Neuroanatomy 4 Flashcards
how is the optic nerve different from the other cranial nerves?
more like an extension of the brain
myelinated by oligodendrocytes rather than schwann cells so technically part of CNS rather than PNS
each component of a cranial nerve (sensory/motor) is associated with what?
a streak/blob of grey matter (collection of neurons) in the brain/brainstem which serves one function
motor components = motor nuclei (groups of efferent nerve cells sending axons into cranial nerve)
sensory = sensory nuclei (groups of nerve cells upon which the sensory neurons of cranial nerves synapse
where is the only site where nerves have direct contact with outside world?
in nose
olfactory vesicles with cilia (extension of olfactory nerves which pierce cribiform plate and stick out into nasal cavity to sense smells)
only sensory modality that does not synapse in the thalamus prior to reaching the cortex
describe olfaction?
…
posterior/anterior horns of spinal cord receive/output what during development?
posterior = sensory input
anterior = motor output
moves during development so sensory nuclei are posterior and lateral while motor nuclei are anterior and medial
somites?
give rise to musculature in most of body
- most head musculature comes from pharyngeal arches instead
nuclei of which cranial nerves are found in the midline of the brain?
motor cranial nerves
3,4 (4 blobs in midbrain) and 6 (dot in pons)
long column nuclei in medulla for hypoglossal (12)
what is present in the Edinger Westphal nucleus?
nerve cell bodies of oculomotor which have parasympathetic function - sphincter pupillae, ciliary muscle
what is contained within the oculomotor nucleus?
nerve cell bodies of oculomotor nerve which have somatic motor function
- LPS
- rectus muscles
- inferior oblique
what is present in the trochlear nucleus?
somatic motor nerve cell bodies of trochlear nerve
travel to superior oblique
- only CN to exit posteriorly, crosses midline
what is present in the abducens nucleus in lower pons?
somatic motor nerve cells bodies of abducens
move to lateral rectus muscle
what is present in hypoglossal nucleus in medulla?
somatic motor nerve cell bodies of hypoglossal nerve
travels to lower tongue muscles
CN emerging from midline of brain indicates what?
somatic motor function
formation of spinal accessory nerve?
fibres emerge from cervical spinal cord and ascend up through the foramen magnum and join with fibres from nucleus ambiguous in the jugular foramen
then splits again and cranial fibres (internal ramus) join vagus while spinal fibres (external ramus) go on to innervate trapezius and sternocleidomastoid
functions of trigeminal nerve?
- somatosensation of face
- proprioception associated with chewing (TMJ, muscles of mastication, teeth)
- motor control (mastication, tensor tympani, mylohyoid, anterior diagstric, tensor veli palatini)
line of neuron cells traveling down from midbrain to upper cervical spinal cord?
receives information from trigeminal nerve
parts of the line of cells?
top = mesencephalic nucleus (receives proprioception info from chewing muscles, cells buried in CNS)
middle swelling = pontine trigeminal nucleus/principle nucleus (receives discriminative touch, vibration)
lower = spinal nucleus (receives pain and temperature information)
motor nucleus of trigeminal nerve?
sits medially to mesencephalic nucleus which receives chewing proprioceptive information
motor nucleus uses this information to coordinate jaw reflexes and tongue movement etc
what happens when the line of neurons receive the information?
2nd order neurons leave and travel up the trigeminothalamic tract
organization of trigeminal pain fibres in the face?
target around the mouth
as you move out, the layers enter the spinal nucleus further down
function of facial nerve?
motor = muscles of facial expression parasympathetic = pterygopalatine and submandibular ganglia taste = anterior 2/3 tongue via chorda tympani
function of glossopharyngeal?
tactile sense, pain and temp from posterior tongue, eustachian tube and upper pharynx
taste (posterior 1/3 tongue)
parasympathetic fibres to otic ganglion (parotid)
motor (stylophayngeus)
vagus functions?
tactile sense, pain and temp from pharynx, larynx, trachea, oesophagus and thoracic and abdominal viscera
taste (epiglottis)
parasympathetic to thoracic and abdominal viscera ganglia
motor (pharynx and larynx)
how does function of mixed nerves relate to nuclei?
several functions means several nuclei
ie - facial nerve has 4 nuclei in the brain due to 4 functions
several nuclei in the brain are shared by more than one cranial nerve, give 3 examples?
solitary nucleus = CNs VII, IX, X
superior and inferior salivatory nuclei = CNs VII and IX
nucleus ambiguous = CNs IX and X (and cranial part of XI)
describe the solitary nucleus?
horseshoe shape
2 parts
- gustatory nucleus (taste)
- commissural nucleus (visceral afferents - carotid sinus/body and aortic arch and viscera (pulmonary stretch receptors))
what is the corticobulbar tract?
part of the corticospinal (pyramidal) tract that gives motor input to cranial nerves
- fibres to CNs V, VII, X and XII
where does in put CNs containing parasympathetic efferents come from?
hypothalamus
- influenced by physiological status and input from other brain regions
CNs III, VII, IX, X
what is reticular formation?
network of loosely aggregated cells with cell bodies (nuclei), axons and dendrites intermingling in the central core of the brainstem
distinct from long pathways (ascending/descending tracts) and cranial nerves
functions of reticular formation?
integrate cranial nerve reflexes
conduction and modulation of pain
influence voluntary movement
regulate autonomic activity
integrate basic functions (resp and sleep etc)
activate cerebral cortex (cause consciousness)
