Cerebellum

Developmental sequence of

brain

Fourth week Fifth week

Location of cerebellum

Lies above

and behind

the medullar

and pons and

occupies

posterior

cranial fossa

Location of cerebellum

External structures

Consists of two cerebellar hemispheres united in the

midline by the vermis

Primary fissure

External structures

Lobules of cerebellum: Anterior lobe, posterior lobe, flocculonodular lobe.

Posterolateral fissure

External structures

• Tonsil of cerebellum

two elevated masses

on inferior surface of

hemispheric portion,

just nearby foramen

magnum

• Cerebellar tonsilar

hernia

Internal structures

• Cerebellar cortex – gray matter Granular layer, piriform (Purkinje) cell layer, molecular layer

• Cerebellar medulla – white matter Superior / Middle / Inferior cerebellar peduncles

• Cerebellar nuclei – gray matter within

white matter Fastigial, globose, emboliform, dentate nuclei

Interposed nucleus

Cerebellar cortex

Molecular

layer

Piriform

cell layer

Granular

layer

White

matter

Cerebellar nuclei

Fastigial, globose, emboliform, dentate nuclei

Cerebellar peduncles

Cerebellar peduncles

inferior cerebellar peduncle (restiform

body) connects with medulla and with

spinal cord, contain both afferent and

efferent fibers

middle cerebellar peduncle

(brachium pontis) connects with pons,

contain afferent fibers

superior cerebellar peduncle

(brachium conjunctivum) connects with

midbrain, contain mostly efferent fibers

Functional divisions of cerebellum

• Vestibulocerebellum

– Archicerebellum

– Flocculonodular lobe

• Spinocerebellum

– Paleocerebellum

– Vermis and intermediate zone

• Cerebrocerebellum

– Neocerebellum

– Lateral zone Flocculonodular lobe

Ve

rmis

Inte

rme

diate zo

ne

Lateral zo

ne

Connections and functions of

cerebellum

Vestibulocerebellum

• Connections

– Afferents: receives inputs from vestibular

nuclei and vestibular ganglion

– Efferents: projects to the vestibular nucleus

→ vestibulospinal tract and medial

longitudinal fasciculus → motor neurons of

anterior horn and cranial nuclei innervating

extraocular muscles

Function: regulation of eyeball movements

and maintenance of body equilibrium.

Spinocerebellum

Connections

• Afferents: receives somatic sensory information via

spinocerebellar tracts

• Efferents:

• Vermis projects to the fastigial nucleus →

vestibular nuclei and reticular formation →

vestibulospinal tract and reticulospinal tract →

motor neurons of anterior horn

• Intermediate zone projects to the interposed

nuclei – Contralateral red nucleus → rubrospinal tract →motor neurons of

anterior horn

– Contralateral VL of thalamus →cerebral cortex→ coticospinal

tract→motor neurons of anterior horn

• Function:

modulate the

muscular tension.

Cerebrocerebellum

• Connections

– Afferents: receives input from the cerebral

cortex via a relay in pontine nuclei

– Efferents: projects to dentate nucleus → VL

of thalamus → primary motor cortex →

corticospinal tract → motor neurons of

anterior horn

• Function:

modulate the

coordination of

voluntary and

fineness

movement,

including

determination of

movement

strength, direction

and amplitude.

Cerebellar functions

• Cerebellum has functions of

1. maintaining body posture,

2. controlling muscular tension,

3. coordinating of voluntary movement,

but NOT initiating and performing

voluntary movement.

Cerebellar injury symptoms

Typical signs of

cerebellar injury:

a. Ataxia:

incoordination of

voluntary movement

b. Nystagmus: tremor

of eyeball

c. Intention tremor

Nose-to-finger test

Diencephalon

Location

Location

Located

between

midbrain and

telencephalon,

mostly

surrounded by

cerebral

hemispheres

Divisions of diencephalon

• (dorsal) thalamus

• metathalamus

• epithalamus

• subthalamus

• hypothalamus

Dorsal thalamus External features

• A large egg-shaped nucleus mass,

• Right and left portion of thalamus are joined by interthalamic adhesion

• Anterior end called anterior thalamic tubercle,

• Posterior end called pulvinar

• Terminal stria

• Hypothalamic sulcus

Dorsal thalamus

Subdivision Principal Nuclei Common

abbreviation

Ant. nuclear group Anterior

Med. nuclear group dorsomedial

Lat. nuclear group

Dorsal layer Lateral dorsal LD

Lateral posterior LP

Pulvinar

Ventral layer Ventral anterior VA

Ventral lateral

(intermediate)

VL (VI)

Ventral posterior VP

Ventral posterolateral VPL

Ventral posteromedial VPM

Functional subdivision

Non-specific projecting nuclei ---- receive afferents from

olfactory brain and reticular formation of brain stem (ascending

reticular activating system), project to hypothalamus, corpus

striatum and diffusely to cerebral cortex.

• Midline nuclei

• Intralaminar nuclei

• Thalamic reticular nuclei

Internuncial nuclei ---- receive a wide variety of afferent fibers

and in turn project widely to association areas of cerebral cortex,

involved in higher nervous activity of brain.

• Anterior nuclear group

• Medial nuclear group

• Dorsal layer of lateral nuclear group

Functional subdivision

Specific relaying nuclei

• Ventral anterior nucleus (VA)

• Ventral lateral nucleus (VL)

Receive inputs from corpus striatum, dentate nucleus, and substantia

nigra, project to motor cortex to regulate body movement.

• Ventral posteromedial nucleus (VPM) －receives trigeminal lemniscus and taste fibers

• Ventral posterolateral nucleus (VPL) －receives medial lemniscus and spinal lemniscus

Projects to primary somatic sensory area via central thalamic

radiations

Metathalamus

Lateral geniculate body (LGN)

Medial geniculate body (MGN)

Specific relaying nuclei

Metathalamus

• Medial geniculate body (MGN)

– Relay station of audition

– Receive fibers from (brachium of) inferior colliculus

– Projects to auditory area via acoustic radiation

• Lateral geniculate body (LGN)

– Relay station of vision

– Receive fibers from retina (optic tract)

– Projects to visual area via optic radiation

Epithalamus

Includes

• Thalamic medullary

stria

• Habenular trigone

• Habenular commissure

• Pineal body: Melatonin

• posterior commissure

Dorsal view

Subthalamus

• Ventrally to the dorsal

thalamus

• Contains subthalamic

nucleus involved in movement regulation.

subthalamic nucleus

Hypothalamus Position－lies ventral to thalamus

Boundaries

• Superior: hypothalamic sulcus

• Inferior:

– optic chiasma

– tuber cinereum

– Infundibulum (hypophysis)

– mamillary body

• Anterior: interventricular foramen

• Posterior: continues with midbrain

tegmentum

Hypothalamus

Hypothalamic divisions

Anterior to posterior

• Preoptic region

• Supraoptic region

• Tuberal region

• Mamillary region

A P

Principal nuclei in hypothalamus • Preoptic region: preoptic nucleus

• Supraoptic region

– Supraoptic nucleus

– Paraventricular nucleus

produce antidiuretic hormone (ADH or vasopressin) and

oxytocin

• Tuberal region

– Infundibular (Arcuate) nucleus

– Ventromedial nucleus

– Dorsomedial nucleus

• Mamillary region

– Mamillary nucleus

– Posterior hypothalamic nucleus

Preoptic nucleus

Supraoptic nucleus

Supra- chiasmatic nucleus

Anterior hypothalamic nucleus

Dorsomedial

nucleus

Paraventricular nucleus

Fornix Anterior commissure

Posterior hypothalamic nucleus

Lateral hypothalamic area

Ventromedial

nucleus

Optic chiasma

Infundibulum

(stalk of the

pituitary gland)

Pituitary

gland

Mammillary

body

The main hypothalamic nuclei

Arcuate nucleus

Hypothalamus -- connection

• Connects with limbic system, brainstem, spinal cord and

dorsal thalamus

• Connects with hypophysis

Hypothalamus -- connection

• Supraoptic nucleus →

supraopticohypophysial tract → posterior lobe of

hypophysis (neurohypophysis)

• Paraventricular nucleus →

paraventriculohypophysial tract → posterior lobe

of hypophysis (neurohypophysis)

Parvicellular neurons in

the arcuate nucleus and

nearby region secrete

releasing and inhibiting

hormones →

tuberoinfundibular tract

→ portal vein of

hypophysis → anterior

lobe of hypophysis

Hypothalamus -- connection

Thyroid-

stimulating

hormone

Adrenocorticot

ropic hormone

Functions of hypothalamus

• Neuroendocrine center

• Subcortical higher regulatory center of the

visceral activity, such as

temperature regulation

food ingestion

reproduction

fluid and electrolyte balance

• Regulate emotional responses and biological

rhythms

Third ventricle

• Position: a narrow ventriclar

cleft lies within diencephalon

– Lateral wall: dorsal thalamus

and hypothalamus

• Communication

Lateral ventricles → third

ventricle →midbrain aqueduct →

fourth ventricle