Microscopy of the hypothalamus, the hypothalamo-hypophyseal system

Viktória Vereczki M.D., PhD.

Department of Anatomy,

Histology and Embryology

Semmelweis University

11.25. 8:00 a.m. 2011.

The structure of hypothalamus

Preoptic area

lateral preoptic nucleus

medial preoptic nucleus: tr. hypothalamo-hypophysealis LHRH

Lateral zone:

Cardiovascular functions, regulation of food and water intake

lateralis hypothalamic nucleus

tuberal nuclei

medial forebrain bundle

Preoptic area

Medial zone

1. regio anterior ( supraoptic region) supraoptic n.: supraopticohypophyseal tract (VAS, OXI) paraventricular n.: paraventriculohypophysealis tract (VAS, OXI) anterior n. suprachiasmatic n.: retinohypothalamic tract (VIP)

2. medial region ( tuberal region) ventromedial n. :satiety center dorsomedial n.: behavioral center arcuate n.: tr. hypothalamo-hypophysealis (relasing hormons)

3. posterior region (mamillary region) mamillary bodies dorsal hypothalamic nucleus

Medial Zone 1.

Medial zone

1. regio anterior ( supraoptic region) supraoptic n.: supraopticohypophyseal tract (VAS, OXI) paraventricular n.:paraventriculohypophysealis tract(VAS, OXI) anterior n. suprachiasmatic n.: retinohypothalamic tract (VIP)

2. medial region ( tuberal region) ventromedial n. :satiety center dorsomedial n.: behavioral center arcuate n.: hypothalamo-hypophyseal tract (releasing hormons)

3. posterior region (mamillary region) mamillary bodies dorsal hypothalamic nucleus

Medial Zone 2.

regio anterior regio posteriorregio medialis

Afferent connections:

1. Fornix hippocampus-subicumum mamillary bodies 2. Medial forebrain bundle septum pellucidum zona lateralis hypothalami

tegmentum mesencephali3. Stria terminalis corpus amygdaloideum zona preoptica, medialis

hypothalamus4. Others: reticular formation (Ser, NA) nucleus of solitary tract parabrachial nucleus dorsomedial nucleus of thalamus retina prefrontal cortex

Afferent connetions of hypothalamus

Efferent connections:

A .

Reciprocal paths to the limbic

systemB. Descending

polysynaptic paths to lower autonomic and motor center

C.

Nervous and vascular links with the hypophysis:

Hypothalamo-hypophyseal

system

Efferent connections:

1. Fornix hippocampus-subicumum mamillary bodies

2. Medial forebrain bundle septum pellucidum zona lateralis hypothalami mesencephalic tementum

3. Stria terminalis corpus amygdaloideum zona preoptica, medialis hypothalamus

4. Mamillothalamic (Vicq d’Azyr) tract , part of the PAPEZ –ring mamillary bodies anterior thalamic nucleus

5. Hypothalamospinal tract paraventricular n. n. dorsalis nervi vagi és dorsomedial n. n. tr. solitarius

6. Dorsal longitudinal fascicle (Schütz-bundle) medial zone of hypothalamus substantia grisea centralis of mesencephalon

7. Mamillotegmental tract: mamillary bodies reticular formation of mesencephalic tementum

Efferent connetions of hypothalamus

Regulation of endocrine organsKözp. idegr.

Releasing hormon (pl. CRF)

Adenohypophysis sejt (pl. corticotrop)

Glandotrop hormon (pl. ACTH)

•Neurosecretion: secreration of

neruon gets to the bloodstream

NEUROENDOCRINOLOGY

„The hypothalamus is the „head

ganglion” of the autonomic nervous

system (Sherrington1947)

•Portal circulation of hypophysys:

hypothalamic factors reach directly

the adenohypophysist

•Glandotrop hormons through

systematic circulation reach endocrin

glands

•Negative feedback: hormons of

targeted organ inhibit the

adenohypophysis

Hypothalamo-hypophyseal system

LPV: Long portal vessels

Vessels of the hypophysis

Arteries (from ICA)SHA: Superior hypophyseal arteryIHA: Inferior hypophyseal artery

SPV: short portal vessels

Portal vesselsCarrying hormone releasing factors

Lateral hypophyseal vein

Drains to cavernous sinus

1.Parvocellular

tuberoinfundibular tract

Tuberal nuclei:

Arcuate nucleus (DA)

Periventricular zone

Paraventricular nucleus parvocellular part

Supraopticus parvocellular part

hypothalamic hormone Effect

CRH POMC: ACTH+

β-LPH+

TRH TSH+

LHRH (GnRH) FSH+, LH+

GHRH GH+

DA PL-

Somatostatin GH-, TH-

Paraventricular nucleus

Tuberal nuclei

2. Magnocellular hypothalmo-neurohypophyseal system

Paraventricular nucleus magnocellular part

Supraoptic nucleus magnocellular part

hormones effect

Antidiuretic or resorption of water

vasopressin

Oxytocin 1. ejection of milk

2. uterine contraction

Herring –bodies store them

(neurophysisn 1 and 2) in the

neurohypophysis

N.paraventricularis N.supraopticus

Eminentia mediana

EZ

TRH

IZ

EZAVP

AVP= Arginin-Vasopressin

TRH= thyreotropin releasing hormon

(Dr. Kántor O.)

Neurohypophysis:

Terminations of Supraotico-paraventriculohypo-physeal tract

Herring –bodies store OXI and Vas(neurophysisn 1 and 2) in the neurohypophysis

Effects of oxytocin, vasopressin

Oxytocin:

♀: uterus: contraction during delivery

breast: contraction of myoepithel cells → ejection of milk

♂: role in ejaculation?

Vasopressin (antidiuretic hormon, ADH):

kidney: distal convoluted tubules and collecting ducts Aquaporin-2 (water channel) → reauptake of water, concentration of urine.

Destruction of the magnocellular hypothalamo-hypophysial tract:

diabetes insipidus

vessels: vasoconstrictor → elevates blood pressure ↑

♂: role in sexual attachment

Functions of hypothalamus

1. thermoregulation2. food intake3. water metabolism4. behavior:emotions, sexual behavior, 5.control of circadian rhytms (SCH, tr retinohypothalamicus

Functions of hypothalamus

1. thermoregulation2. food intake3. water metabolism4. behavior:emotions, sexual behavior, 5.control of circadian rhytms (SCH, tr retinohypothalamicus

Functions of hypothalamus

1. thermoregulation2. food intake3. water metabolism4. behavior:emotions, sexual behavior, 5.control of circadian rhytms (SCH, tr retinohypothalamicus

Functions of hypothalamus

1. thermoregulation2. food intake3. water metabolism4. behavior:emotions, sexual behavior, anger reactions 5.control of circadian rhytms (SCH, tr retinohypothalamicus

Functions of hypothalamus

1. thermoregulation2. food intake3. water metabolism4. behaviour:

emotions, sexual behavior, anger,etc.5. control of circadian rhytms (SCH, tr retinohypothalamicus

ICC of Orexin in narcoleptic patient compared to control

Medial zoneSuprachiasmaticus nucleus (VIP) : retinohypothalamic tract of rat(Scale: 100 µm. OX= optic chiasm;SCH=suprachiasmatic nucleus)

5. control of circadian rhytms: retinohypothalamic tract

Clinical disorders associated with hypothalamic lesions

-Obesity and wasting

-bulimia or anorexia

-Sexual disorders :

In childood: pubertas precox,

sexual retardation

After puberty: impotence or amenoohea

4,5 years old boy suffering in pubertas precox

-Hyperthermia and hypothermia

-Diabetes insipidus

Literature

Williams PL, Marwick R, Dyson M, Bannister LH. Gray’s Anatomy 37th ed. (Churchill Livingstone, 1989)

Antony L. Mescher: Junqueira’s Basic Histology 12th ed.( Mc Gaw Hil, 2010)

Netter’s concise Neuroanatomy

Richard S. Snell: Clinical Neuroanatomy for medical students 3rd ed.(Little, Brown and Co. 1992)