DIENCEPHALON
the function:
1. main subcortical sensory centre
2. subcortical motor centre - a part of the extrapyramidal system
3. higher autonomic centre and the centre of the metabolism
4. a part of the reticular formation
5. a part of the limbic system
Consists of: thalamus (function 1,2,4,5)
metathalamus (function 1)
epithalamus (function 5)
subthalamus (function 2)
hypothalamus (function 2,3,5)
Thalamus
Function:
• main subcortical sensory centre (general sensations, pain, taste)
• subcortical motor centre - a part of the extrapyramidal system
• a part of the reticular formation
• a part of the limbic system
is a large ovoid mass of grey matter
- its lateral surface is embedded into the white matter of hemisphere
Superiorly thalamus is related to the caudate nucleus - separated from it by stria terminalis containing thalamostriate vein
- superior surface of the thalamus forms the floor of lateral ventricle
- medial to it the roof of 3rd ventricle is attached
attached portion of the roof of the 3rd ventricle is named
stria medullaris thalami - terminates posteriorly in
the habenular trigone (this is a part of epithalamus)
- medial surface of the thalamus borders the 3rd ventricle
- anterior end projects into the tubercle
- two thalami are connected by the interthalamic adhesion
- hypothalamic sulcus separates the thalamus from the hypothalamus
- posterior end of the thalamus is expanded – the pulvinar
INTERNAL STRUCTURE OF THE THALAMUS
grey matter is subdivided by internal medullary lamina into
- anterior part - nuclei - belong to the limbic system
- medial part - nuclei - belong to the limbic system
- lateral part (many nuclear groups..........)
- subcortical sensory centres
- subcortical motor centres
- in addition – small nuclear groups – a part of the reticular formation
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- intralaminar nuclei
- reticular nucleus
- midline nuclei
- pulvinar nuclei
- posterior part - pulvinar nuclei – limbic system
CONNECTIONS OF THALAMUS
thalamus is involved in activities of all major regions of the CNS:
- whole sensory system (except olfactory)
- cerebral cortex
- basal nuclei
- cerebellum
- reticular formation
all project to the thalamic nuclei and most receive reciprocal thalamic connection
1. Lateral part of thalamic nuclei (neothalamus) subcortical sensory and motor centres
afferents: from the lower sensory centres:
- spinothalamic
- medial lemniscus
- trigeminal lemniscus
- solitariothalamic tract
efferents: to the cortex - sensory area
afferents from the subcortical motor centres:
- basal nuclei
- cerebellum
- red nucleus
Efferents - to the motor area
- to the other subcortical centres
2. Anterior and posterior part (paleothalamus)
is included in the limbic system
3. Medial part (paleothalamus)
takes part in the integration of visceral and somatic activities
afferents and efferents: - hypothalamus
- frontal cortex
- basal nuclei
4. Intralaminar, reticular, midline nuclei
represent thalamic reticular system
afferents: from the reticular formation
efferents: to the cerebral cortex
Metathalamus
F: main subcortical sensory centre (visual, auditory)
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Medial geniculate body – the subcortical auditory centre
(is connected with the inf. colliculus by the brachium of inf. coll.)
afferents: from the lateral lemniscus (auditory pathway)
efferents: to the temporal cortex – the cortical (higher) auditory centre (acoustic radiation)
Lateral geniculate body – the subcortical visual centre
(is connected with the sup. colliculus by the brachium of sup. coll.)
afferents: from the optic tract (larger portion)
efferents: to the occipital cortex (optic radiation)
Epithalamus
F: a part of the limbic system
comprises: habenular trigone
habenular commissure
pineal body
posterior commissure
habenular trigones contain habenular nuclei
afferents: from olfactory centres (some fibres are crossed in the habenular commissure)
efferents: to the reticular formation and autonomic centres
Mediate autonomic response to the olfactory stimuli
Subthalamus
F: subcortical motor centre - a part of the extrapyramidal system
contains subthalamic nucleus – shaped like biconvex lens
zona incerta – a narrow plate of grey matter
afferents: - from cortex
- basal nuclei
- thalamus
efferetns: to - the red nucleus
- reticular formation
- hypothalamus
Hypothalamus
F:
• higher autonomic centre and the centre of the metabolism
• subcortical motor centre - a part of the extrapyramidal system
• a part of the limbic system
forms the floor of the 3rd ventricle
externally comprises:
mamillary bodies - contained grey matter is a part of the limbic system
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tuber cinereum – is placed in front of the mamillary bodies, contains tuberal nuclei
infundibulum – pituitary gland is attached to it
internal structure:
grey matter of the hypothalamus is subdivided into:
1. anterior hypothalamic region – contains supraoptic and paraventricular nuclei –
produce neurohormons oxitocin and adiuretic hormon
2. intermediate hypothalamic region – contains tuberal nuclei – influence secretion of all
the hypophysial hormons
3. lateral hypothalamic region – contained grey matter represents some control centres of
the metabolism
4. posterior hypothalamic region – contained mamillary nuclei are involved in the limbic
system
connections of the hypothalamus:
afferents:
from the reticular formation of midbrain
from the thalamus (somatosensory and viscerosensory fibres)
from the basal nuclei
from the olfactory area (to the mamillary nuclei)
efferents:
to the cortex
to the reticular formation and to the lower autonomic centres
- parasympathetic nuclei in the brainstem (cranial nerves nuclei) and
- sympathetic and parasympathetic nuclei in the spinal cord
to the thalamus
to the basal nuclei
to the pituitary gland – hypophysis – hypothalamohypophysial tract
Hypothalamohypophysial tract:
is represented by the axons of nerve cells contained in some hypothalamic nuclei
axons terminate in the hypophysis
1. supraoptic and paraventricular nuclei – send the axons to the neurohypophysis –
neurohormones (adiuretic and oxitocin) are conveyed and released to the capillaries in the
neurohypophysis
2. tuberal nuclei send the axons transporting special substances to the infundibule. The
substances are released to the capillaries contained in the infundibule. The substances releasing and inhibiting the secretion of adenohypophysial hormones are transported to the
adenohypophysis via hypophysial portal venous system.
Hypophysial portal venous system – serves for the transport of releasing and inhibiting
substances from the infundibule to the adenohypophysis.
It is represented by two capillary networks connected by thin veins – hypophysial portal veins.
One capillary nettwork is located in the infundibule, the other in the anterior lobe.
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