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DIENCEPHALON
Diencephalon: Thalamus, Pituitary and Pineal Glands
Learning Objectives
1. To become familiar with the four major anatomical divisions of the
diencephalon.
2. To understand the main structure, connections and functions of the
various parts of the diencephalon.
Orientation
Orientation
EXPLORING THE BRAIN
EXPLORING THE BRAIN
EXPLORING THE BRAIN
EXPLORING THE BRAIN
EXPLORING THE BRAIN
CAT
Photography
PET
MRI
Source: modified from Posner & Raichle, Images of Mind
EXPLORING THE BRAIN
MRI studies brain anatomy.
Functional MRI (fMRI)
studies brain function.
EXPLORING THE BRAIN
Brodmann’s
Areas
Brodmann (1905):
Based on cytoarchitectonics: study of
differences in cortical layers between areas
Most common delineation of cortical areas
More recent schemes subdivide
Brodmann’s areas into many smaller
regions
Monkey and human Brodmann’s areas not
necessarily homologous
GENERAL INFORMATION
1. Commissural tracts
2. Association tracts
3. Projection tracts
Neural development at 4 weeks
Diagram depicting the main subdivisions of the embryonic vertebrate
brain. These regions will later differentiate into forebrain, midbrain and
hindbrain structures.
FORAMINA OF CSF
diencephalon
The region of the human brain, specifically the human forebrain, that
includes the thalamus, the hypothalamus, the epithalamus, the
prethalamus or subthalamus, and the pretectum.
Functions of the Diencephalon
• The diencephalon ("interbrain") is the region of the vertebrate neural tube that
gives rise to posterior forebrain structures.
• In development, the forebrain develops from the prosencephalon , the most
anterior vesicle of the neural tube that later forms both the diencephalon and
the telencephalon.
• In adults, the diencephalon appears at the upper end of the brain stem, situated
between the cerebrum and the brain stem.
• Organization diencephalon mid-diencephalic territory prethalamus zona limitans
intrathalamica thalamus hypothalamus epithalamus pretectum pineal gland
metathalamus The diencephalon is the region of the embryonic vertebrate neural
tube that gives rise to posterior forebrain structures including the thalamus,
hypothalamus, posterior portion of the pituitary gland, and pineal gland.
• Distinct parts of diencephalon perform numerous vital functions, from regulating
wakefulness to controlling the autonomic nervous system.
Midbrain
The midbrain plays major roles in both wakefulness and regulation of
homeostasis.
• Caudally the mesencephalon adjoins the pons (metencephalon) and
rostrally it adjoins the diencephalon (Thalamus, hypothalamus, etc.).
• It does not split into other brain areas while the prosencephalon, for
example, divides into the telencephalon and the diencephalon.
MIDBRAIN KEY POINTS
• The midbrain or mesencephalon is a portion of the central nervous
system associated with vision, hearing, motor control, sleep/wake,
arousal (alertness), and temperature regulation.
• Anatomically, the midbrain comprises the tectum (or corpora
quadrigemina), tegmentum, ventricular mesocoelia (or "iter"), and
the cerebral peduncles, as well as several nuclei and fasciculi.
• During embryonic development, the midbrain arises from the second
vesicle, also known as themesencephalon, of the neural tube.
• The mesencephalon is considered part of the brainstem.
Thalamus
The thalamus is a small structure in the center of the brain that acts as
a relay center for sensory and motor information.
Thalamus KEY POINTS
• The thalamus's functions include relaying sensory and motor signals to
the cerebral cortex and the regulation of consciousness, sleep, and
alertness.
• The thalamus is the largest structure derived from the
embryonic diencephalon.
• Together, the two halves of the thalamus are a prominent bulb-shaped
mass, about 5.7 cm in length, located obliquely and symmetrically on each
side of the third ventricle.
• The thalamus has a system of myelinated fibers that separate the different
thalamic subparts. These areas are defined by distinct clusters of neurons.
• Every sensory system (with the exception of the olfactory system) has a
thalamic nucleus that receives sensory signals and sends them to the
associated primary cortical area.
THALAMIC NUCLEI
• Nuclear groups of the thalamus include:
• anterior nuclear group
•
•
•
•
anteroventral nucleus
anterodorsal nucleus
anteromedial nucleus
superficial ("lateral dorsal")
• medial nuclear group (or dorsomedial nucleus)
• parvocellular part
• magnocellular part
• midline nuclear group or paramedian
•
•
•
•
paratenial nucleus
parventricular nucleus
reuniens nucleus
rhomboidal nucleus
• Intralaminar nuclear group (Intralaminar nuclei)
• anterior (rostral) group
• paracentral nucleus
• central lateral nucleus
• central medial nucleus
• posterior (caudal) intralaminar group
• centromedian nucleus
• parafascicular nucleus
• lateral nuclear group in fact a false entity replaced by
posterior region
pulvinar
lateral posterior nucleus belongs to pulvinar
(lateral dorsal nucleus) belongs to anterior group
ventral nuclear group
ventral anterior nucleus
ventral lateral nucleus
ventral posterior nucleus
ventral posterolateral
ventral posteromedial
• metathalamus no more used for the geniculate group
medial geniculate body
lateral geniculate body
• thalamic reticular nucleus part of the ventral thalamus
Functions of the Diencephalon KEY POINTS
Distinct parts of diencephalon perform numerous vital functions, from regulating wakefulness to
controlling the autonomic nervous system.
Diencephalon is made up of four distinct components:
the thalamus, the subthalamus, the hypothalamus, and the epithalamus.
The hypothalamus is an integral part of the endocrine system, with one of the
most important functions being to link the nervous system to the endocrine
system via the pituitary gland.
The thalamus is critically involved in a number of functions including relaying
sensory and motor signals to the cerebral cortex, and regulating consciousness,
sleep, and alertness.
The epithalamus functions as a connection between the limbic system to other
parts of the brain. Some functions of its components include the secretion of
melatonin by the pineal gland (involved in circadian rhythms) and regulation
of motor pathways and emotions.
Epithalamus KEY POINTS
The epithalamus connects the limbic system to other parts of the brain.
The epithalamus is a dorsal posterior segment of
the diencephalon, which includes the habenula and their
interconnecting fibers the habenular commissure, the stria
medullaris, and the pineal body.
A main function of the epithalamus is the secretion of
melatonin by the pineal gland.
The epithalamus is connected with both the limbic system and
the basal ganglia.
Epithalamus
• The epithalamus is a dorsal posterior segment of the diencephalon.
• The diencephalon ("interbrain") is the region of the vertebrate neural
tube that gives rise to posterior forebrain structures.
• In development, the forebrain develops from the prosencephalon, the
most anterior vesicle of the neural tube which later forms both
the diencephalon and the telencephalon.
• In adults, the Diencephalon appears at the upper end of the brain
stem, situated between the cerebrum and the brain stem.
• The habenular commissure is a brain commisure (a band of nerve
fibers) situated in front of the pineal gland that connects the
habenular nuclei on both sides of the diencephalon.
Epithalamus
bent asparagus
Egyptian Eye of Horus (or Eye of Ra)
Egyptian Eye of Horus (or Eye of Ra)
3rd EYE!
Holy of Holies