Overview of brainstem organisation

Question 1

What does the brainstem act as a gateway between?

Answer 1

Spinal cord and higher cortical areas

Question 2

What are the functions of the brainstem?

Answer 2

Reflexive and unconscious behaviour

Modulation of various arousal and conscious states

Question 3

What are the three major components of the brainstem?

Answer 3

Midbrain

Pons

Medulla

Question 4

Describe the location of the brainstem?

Answer 4

Posterior cranial fossa

Extends from mamillary bodies rostrally to pyramidal decussation caudally

Question 5

Describe the characteristic features of the midbrain, pons and medulla on the dorsal aspect of the brainstem?

Answer 5

Midbrain: superior and inferior colliculi

Pons: limited by fourth ventricle, facial collculi

Medulla: dorsal columns, nuclei-gracile and cuneate tubercle

Question 6

Which part of the brainstem connects to the cerebellum?

Answer 6

Pons

Question 7

Describe the characteristic features of the mibrain, pons and medulla on the ventral aspect of the brainstem?

Answer 7

Mibrain: cerebral peduncles

Pons: cerebellar peduncles (superior, middle, inferior)

Medulla: inferior olivary nuclei, pyramidal decussation

Question 8

What are peduncles?

Answer 8

Large white matter tracts

Question 9

How is the pins attached to the cerebellum?

Answer 9

Via the cerebellar peduncles

Question 10

What is the tectum?

Answer 10

The roof of the brainstem

Part of the midbrain

Question 11

What is the tegmentum?

Answer 11

Stucutre that is continuous with the spinal cord

Question 12

What are the important features of the tectum?

Answer 12

Inferior and superior colliculi

Question 13

What are the important features of the tegmentum?

Answer 13

Cranial nerve nuclei

Reticular formation

Question 14

What is the basis in the brainstem?

What is it important for?

Answer 14

Basilar pons

Important for descending motor control

Question 15

Describe the functional divisions of the brainstem?

Answer 15

Ventral: motor control

Dorsal: cranial nerves and their regulation

Question 16

Decsribe the proportion of tectum, tegmentum and basis at each level of the brainstem?

Answer 16

Blue - tectum; Green - tegmentum; Red - basilar part

From superior to inferior: mibrain, pons, medulla

Question 17

Describe the way in which the cranial nerves exit the cranium?

Answer 17

CN III-XII exit brainstem in order, rostral to caudally

Most exit ventral surface, except CN IV

Question 18

Describe the rule of four for the cranial nerves?

Answer 18

4 CN exit the medulla (CNIX-XII)

4 CN exit the pons (CNV-VIII)

4 CN exit above the pons (2 in the midbrain- CNIII&IV)

Question 19

Where do sensory nuclei of the cranial nevres develop from? Where do motor nuclei develop from?

Answer 19

Sensory: alar plate

Motor: basal plate

Question 20

How are the cranial nerve nuclei organised within the brainstem?

Answer 20

Positioned in columns (6 either side of midline)

Grouped based on similar functions

Motor nuclei - midline

Sensory nuclei - lateral

Question 21

What are the three motor and three sensory columns for cranial nerve nuclei that lie within the brainstem?

Answer 21

MOTOR: general somatic motor, branchial motor, general visceral

SENSORY: general and special visceral, general somatic, special somatic

Question 22

Within which structure is the reticular formation found?

Answer 22

Tegmentum

Question 23

What is the reticular formation continuous with rostrally and caudally?

Answer 23

Rostrally: nuclei in the thalamus

Caudally: intermediate grey matter of spinal cord

Question 24

What are the functions of the rostral and caudal elements of the reticular formation?

Answer 24

Rostral (midbrain and upper pons): maintain alert conscious state

Caudal (pons and medulla): motor reflex and autonomic functions

Question 25

What is the ascending reticular activating system?

Answer 25

Rostral element of the reticular formation Long projection systems that modulate forebrain activity

Question 26

At which levels of the brainstem is the reticular formation found?

Answer 26

All levels

Question 27

What are the two major ascending pathways that traverse the brainstem?

Answer 27

Dorsal column-medial lemniscus system Anterolateral system

Question 28

What is the major descending pathway that traverses the brainstem?

Answer 28

Corticospinal tract

Question 29

What do the dorsal aspects of the brainstem contain? What do the ventral spects contain?

Answer 29

Dorsal: cranial nerve nuclei, reticular formation Ventral: structures associated with descending motor tracts