Gross structure of hypothalamus

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					         Gross structure of hypothalamus

Learning objectives
At the end of the lecture the student should be able to:
Know the gross features of hypothalamus
Identify the medial and lateral nuclei of hypothalamus
Recognize the hormones secreted by hypothalamus
Know the effect of hypothalamus on the endocrine system

Gross divisions of brain
Forebrain
    Cerebrum (cerebral
    hemispheres)
    Diencephalon
Midbrain
Hindbrain
    Medulla oblongata
    Pons
    Cerebellum


Diencephalon consists of:
Thalamus
Hypothalamus
Subthalamus
Epithalamus
Hypothalamus
 hypo        thalamus
“Under” “room,chamber”
Extends from the region of optic
chiasma to mammillary bodies
Below thalamus
Above the pituitary gland
Forms floor and inferior part of lateral
walls of third ventricle.
Size of an almond

Surfaces of hypothalamus
Lateral surface
contiguous with the thalamus, subthalmus and internal capsule
Medial surface
extending to the wall of the third ventricle
Superior surface
Hypothalamic sulcus that separates the hypothalamus from the central
mass of the thalamus
Inferior surface
Floor of the third ventricle
Preoptic area
Anterior to hypothalamus
Extends from optic chiasma to lamina
terminalis and anterior commissure

The external surface of the
hypothalamic floor
Tuber cinereum is a hollow eminence
of gray matter situated between the
mammillary bodies and the optic
chiasm
Infundibulum or median eminence is
a hollow conical process, projects
from the tuber cinereum. The
infundibulum extends forward and
down where it is attached to the
posterior lobe of the pituitary gland.
Two additional symmetric
eminences, the lateral eminences,
corresponding to the most lateral
portion of the hypothalamic wall
Mammillary bodies (mamillary bodies) are a pair of small round
bodies, located on the undersurface of the brain
Hypothalamic nuclei
Medial zone
     Part of preoptic nucleus
     Anterior nucleus
     Part of suprachaismatic nucleus
     Paraventricular nucleus
     Dorsomedial nucleus
     Ventromedial nucleus
     Infundibular nucleus
     Posterior nucleus
Lateral zone
     Part of preoptic nucleus
     Part of suprachiasmatic nucleus
     Supraoptic nucleus
     Lateral nucleus
     Tuberomammillary nucleus
     Lateral tuberal nucleus

Connections with hypophysis
cerebri
Hypothalamus is connected to
hypophysis cerebri by two pathways
(a) Nerve fibres that travel from
supraoptic and paraventricular nuclei to
posterior lobe of pituitary.
(b) Long and short portal blood vessels
that connect hypothalamus to anterior
lobe of pituitary
Hypothalamus and anterior pituitary




Hypothalamic releasing
hormones
Posterior pituitary:
An outgrowth of the hypothalamus
composed of neural tissue.
Hypothalamic neurons pass
through the neural stalk and end in
the posterior pituitary.
The upper portion of the neural
stalk extends into the
hypothalamus and is called the
median eminence.


Hypothalamus and posterior pituitary




Neurophysins
Carrier proteins for the hormones
generated in the hypothalamus and
distributed from the posterior pituitary.
There are two types:
     Neurophysin I - oxytocin
     Neurophysin II - vasopressin
Vesopressin
Mainly from supraoptic nucleus
Controls the reabsorption in the tubules of
the kidneys by affecting the tissue's
permeability
Increases peripheral vascular resistance,
which increases arterial blood pressure
Plays a key role in homeostasis, and the
regulation of water, glucose, and salts in the
blood



Oxytocin
Mainly in paraventricular nucleus
1) It is released in large amounts
after distension of the cervix and
uterus during labor
2) After stimulation, facilitate birth
and breastfeeding.




Functions of hypothalamus
Regulate certain metabolic processes
Regulate activities of the autonomic nervous system.
Synthesizes and secretes certain
neurohormones.
The hypothalamus controls
     Body temperature
     Hunger
     Thirst
     Fatigue
     Sleep
     Circadian cycles

				
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posted:8/27/2011
language:English
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