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Czehlár Boróka
AAR8AO
Diencephalon
Features of the diencephalon:
Diencephalon is part of the prosencephalon (the forebrain), which develops from the foremost
primary cerebral vesicle
Diencephalon is the rostral continuation of the brain stem, except its ventral part and it is
covered by the thelencephalon.. This structure surrounds the third ventricle.
Diencephalon is primarily made of brain nuclei.
Structure:
Diencephalon is composed of the thalamus, hypothalamus, epithalamus, metathalamus and
subthalamus.
Thalamus:
It is a midline symmetrical structure,which is made of two egg-shaped parts. It is located at
the crossroad of many nervous structures, interposed between the brainstem and the cerebral
cortex. It includes tons of synapses.
One of its main functions is the relaying of sensory and motor signals to the cerebral cortex.
With the exception of the olfactory system, every sensory system includes a thalamic nucleus.
In the visual system, the thalamus receives input from the retina, which is relayed to the brain
via the optic nerve. The singnals are sent to the lateral geniculate nucleus of the thalamus,
which forwards them onto the visual cortex in occipital lobe. Another important example is
the auditory system. The medial geniculate nuclei relay the auditory information between the
inferior colliculus and the primary auditory cortex.
Thalamus also plays an important role in arousal,wakefullness and alertness. Damage to the
thalamus is associated with a significant risk of coma.
Hypothalamus:
Hypothalamus is an almond-size structure, located below the thalamus. It is responsible for
the production of many of the body’s essential hormones and it is involved in many necessary
processes of the body e.g. behavorial, autonomic and endocrine functions.
The magnocellular neurons located in the paraventricular nuclei and the supraoptic nuclei.
They produce oxytocin and vasopressin and transport them down to the posterior pituitary and
they are released to the systemic circulation.
Parvocellular neurons, in the paraventricular nuclei release hormones (e.g. corticotropinreleasing hormone) into portal system.
Hypothalamus controls hunger, sleep, mood, body temperature, circadian rhythms and the
release of other hormones of the body.