Neuro 1 - Organisation of the Brainstem and Cranial Nerves Flashcards
Where are the colliculi found and what are their functions?
Roof of the midbrain
superior - coordination of head and eye movements
inferior - auditory reflexes
Describe the location of the pons relative to the ventricular system
The pons is the floor of the 4th ventricle
Name an important unpaired midline structure of the posterior aspect of the brainstem.
Pineal gland
What is the role of the pineal gland?
produces melotonin, involved in circadian rhythm
Which cranial nerve emerges from the back of the brainstem?
Trochlear
What is the role of the trochlear nerve?
supplies the superior oblique muscle
What structure defines the medulla in the dorsal aspect and what pathways are found within this structure?
Dorsal columns
- sensory pathways - touch and proprioception
What three things can be seen superior to the pons when viewing the brainstem from an anteroinferior view?
optic chiasm
Pituitary stalk
Mamimillary bodies
What are the mammillary bodies?
part of limbic system
Which cranial nerve emerges in the midline just above the transverse fibres of the pons?
Oculomotor
What are the cerebral peduncles?
descending motor tracts coming fro the motor cortex
+ holds cerebrum onto the brainstem
Name the cranial nerve that emerges from the lateral aspect of the pons?
Trigeminal
What is the role of the trigeminal nerve?
Touch and sensation throughout the head and neck
What is the main motor unit of the trigeminal nerve innervating?
muscles of mastication
Which 3 nerves emerge at the pontomedullary junction?
Abducens, Facial, Vestibulocochlear
What is the role of the abducens, facial and vestibulocochlear nerves?
Abducens - lateral rectus of eye
Facial - innervates the muscles of facial expression + taste for anterior 2/3
Vestibulocochlear - involved in balance and hearing
Which 3 nerves emerge from the lateral medulla?
glossopharyngeal, vagus and accessory
What is the role of the glossopharyngeal, vagus and accessory nerves?
glossopharyngeal - sensory and motor innervation of the tongue and pharynx
vagus - main parasympathetic nerve descending down to the viscera
accessory - supplies trapezius and sternocleidomastoid
What is the last cranial nerve?
Hypoglossal - supplies musculature of tongue
The motor fibres coming down from the motor cortex come via the cerebral peduncles then disappear behind the transverse fibres of the pons. What structure do they re-emerge as, inferior to the transverse fibres?
Pyramids
What percentage of motor fibres cross to the contralateral side of the body in the brainstem and where does this changing of the sides take place?
90-95%
pyramids
What are the four functional subtypes of the cranial nerves and what are their actions?
General Somatic Afferent
● Sensation from the skin and mucous membranes
General Visceral Afferent
● Sensation from the GIT, heart, vessels and lungs
General Somatic Efferent
● Muscles for eye and tongue movements General
Visceral Efferent
● Preganglionic parasympathetic
What are the special subtypes of cranial nerves and what are their actions?
Special Somatic Afferent
● Vision, hearing and equilibrium
Special Visceral Afferent
● Smell and Taste (comes from three nerves that converge on the nucleus solitarius)
Special Visceral Efferent
● Muscles involved in chewing, facial expression, swallowing, vocal sounds and turning the head
What structure separates the sensory nuclei from the motor nuclei in the spinal cord and brainstem?
Sulcus Limitans
What happens in the formation of the rhombencephalon and how does this affect the arrangement of the nuclei?
Alar plate opens up
opening of alar means motor nuclei are medial and sensory are lateral in the brainstem
Describe the arrangement of different groups of columns within the brainstem.
Motor - medial
Sensory - Lateral
Motor - medial to later = GSE SVE GVE
Sensory - medial to lateral = GVA/SVA, GSA, SSA
State the nuclei that are in the general somatic efferent group and desribe the location within the brainstem.
Oculomotor - midbrain
trochlear - midbrain
Abducens - pons
Hypoglossus - medulla
State the nuclei which are in the special visceral efferent group and describe their location within the brainstem.
Trigeminal - pons
Facial - pons
Ambiguus - medulla
Accessory - cervical spinal cord
State the nuclei that are in the general visceral efferent group and describe their location in the brainstem.
Edinger Westphal - midbrain
Salivatory - ponto-medullary border
Vagus - Pons
State the nuclei that are in the special somatic afferent group and describe their location?
Vestibulocochlear - pons and medulla
State the nuclei that are in the general somatic afferent group and describe their location within the brainstem.
Trigeminal - in all 3 parts + cervical spinal cord
State the nuclei that are in the general visceral afferent and special visceral afferent groups and describe their location within the brainstem.
Solitarius - mainly in the medulla
Describe the appearance of a cross section of the midbrain?
mickey mouse appearance
ears = cerebral peduncles
substantia nigra
What is the substantia nigra? Describe its clinical significance?
group of dopaminergic neurones
produce neuromelatonin
Parkinson’s = loss of these neurones
Describe the appareance of a cross section of the pons.
4th ventricle
transverse fibres seen
Describe the appearance of a cross section of the medulla?
pyramids seen
inferior olivary nucleus
4th ventricle still visible
Describe the appearance of the lower medulla.
more round
central canal
dorsal columns
pyramidal decussation
Name the 2 columns that make up the dorsal columns.
Gracilis - more medial - lower limb sensory
Cuneate - more later - upper limb sensory
What is lateral medullary syndrome?
occulsion of vertebral arteries or PICS causes - horner's vertigo ipsilateral loss of pain on face - contralteral loss of pain in trunk ataxia
What are the symptoms of Horner’s syndrome?
ptosis
loss of sweating around eye
hoarseness
difficulty swallowing
