Diencephalon, brain stem, cerebellum, basal ganglia.

Sándor Katz M.D.,Ph.D.

Diencephalon - overview

• Located below thecorpus callosum andabove the midbrain

• Part of thetelencephalon

• Forms the lateral wallof the third ventricle

Diencephalon

Diencephalon - parts

• Epithalamus

• Thalamus

• Subthalamus

• Hypothalamus

Pineal body

Thalamus

• Almost all of the sensorypathways are relayed via thethalamus and project to thecerebral cortex.

• Major descending motortracts from the cerebralcortex generally bypass thethalamus.

Thalamus

Consequently, a lesionof the thalamus or itscortical projectionfibers caused by astroke or other diseaseleads to sensorydisturbances.

Thalamic NucleiSpecific nuclei:• Anterior nuclei(Recive afferent fibers from the mammillary body.)

• Medial nuclei(Recive afferent fibers from ventral and intralaminar nuclei,hypothalamus, mesencephalon and globus pallidus.)

• Ventral nuclei: VA, VL, VPL, VPM(Recive afferent fibers- position sense,vibration, pressure, touch, pain andtemperature- from the trunk and limbs.)

• Dorsal nuclei: LD, LP, Pulvinar(Recive afferent fibers from other thalamic nuclei.)

They have direct connections withspecific areas of the cerebral cortex.

Nonspecific nuclei: have no direct connections with the cerebral cortex.Part of the general arousal system, they are connected directly to the brainstem.

Thalamic Nuclei - Metathalamus

• Lateral geniculate body(component of the visualpathway)

• Medial geniculate body(component of the auditorypathway)

They belong to the category ofspecific thalamic nuclei.

Subthalamus

• Subthalamic nuclei

• Zona incerta

• Globus pallidus

Hypothalamus - overview

• It is the lowest level of thediencephalon, situatedbelow the thalamus.

• The hypothalamus is thecommand center for allautonomic functions in thebody.

• Over 30 hypothalamicnuclei located in the lateralwall and floor of the thirdventricle.

Hypothalamus

Hypothalamic NucleiAnterior (rostral) group: Hormonesynthesis.• Preoptic nucleus• Paraventricular nucleus• Supraoptic nucleus

Middle (tuberal) group: Controlshormone release from the anterior lobeof the pituitary gland.• Dorsomedial nucleus• Ventromedal nucleus• Tuberal nuclei

Posterior (mammillary) group:Activates the sympathetic nervoussystem when stimulated.• Posterior nucleus• Mammillary nuclei of mammillary

body

Functions of the hypothalamusRegion or nucleus

• Anterior preoptic region

• Midanterior and posteriorregions

• Paraventricular and anteriorregions

• Supraoptic and paraventricularnuclei

• Anterior nuclei

Function

• Maintain constant body temperature. Lesion: central hypothermia.

• Activate sympathetic nervous system

• Activate parasympathetic nervoussystem

• Oxitocin production - uterinecontractions. Vasopressin - regulation of water balance, lesion: diabetes insipidus.

• Regulate appetite and food intake. Lesion: obesity or anorexia.

Brain stem – overview

It is divided macroscopicallyinto three parts:

• Mesencephalon

• Pons

• Medulla oblongata

Brain stem

Midbrain - mesencephalon

Tectum (quadrigeminal plate):

• Superior colliculi (part of thevisual pathway)

• Inferior colliculi (part of theauditory pathway)

Cerebral aqueduct

Tegmentum (nuclei, ascending-,descending pathways)

Cerebral peduncles

Midbrain

Pons and medulla oblongata

Dorsal wall is formedby the rhomboidfossa.

Pons

Reticular Formation

• Respiratory and circulatory regulation

• Swallowing center

• Vomiting center

• Reticular activating center (wake upfunction)

• Effect on the motor system

Cranial Nerves

Cranial Nerves

Cerebellum - overview

Cerebellum - overview

Cerebellum - peduncles

Cerebellum - functions

Cerebellum - histology

Cerebellum - histology

Cerebellum - histology

Basal Ganglia

Basal Ganglia - functions• Modulate and regulate specific cortical functions• Preparation, planning, execution of motor activity

• Related nuclei: • subthalamic nucleus of diencephalon• substantia nigra of mesencephalon• VA, VL thalamic nuclei

Increases cortical activation (from Dr. Nemeskéri’s lecture) Decreases cortical activity

Thank you for your attention.References:A.D.A.M.McGraw-Hill Company’s picturesWebPathNature ReviewsPearson EducationSinauer Associatestudyblue.com