Brain Stem & Cranial Nerves Flashcards
What are the 3 major anatomical divisions of the brainstem?
- Midbrain
- pons
- medulla
Describe the midbrain
- 1.5cm long
- from pons to mamillary bodies
- has basis peduncles on ventral side
- dorsal surface as superior and inferior colliculi (tectum)
- 2 cranial nerves come out - III (medial) and IV (lateral)
Describe the Pons
- anatomically distinct “bridge” wrapping around to cerebellum
- 1 cranial nerve comes out the middle (V) & 3 come out the bottom (VI, VII, VIII)
- part lateral to CNV becomes cerebellar peduncles
- the dorsal aspect is the tegmentum
- 2.5cm long
Describe the medulla oblongata
- From bottom of pons to foramen magnum (where it pokes out of skull)
- 3cm long
- continuation of spinal cord
- has pyramids on ventral surface, with inferior olive lateral to pyramids
- 4 cranial nerves come off (IX, X, XI lateral to olive, XII lateral to pyramids)
What are the major ascending pathways passing through the brainstem?
- dorsal column medial lemniscus
* touch, vibration, proprioception
* synapses at the gracile/cuneate nuclei of medulla (before continuing up to cortex) - Spinothalamic & spinotectal
* pain, temp, touch
* passes through, traversing lateral brainstem on the way to thalamus
* combine to form spinal lemniscus - spinoreticular & spinomesencephalic
* pain
* synapse in medullar & pontine reticular formation - spinocerebellar tracts
* proprioception
* through pons into cerebellum
What are the major descending tracts passing through the brainstem?
- corticospinal tract
* through midbrain basis peduncles, through medullary pyramids & down spinal cord - just passes through
* motor control - central tegmental tract
* red nucleus to inferior olive
* small projection continues down spinal cord as rubrospinal tract - tectospinal tract
* from superior colliculi to pons/medulla reticular formation
* reflexive control of eyes
What are some important nuclei/structures/areas of the brainstem and their function/importance?
- pretectal area (in midbrain)
* involved in reflex pathway constricting pupils at night - tegmentum (midbrain)
* includes red nucleus - substantia nigra (midbrain)
* dopaminergic area modulating movement - red nucleus
- cranial nerve cell bodies (except CNI & CNII)
Name the 12 cranial nerves in order
- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducent
- facial
- vestibulocochlear
- glossopharyngeal
- vagus
- accessory
- hypoglossal
Identify whether each cranial nerve is sensory, motor or both
- Sensory
- Sensory
- Motor
- Motor
- Both
- Motor
- Both
- Sensory
- Both
- Both
- Motor
- Motor
What is the origin, function & implication of disease for cranial nerve I
- Olfactory nerve
- sensory
- sense of smell
- from olfavtory receptor cells to olfactory bulb
- anosmia - loss of smell
What is the origin, function & implication of disease for cranial nerve II
- optic nerve
- sensory
- sense of vision
- from retinal ganglion cells to lateral geniculate nucleus of thalamus
- impacted vision (due to MS, optic neuritis or lesions)
What is the origin, function & implication of disease for cranial nerve III
- Oculomotor nerve
- motor
- eye movements & pupil constriction
- emerges below mamillary bodiy, to extraocular muscles (4 of the 6)
- oculomotor palsy, dilated pupil, loss of pupillary reflex
What is the origin, function & implication of disease for cranial nerve IV
- Trochlear nerve
- motor
- eye rotation
- from midbrain lateral to peduncles to extraocular uscle
- eyeball cannot turn inferomedially
What is the origin, function & implication of disease for cranial nerve V
- Trigeminal nerve
- both sensory & motor
- largest cranial nerve, sensation from face, motor (mastication)
- from pons to skin of head & face, muscles for chewing, 3 branches (Va, V2, V3 which is the motor one)
- inability to chew, loss of facial sense of touch/temp/pain
What is the origin, function & implication of disease for cranial nerve VI
- Abducent nerve
- motor
- eye abduction (moving outwards)
- from between pons & medulla to extraocular muscle
- eye medial deviation
What is the origin, function & implication of disease for cranial nerve VII
- Facial nerve
- both sensory & motor
- taste, motor (facial expressions)
- fromj between pons & medulla to face/head and tongue, 5 branches
- Bell’s palsy, facial droop, paralysis
What is the origin, function & implication of disease for cranial nerve VIII
- vestibulocochlear nerve
- sensory
- sense of hearing & balance
- between pons & medulla to cochlea & vestibular apparatus
What is the origin, function & implication of disease for cranial nerve IX
- Glossopharyngeal nerve
- both sensory & motor
- taste, motor (pharynx), BP/blood gas info
- from medulla (lateral to olive) to face, pharynx, carotid body
- impaired taste, difficulty swallowing, inpaired gag reflex, dry mouth
What is the origin, function & implication of disease for cranial nerve X
- Vagus nerve
- Both sensory & motor
- Taste, chemo&baro receptors, parasympathetic innervation
- from medulla (lateral to olive) to visceral organs (4 divisions)
- digestive, breathing, cardio problems, autonomic dysfunction
What is the origin, function & implication of disease for cranial nerve XI
- Accessory nerve
- motor
- neck & trapezius muscle movements
- from medulla (lateral to olive) down spinal cord a bit, to neck/trapezius
- shoulder droop, neck weakness/paralysis
What is the origin, function & implication of disease for cranial nerve XII
- Hypoglossal nerve
- motor
- tongue motor control
- from medulla (between pyramid and olive) to tongue
- difficulty with speech and articulation
What are the 5 types of fibres that can be carried in cranial nerves?
- somatic motor
- visceral motor
- somatic sensory
- visceral sensory
- special sensory
