Reflex and nerve anatomy Flashcards
What does the opthalmic nerve CNVI supply?
upper eyelid
cornea
conjunctiva
skin of root/bridge/tip of nose
What does the maxillary nerve CN V2 supply?
lower eyelid
maxilla
ala of nose
mucosa of lip
What is the affernt nerve for the blink reflex?
opthalmic nerve CNVI to trigeminal ganglion CNV to the pons
What is the efferent nerve for the blink reflex?
CNVII facial nerve
What is the pathway of the oculomotor nerve?
connects with the CNS at the junction between the midline and pons
What is the role of the ciliary nerves?
control the diameter of the iris and refractive shape of the lens
in far vision - ciliary body relaxes - lens flattens
in near vision - ciliary body contracts - lens spherical
What supplys the long cillary nerves?
sympathetic and somatic sensory
What supplys the short cillary nerves?
sympathetic and parasympathetic
What is the vestibo-ocular reflex?
turns eye in the opposite direction to head movement
What is teh oculocardiac reflex?
reflex bradycardia in response to tension on extraocular muscles or pressure in the eyes
What are the sympathetic responses from eyes?
eyes wider dilate pupil more light into the eyes focus on far objects emotional lacrimation
What are the parasympathetic responses from the eyes?
eyes narrower
pupil constricts
focus on close up objects
reflex lacrimation
How does the levator palpebrae superioris open the eyes wider?
post synaptic sympathetic fibres
What is a mydriatic pupil?
non physiologically enlarged pupil e.g. due to drugs
What is a miotic pupil?
non physiologically constricted pupil (opiates)
What does a fixed pupil indicate?
CN II pathology - optic nerve
What are the two types of dilator pupil fibres?
fixed - originate around the external circumferance of the iris
mobile - insert around internal circumference
What are the afferent signals for the eye?
optic nerve CNII
What are the efferent signals for the eye?
oculomotor nerve CN III
What are the 3 components of the accomodation reflex?
bilateral pupillary constriction
bilateral convergance - medial rotation of both eyes
bilateral relaxation of the lens - spherical
ALL DONE BY CNIII
What are the 3 types of lacrimation tears?
basal
reflex
emotional
What are basal tears?
contain lysozomes - enzymes that hydrolyse the bacteria wall - nourish the cornea
What are reflex tears?
released in response to mechanical or chemical stimulation
afferent - CN VI
efferent - CN VII
What are emotional tears?
in response to happy, sad, frightened
What happens to the zonules when ciliary bodies relax?
zonules contract, lens becomes flat
What happens to the zonules when ciliary bodies contract?
zonules relax, lens becomes spherical, increases refractory power for close up reading
What happens to the lens at the age of 40?
becomes harder so it struggles to become spherical
What happens to the lens at the age of 40?
becomes harder so it struggles to become spherical
What is horners syndrome?
impaired sympathetic innervation to the head and neck due to: root of neck trauma, carotid dissection, internal jugular vein engorgement, deep cervical node metastases, pancoast tumour - apex of the lung
