Subthalamus Hypothalamus by mikeholy

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									DIENCEPHALON
 Subthalamus
       &
 Hypothalamus

 Dr Zeenat Zaidi
SUBTHALAMUS
            SUBTHALAMUS
 Region  of
  diencephalon
  located below
  the thalamus &
  dorsolateral to      Th
  hypothalamus
 Continues
  caudally with the
  midbrain            Hypothalamus
                  Contents
 Rostral extension of:
    Red nucleus

    Substantia nigra

    Brainstem reticular formation as Zona incerta

 Long tracts passing through brain stem and
  heading toward thalamus
    Spinothalamic & Trigeminothalamic tracts

    Medial lemniscus

    Dentatothalamic fibers

 Pallidothalamic fibers (fasciculus lenticularis,
  Ansa lenticularis & thalamic fascicle)
 Subthalamic nucleus
         Subthalamic Nucleus
 Resembles    a
  biconvex lens in
  shape
 Located in the
  ventrolateral part of   I
                          C
  the subthalamus
 Lies against the
  medial surface of
  the internal capsule
                 Connections
 Has    reciprocal
    connections
    with ipsilateral:
   Globus pallidus
    via subthalamic
    fasciculus,
    which passes
    through the
    internal capsule
   Substantia
    nigra
                                Lesions
     Functions           Rare
                         Usually of
   Plays an              cerebrovascular origin
    important role in    Results in Hemiballism
    normal                (sudden, forceful
    functioning of        involuntary, violent or
    basal ganglia         jerky, movements of the
                          limbs) on the
                          contralateral side
                  Zona Incerta
 Rostral extension
  of the brainstem
  reticular
  formation
 Enveloped by
  pallidothalamic
  fibers (lies
  between the
  lenticular fascicle
  and the thalamic
  fascicle)
HYPOTHALAMUS
                 Hypothalamus
 Most ventral part of
                                     CC
  diencephalon
 Lies beneath the          F
  thalamus and
  ventromedial to the           TH
  subthalamus
 Forms the floor and       H
  lower part of the
  lateral wall of the 3rd
  ventricle
 Most of the hypothalamus             oc
  is hidden except the
  inferior surface, that can
  be seen on the inferior
  surface of the brain,                     tc
  cranial to the cerebral      I
                                            mb
  peduncles
 Parts of hypothalamus
  seen on the base of the
  brain include:                   P
    Infundibulum

    Tuber cinerium

    Mammillary bodies
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




                                             F




                                                 mb
Medial Nuclei




Lateral Nuclei
                  Lateral part
 Lies medial and
  ventral to the
  subthalamus
 Traversed by many
  fibers including medial
  forebrain bundle
 Controls food and
  water intake (feeding
  centre)
 Lesions cause
  aphagia and adipsia
                           Medial part
 Forms lateral wall of
  the 3rd ventricle
 Contains:
    •   Anterior nucleus
    •   Supraoptic nucleus
    •   Preoptic nucleus
    •   Paraventricular nucleus
    •   Dorsomedial nucleus
    •   Ventromedial nucleus
    •   Posterior nucleus
    •   Mammillary nuclei
    •   Infundibular nucleus
   Supraoptic nucleus produces
    vasopressin which increases
    water reabsorption by the
    kidney
   Paraventricular nucleus
    produces oxytocin
   The axons of cells in
    supraoptic and paraventricular
    nuclei pass to the
    neurohypophysis in the
    hypothalamo-hypophyseal
    tract
   The hormones are transported
    in this tract and released into
    the capillary bed
   Suprachiasmatic
    nucleus:
•   concerned with the
    control of diurnal rhythm
    and sleep/awake cycle
•   Receives some afferent
    fibers directly from the
    retina
   Ventromedial nucleus:
•    acts as satiety centre
•   Lesions cause
    polyphagia, polydipsia
 Mammillary nuclei:
• Part of the limbic
  system
• Receive afferents
  from the
  hippocampus
  through fornix
• Project to the:
    Anterior nucleus of thalamus through
    mammillo-thalamic tract
    Brainstem through the mamillotegmental tract
1.   Optic tract
2.   Mamillary body
3.   Column of fornix
4.   Thalamus
5.   Superior & inferior
     colliculi
6.   Caudate nucleus
7.   Anterior commissure
8.   Mamillothalamic tract
   Hypothalamus also synthesizes releasing factors & release-
    inhibiting factors, that control the release of hormones by the
    adenohypophysis
   These factors are released from the terminals of
    hypothalamic neurones into the capillary bed of the pituitary
    portal system, which conveys the release agents to the
    anterior pituitary
                                   Functions
1.     Co-ordination of homeostatic mechanism
2.     Controls the release of hormones from the pituitary gland.
3.     Center for regulation of autonomic activity --- controls medulla oblongata nuclei for
       cardiovascular, respiration
          Activation of posterior region associated with sympathetic responses
          Activation of anterior region associated with parasympathetic responses
4.     The mammillary nuclei are associated with the emotional behaviour and memory
5.     The suprachiasmatic nucleus is concerned with diurnal rhythm & sleep/waking
       cycle
6.     The lateral hypothalamus & the ventromedial nucleus regulate feeding and drinking
7.     Center for Feeding reflexes—licking, swallowing, etc.
8.     Controls subconscious skeletal muscle movements—facial expressions, sexual
       movements
9.     Coordinates autonomic response to conscious input—thought of fear produces
       accelerated heart rate, etc.
3rd Ventricle: The cavity of the
        Diencephalon
                  Boundaries
 Anterior: Lamina
  terminalis, a membrane
  stretching between
  anterior commissure (ac)
  & optic chiasma (oc)
 Posterior: Pineal gland             TH
                                           p
 Lateral walls:             ac
                                  H
    medial surface of

     thalamus above &        oc
    hypothalamus below

     the hypothalamic
     sulcus
 Roof:
 Ependyma
 stretching
 between the
 two stria
 medullaris
 thalami
 Floor:
  Anteroposteriorly:
1. optic chiasma
2. Infundibulum
3. tuber cinerium
4. mammillary bodies
5. tegmentum of
   midbrain
                                         5
 Cavity is crossed by
  interthalamic          1       3
                                     4
  adhesion (black            2
  arrow)
                   Recesses
 Are extensions
 of the cavity:
   Supraoptic

   Infundibular

   Pineal

   Suprapineal
               Communications
 Rostrally:
  communicates on
  each side with the
  lateral ventricle
  through
  interventricular
  foramen of Monro
 Caudally: with 4th
  ventricle through
  cerebral aqueduct
    Interventricular Foramen of
               Monro
 Paired foramina
 Each bounded:
    Anteriorly by

     column of fornix
    Posteriorly by

     anterior pole of the
     thalamus
 Communicate 3rd
  ventricle with the two
  lateral ventricles
      Choroid Plexus of 3rd ventricle
   Tuft of capillaries enclosed
    within ependyma
   Invaginates from its roof
   Extends rostrally till the
    interventricular foramen
   Continues laterally with the
    choroid plexus of lateral
    ventricle
   Produces cerebrospinal
    fluid
               Clinical Anatomy
 Obstruction of cerebral
  aqueduct leads to
  dilatation of 3rd ventricle
  and both lateral ventricles
 Unilateral/bilateral
  obstruction of
  interventricular foramen
  leads to dilatation of one
  or both lateral ventricles
  respectively
 In both cases symptoms
  and signs of
  Hydrocephalus develop
Thank You & Good Luck

								
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