14 - Overview of Brainstem Organisation

Question 1

Proportion of CNS represented by the brainstem in lower animals

Answer 1

~90%

Question 2

How can anencephalic babies survive for a few days?

Answer 2

Brainstem is intact

Question 3

Broad functions of brainstem

Answer 3

Reflexive and unconscious behaviour. Modulation of various arousal and conscious states

Question 4

Three regions of brainstem

Answer 4

Mid-brain (most rostral) Pons Medulla oblongata

Question 5

Where in the skull is the brainstem located?

Answer 5

Posterior cranial fossa

Question 6

Extension of the brainstem

Answer 6

(Rostral) Mammillary bodies to (caudally) pyramidal decussation

Question 7

Pyramidal decussation

Answer 7

Where white fibre tracts involved in motor function cross over.

Question 8

Gross physical characteristics of midbrain (dorsal)

Answer 8

Has two pairs of bumps called the superior and inferior colliculi.

Question 9

Gross physical characteristics of pon (dorsal)

Answer 9

1) Linked with cerebellum 2) Limited by the 4th ventricle 3) Along floor of 4th ventricle are the facial colliculi formed by the abducens nucleus and fibres of SN VII

Question 10

Role of superior colliculi

Answer 10

Eye movements

Question 11

Role of inferior colliculi

Answer 11

Relay station for hearing

Question 12

Location of 4th ventricle

Answer 12

Between pons and cerebellum

Question 13

Gross physical characteristics of medulla (dorsal)

Answer 13

Caudally: dorsal columns and nuclei (gracile and cuneate tubercle).

Question 14

Gross physical characteristics of midbrain (ventral)

Answer 14

Cerebral peduncles (between interpeduncular fossa)

Question 15

Gross physical characteristics of pons (ventral)

Answer 15

Attached to cerebellum dorsolaterally by cerebellar peduncles (superior, middle, inferior)

Question 16

Gross physical characteristics of medulla (ventral)

Answer 16

Rostral: Two bulges - inferior olivary nuclei Pyramids descending to the pyramidal decussation

Question 17

Role of inferior olivary nuclei

Answer 17

Location of a sound in space

Question 18

Four important brainstem structures

Answer 18

1) Cranial nerve nuclei and related structures 2) Reticular formation and related structures 3) Long fibre tracts 4) Cerebellar circuitary

Question 19

Role of reticular formation

Answer 19

Important in complex reflexes (eg: sneezing, vomiting)

Question 20

Tectum

Answer 20

‘Roof’ Roof of the 4th ventricle.

Question 21

Tegmentum

Answer 21

‘Covering’ Region of the brainstem that is continuous with the spinal cord.

Question 22

Three broad regions of mid-brain

Answer 22

Tectum, tegmentum and basis

Question 23

Broad regions of pons

Answer 23

Tegmentum (dorsally) and a lot of basis (ventrally)

Question 24

Generalised role of basis

Answer 24

Descending motor control

Question 25

Generalised role of tegmentum

Answer 25

Like the spinal cord. Cranial nerves. Reticular formation.

Question 26

General types of nerves emerging from the spinal cord

Answer 26

General somatic nerves (innervate skeletal muscle, skin) General visceral nerves (innervate viscera)

Question 27

Where do spinal nerves end?

Answer 27

C2

Question 28

Role of cranial nerves 1 2

Answer 28

1) Supply somatic and visceral motor and sensory information to head. 2) NIX & X-also supply visceral sensory and motor innervation to neck, chest and most abdominal organs.

Question 29

Number of pairs of cranial nerves

Answer 29

12

Question 30

Order in which cranial nerves exit brainstem

Answer 30

In numerical order (rostral to caudal)

Question 31

Orientation in which cranial nerves exit brainstem

Answer 31

Most exit ventral surface except IV

Question 32

Exclusively motor cranial nerves

Answer 32

III, IV, VI control eye movements. XI, XII

Question 33

Exclusively sensory cranial nerves

Answer 33

I, II, VIII

Question 34

Mixed sensory and motor cranial nerves

Answer 34

V, VII, IX, X

Question 35

Rule of 4 for cranial nerves 1 2 3

Answer 35

1) 4 cranial nerves exit the medulla \* CNIX-XII 2) 4 exit the pons \* CNV, VI, VII, VIII 3) 4 exit above the pons \* CNIII, IV

Question 36

Organisation of motor and sensory parts of brainstem

Answer 36

Similar to spinal cord. Dorsal part is sensory. Ventral part is motor.

Question 37

Effect of motor nuclei developing from basal plate

Answer 37

Located at the midline

Question 38

Broad locations of motor and sensory cranial nerves

Answer 38

Sensory are lateral. Motor and in midline.

Question 39

\*Columns within which cranial nerves sit in brainstem

Answer 39

Question 40

Role of general somatic efferent motor nerves

Answer 40

Innervate muscle of the face

Question 41

Role of general visceral efferent cranial nerves

Answer 41

For visceral smooth muscle

Question 42

General and special visceral afferent cranial nerves

Answer 42

EG: taste

Question 43

Role of general somatic sensory cranial nerves

Answer 43

Sensory information from face

Question 44

Location of all cranial nerve cell bodies

Answer 44

Dorsal half of brainstem, near 4th ventricle

Question 45

What is in the ventral half of brainstem?

Answer 45

White matter dorsal tracts of sensory nerves

Question 46

Location of reticular formation

Answer 46

Continuous rostrally with certain nuclei in the thalamus. Continuous caudally with intermediate grey of the spinal cord. Within the tegmentum of the brainstem

Question 47

Broad divisions of the reticular formation

Answer 47

Rostral and caudal halves

Question 48

Rostral reticular formation broad roles

Answer 48

Maintain alert and conscious state.

Question 49

Parts of midbrain in rostral reticular formation

Answer 49

Midbrain, upper pons

Question 50

Rostral reticular formation broad roles

Answer 50

Work together with cranial nerve nuclei and spinal cord to carry out a variety of important motor reflex and autonomic functions. Modulation of forebrain activity

Question 51

What dominates caudal reticular formation activity?

Answer 51

Long projection systems Defined by neurotransmitters

Question 52

Examples of neurotransmitters of long projection system in caudal reticular formation 1 2 3 4

Answer 52

1) Noradrenergic (locus ceruleus) 2) Dopaminergic (eg substantia nigra) 3) Serotonergic (dorsal raphe nucleus) 4) Cholinergic

Question 53

Examples of caudal reticular formation functions 1 2 3 4 5 6

Answer 53

Ventrolateral medullary reticular formation 1) Regulate visceral functions of X (Vagus). 2) GI responses (swallowing, vomiting) 3) Respiratory activities: \*Rhythm, coughing, hiccupping, sneezing. \*Cardiovascular responses Other regions: 4) Lateral medullary, pontine RF 5) Important for chewing 6) Region surrounding facial nucleus: crying, smiling

Question 54

Three major pathways traversing brainstem

Answer 54

Ascending pathways: (ie touch and pain) 1. Dorsal column - medial lemniscus system \* Fine touch-tactile, vibration \* Crosses in medulla (medial lemniscus) 2. Anterolateral system (pain) \* Crosses in spinal cord \* Three pathways each terminating in different region. \* Thalamus, midbrain, reticular formation 3. Descending pathway: corticospinal tract \* Controls motor function \* Crosses at pyramidal decussation (most-caudal part of brainstem) \* Descends through ventral brainstem