it was found in the supraoptic region
also found in the tuberal region
what is the function of supraoptic and paraventricular nuclei?
secrete ADH —> supraoptic
secrete oxytocin —> paraventricular
both are found in the supraoptic region only
damage would lead too –> less ADH ( supraoptic ) –> diabetes insipidus
where do the axons of paraventricular and supraoptic?
since they produce ADH and oxytocin which are posterior pituitary gland hormones
they are going directly to the posterior pituitary –> neurohypophysis NOT THE MEDIAN EMINENCE
what is the function of arcuate/infundibular nucleus and where is it found?
found in the tuberal region ( third one ) js below the 3rd ventricle
produce hypothalamic releasing and inhibiting hormones most notability GHRH
where do the arcuate nucleus axons go to?
since it produces releasing and inhibitory hormones this means they go to the anterior pituitary gland —> median eminence ( capillary bed ) –> adenohypophysis
what is the function of periventricular nucleus and where is it found?
it is found in both 2nd ( supraoptic ) and 3rd ( tuberal ) regions like the lateral hypothalamic ( induces eating )
it produces TRH
where do the axons of periventricular nucleus go to?
it produces TRH will go the anterior pituitary –> so median eminence ( adenohypophysis )
what is the master of endocrine glands?
pituitary gland
where is the location of the pituitary gland ?
middle cranial fossa
inside sella turcica of the sphenoid bone ( BODY OF THE SPHENOID BONE )
describe the sella turcica?
saddle shaped fossa it is in the middle of the sphenoid body
also called hypophyseal fossa
where is the location of pituitary fossa?
in the middle of the sella turcica
what will a tumor compress if it grows anteriosuperioly?
structures that are anterior to the sella turcica ( optic canal and superior orbital fissure )
optic chiasm ( optic nerves ) –> cranial nerve 2
oculomotor nerve –> cranial nerve 3
trochlear nerve –> cranial nerve 4
abducens nerve –> cranial nerve 6
Trigeminal nerve 1st branch opthalmic ( cranial nerve 5 )
all these run in the optic canal (optic nerve ) and superior orbital fissure
what is the condition that result from tumor progressing anteriorly and presses on optic chiasm?
bitemporal hemianopia
what will the tumor compress if it goes posteriorly ?
the tumor will compress the brainstem and basilar artery —> high mortality
what will the tumor compress if it goes superiorly?
on top of the sella tunica theres dura matter the tumor has to break through it to expand more
what is the name of the dura matter above the sella tunica?
diaphragma sella
what will the tumor compress if it grows laterally?
the cavernous sinus which has cranial nerves and blood vessels
what will the tumor compress if it grows downwards?
sphenoid sinus –> empty on spheno ethmoidal sinus
what are the parts of the anterior lobe and adenohypophysis ?
Pars distalis ( anterior )
Pars intermedia
Pars tuberalis
what is pars distalis / anterior?
the true glandular part of the anterior pituitary gland that has the endocrine cells and secrete hormones
what is pars intermedia?
cyst full of colloid fluid
has cells that secrete melanocytes stimulating hormone ( MSH
what is pars tuberalis?
glandular tissue that surrounds the median eminance and the infundibular stem
contain portal venules of hypophyseal portal system
what is infundibular stem?
neurotissue that descends down to connect the hypothalamus to the pituitary glands –> neurohypophysis
it surrounded by pars tuberalis
what is infundibulum?
infundibular stem + pars tuberalis and the hypophyseal portal vessels
describe posterior pituitary gland ( neurohypophysis )?
connected to the hypothalamus through hypothalamo hypophyseal tract – stores hormones secreted by hypothalamic nuclei
what are the 3 parts of posterior pituitary gland?
pars nervosa
infundibular stem ( neural tissue connecting the hypothalamus to the pituitary gland )
median eminence ( where the axons empties into capillaries )
what is the origin of adenohypophysis ?
rathkes pouch
adenohypophysis is not neural tissue
what is rathkes pouch ?
ectoderm part outpocketing from the roof of the primitive mouth
it grows upward and moves towards the brain and pinches off from the oral cavity towards the base of diencephalon
what will the anterior part of rarthkes pouch give raise to?
pars distalis –> the true endocrine part
what will the posterior part of ratthkes pouch give raise to?
pars intermedia –> cyst filled with colloid –> secretes melanocyte stimulating hormones
what will the neurohypophysis descend downward as?
it is from neuroectoderm and it will go downward as infundibulum stem to the rathkm the pouch then it is gonna get surrounded by pars tuberalis to anchor the pouch
what will the infudibulum extend down as?
pars nervosa main part of posterior pituitary gland
what is the upper portion of infudibulum will be?
median eminence
what is an congenital anomaly related to the rathk pouch?
it doesnt migrate fully to its supposed to location and then it gets stuck in the nasopharynx
it will be indicates as a dimple in the mucosa above the nasopharyngeal tonsil in the adult
what is the location where rathkes supposed to be at?
stomedeum
what will happen if the rathke pouch stays in the nasal cavity?
it will become accessory anterior lobe in the pharyngeal wall
may become tumor –> cranio pharyngiomas inside the sphenoid bone
what is diaphragma sellae?
dura matter that is found superiorly to the sella tuncica and it separates the pituitary from the hypothalamus
ONLY DURA MATTER COVERES THE PITUITARY GLAND NO ARCHNOID OR PIA MATTER
why is there no archnoid or pia matter covering pituitary gland?
cuz it should be protected from the CSF presure
what is empty sella syndrome?
when the central aperture of the the diaphragma sellae where the infudibulum pass through becomes larger than it should be and archnoid matter and pia matter pass through
will lead to CSF accumulation and compression of gland and atrophy
what are the relations of sellae turcica?
superiorly —> diaphragma sellae
inferiorly –> sphenoidal air sinus
anterio superiorly –> optic chiasm
posteriorly –> dorsum selle and brainstem + basilar artery
laterally cavernous sinuses and its contents
which cranial nerve is CN1?
olfactory
which cranial nerve is CN2?
optic
which cranial nerve is CN3?
oculomotor
which cranial nerve is CN4?
trochlear nerve
which cranial nerve is CN5?
Trigeminal nerve
what are the components of trigeminal nerve?
1 –> opthalmic nerve
2—-> maxillary nerve
3—-> mandible nerve
what is cranial nerve 6?
aducens nerve
what is an adenoma?
commonest tumor of pituitary gland –> from chromophobe cells
what are the signs and symptoms of adenoma?
pressure on cavernous sinsus —> exophthalmos ( bulging of the eye ) and paralysis of the eye muscles supplied by CN 3 ( OCULOMOTOR ), CN4 ( TROCHLEAR ), CN 6 ( ABDUCENS )
pressure on the central part of the optic chiasm –> loss of temporal fields vision
downward growth of tumor —> breaks sella turcica –> enlargement of the hypophysial fossa
what does the neurohypophysis of the pp have?
axons of the supra optic ( ADH ) and paraventricular nuclei ( oxytocin )
what is the name of the terminal end of the supraoptic/paraventricular nuclei axon?
herring bodies
how does the adenohypophysis communicates with the hypothalamus?
via portal veins
the cell bodies are located in the hypothalamus transport and releasing and inhibitory hormones to the adenohypophysis
the axons of the hypothalamus nuclei will empty into the capillary bed in the median eminence
what are the arteries the blood supply of pituitary gland?
superior and inferior hypophyseal arteries –> branches of internal carotid artery )
what does the superior hypophyseal artery supply?
infundibulum and forms capillary network which vessels pass downward and form sinusoid into the anterior lobe of pituitary gland –> hypophyseal portal system
what does the inferior hypophyseal artery supplies?
supplies posterior lobe of the pituitary gland
what are the veins of the blood supply of the pituitary gland?
hypophyseal veins drain into cavernous sinuses
what is the approach used to remove pituitary tumor?
trans nasal / trans sphenoidal approach
gland approached via the roof of nasal cavity ——-> removing rostrum of sphenoid bone and then passing through the sphenoid sinus to reach the pituitary gland
what structures passes through optic canal?
cranial nerve 2 –> optic nerve
ophthalmic artery
what structures pass through the superior orbital fissure?
cranial nerve 3 –> oculomotor nerve
cranial nerve 4 —> trochlear nerve
cranial nerve 5.1 –> ophthalmic division of trigeminal
cranial nerve 6–> abducens nerve
superior ophthalmic vein
what structures pass through foramen rotundum ?
cranial nerve 5.2 —> maxillary division of trigeminal nerve
what structures pass through foreman ovale?
cranial nerve 5.3 –> mandibular division of trigeminal nerve
