Organisation Of Brainstem And Cranial Nerves

Question 1

Brainstem

Answer 1

That part of the CNS, exclusive of the cerebellum, that lies between the cerebrum and the spinal cord.

Major divisions:
Medulla oblongata
Pons
Midbrain

Sits in posterior cranial fossa

Slide 5 [pic]

Question 2

Posterior view (fourth ventricle and cerebellum)

Answer 2

Slide 8 [pic]

Roof of midbrain = pineal gland (melatonin and circadian rhythm
Superior colliculus = coordinated neck and eye movements
Inferior colliculus = basic survival functions (auditory reflex)
Trochlear nerve = supplies one of the muscles involved in eye movement
4th ventricle = diamond shaped recess. Floor of 4th ventricle is back of the pons
Dorsal columns = 2 dorsal columns (one from leg - medial, lateral one - upper arm)

Question 3

Brainstem anteroinferior view

Answer 3

Optic chiasm
Pituitary stalk
Cranial nerve 1 = olfactory
Cranial nerve 2 = optic nerve (crosses over and goes to the back of the brain)
Mammillary body (base of hypothalamus)
Cranial nerve 3 = oculomotor (eye movement)
cerebral peduncle (main motor tracks) = allow voluntary control
Trigeminal nerve (sensory nerve for head and neck - touch and sensation) - emerges at level of the pons
Abducens (lateral eye movement), facial (muscles for facial expression) and vestibulocochlear (balance and hearing - goes into inner ear) nerves emerge at level of pontomedullary junction
Glossopharyngeal (tongue and pharynx - swallowing and mastication), vagus (parasympathetic)and accessory (muscles of your shoulder) nerves
Hypoglossal nerves (supplies muscle of tongue)
Pyramids (cerebral peduncle emerges from the pons as pyramids)
Pyramidal decussation (90-95% of nerves cross over at the medulla)

Question 4

Functional classification

Answer 4

General somatic afferent (GSA)
- sensation from skin and mucous membranes
General visceral afferent (GVA)
- sensation fromGi tract, heart, vessels and lungs
General somatic efferent (GSE)
- muscles for eye and tongue movements
General visceral efferent (GVE)
- preganglionic parasympathetic

Special somatic afferent
     - vision, hearing and equilibrium
Special visceral afferent
     - smell and taste
Special visceral efferent
     - muscles involved in chewing, facial expression, swallowing, vocal sounds and turning head

Question 5

Embryonic spinal cord

Answer 5

Slide 14 [pic]

Question 6

Embryonic rhombencephalon

Answer 6

Slide 15 [pic]
Sensory = lateral
Motor = medial

Question 7

Cranial nerves

Answer 7

Slide 17 [pic]
Bilateral

GENERAL SOMATIC EFFERENT
Midbrain: oculomotor, trochlear
Pons: abducens
Medulla: Hypoglossal

SPECIAL VISCERAL EFFERENT
Trigeminal motor
Facial
Ambiguus
Accessory

GENERAL VISCERAL EFFERENT
Edinger Westphal (parasympathetic innervation of the eye)
Salivatory (x2)
Vagus motor

GENERAL VISCERAL AFFERENT
Solitarius

GENERAL SOMATIC AFFERENT
Trigeminal (x3)

SPECIAL SOMATIC AFFERENT
Vestibulocochlear

Question 8

Brainstem internal structure

Midbrain

Answer 8

Slide 19-21[pic]

“Mickey mouse”

Cerebral aqueduct - only present in midbrain
Cerebral peduncle
Inferior colliculus - just about see the bump on the surface
Substantia nigra - black substance (neuromelanin - found in dopaminergic cells. Important in parkinsons)

Question 9

Brainstem internal sttructure

Pons

Answer 9

Slide 22 [pic]

4th ventricle = level of pons
Lots of transverse fibres
Middle cerebellar peduncle

Question 10

Brainstem internal structure

Medulla

Answer 10

Slide 23 [pic]

4th ventricle
Pyramids
Inferior olivary nucleus

Question 11

Brainstem internal structure

Lower medulla

Answer 11

Slide 24 [pic]

Dorsal columns
Central canal
Pyramidal decussation (fibres crossing over - descending corticospinal track)

Question 12

Lateral medullary syndrome

Answer 12

Thrombosis of vertebral artery or PICA

 - vertigo
 - ipsilateral cerebellar ataxia
 - ipsilateral loss of pain/thermal sense (face)
 - Horner’s syndrome (loss of sympathetic control, lack of sweating)
 - hoarseness, difficulty in swallowing
 - contralateral loss of pain/thermal sense (trunk and limbs)

Slide 27 [pic]

Lateral medulla:
Blood clot stops supply of blood into this part of the medulla
Vestibular nuclei = vertigo
Inferior cerebella peduncle = lack of balance
Trigeminal = loss of pain and temperature sensation
Sympathetic tract = loss sympathetic control of eye area (Horner’s)
Ambiguus = problems with normall speaking
Spinothalamic tract = loss of pain/thermal sense (contralateral)