DIENCEPHALON PITUITARY GLAND TELENCEPHALON DIENCEPHALON The - - PowerPoint PPT Presentation

DIENCEPHALON PITUITARY GLAND TELENCEPHALON

DIENCEPHALON

The diencephalon, which translates as “between brain”. The diencephalon sits “atop” the brainstem. The third ventricle is situated between the two thalami. Two thalami are often connected across the midline by nervous tissue, the massa intermedia The diencephalon is situated within the brain below the level of the body of the lateral ventricles - the thalamus forms the “floor” of this part of the ventricle.

The narrow anterior pole of thalamus lies close to the midline and forms the posterior boundary of the interventricular foramen. Posteriorly, an expansion, the pulvinar, extends beyond the third ventricle to overhang the superior colliculus. The brachium of the superior colliculus (superior quadrigeminal brachium) separates the pulvinar above from the medial geniculate body below. A small oval elevation, the lateral geniculate body, lies lateral to the medial geniculate.

The superior (dorsal) surface of the thalamus is covered by a thin layer

• f white matter, the stratum zonale.

The stratum zonale extends laterally from the line of reflection of the ependyma (taenia thalami) and forms the roof of the third ventricle. This curved surface is separated from the overlying body of the fornix by the choroid fissure, with the tela choroidea within it.

The lateral border of the superior surface of the thalamus is marked by the stria terminalis and the overlying thalamostriate vein, which separate the thalamus from the body of the caudate nucleus. The medial surface of the thalamus is the superior (dorsal) part of the lateral wall of the third ventricle. The medial surface of the thalamus is usually connected to the contralateral thalamus by an interthalamic adhesion behind the interventricular foramina.

The boundary with the hypothalamus is marked by an indistinct hypothalamic sulcus, which curves from the upper end of the cerebral aqueduct to the interventricular foramen. The diencephalon, including both thalamus and hypothalamus and some other subparts, is situated between the brainstem and the cerebral hemispheres, deep within the brain. In a horizontal section of the hemispheres, the two thalami are located at the same level as the lentiform nucleus of the basal ganglia.

The thalamus is usually described as the gateway to the cerebral cortex.

THALAMUS

The most thalamic nuclei that project to the cerebral cortex also receive input from that area - these are called reciprocal connections. The major function of the thalamic nuclei is to process information before sending it on to the select area of the cerebral cortex. This is particularly so for all the sensory systems, except the olfactory sense.

Two subsystems of the motor systems, the basal ganglia and the cerebellum, relay in the thalamus before sending their information to the motor areas of the cortex.

THALAMUS

Other thalamic nuclei are related to areas of the cerebral cortex, which are called association areas, vast areas of the cortex that are not specifically related either to sensory or motor functions. The major function of the thalamic nuclei is to process information before sending it on to the select area of the cerebral cortex.

THE THALAMUS

THALAMUS

THE THALAMUS largest division of the diencephalon receives precortical input from all sensory systems except the

• lfactory system.

largest input received from the cerebral cortex projects primarily to the cerebral cortex and to a lesser degree to the basal nuclei and hypothalamus plays an important role in sensory and motor system integration

THALAMUS

Other parts of the DIENCEPHALON:

• hypothalamus, one in each hemisphere, is composed of a number
• f nuclei that regulate homeostatic functions of the body, including

water balance.

• pineal is sometimes considered a part of the diencephalon. This

gland is thought to be involved with the regulation of our circadian

• rhythm. Many people now take melatonin, which is produced by

the pineal, to regulate their sleep cycle and to overcome jetlag.

• subthalamic nucleus

THALAMUS

THALAMIC NUCLEI both project to and receive fibres from the cerebral cortex.

THALAMUS

The thalamus is the major route by which subcortical neuronal activity influences the cerebral cortex, and the greatest input to most thalamic nuclei comes from the cerebral cortex. Each cortical area projects in a topographically organized manner to all sites in the thalamus from which it receives an input. Internally, the thalamus is divided into anterior, medial and lateral nuclear groups by a vertical Y-shaped sheet of white matter, the internal medullary lamina. The intralaminar nuclei lie embedded within, and surrounded by, the internal medullary lamina.

THALAMIC NUCLEI - ANTERIOR NUCLEUS

• receives hypothalamic input from the mammillary nucleus via the

mammillothalamic tract.

• receives hippocampal input via the fornix.
• projects to the cingulate gyrus (anterior limbic area).
• part of the Papez circuit of emotion (the limbic system, control of

expression).

• are believed to be involved in the regulation of alertness and

attention and in the acquisition of memory.

THALAMUS

THALAMIC NUCLEI - DORSOMEDIAL NUCLEUS (MEDIODORSAL NUCLEUS) This most important nucleus relays information from many of the thalamic nuclei as well as from parts of the limbic system (hypothalamus and amygdala) to the prefrontal cortex

THALAMUS

THALAMUS

THALAMIC NUCLEI - DORSOMEDIAL NUCLEUS (MEDIODORSAL NUCLEUS)

• reciprocally connected to the prefrontal cortex.
• has abundant connections with the intralaminar nuclei.
• receives input from the amygdala, the temporal neocortex, and

the substantia nigra.

• part of the limbic and striatal systems.
• when destroyed results in memory loss (Wernicke–Korsakoff

syndrome).

• plays a role in the expression of affect, emotion, and behavior

(limbic function).

• damage may lead to a decrease in anxiety, tension, aggression or
• bsessive thinking.
• there may also be transient amnesia, with confusion developing
• ver time.

THALAMIC NUCLEI - INTRALAMINAR NUCLEI intralaminar, midline, and reticular nuclei - these nuclei receive from

• ther thalamic nuclei and from the ascending reticular activating

system, as well as receiving fibers from the “slow” pain system; they relay to widespread areas.

THALAMUS

THALAMIC NUCLEI - INTRALAMINAR NUCLEI

• receive input from the brainstem reticular formation, the ascending

reticular system, and other thalamic nuclei.

• receive spinothalamic and trigeminothalamic input.
• project diffusely to the neocortex.
• projects to the dorsomedial nucleus.

THALAMIC NUCLEI - INTRALAMINAR NUCLEI

• 1. Centromedian nucleus

largest of the intralaminar nuclei reciprocally connected to the motor cortex (area 4) receives input from the globus pallidus projects to the striatum projects diffusely to the neocortex

• 2. Parafascicular nucleus

projects to the striatum and the supplementary motor cortex (area 6)

THALAMUS

THALAMIC NUCLEI DORSAL TIER NUCLEI

• 1. Lateral dorsal nucleus
• 2. Lateral posterior nucleus
• 3. Pulvinar

THALAMUS

THALAMIC NUCLEI - DORSAL TIER NUCLEI

• 1. Lateral dorsal nucleus
• a posterior extension of the anterior nuclear complex
• receives mammillothalamic input
• projects to the cingulate gyrus
• has reciprocal connections with the limbic system

THALAMUS

• 2. Lateral posterior nucleus
• located between the lateral dorsal nucleus and the pulvinar
• has reciprocal connections with the superior parietal cortex (areas

5 and 7)

• 3. Pulvina

This nucleus is part of the visual relay, but relays to visual association areas of the cortex, areas 18 and 19

THALAMIC NUCLEI - DORSAL TIER NUCLEI

• 3. Pulvinar
• the largest thalamic nucleus
• has reciprocal connections with the association cortex of the
• ccipital, parietal, and posterior temporal lobes
• receives input from the lateral and medial geniculate bodies and

the superior colliculus

• concerned with the integration of visual, auditory, and somesthetic

THALAMUS

THALAMIC NUCLEI VENTRAL TIER NUCLEI include primarily specific relay nuclei:

• 1. Ventral anterior nucleus
• 2. Ventral lateral nucleus
• 3. Ventral posterior nucleus
• a. Ventral posterolateral (VPL) nucleus
• b. Ventral posteromedial (VPM) nucleus
• c. Ventral posteroinferior (VPI) nucleus

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 1. Ventral anterior nucleus
• receives input from the globus pallidus and the substantia nigra
• projects diffusely to the prefrontal and orbital cortices
• projects to the premotor cortex (area 6)

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 2. Ventral lateral nucleus
• receives input from the globus pallidus, substantia nigra, and the

cerebellum (dentate nucleus)

• projects to the motor cortex (area 4) and to the supplementary

motor area (area 6)

• influences somatic motor mechanisms via the striatal motor system

and the cerebellum

• stereotactic destruction reduces Parkinsonian tremor

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 3. Ventral posterior nucleus

the nucleus of termination of general somatic afferent (GSA; pain and temperature) and special visceral afferent (SVA; taste) pathways

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 3. Ventral posterior nucleus

contains three subnuclei:

• a. Ventral posterolateral (VPL) nucleus
• b. Ventral posteromedial (VPM) nucleus
• c. Ventral posteroinferior (VPI) nucleus

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 3a. Ventral posterolateral (VPL) nucleus
• receives the spinothalamic tracts and the medial lemniscus.
• projects to the somesthetic (sensory) cortex (areas 3, 1, 2).
• lesion results in contralateral loss of pain and temperature

sensation as well as loss of tactile discrimination in the trunk and extremities.

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 3b. Ventral posteromedial (VPM) nucleus
• receives the trigeminothalamic tracts.
• receives the taste pathway via the solitary nucleus and the

parabrachial nucleus.

• projects to the somesthetic cortex (areas 3, 1, and 2).
• lesion results in contralateral loss of pain and temperature

sensation, and loss of tactile discrimination in the head; results in ipsilateral loss of taste.

THALAMUS

THALAMIC NUCLEI - VENTRAL TIER NUCLEI

• 3c. Ventral posteroinferior (VPI) nucleus
• receives vestibulothalamic fibers from the vestibular nuclei.
• projects to the vestibular area of the somesthetic cortex.

THALAMIC NUCLEI LATERAL GENICULATE BODY (LGB)

• a visual relay nucleus.
• receives retinal input via the optic tract.
• projects to the primary visual cortex (area 17, the lingual gyrus and

the cuneus) via the optic radiation.

THALAMUS

THALAMIC NUCLEI MEDIAL GENICULATE BODY (MGB)

• an auditory relay nucleus.

THALAMUS

THALAMIC NUCLEI MEDIAL GENICULATE BODY (MGB)

• an auditory relay nucleus.
• receives auditory input via the brachium of the inferior colliculus.
• projects to the primary auditory cortex (areas 41 and 42) via the

auditory radiation.

INTERNAL CAPSULE

INTERNAL CAPSULE

INTERNAL CAPSULE

• a layer of white matter (myelinated axons) that separates the

caudate nucleus and thalamus medially from the lentiform nucleus laterally. consists of three divisions:

• Anterior limb
• Genu
• Posterior limb

INTERNAL CAPSULE

INTERNAL CAPSULE ANTERIOR LIMB located between the caudate nucleus and the lentiform nucleus. GENU contains corticobulbar fibers. POSTERIOR LIMB

• located between the thalamus and the lentiform nucleus.
• contains the sensory radiations (pain, temperature, and touch).
• contains the corticospinal fibers.
• contains the visual and auditory radiations.

INTERNAL CAPSULE

THE HYPOTHALAMUS

HYPOTHALAMUS

THE HYPOTHALAMUS

• a division of the diencephalon.
• lies within the floor and ventral part of the walls of the third

ventricle.

• functions primarily in the maintenance of homeostasis.
• subserves three systems: the autonomic nervous system (ANS), the

endocrine system, and the limbic system.

HYPOTHALAMUS

HYPOTHALAMUS

THE HYPOTHALAMUS

• visible only from the inferior aspect of the brain.
• lies between the optic chiasm and the interpeduncular fossa

(posterior perforated substance).

• hypothalamic sulcus forms superior border.

THE HYPOTHALAMUS includes the following ventral surface structures:

• Infundibulum
• Tuber cinereum
• Mammillary bodies
• Cerebral arterial circle

HYPOTHALAMUS

THE HYPOTHALAMUS INFUNDIBULUM

• the stalk of the hypophysis.
• contains the hypophyseal portal vessels.
• contains the supraopticohypophyseal and tuberohypophyseal

tracts.

HYPOTHALAMUS

TUBER CINEREUM

• the prominence between the infundibulum and the mammillary

bodies.

• includes the median eminence, which contains the arcuate nucleus.

MAMMILLARY BODIES

• contain the mammillary nuclei.

CEREBRAL ARTERIAL CIRCLE

• surrounds the inferior surface of the hypothalamus and provides its

blood supply.

THE HYPOTHALAMUS

• visible only from the inferior aspect of the brain.
• lies between the optic chiasm and the interpeduncular fossa

(posterior perforated substance).

• hypothalamic sulcus forms superior border.

includes the following ventral surface structures:

• Infundibulum
• Tuber cinereum
• Mammillary bodies
• Cerebral arterial circle

HYPOTHALAMUS

PINEAL GLAND

PITUITARY GLAND

PINEAL GLAND The pineal gland, or epiphysis cerebri, is a small, reddish grey organ

• ccupying a depression between the superior colliculi.

The pineal is an endocrine gland of major regulatory importance. It modifies the activity of the adenohypophysis, neurohypophysis, endocrine pancreas, parathyroids, adrenal cortex, adrenal medulla and gonads. Melatonin and its precursor serotonin are secreted into the surrounding network of fenestrated capillaries. From the second decade, calcareous deposits accumulate in pineal extracellular matrix, where they are deposited concentrically as corpora arenacea or ‘brain sand’

PINEAL GLAND

PITUITARY GLAND

PITUITARY GLAND

PITUITARY GLAND The pituitary gland, or hypophysis cerebri, is a reddish grey ovoid body The pituitary gland is continuous with the infundibulum, a hollow, conical inferior process from the tuber cinereum of the hypothalamus. The pituitary gland lies within the pituitary fossa of the sphenoid bone, where it is covered superiorly by a circular diaphragma sellae of dura mater.

PITUITARY GLAND

PITUITARY GLAND The pituitary has two major parts:

• neurohypophysis
• adenohypophysis

which differ in their origin, structure and function. The neurohypophysis is a diencephalic downgrowth connected with the hypothalamus. The adenohypophysis is an ectodermal derivative of the stomatodeum. Both include parts of the infundibulum (whereas the older terms ‘anterior lobe’ and ‘posterior lobe’ do not). The infundibulum has a central infundibular stem that contains neural hypophysial connections and is continuous with the median eminence of the tuber cinereum.

PITUITARY GLAND