Neuroanatomy 4

Question 1

how is the optic nerve different from the other cranial nerves?

Answer 1

more like an extension of the brain

myelinated by oligodendrocytes rather than schwann cells so technically part of CNS rather than PNS

Question 2

each component of a cranial nerve (sensory/motor) is associated with what?

Answer 2

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

Question 3

where is the only site where nerves have direct contact with outside world?

Answer 3

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

Question 4

describe olfaction?

Answer 4

…

Question 5

posterior/anterior horns of spinal cord receive/output what during development?

Answer 5

posterior = sensory input
anterior = motor output
moves during development so sensory nuclei are posterior and lateral while motor nuclei are anterior and medial

Question 6

somites?

Answer 6

give rise to musculature in most of body

- most head musculature comes from pharyngeal arches instead

Question 7

nuclei of which cranial nerves are found in the midline of the brain?

Answer 7

motor cranial nerves
3,4 (4 blobs in midbrain) and 6 (dot in pons)
long column nuclei in medulla for hypoglossal (12)

Question 8

what is present in the Edinger Westphal nucleus?

Answer 8

nerve cell bodies of oculomotor which have parasympathetic function - sphincter pupillae, ciliary muscle

Question 9

what is contained within the oculomotor nucleus?

Answer 9

nerve cell bodies of oculomotor nerve which have somatic motor function

• LPS
• rectus muscles
• inferior oblique

Question 10

what is present in the trochlear nucleus?

Answer 10

somatic motor nerve cell bodies of trochlear nerve
travel to superior oblique
- only CN to exit posteriorly, crosses midline

Question 11

what is present in the abducens nucleus in lower pons?

Answer 11

somatic motor nerve cells bodies of abducens

move to lateral rectus muscle

Question 12

what is present in hypoglossal nucleus in medulla?

Answer 12

somatic motor nerve cell bodies of hypoglossal nerve

travels to lower tongue muscles

Question 13

CN emerging from midline of brain indicates what?

Answer 13

somatic motor function

Question 14

formation of spinal accessory nerve?

Answer 14

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

Question 15

functions of trigeminal nerve?

Answer 15

1. somatosensation of face
2. proprioception associated with chewing (TMJ, muscles of mastication, teeth)
3. motor control (mastication, tensor tympani, mylohyoid, anterior diagstric, tensor veli palatini)

Question 16

line of neuron cells traveling down from midbrain to upper cervical spinal cord?

Answer 16

receives information from trigeminal nerve

Question 17

parts of the line of cells?

Answer 17

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)

Question 18

motor nucleus of trigeminal nerve?

Answer 18

sits medially to mesencephalic nucleus which receives chewing proprioceptive information
motor nucleus uses this information to coordinate jaw reflexes and tongue movement etc

Question 19

what happens when the line of neurons receive the information?

Answer 19

2nd order neurons leave and travel up the trigeminothalamic tract

Question 20

organization of trigeminal pain fibres in the face?

Answer 20

target around the mouth

as you move out, the layers enter the spinal nucleus further down

Question 21

function of facial nerve?

Answer 21

motor = muscles of facial expression
parasympathetic = pterygopalatine and submandibular ganglia
taste = anterior 2/3 tongue via chorda tympani

Question 22

function of glossopharyngeal?

Answer 22

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)

Question 23

vagus functions?

Answer 23

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)

Question 24

how does function of mixed nerves relate to nuclei?

Answer 24

several functions means several nuclei

ie - facial nerve has 4 nuclei in the brain due to 4 functions

Question 25

several nuclei in the brain are shared by more than one cranial nerve, give 3 examples?

Answer 25

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)

Question 26

describe the solitary nucleus?

Answer 26

horseshoe shape
2 parts
- gustatory nucleus (taste)
- commissural nucleus (visceral afferents - carotid sinus/body and aortic arch and viscera (pulmonary stretch receptors))

Question 27

what is the corticobulbar tract?

Answer 27

part of the corticospinal (pyramidal) tract that gives motor input to cranial nerves
- fibres to CNs V, VII, X and XII

Question 28

where does in put CNs containing parasympathetic efferents come from?

Answer 28

hypothalamus
- influenced by physiological status and input from other brain regions
CNs III, VII, IX, X

Question 29

what is reticular formation?

Answer 29

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

Question 30

functions of reticular formation?

Answer 30

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)