Organizations of the Brainstem

Divisions of the brainstem in descending order

1. Midbrain

2. Pons

3. Medulla

(Pons + medulla = hindbrain)

Structures in the midline of the brainstem

• Motor pathway

• Medial lemniscus

• MLF

• Motor nucleus and nerve

Structures located laterally in the brainstem

• Spinocerebellar pathways

• Spinothalamic pathway

• Sensory nucleus of CN 5

• Sympathetic pathways

1

Midbrain

2

Pons

3

Medulla

1

Cerebral peduncle

2

Pons

3

Inferior olive

4

Pyramid

1

Tectum

2

Cerebral peduncle

6

Cerebellum

4

Pons

Structures in the medulla

• Pyramids

• Pyramidal decussation

• Inferior olives

• Medial lemniscus

• Spinothalamic tract

1 (white part and black part)

• White part: solitary nucleus

• Black part: solitary tract

2

Inferior olive

3

Pyramids

4

Hypoglossal nuc.

CN XII

5

Dorsal vagal nuc.

CN X

Inferior olives

1

Cochlear nuc.

CN VIII

2

Vestibular nuc.

CN VIII

1

Spinal nuc.

CN V

2

Accessory nuc.

CN XI

3

Pyramidal decussation

The _____ extends from the rostral midbrain to the caudal medulla

reticular formation

Notable zone(s) of the reticular formation

Raphe nuclei

Pons

Structures of the pons

• Corticospinal tract

• Cerebellar peduncles

Rostral pons

Caudal pons

1

Trigeminal sensory nuc.

CN V

2

Trigeminal motor nuc.

CN V

Main regions of the midbrain

• Tectum

• Tegmentum

• Cerebral peduncles

1

Tectum

2

Tegmentum

3

Cerebral peduncle

Cerebral peduncle

Cerebral peduncle

Cerebral peduncles

Cerebral peduncle

1

Tegmentum

2

Tectum

Colliculi of the tectum

• Superior colliculus (2)

• Inferior colliculus (2)

The tectum forms the _____

ceiling of the brainstem

(the dorsal roof of the cerebral aqueduct)

Superior collicilus

• Part of visual pathway

• Origin of tectospinal tract

Inferior colliculus is part of the _____

auditory pathways

1

Superior colliculus

2

Inferior colliculus

1

Superior colliculus

2

Inferior colliculus

Superior colliculus

1

Inferior colliculus

2

Trochlear nuc.

CN IV

Inferior colliculus

Main structures of the tegmentum

• Red nucleus

• Substantia nigra

• Periaqueductal gray (PAG)

1

Oculomotor nuc.

CN III

2

Substantia nigra

3

PAG

4

Cerebral peduncle

5

Red nucleus (involved in motor coordination)

The red nucleus is situated within…

the tegmentum of the rostral/ventral midbrain

Most important efferent projection of the red nucleus is to the…(+ name of projection)

contralateral spinal cord - rubrospinal projection

Red nucleus

Red nucleus

The medial longitudinal fasciculus (MLF) connects…(+ what does it control)

eye muscle nuclei (CN III, IV, VI) with the vestibular system (CN VIII)

Controls coordinated head and eye movements

MLF

MLF

MLF