Brain stem and cranial nerves Flashcards
What is the first cranial nerve?
Olfactory (sensory)
What is the function of the first cranial nerve?
Innervates the olfactory epithelium (olfaction)
What are the entry points of the first cranial nerve?
Cribiform plate (skull)
Anterior perforated substance (brain)
What is the second cranial nerve?
Optic (sensory)
Whats the function of the second cranial nerve?
Eye and vision
What are the entry points of the second cranial nerve?
Optic canal (skull)
What is the third cranial nerve?
Occulomotor (motor)
Whats the function of the third cranial nerve?
Eye movement
Innervates all extraoccular muscles apart form superior oblique and lateral rectus
What happens if the third cranial nerve is damaged?
Causes pupil to be down and out
What is the 4th cranial nerve?
Trochlear (motor)
Whats the function of the 4th cranial nerve?
Eye movement: superior oblique muscle of eye (pulls eye down)
What are the exit points of the 4th cranial nerve?
Superior orbital fissure (skull)
Midbrain: below inferior colliculus (brain), passes through cavernous sinus
What are the exit points of the 3rd cranial nerve?
Superior orbital fissure (skull)
Midbrain: posterior to mammillary bodies (brain), passes through cavernous sinus
What is the fifth cranial nerve?
Trigeminal:
- opthalamic (V1) sensory
- maxillary (V2) sensory
- mandibular (V3) both
What does the opthalamic branch of the trigeminal nerve do?
Sensations in eye, skin of nose, eyelid and forehead
What does the maxillary division of the trigeminal nerve do?
Sensation from upper teeth, mucosa of nasal cavity (middle of face)
What does the mandibular division of the trigeminal nerve do?
Sensations in skin over the mandible
Motor neurons involved in mastication (chewing)
Where does the 5th cranial nerve arise in the brain?
Pons
Where does V1 of trigeminal nerve enter the skull?
Superior orbital fissure
Where does V2 of trigeminal nerve enter the skull?
Foramen retundum
Where does V3 of trigeminal nerve enter/exit the skull?
Foramen ovalae
What is the 6th cranial nerve?
Abducent (motor)
What does the 6th cranial nerve do?
Abducts the eye (lateral rectus muscle)
Where does the 6th cranial nerve exit from?
Superior orbital fissure (skull)
Pons (brain)
Whats 7th cranial nerve?
Facial (motor and sensory)
What does the 7th cranial nerve do?
Motor: facial expressions
Sensory: taste sensation of anterior 2/3 of the tongue
Where does the 7th cranial nerve enter/exit?
Joins in internal acoustic meatus but exits through stylomastiod formaina (skull)
Pons (brain)
Whats the 8th cranial nerve?
Vestibularcochlear (sensory)
What does the 8th cranial nerve do?
Coordination and balance (semi-circular canals)
Hearing (cochlear)
What are the entry points of the 8th cranial nerve?
Internal acoustic meatus and terminates in petrous part of temporal bone(skull)
Pons (brain)
Whats the 9th cranial nerve?
glossopharyngeal (motor and sensory)
What does the 9th cranial nerve do?
Sensory: taste from posterior 1/3 of tongue
Motor: Elevating the larynx and pharynx (speaking and swallowing)
Where does the 9th cranial nerve enter/exit?
Jugular formina (skull)
Lateral sulcus of medulla (brain)
Whats the 10th cranial nerve?
Vagus (sensory and motor)
What does 10th cranial nerve do?
Regulation of internal organ functions (down to transverse colon): digestion, heart rate, and respiratory rate, vasomotor activity
Certain reflex actions: coughing, sneezing, swallowing,
vomiting
What are the entry/exit points of 10th cranial nerve?
Jugular formina (skull)
Lateral sulcus (medulla)
Whats the 12th cranial nerve?
hyopglossal (motor)
Function of 12th cranial nerve?
Intrinsic muscles of tongue (tongue movement)
Exit point of 12th cranial nerve?
Hypoglossal canal (skull)
Anterolateral sulcus of medulla (brain)
11th cranial nerve?
Accessory (motor)
Function of 11th cranial nerve?
Movement of neck muscles (sternocleidomastoid and trapezius)
Entry/exit point of 11th cranial nerve?
Jugular foramina (skull)
Medulla (brain)
What is bulbarpalsy?
Lower motor neuron palsy of cranial nerves 9-12
Symptoms: dysphagia, slurring of speech, dysphonia etc.
Common causes: brainstem stroke, tumour
What is Bells palsy?
Damage to facial nerve
Causes temporary weakness or lack of movement affecting 1 side of the face
Exact cause unknown
After the optic chiasm, which tracts decussate?
Lateral fibres carry on same side
Medial fibres decussate
After the optic chiasm, where do the tracts go?
Lateral geniculate body (part of thalamus and where fibres synapse)
After the lateral geniculate body, where do the fibres from the inferior part of the eye go on the way to the occipital lobe?
Temporal lobe
Which fibres go to parietal lobe after the lateral geniculte body and before the occipital lobe?
Fibres from superior part of eye
How is the image different with a lens?
lower half looks up (vice versa), outside of retina looks inwards (vice versa)
What happens if there is a lesion of optic chiasm?
Bitemporal hemianopia (impaired peripheral vision in outer temperal halves of the visual field of each eye)
Lesion posterior to optic chiasm?
Homonymous hemianopia (vision loss on same side of visual field in both eyes)
What causes quantantinopia?
Lesion in posterior part of brain (after 2nd synapse in lateral geniculate body)
quarter of visual field in each eye is lost
Common cause of lesion of optic chiasm?
Pituitary tumour (pituitary sits under chiasm)
Function of midbrain?
Connecting stalk between ventral diencephalon and pons
What are the parts of the midbrain?
Tectum (posterior) and tegmentum (anterior)
Where are the inferior and superior colliculi found and what do they do?
Tectum
Inferior: auditory reflexes
Superior: visual reflexes
Structures in tegmentum?
Reticular formation, red nucleus, VTA and periaqueductal grey matter, cerebral aqueduct, substantia nigra
What does cerebral aqueduct do?
CSF from third to fourth ventricle
What does substantia nigra do?
Dopamine neurons, involved in movement
Project to basal ganglia
Degeneration is hallmark of PD
What does the red nucleus do?
High iron levels make it appear pink
Involved in fine movement, crawling in babies, arm swinging in walking, cat landing on feet
What is crus cerebri?
most anterior part of midbrain (includes cortiospinal tract)
What are the three roles of the pons?
Relay station
Involuntary functions (breathing and REM sleep)
Houses cranial nerve nuclei 5-8
What is the bublopontine sulcus?
junction between pons and medulla
Locus coerulus?
regulates amount of noradrenlaine
What nuclei is contained in ventral pons?
Pontine nuclei: corticopontine fibres and descending cortiospoinal fibres
WHere is the reticular formation found and what does it do?
Lateral pons and contains ascending sensory tracts
What happens if the myelin in the pons is destroyed?
Central pontine myelinolysis
- causes confusion, balance problems, dysphagia, hallucinations
- happens when sodium levels are corrected too quickly
Function of medulla oblongata?
Autonomic (involuntary) functions including HR, breathing, vomiting and BP
Houses cranial nerve nuclei 8-12
What are the olives in the medulla?
swellings lateral to ventrolateral sulcus and mark underlying olivary nucleus (movement control)
Pyramids of medulla?
Contain corticospinal tracts (80% of fibres decussate here)
What are the gracile and cuneate tubercles?
Ascending (afferent) pathways conveying sensory information form legs (gracile) and arms (cuneate)
What is lateral geniculate body for?
Visual system
What is the medial geniculate body for?
auditory system
whats on either side of the two pyramids on medulla?
inferior olivary nuclei
what do the inferior olivary nuclei communicate with?
cerebellum
what does the superior colliculus project to?
lateral geniculate nucleus of thalamus (deals with vision)
