hnL5 - cranial nerves VII, IX, XII

• explain the divisions of the nervous system:

  CNS

  • brain
  • spinal cord

  PNS

  • 12 cranial nerves
  • 31 spinal nerves

  somatic - external environment (see or feel the danger)

  autonomic - monitors and controls internal environment (deals with danger).
• explain the somatic nervous system:

  sensory nerves: collect info about pain, touch, temp throughout the body and carry it to the CNS.

  motor nerves: convey instructions from CNS to striated (voluntary) muscles. mostly under conscious control but protective reflexes override conscious control.
• explain the autonomic nervous system:

  involuntary

  effects achieved by stimulating glands and smooth muscle

  subdivided into two systems which oppose each others actions:

  1. sympathetic nervous system = 'fight or flight' response
  2. parasympathetic nervous system = returns things to normal 'rest and digest'.
• name all the cranial nerves in order and state their function:

  I - (on) olfactory = sensory

  II - (occasion) optic = sensory

  III -(our) oculomotor = motor

  IV -(trusty) trochlear = motor

  V -(truck) trigeminal = both motor + sensory

  VI - (acts) abducens = motor

  VII - (funny) facial = both

  VIII - (very) vestibulocochlear = sensory

  IX - (good) glossopharyngeal = both

  X - (vehicle) vagus = both

  XI - (any) accessories = motor

  XII - (how) hypoglossal = motor
• describe the functions of the parasympathetic nervous system:

  • constricts pupils
  • stimulates salivation
  • constricts bronchi
  • decreases heart rate
  • stimulates digestive activity
  • stimulates gallbladder
  • inhibition of adrenaline production
  • contracts bladder
  • relaxes rectum
• describe the functions of the sympathetic nervous system:

  • dilates pupil
  • inhibits salivation
  • relaxes bronchi
  • increases heart rate
  • inhibits digestive activity
  • stimulates glucose release by liver
  • stimulates epinephrin and norepinephrin release
  • relaxes bladder
  • contracts rectum
• what is the ganglia?

  where the information is passed to another neuron (preganglionic and post ganglionic).

  the cell body of the recipient neuron forms a bulge in the nerve. this is called a ganglion.
• describe the cranial nerves:

  • 12 cranial nerves
  • originate from part of the CNS that is enclosed within the cranium
  • occur in pairs, one for each side of the body
  • some more specialised than others
  • most only associated with structures in the head and neck
• what does the cranial nerve VII supply:

  motor fibres - to the muscles of facial expression

  sensory taste fibres - to anterior 2/3 of the tongue via lingual nerve

  parasympathetic fibres - to lacrimal (tears), palatal, submandibular, sublingual (saliva) and nasal (mucous) glands via branches of the trigeminal nerve.
• how does the cranial nerve VII exit the cranium:

  via the internal auditory meatus

  enters the facial canal in the petrous temporal bone

  within the canal it gives off two small branches:

  • chorda tympani
  • greater petrosal nerve
• describe the function of the chorda tympani:

  joins lingual nerve

  contains taste fibers from the anterior 2/3 of the tongue

  passes parasympathetic fibers via lingual nerve to submandibular ganglion

  these then pass to the submandibular and sublingual salivary glands.
• describe the function (route followed) of the greater petrosal nerve:

  carries parasympathetic fibers to the pterygopalatine ganglion.

  fibers then accompany branches of the maxillary division of the trigeminal nerve.

  branches supply the mucous membrane of the palate and nasal cavity.
• where does the facial nerve exit its canal:

  through the stylomastoid foramen

  it gives off motor branches to:

  • the posterior belly of digastric
  • the stylohyoid muscles
• what are the 5 terminal motor branches the facial nerve gives off after entering the parotid gland:

  • temporal
  • zygomatic
  • buccal
  • mandibular
  • cervical

  these supply the muscles of facial expression.
• explain the function and where the glossopharyngeal nerve (cranial nerve IX) exits the cranium:

  exits cranium vie the jugular foramen

  supplies sensory and motor fibres to the soft palate and pharynx.

  • supplies sensory and taste fibres to the posterior 1/3 of the tongue.
  • passes parasympathetic fibres to the otic ganglion via the auriculotemporal nerve (mandibular division V) to supply the parotid gland.
• explain where the hypoglossal nerve (cranial nerve XII) exits and enters the cranium:

  exits via the hypoglossal canal

  enters the tongue posteriorly at the level of the angle of the mandible.
• explain the function of the hypoglossal nerve (cranial nerve XII):

  • supplies motor and sensory fibres to the muscles of the tongue
  • loss of function results in the inability to move one side of the tongue

  !!! stroke patients !!!