Flashcards in Brainstem and cranial nerves Deck (50):
What does the pineal gland do?
Circadian rhythm generation for hormone release via secretion of melatonin - trained via the eye
What is the purpose of the superior colliculus?
Eye and neck movement
What is the purpose of the inferior colliculus?
Auditory response (protective reflex)
What is the only cranial nerve that emerges from the back the brainstem?
Trochlear nerve (CN IV)
What are the dorsal columns responsible for?
fine touch and proprioception
What muscle does the trochlear nerve innervate?
The superior oblique muscle
What makes the roof of the midbrain?
The superior and inferior colliculi (tectum)
What is CN I, where can you find it and what does it innervate?
Olfactory nerve (sensory)
Inferior surface of frontal lobes
Olfactory nerves pass through Cribriform plate -> olfactory bulbs -> olfactory tract
What is CN II, where can you find it and what does it innervate?
Optic nerve (sensory)
-> innervates retina
Crosses over at the optic chiasm
What are the mamillary bodies for and where are they?
In the hypothalamus; important in memory and part of the limbic system
What is CN III, where is it found and what does it innervate?
Midbrain, in the midline
Goes to superior, inferior and medial rectus and inferior oblique, levator palpebrae -> movement of eyeball
Pupillary constrictor and ciliary muscle (PNS); for constriction and accommodation
What is the purpose of the cerebellar peduncles?
Connects the cerebellum to the brainstem.
What are the main fibres in the cerebellar peduncles?
Corticospinal tract; communicates with alpha motor neurones -> musculature
How do you easily identify the pons?
Transverse bridging fibres (hides the corticospinal tract)-connects the cerebellum via the middle cerebral peduncles.
What is CN V?
Trigeminal nerve (ophthalmic, maxillar, mandibular);
Sensory; face, scalp, cornea, nasal and oral cavities, cranial dura mater
The smaller root is the motor (muscles of mastication, tensor tympani muscle)
What three nerves emerge at the ponto-medullary junction?
The Abducens, Facial and Vestibulococchlear.
What is CN VI?
Abducens; innervates the (extrinsic) lateral rectus muscle, movement of the eyeball
The nucleus is located in the pons
What is CN VII?
Facial nerve; sensory-anterior 2/3 of tongue for taste
Motor- muscles of facial expression, tension on bones of middle ear
PNS; salivary and lacrimal glands
What is CN VIII?
Vestibulococchlear; vestibular apparatus (position and movement of head)
What is CN IX?
General taste and sensation
What is CN X?
general sensation, chemo- and baroreception visceral sensation, speech and swallowing
Control of cardiovascular, respiratory and gastrointestinal tracts
What is CN XI?
Accessory nerve; sternomastoid and trapezius muscles, movement of head and shoulders
Special visceral efferent
What is CN XII?
Hypoglossal; Intrinsic and extrinsic muscles of the tongue
Where are the 'pyramids' found and their purpose?
Found in the medulla, it is the re-emergence of the corticospinal tract. This is where pyramidal decussation occurs (90-95% fibres cross).
Which cranial nerves are general somatic efferent?
III, IV, VI, XII
Which cranial nerves are special visceral efferent?
V, VII, IX, X, XI
Which cranial nerves are general visceral efferent?
III, VII, IX, X
Which cranial nerves are general somatic afferent?
V, VII, IX, X
Which areas of the brainstem do the GSA fibres of the trigeminal nerve return to?
Mesencephalic trigeminal nerve
Pontine trigeminal nerve
Spinal trigeminal nerve
What do the SVE fibres of the trigeminal nerve innervate?
Muscles of mastication; sensory tympani, tensor veil palatini, mylohyoid, anterior belly of digastric
What does V1 branch into and how does it exit?
Opthlamic branches into; frontal, lacrimal (sensation) and nasociliary nerves
Exits via the superior orbital fissure
How does V2 exit the skull?
Via foramen rotundum, going to the pterygopalatine fossa
What is the exit of V3 and what does it innervate?
Sensory: anterior 2/3rds of tongue, lower face
Motor: four muscles of mastication (temporals, masseter, medial and lateral pterygoids), tensor tympani, tensor veli palatine. Anterior belly of the digastric, and the mylohyoid muscles
How does the abducens nerve leave the brainstem?
At the ponto-medullary junction, it crosses the superior edge of the petrous part of the temporal bone and enters the cavernous sinus inferolateral to the internal carotid artery. Enters via the superior orbital fissure.
What fibres are part of the facial nerve and where are they located in the brainstem?
Facial nerve arises from the ponto-medullary junction
GVE: inferior pons and medulla (superior salivatory nucleus)
SVE: pons (lateral to VI and medial to VIII)
SVA: medulla (nucleus solitaris), taste
GSA: return to sensory nucleus of CNV
What is the route of exit for the facial nerve?
Exit cranial cavity via internal acoustic meatus
Enters the facial canal in the petrous part of temporal bone, the motor and sensory roots fuse (facial nerve), goes to the geniculate ganglion
Facial nerve gives off branches to the stapedius and chorda tympani and enters via stylomastoid foramen
What are the five branches of the facial nerve?
How does the vestibulococchlear nerve enter the cranial cavity and location in the brainstem and fibre location?
Enters through the internal acoustic meatus
Enters the brainstem at the ponto-medullary junction
Fibres are located in the inferior pons and upper medulla, lateral to CNVII
What are the different fibres of CNIX?
SVE: nucleus ambiguus in the medulla, innervate sytlopharyngeus for swallowing
GVE: inferior salivatory nucleus in the medulla; parotid gland
SVA: nucleus solitaris; taste for posterior third of tongue
Which muscles does the vagal SVE fibres innervate?
All muscles of the larynx
Muscles of the pharynx apart from the stylopharyngeus
Muscles of the soft palate apart from tensor veli palatini
Where do the accessory nerve fibres arise from and how do they enter and exit the cranial cavity?
Pass into via foramen magnum and exit through jugular foramen
Where are the CNXII fibres located, innervate and exits the cranial cavity?
Medial in the medulla
All extrinsic and intrinsic muscle apart from palatoglossus e.g. genioglossus, hyoglossus, styloglossus
Exits via hypoglossal canal
What are the key identifying features of the midbrain?
'Mickey mouse' sign
Cerebral aqueduct (CSF passes through here)
Cerebral peduncles (CNIII passes through them)
Substantia nigra (neuromelanin is produced by dopamine metabolism)
[Superior colliculi are not seen on cross-section but located rostral and dorsal aspect of the midbrain]
Inferior colliculi make up the roof of the midbrain
What are the key identifying features of pons?
Transverse fibres connecting the two middle cerebellar peduncles
Middle cerebellar peduncles connect the cerebellum to the pons
Fourth ventricle located at the top and relays CSF in the pons and upper medulla
The trigeminal nerve emerges laterally from the pons
What are the key identifying features of the upper medulla?
Fourth ventricle is present in a cross section
Inferior olivary nucleus is present; involved in fine tuning movements
Pyramids (reemergence of corticospinal tract)
Hypoglossal nerve is present
What are the key identifying features of the lower medulla?
Dorsal columns; medially is the gracile fasciculus (lower limb) and laterally is the cuneate fasciculus (upper limbs)
Central canal which connects ventricular system to the spinal cord
Pyramidal decussation; corticospinal fibres cross over here
What is the locus coerulus?
Small nucleus located in the pons which produces noradrenaline as a response to stress or panic.
What functions is the reticular formation involved with?
Somatic motor control e.g. reticulospinal tract
Cardiovascular control; cardiac and vasomotor control centres in the medulla oblongata
Sleep and consciousness
What is lateral medullary syndrome?
Damage to the vertebral artery or PICA (posterior inferior cerebellar artery);
Spinothalamic damage; contralateral loss of pain and heat sensation
Vestibular damage; loss of balance, vertigo
Spinal nucleus; contralateral loss of heat and pain sensation in the face
Inferior cerebellar peduncles; ipsilateral cerebellar ataxia
Nucleus ambiguus; damage results in hoarseness
Sympathetic tract; damage results in Horner's syndrome