brainstem

Question 1

brainstem

Answer 1

mesencephalon (midbrain) + pons + medulla oblongata

Question 2

Functions

Answer 2

Conduit for ascending (sensory) & descending (motor) tracts
• Contains nuclei of cranial nerves III to XII (head’s equivalent of spinal nerves + special sensory)
• Reticular formation reticula = network
• Visceral reflex centres (respiratory & cardiovascular CPG’s)
• Muscle tone & postural reflexes
• Level of arousal / consciousness
• Modulation of pain transmission

Question 3

BLOOD SUPPLY

Answer 3

vertebrobasilar system

Question 4

Mesencephalon

Answer 4

Cerebral peduncles 
•Crus cerebri 
•Interpeduncular fossa 
•CN III
•Superiorcolliculi (littlehills) 
•Inferior colliculi
•CN IV

Question 5

Pons

Answer 5

• Transverse fibres
• CN V
• CN VI
• CN VII & VIII
• Superior cerebellar peduncles
• Superior medullary velum
• Middle cerebellar peduncles
• Rostral floor of the 4th ventricle
• Median sulcus
• Medial eminence
• Sulcus limitans
• Facial colliculus
• Vestibular area

Question 6

Medulla oblongata:

Answer 6

• Anterior median fissure
• Pyramids
• Decussation of pyramids
• Anterolateral sulci
• Olives
• CN IX, X, XI
• CN XII
• Open medulla
• Inferior cerebellar peduncles
• Closed medulla
• Gracile tubercle
• Cuneate tubercle

Question 7

The internal structure of the brainstem can be divided anteroposteriorly into 3 longitudinal layers:

Answer 7

1. Base = descending projection fibres (motor pathways)
2. Tegmentum = ascending sensory pathways & descending extrapyramidal pathways;
   cranial nerve nuclei; reticular formation neurons 3. 3. Tectum (roof) = superior & inferior colliculi in the midbrain

Question 8

Reticular formation

Answer 8

• Network of neurons located in the tegmentum of the brainstem
• Large fields of dendrites allow them to receive inputs from multiple sources
• Extensive connections
• Spinal cord
• Throughout brainstem
• Diencephalon
• Basal nuclei
• Cerebral cortex

Question 9

Reticular formation FUNCTIONS

Answer 9

• Control of movement (connections with cerebellum; CPG’s)
• Cranial nerve reflexes
• Visceral reflexes
• Modulation of pain
• Control of arousal and consciousness

Question 10

Location of sensory & motor cranial nerve nuclei in the brainstem: Spinal cord

Answer 10

Sulcus limitans separates dorsal sensory from ventral motor

Question 11

Location of sensory & motor cranial nerve nuclei in the brainstem: rostral medulla / caudal pons

Answer 11

Sulcus limitans separates
lateral sensory from
medial motor cranial nerve nuclei

Question 12

Mesencephalon

Answer 12

•Cerebral peduncles
•Crus cerebri
•Substantia nigra
•Level of superior colliculus = oculomotor N & red nucleus* - *processes information
going from cerebellum to thalamus
•Level of inferior colliculus = trochlea N

Question 13

Features of a lower cervical spinal cord cross section

Answer 13

• oval shape
• large amount of white matter
• fasciculus cuneatus & fasciculus gracilis
  wide base of the ventral horn

Question 14

Features of a thoracic spinal cord cross section

Answer 14

• lateral horn present
• narrow ventral horn
• Clarke’s nucleus present
• fasciculus cuneatus present in levels above T6, absent below

Question 15

Clarke’s nucleus

Answer 15

extends from C8 to L3. It is formed by cell bodies of sensory neurons transmitting nonconscious proprioceptive information.

Question 16

lateral horn

Answer 16

is present in levels T1 - L2 & contains the cell bodies of preganglionic sympathetic neurons

Question 17

Features of a lumbar spinal cord cross section

Answer 17

• only 1 fasciculus present in each dorsal column
• relatively wide ventral horn due to increased number of motor neurons required to innervate the lower limb muscles
  no lateral horn below L2

Question 18

Features of a sacral spinal cord cross section

Answer 18

• minimal white matter present
• small fasciculus gracilis & no fasciculus cuneatus
  predominantly grey matter

Question 19

adult brainstem subdivision - midbrain

Answer 19

secondary vesicle- mesencephalon

associated adult ventricle - cerebral aqueduct

Question 20

adult brainstem subdivision - pons

Answer 20

secondary vesicle- mesencephalon

associated adult ventrice - 4th ventrical

Question 21

adult brainstem subdivision - medulla

Answer 21

secondary vesicle- mylencephalon

associated adult ventrice - 4th ventrical and central canal