anatomy Flashcards
What are the landmarks that surround the hypothalamus?
Hypothalamic sulcus
anterior sulcus
lamina terminalis
chismatic cistern
optic chiasm
interpeduncular cistern
mammillary body
midbrain mass intermedia
What does the 3rd ventricle seperate?
what is the floor of the hypothalmus?
walls of the hypothalmus
The floor of the hypothalamus includes the tuber cinereum and median eminence
What are the medial/lateral amd anterior/posterior of the hypothalmus?
medial/lateral- optic tracts
anterior-optic chiasm
posterior- posterior perforated substance
hypothalmus with nuclei and tracts?
What descends the hypothalmic grey?
the fornix (circled in green)
What doe sthe fornix connect?
a large, myelinated limbic fiber bundle that connects hippocampus to mammillary nucleus
optic tracts
What is a major landmark of the hypothalamus?
Optic Chiasm
What does the fornix divide the hypothalamus into?
medial zone
lateral zone
periventricular zone is adjacent to the 3rd ventricle
What is lateral to the lateral hypothalamus?
What does it include?
Lateral to lateral hypothalamus is the substantia innominata (part of the general area called the basal forebrain)
Area includes nucleus basalis of Meynert, a major player in cortical function
What passes rostrocaudally through the lateral hypothalamic zone?
Medial forebrain bundle
What is the hypothalamic nuclei subdivided into?
What lies between the 3rd ventricle and the fornix in the medial hypothalamic zone?
anterior (preoptic)
middle(tuberal)
posterior (mammillary)
Between 3rd ventricle & fornix column are 10 nuclei named for position or shape
What nuclei lie in the anterior zone?
5 nuclei: 3 anteriormost named in relation to the optic system
Preoptic nucleus
suprachiasmatic nucleus
supraoptic nucleus
anterior nucleus
paraventricular nucleus
What nuclei lie in the middle zone?
3 nuclei
Ventromedial
dorsomedial
arcuate
Which nuclei lie in the posterior zone?
2 nuclei
posterior
mammillary
Which tract ascends out of the mammillary nucleus?
mammillothalmic tract
How does the lateral hypothalmus send and receive fibers?
What is the cousre of the medial forebrain?
Lateral hypothalamus sends and receives fibers via medial forebrain bundle (MFB) as do other parts of the hypothalamus.
MFB courses from forebrain rostrally through brainstem caudally.
What is the tubermammillary nucleus of the LHA function for the brain?
part of the brain’s sleep-wake circuitry and is involved in wakefullness (cortical arousal).
Where is the only source of orexineergic nuerons in the CNS?
what is the role of orexin?
where does orexin neurons output to?
Lateral hypothalamus is the only source of orexinergic neurons in the CNS.
Neurotransmitter orexin plays a primary role in wakefullness.
Orexin neurons output to other neurotransmitter systems involved in arousal.
What is the affect of dysregulatin orexin?
Dysregulation or degeneration of LHA orexin neuron circuits is implicated in excssive sleepiness (hypersomnolence), cataplexy (loss of muscle tone), and narcolepsy (sudden wake to REM sleep-like state).
What type of regulation is the lateral hypothalmus involved in?
What is the affect of stimulating the lateral hypothalmus?
What do lesions in the lateral hypothalmus produce?
Lateral hypothalamus is involved in appetite control (regulation of food intake)
stimulation causes hyperphagia
lesion produces anorexia
What is the function of the Ventromedial hypothalmus?
What does stimulation of the ventromedial cause?
What does lesions of the ventromedial hypothalmus cause?
LHA in regulation of food intake
Considered a satiety center (deciding when to stop eating)
stimulation inhibits eating (anorexia)
lesion causes overeating (hyperphagia)
How does leptin(anorexigenic) and ghrelin (orexigenic) molecules gain acces to the hypothalamic feeding regulation nueral network?
qprobably through the median eminence, one of the leaky-capillaried circumventricular organs (CVO)
What is the anterior hypothalamic nucleus regulate?
What does the anterior (preoptic) area have for this regulation?
Anterior hypothalamic nuc. is involved in temperature regulation
anterior (preoptic) area has both cold and heat sensitive neurons (thermostat)
at high blood temperature, regulates mechanisms of heat dissipation
What is the posterior hypothalamic nucleus involved in?
How does it regulate this?
Posterior hypothalamic nucleus is involved in temperature regulation
regulates mechanisms of heat production when blood temp. is low
What is the dorsalmedial hypothalamic nucleus involved in?
What does stimulation of the dorsalmedial hypothalamic nucleus?
Dorsomedial hypothalamic nuc. is involved in regulating emotion (aggression)
Stimulation can elicit defensive-aggressive behaviors (“sham-rage”) in the absence of any contextual elicitors.
How does the mammillothalmic tract reach the anterior nucleus?
mamillothalamic tract ascends into and through thalamus to reach anterior nuc.
external view of the mammillothalmic tract.
large vertically oriented myelinated bundle
Which tract is the main regulator ofthe autonomic system?
paraventricular nucleus
Projects to both parasympathetic & sympathetic preganglionic neurons via the hypothalmospinal
Hypothalamospinal tract lesion effects would include ipsilateral Horner syndrome
What is the suprachiasmatic nucleus helps regulate?
where does it receive input/output from?
Suprachiasmatic nuc. is involved in regulation of circadian rhythms (≈ 24hr)
Receives retinohypothalamic fibers with info about presence/absence of light
Output via sympathetic system stimulates pineal to secrete melatonin in the dark
What lies on the floor of the 3rd ventricle and what is it continuous with?
infundibulum it is continuous with the pituitary
the pituitary is regulated by the hypothalamus
What are the cells of the pituitary?
Adenohypophysis is secretory cell rich (dark, cell bodies stained with H&E)
Neurohypophysis is axon rich (pale, poorly stained with H&E)
What is the median emminance?
The median eminence is a ridge of gray just posterior to the pituitary stalk
What is Supraoptic and the paraventricular nucei involved in?
How are oxytocin and antidiuretic hormone transported?
Where does nerve terminals release these hormones?
in neuroendocrine regulation via posterior pituitary (neurohypophysis; pars nervosa)
Oxytocin and antidiuretic hormone (ADH) [argenine vasopressin (AVP)] are transported via supraopticohypophyseal tract axons to posterior pituitary
Nerve terminals release hormones near inferior hypophyseal a. capillaries
Where does the supraoptic and paraventricular nuclear axons project?
What are these projections
where does the axon terminals dump oxytocin and ADH?
Supraoptic and paraventricular nuclear axons project to posterior pituitary
These projecting neurons are large (magnocellular)
Axon terminals dump oxytocin & ADH into space around fenestrated capillaries
Where does the stimulus for ADH (to retain water) originate?
from osmolality detecting neurons of the nearby organum vasculosum of the lamina terminalis (OVLT)
What role doe the MFB play in oxytocin release?
MFB plays a major role in reproduction by transmitting feedback from cervix (prepartum) and breast (postpartum) to hypothalamus to stimulate oxytocin release
What role does the proptic and arcuate nuclei play in neuroendocrine release?
where does their axons terminate?
preoptic & arcuate nuclei are involved in neuroendocrine regulation via anterior pituitary (adenohypophysis; pars distalis)
Axons terminate near superior hypophyseal a. leaky capillaries in the medial eminence of the infundibulum
Where does the preoptic and arcuate axons dump regulatory axons?
preoptic & arcuate axons dump regulatory hormones (trophic [tropic] factors) into portal veins
anterior pituitary cells in turn dump hormones into systemic veins
The 2 pathways of neuroendocrine integration (parvi- and magno- )
