Brainstem & Cranial Nerves

• special nuclear groups

  
  

  what is the function of the Nucleus Tractus Solitarius (solitary nucleus)?

  Visceral Sensory: tongue, carotid body, carotid sinus, GIT,

  trachea, bronchi

  
  

  - Chemoreception (inc taste, pCO2/[H+] monitoring, gut distension, blood pressure monitoring
• special nuclear groups

  
  

  what is the function of the Nucleus Ambiguus?

  Motor: larynx, pharynx, upper oesophagus

  
  

  -Vomiting, swallowing, modulation of phonation
• special nuclear groups

  
  

  what are 2 special nuclear groups?

  - Nucleus Ambiguus:

  composed of some fibres from C9 & C10

  
  

  - Nucleus Tractus Solitarius (solitary nucleus):

  composed of some fibres from C7 & C9 & C10
• special nuclear groups

  
  

  what is a nuclear group?


  collection of neuronal cell bodies
• cranial nerves

  
  

  where is the C12 Hypoglossal nerve?

  - emerges from medulla

  - through hypoglossal canal

  - innervates tongue muscles
• cranial nerves

  
  

  what is the function of the C12 Hypoglossal nerve?

  Motor

  - Intrinsic muscles of tongue

  - Most extrinsic tongue muscles
• cranial nerves

  
  

  where is the C11 Spinal Accessory nerve?


  - has roots that begin on the cervical segments of the spinal cord. The roots travel up through the foramen magnum and join the cranial fibres to form the accessory nerve which then pass through the jugular foramen to carry somatic motor information to skeletal muscles of the neck and upper back.
• cranial nerves

  
  

  what is the function of the C11 Spinal Accessory nerve?


  involved Innervation of muscles associated with shoulder and head movement (eg sternocleidomastoid and trapezius)
• cranial nerves

  
  

  where is the C10 Vagus nerve?

  The vagus nerve provides parasympathetic innervation to the majority of the abdominal organs.

  
  

  It sends branches to the oesophagus, stomach and most of the intestinal tract - up to the splenic flexure of the large colon.

  (wanders into thorax and abdomen)
• cranial nerves

  
  

  what is the function of the C10 Vagus nerve?

  • Sensory

  - somatosensory - mucous membranes of laryngo-pharynx, larynx and upper trachea

  - visceral - trachea, lungs, carotid sinus,abdominal veins, gut (to splenicflexure)

  
  

  • Motor

  - somatic - lower pharynx, upper oesophagus (swallowing and vomiting)

  - parasympathetic - cardiac muscle (control of heart beat), smooth muscle in GIT (GI motility), trachea and bronchi (airway diameter)
• cranial nerves

  
  

  where is the C9 Glossopharyngeal nerve?

  • posterier 1/3 of tongue

  • carotid sinus

  • musculature of pharynx

  • parotid gland
• cranial nerves

  
  

  what is the function of the C9 Glossopharyngeal nerve?

  •Special sensory - taste (posterior 1/3 of tongue)

  •Visceral sensory - blood pCO2/[H+] monitoring (carotid body)

  •Sensory - post 1/3 of tongue & oropharynx

  •Motor - upper pharynx

  • Parasympathetic - parotid gland
• cranial nerves

  
  

  where is the C8 vestibulocochlear nerve?

  vestibular: arises from base of semicircular canal

  cochlear branch: arises from organ of corti within cochlea

  
  

  - the branches exit together and enter pontine angle (junction of pons/medulla/cerebellum)
• cranial nerves

  
  

  what is the function of the C8 vestibulocochlear nerve?

  Vestibular branch: balance / position / movement

  Cochlear branch: hearing
• cranial nerves

  
  

  where does the C7 Facial nerve branch?

  the posterior edge of the parotid gland.
• cranial nerves

  
  

  what are the 5 branches of the C7 Facial nerve?

  frontal (or temporal), zygomatic, buccal, marginal mandibular, and cervical.
• cranial nerves

  
  

  how many branches does the C7 Facial nerve have?

  five
• cranial nerves

  
  

  what is the function of the C7 Facial nerve?

  primary role is to control facial movement and expression.

  
  

  • Motor - muscles of facial expression (mimetic muscles)

  • Sensory - skin of external auditory meatus, eardrum

  • Special sensory - taste (ant 2/3 of tongue); palate

  • Parasympathetic - innervation of salivary glands (but NOT

  parotid). Supplies the lacrimal glands
• cranial nerves

  
  

  where does the C6 Abducens nerve synpase?

  the lateral rectus muscle
• cranial nerves

  
  

  what is the function of the C6 Abducens nerve?

  innervates the lateral rectus muscle which moves the eyeball away from the midline
• cranial nerves

  
  

  where do the 3 branches of the C5 Trigeminal nerve branch off at?

  trigeminal ganglia, which is located within the Meckel's cave of the middle cranial fossa
• cranial nerves

  
  

  what are the 3 branches of the C5 trigeminal nerve

  • opthalmic branch

  - forehead + upper orbit

  
  

  • mandibular branch

  - lower jaw + tongue

  
  

  • maxillary branch

  - cheeck + lower orbit
• cranial nerves

  
  

  what is the function of the C5 Trigeminal nerve?


  primary function is to provide sensory innervation to the face.

  
  

  • Motor nucleus (muscles of mastication)

  • Spinal nucleus (sensory)

  - thermal/nociception from head and neck

  • Principal nucleus (sensory)

  -touch, proprioception

  • Mesencephalic nucleus

  -jaw reflexes (unconscious proprioception)
• cranial nerves

  
  

  where does the C4 Trochlear nerve synpase?

  the superior oblique muscle
• cranial nerves

  
  

  what is the function of the C4 Trochlear nerve?

  innervates the superior oblique muscle which depresses the eyeball and moves it laterally
• cranial nerves

  
  

  where does the C3 Oculomotor nerve go?

  enters the orbit through the superior orbital fissure and innervates extraocular (outside eyeball) muscles that enable most movements of the eye
• cranial nerves

  
  

  what is the function of the C3 Oculomotor nerve?

  Somatomotor:

  primary innervator for 4 extraocular muscles

  
  

  Parasympathetic:

  constrict pupillary muscles (light reflex) & ciliary muscles (accommodation reflex)
• cranial nerves

  
  

  where is the C2 optic nerve?

  nerve: between retina & optic chiasm (rest is optic tract)

  synapse: lateral geniculate nucleus of thalamus
• cranial nerves

  
  

  what is the function of the C2 optic nerve?

  vision (special sensory nerve)
• cranial nerves

  
  

  where is the C1 olfactory nerve?

  nerve: the cribriform plate of ethmoid

  synapse: within olfactory bulb
• cranial nerves

  
  

  what is the function of the C1 olfactory nerve?

  smell (special sensory nerve)
• cranial nerves

  
  

  why is cranial nerve testing important and frequently performed?

  to test CNS integrity, particularly the integrity of the brainstem.
• cranial nerves

  
  

  do all cranial nerves exit/enter the brainstem nuceli?

  yes. except for the olfactory nerve
• cranial nerves

  
  

  which cranial nerve does not come from the ventral surface and where instead?

  trochlear nerve

  
  

  - it emerges from the back of the pons (dorsally)
• cranial nerves

  
  

  where do all cranial nerve exit/enter from (except for one)?

  the ventral surface
• cranial nerves

  
  

  list the 12 cranial nerves

  1. Olfactory

  2. Optic

  3. Oculomotor

  4. Trochlear

  5. Trigeminal

  6. Abducens

  7. Facial

  8. Vestibulocochlear

  9. Glossopharyngeal

  10. Vagus

  11. Spinal Accessory

  12. Hypoglossal

  
  

  (only one of the two atheletes felt very good victorious and healthy)
• cranial nerves

  
  

  how many cranial nerves are there

  12 ( they are all paired)

  
  

  - mixed nerves from motor, sensory, (visceral or somatic), special sensory or parasympathetic classes
• brainstem

  
  

  describe structure of closed medulla


  • round dorsal surface

  • gracile/cuneate fasciculi: contain axons synapsing in gracile/cuneate nuclei (ascending)

  • pyramids: contain axons of corticospinal tract (descending) to cross midline (from cortex to spinal cord)- motor pathway

  • CSF-filled canal continuous with 4th ventricle above& canal of spinal cord below

  • grey blocks: nuclei of cranial nerves

  
• brainstem

  
  

  describe structure of pons

  • ventral bulge = basilar pons

  • dorsal hole: start of cerebral aqueduct

  • periaqueductal grey matter is around the aqueduct

  • pontocerebellar axon tracts run horizontally through pons and takes motor information from pontine nuclei through middle cerebellar peduncle to cerebellum

  • corticospinal axon tracts run vertically through pons

  • corticobulbar axon tracts to cranial nerve motor nuclei to supply muscles in head & neck

  
• brainstem

  
  

  describe structure of midbrain


  • inferioir colliculus (2 dorsal bumps)

  - move eye in response to sound

  
  

  • cerebral peduncles (2 big ventral white matters)

  - contain descending axons corticospinal & corticobulbar tracts

  
  

  • substantia nigra:

  - contains cell bodies