BRAIN DAYSPART IIIDIENCEPHALON

Kaan Yücel M.D.,Ph.D.IN 10 QUESTIONS

Learning Objectives

Explain the components of the diencephalon

Explain the anatomical features of the structures in diencephalon

1. DiencephalonProsencephalon [Forebrain]

1. Telencephalon2. Diencephalon

2. Diencephalon is composed of…(1) thalamus (2) subthalamus [-sub: 'inferior to”](3) epithalamus [-epi: “superior to”](4) hypothalamus [-hypo: “under” ]

posteriorly where 3rd ventricle becomes continuous with the cerebral aqueduct anteriorlyinterventricular foramina

A midline structure with symmetrical right and left halves

2. Diencephalon extends...

• Only area exposed to the surface in the intact brain.

• Formed by hypothalamic and other structures, which include, from anterior to posterior:o optic chiasma o infundibulum with the tuber cinereum [x]o mammillary bodies

2. Diencephalon’s inferior surface

[x]

• Concealed by the fornix.

• The actual superior wall of the diencephalon is formed by roof of the third ventricle.

• A pair of vascular processes, choroid plexuses of the third ventricle, project downward from the midline into the cavity of the third ventricle and CSF is produced here.

2. Diencephalon’s superior surface

Bounded by the internal capsuleoconsists of nerve fibers oconnect the cerebral cortex with parts of the brainstem and spinal cord. MRI of the brain, T1-weighted axial cut

2. Diencephalon’s lateral surface

1. Insula2. Internal capsule3.Caudate nucleus4. Putamen5. Internal capsulePosterior limb 6. Splenium, corpus callosum 7.Thalamus

2. Diencephalon’s medial surfacea.k.a. Lateral wall of the third ventricle

Superior part by medial surface of thalamus hypothalamic sulcus Inferior party by hypothalamus

stria medullaris thalami •Afferent fibers to the habenular nucleus

•Forms a ridge along the superior margin of the medial surface of the diencephalon

3. Thalamus L. thalamus "inner chamber," from Gk. thalamos "inner chamber, bedroom"

Large ovoid mass of gray matter that forms the major part of the diencephalon.

On each side of the third ventricle.

3. Thalamus

The superior surface of the thalamus is covered medially by the tela choroidea and the fornix

The inferior surface is continuous with the tegmentum of the midbrain.

3. Thalamus The medial surface of the thalamus forms the superior part of the lateral wall of the third ventricle

Usually connected to the opposite thalamus by a band of gray matter, interthalamic connection (interthalamic adhesion- adhesio interthalamica- massa interrmedia)

Found in 70-80% of humans

Axial T2-weighted MR image C = caudate nucleus G = globus pallidus L = lentiform nucleus (G+P) P = putamen T = thalamus

Important station that receives the main sensory tracts (except the olfactory pathway).

A station where much of the information is integrated and relayed to the cerebral cortex and many other subcortical regions.

A key role in the integration of visceral and somatic functions.

3. Thalamus Anterior thalamic nuclei, which receive the mammilothalamic tract from the mammillary nuclei.

Associated with of that of the limbic system and is concerned with emotional tone and the mechanisms of recent memory.

3. Thalamus Medial part of the thalamus large dorsomedial nucleus and several smaller nuclei. 2 connections with the whole prefrontal cortex and hypothalamic nuclei.

Responsible for

integration of a large variety of sensory information

relation of this information to one’s emotions

3. Thalamus

Stria terminalis: Runs @ lateral margin of thalamusFrom amygala to hypothalamusMajor output of amygdala

4. Hypothalamus

CHIEF OF THE HORMONES

from the region of the optic chiasma to the caudal border of the mammillary bodies

4. Hypothalamus four distinct groups in the rostral-caudal plane of the third ventricle: 1. preoptic (above and in front of the optic chiasm - telencephalic

extension of the basal forebrain, but functionally diencephalonic)

2. chiasmatic (above and around the optic chiasm)

3. tuberal (above and around the "tuber cinereum", i.e. pituitary stalk)

4. posterior region which includes the mammillary bodies.

4. Hypothalamus When observed from below, the hypothalamus is seen to be related to the following structures, from anterior to posterior: (1) optic chiasma(2) tuber cinereum & infundibulum(3) mammillary bodies

5. SubthalamusInferior to thalamusBetween thalamus-midbrainAnteriomedially- hypothalamusImportant connections with the striatumFxn: Control of muscle activity

AC

Adhesiointerthalamica

Septum pellicidum

Thalamus

Hypothalamus

Cerebral aqueduct

Mamillary body

Optic chiasm

Anterior commissure Posterior

commissure

Pineal gland

Pituitary gland

Corpora quadrigemina

6. Pituitary gland SIDEKICK OF THE HYPOTHALAMUS

Hormone Stimulated by the hypothalamic hormone

Does

Anterior pituitary gland (Adenohypoysis)

Growth Hormone (GH) Growth Hormone-Releasing Hormone (GHRH)

Growing

Thyroid-stimulating hormone (TSH)

Thyrotropin-Releasing Hormone (TRH) Metabolism of the body

Adrenocorticotropic hormone (ACTH)

Corticotropin-Releasing Hormone (CRH) Production and release of corticosteroids from the adrenal glands

Prolactin (PRL) Long list of chemical substances, inhibited by dopamine

Stimulation of milk production in breasts

Luteinizing hormone (LH) Gonadotropin-Releasing Hormone (GnRH)

Triggers ovulationICHS production of testosterone

Follicle-stimulating hormone (FSH)

Gonadotropin-Releasing Hormone (GnRH)

Regulates the development, growth, pubertal maturation, and reproductive processes of the body

Posterior pituitary gland (Neurohypoysis)

Oxytocin Secreted from the hypothalamus and carried to the pituitary gland

Distension of the cervix and uterus during labor, facilitating birth, and after stimulation of the nipples, facilitating breastfeeding.

Antidiuretic hormone (ADH)

Secreted from the hypothalamus and carried to the pituitary gland

Increases water absorption in the the kidney

7. Tuber CinereumInterthalamic adhesion

8. Mammillary bodiesTwo small hemispherical bodies situated side by side posterior to the tuber cinereum.

Possess a central core of gray matter invested by a capsule of myelinated nerve fibers.

Korsakoff’s SyndromeWernicle-Korsakoff Syndrome

Yoneoka Y, Takeda N, Inoue A, Ibuchi Y, Kumagai T, Sugai T, Takeda K, Ueda K. Acute Korsakoff syndrome following mammillothalamic tract infarction.AJNR Am J Neuroradiol. 2004;25(6):964-968.

Vann SD. Re-evaluating the role of the mammillary bodies in memory. Neuropsychologia. 2010;48(8):2316-2327.

Copenhaver BR, Rabin LA, Saykin AJ, Roth RM, Wishart HA, Flashman LA, Santulli RB, McHugh TL, Mamourian AC. The fornix and mammillary bodies in older adults with Alzheimer's disease, mild cognitive impairment, and cognitive complaints: a volumetric MRI study. Psychiatry Res. 2006 Oct 30;147(2-3):93-103.

Septum pellicidum

Fornix

Thalamus

PC

Mammillary bodies

AC

Pituitarygland

Opticchiasma

Hypothalamus

Optic chiasm

Pituitary gland

Thalamus

HypothalamusAC

PC

Lamina terminalis

Pineal glandTuber cinerum

Infundibulum

Habenula

Interthalamic adhesionFornix

8. Epithalamus Pineal gland+habenular nucleus+stria medullaris thalami

Haber SN, Knutson B. The reward circuit: linking primate anatomy and human imaging. Neuropsychopharmacology. 2010;35(1):4-26.

Pineal gland:Inhibition of hormonesCircadian rhythm day & nigh timeMelatonin

Habenula:potential importance ofthe lateral habenular nucleus in regulating the dopamine reward signal

9. Third ventricleBetween two thalamiLateral VentricleInterventricular foramina (foramina of Monro)4th VentricleCerebral aqueduct (of Sylvius)

9. Third ventricleAnterior wallLamina terminalisACPosterior wallCerebral aqueductSuperior to PC pineal recessSuperior to pineal recess habenular commissureLateral wallSup:Medial surface of thalamus Inf: HypothalamusSuperiorly limited by stria medullaris thalami.

Anterior commissure (AC)Connecting temporal lobesPosterior commissure (PC)Pupillary eye reflex