subthalamus & hypothalamus dr zeenat zaidi diencephalon
TRANSCRIPT
SubthalamusSubthalamus & &
HypothalamuHypothalamuss
Dr Zeenat ZaidiDr Zeenat Zaidi
DIENCEPHALON
SUBTHALAMUSSUBTHALAMUS
SUBTHALAMUSSUBTHALAMUS Region of Region of
diencephalon diencephalon located located below below the thalamus the thalamus & & dorsolateral to dorsolateral to hypothalamushypothalamus
Continues Continues caudally with the caudally with the midbrainmidbrain
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Hypothalamus
ContentsContents Rostral extension of:Rostral extension of:
Red nucleusRed nucleus Substantia nigraSubstantia nigra Brainstem reticular formation as Brainstem reticular formation as Zona incertaZona incerta
Long tracts passing through brain stem and Long tracts passing through brain stem and heading toward thalamusheading toward thalamus Spinothalamic & Trigeminothalamic tractsSpinothalamic & Trigeminothalamic tracts Medial lemniscusMedial lemniscus Dentatothalamic fibersDentatothalamic fibers
Pallidothalamic fibers Pallidothalamic fibers (fasciculus lenticularis, (fasciculus lenticularis, Ansa lenticularis & thalamic fascicle) Ansa lenticularis & thalamic fascicle)
Subthalamic nucleusSubthalamic nucleus
Subthalamic Nucleus Subthalamic Nucleus Resembles a Resembles a
biconvex lens biconvex lens in in shapeshape
Located in the Located in the ventrolateral part of ventrolateral part of the subthalamusthe subthalamus
Lies against the Lies against the medial surface of medial surface of the the internal capsuleinternal capsule
IICC
ConnectionsConnections Has reciprocal Has reciprocal
connections with connections with ipsilateral:ipsilateral:
Globus pallidus Globus pallidus via via subthalamic subthalamic fasciculusfasciculus, , which passes which passes through the through the internal capsuleinternal capsule
Substantia nigraSubstantia nigra
Plays an Plays an important role in important role in normal normal functioning of functioning of basal gangliabasal ganglia
RareRare Usually of Usually of
cerebrovascular origincerebrovascular origin Results in Results in Hemiballism Hemiballism
(sudden, forceful (sudden, forceful involuntary, violent or involuntary, violent or jerky, movements of the jerky, movements of the limbs) on the limbs) on the contralateral sidecontralateral side
FunctionsFunctions
LesionsLesions
Zona Zona IncertaIncerta Rostral extension Rostral extension
of the of the brainstem brainstem reticular reticular formationformation
Enveloped by Enveloped by pallidothalamic pallidothalamic fibersfibers (lies (lies between the between the lenticular fascicle lenticular fascicle and the and the thalamic thalamic fasciclefascicle))
HYPOTHALAMUSHYPOTHALAMUS
Hypothalamus Most Most ventral partventral part of of
diencephalondiencephalon Lies Lies beneath the beneath the
thalamusthalamus and and ventromedial to the ventromedial to the subthalamussubthalamus
Forms the Forms the floorfloor and and lower part of the lower part of the lateral walllateral wall of the of the 33rdrd ventricleventricle
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Most of the hypothalamus Most of the hypothalamus is hidden except the is hidden except the inferior surface, that can inferior surface, that can be seen on the inferior be seen on the inferior surface of the brain, surface of the brain, cranial to the cerebral cranial to the cerebral pedunclespeduncles
Parts of hypothalamus Parts of hypothalamus seen on the base of the seen on the base of the brain include: brain include: InfundibulumInfundibulum Tuber cineriumTuber cinerium Mammillary bodiesMammillary bodies
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The anterior column of the fornix passes vertically through the substance of hypothalamus (to terminate in the mamillary body) and divides it into medial and lateral zones
Medial NucleiMedial Nuclei
Lateral NucleiLateral Nuclei
Lateral partLateral part Lies medial and Lies medial and
ventral to the ventral to the subthalamussubthalamus
Traversed by many Traversed by many fibers including fibers including medial medial forebrain bundleforebrain bundle
Controls food and Controls food and water intake (feeding water intake (feeding centre)centre)
Lesions cause Lesions cause aphagiaaphagia and and adipsiaadipsia
Medial partMedial part Forms lateral wall of Forms lateral wall of
the 3the 3rdrd ventricle ventricle Contains:Contains:
• Anterior nucleusAnterior nucleus• Supraoptic nucleusSupraoptic nucleus• Preoptic nucleusPreoptic nucleus• Paraventricular nucleusParaventricular nucleus• Dorsomedial nucleusDorsomedial nucleus• Ventromedial nucleusVentromedial nucleus• Posterior nucleusPosterior nucleus• Mammillary nucleiMammillary nuclei• Infundibular nucleusInfundibular nucleus
Supraoptic nucleusSupraoptic nucleus produces produces vasopressin which increases vasopressin which increases water reabsorption by the water reabsorption by the kidneykidney
Paraventricular nucleusParaventricular nucleus produces oxytocinproduces oxytocin
The axons of cells in The axons of cells in supraoptic and paraventricular supraoptic and paraventricular nuclei pass to the nuclei pass to the neurohypophysisneurohypophysis in the in the hypothalamo-hypophyseal hypothalamo-hypophyseal tracttract
The hormones are transported The hormones are transported in this tract and released into in this tract and released into thethe capillary bed capillary bed
Suprachiasmatic Suprachiasmatic nucleusnucleus: :
• concerned with the concerned with the control of diurnal rhythm control of diurnal rhythm and sleep/awake cycleand sleep/awake cycle
• Receives some afferent Receives some afferent fibers directly from the fibers directly from the retinaretina
Ventromedial nucleus:Ventromedial nucleus:• acts as satiety centreacts as satiety centre• Lesions cause Lesions cause
polyphagia, polydipsiapolyphagia, polydipsia
Mammillary nuclei:Mammillary nuclei:• Part of the limbic Part of the limbic
systemsystem• Receive afferents Receive afferents
from the from the hippocampus hippocampus through fornixthrough fornix
• Project to the:Project to the:
Anterior nucleus of thalamus through mammillo-thalamic tractBrainstem through the mamillotegmental tract
1.1. Optic tract Optic tract
2.2. Mamillary body Mamillary body
3.3. Column of fornix Column of fornix
4.4. Thalamus Thalamus
5.5. Superior & inferior Superior & inferior colliculi colliculi
6.6. Caudate nucleus Caudate nucleus
7.7. Anterior commissure Anterior commissure
8.8. Mamillothalamic tract Mamillothalamic tract
Hypothalamus also synthesizes releasing factors & release-Hypothalamus also synthesizes releasing factors & release-inhibiting factors, that control the release of hormones by the inhibiting factors, that control the release of hormones by the adenohypophysisadenohypophysis
These factors are released from the These factors are released from the terminals of terminals of hypothalamic neuroneshypothalamic neurones into the capillary bed of the into the capillary bed of the pituitary pituitary portal systemportal system, which conveys the release agents to the , which conveys the release agents to the anterior pituitaryanterior pituitary
Functions1.1. Co-ordination of Co-ordination of homeostatic mechanismhomeostatic mechanism
2.2. Controls the Controls the release of hormones from the pituitary gland.release of hormones from the pituitary gland.
3.3. Center for Center for regulation of autonomic activity ---regulation of autonomic activity --- controls medulla oblongata nuclei for controls medulla oblongata nuclei for cardiovascular, respirationcardiovascular, respiration
Activation of Activation of posterior region posterior region associated with associated with sympatheticsympathetic responsesresponses Activation of Activation of anterior region anterior region associated with associated with parasympatheticparasympathetic responses responses
4.4. The The mammillary nuclei mammillary nuclei are associated with the are associated with the emotional behaviour and memoryemotional behaviour and memory
5.5. The The suprachiasmatic nucleus suprachiasmatic nucleus is concerned with is concerned with diurnal rhythm & sleep/waking diurnal rhythm & sleep/waking cyclecycle
6.6. The The lateral hypothalamus lateral hypothalamus & the & the ventromedial nucleus ventromedial nucleus regulate feeding and drinkingregulate feeding and drinking
7.7. Center for Feeding reflexes—licking, swallowing, etc.Center for Feeding reflexes—licking, swallowing, etc.
8.8. Controls Controls subconscious skeletal muscle movementssubconscious skeletal muscle movements—facial expressions, sexual —facial expressions, sexual movementsmovements
9.9. Coordinates autonomic response to conscious inputCoordinates autonomic response to conscious input—thought of fear produces —thought of fear produces accelerated heart rate, etc.accelerated heart rate, etc.
3rd Ventricle: The cavity of the 3rd Ventricle: The cavity of the DiencephalonDiencephalon
BoundariesBoundaries AnteriorAnterior: : Lamina Lamina
terminalisterminalis, a membrane , a membrane stretching between stretching between anterior commissure anterior commissure (ac) (ac) & & optic chiasma optic chiasma (oc)(oc)
PosteriorPosterior: : Pineal gland Pineal gland Lateral wallsLateral walls::
medial surface of medial surface of thalamusthalamus above & above &
hypothalamus hypothalamus below below the hypothalamic the hypothalamic sulcussulcus
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acac
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RoofRoof: : Ependyma Ependyma stretching stretching between the between the two two stria stria medullaris medullaris thalamithalami
FloorFloor: : Anteroposteriorly:Anteroposteriorly:
1.1. optic chiasmaoptic chiasma
2.2. InfundibulumInfundibulum
3.3. tuber cineriumtuber cinerium
4.4. mammillary bodiesmammillary bodies
5.5. tegmentum of tegmentum of midbrainmidbrain
Cavity is crossed by Cavity is crossed by interthalamic interthalamic adhesionadhesion (black (black arrow)arrow)
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RecessesRecesses Are extensions Are extensions
of the cavity:of the cavity: SupraopticSupraoptic InfundibularInfundibular PinealPineal SuprapinealSuprapineal
Communications RostrallyRostrally: :
communicates on communicates on each side with the each side with the lateral ventricle lateral ventricle through through interventricular interventricular foramen of Monroforamen of Monro
Caudally:Caudally: with 4 with 4thth ventricle through ventricle through cerebral aqueductcerebral aqueduct
Interventricular Foramen of Interventricular Foramen of MonroMonro
Paired foraminaPaired foramina Each bounded:Each bounded:
AnteriorlyAnteriorly by by column of fornix column of fornix
PosteriorlyPosteriorly by by anterior pole of the anterior pole of the thalamusthalamus
Communicate 3Communicate 3rdrd ventricle with the two ventricle with the two lateral ventricleslateral ventricles
Choroid Plexus of 3Choroid Plexus of 3rdrd ventricleventricle
Tuft of capillaries Tuft of capillaries enclosed enclosed within ependymawithin ependyma
Invaginates from its Invaginates from its roofroof Extends rostrally till the Extends rostrally till the
interventricular forameninterventricular foramen Continues laterally with the Continues laterally with the
choroid plexus of lateral choroid plexus of lateral ventricleventricle
Produces cerebrospinal Produces cerebrospinal fluidfluid
Clinical AnatomyClinical Anatomy Obstruction of cerebral Obstruction of cerebral
aqueductaqueduct leads to leads to dilatation of 3dilatation of 3rdrd ventricle ventricle and both lateral ventriclesand both lateral ventricles
Unilateral/bilateral Unilateral/bilateral obstruction of obstruction of interventricular forameninterventricular foramen leads to dilatation of one leads to dilatation of one or both lateral ventricles or both lateral ventricles respectivelyrespectively
In both cases symptoms In both cases symptoms and signs of and signs of HydrocephalusHydrocephalus develop develop
Thank You & Good Luck