week 1 anatomy eye autonomics Flashcards
what are the three division of the trigeminal nerve called?
ophthalmic V1
maxillary V2
mandibular V3
what does the ophthalmic nerve supply?
upper eyelid cornea conjunctiva skin of the root/bridge/tip of the nose (SENSORY)
what does the maxillary nerve supply?
skin of the lower eyelid skin over the maxilla skin of the ala of the nose skin/mucosa of the upper lip (SENSORY)
what does the mandibular nerve supply?
skin over the mandible and temporomandibular joint
apart from the angle of the mandible – supplied by C2,3 spinal nerves
(SENSORY)
what is the purpose of the blink (corneal) reflex?
to wash away foreign body, nourish cornea,stops eye drying out
describe in detail the blink reflex
Action potentials conducted from cornea via CN V1 branches
To trigeminal ganglion, then along CN V
To pons
Central CNS connections between CN V and CN VII
Motor (efferent) limb:
Action potentials conducted via CN VII
To eyelid part of orbicularis oculi
what are the organs of the head?
Skin
sympathetic innervation of arterioles of the head
sympathetic innervation of sweat glands
sympathetic innervation of arrector muscles
Brain
insensitive
no motor function (muscle!)
Eyes
anterior surface sensitive to touch: somatic-V1
smooth muscle of iris (pupil diameter)
smooth muscle of the ciliary body associated with the lens (focussing)
Lacrimal Glands (lacrimal fluid production – tears)
Salivary Glands (saliva production)
what is the route taken by sympathetic ganglions to reach the organs of the body/head & neck (in general)
Originates from autonomic centres in the brain
Passes down spinal cord
Exits spinal cord with T1-L2 spinal nerves
Travel to sympathetic chains running the length of vertebral column
Pass into all spinal nerves (anterior and posterior rami)
Pass into splanchnic nerves to eventually supply organs
Describe the route taken by sympathetic axons to reach the smooth muscle/ arterioles/ lacrimal gland of the orbit (in particular)
presynaptic sympathetic axons from CNS:
-exit spinal cord in T1 spinal nerve
- ascend within sympathetic trunk
- synapse in superior cervical sympathetic ganglion
post-synaptic sympathetic axons :
-enter internal and external carotid nerves
- pass onto surface of the internal & external carotid arteries
- carried to the organs of the head on the surface of the branches of these arteries
- ophthalmic artery carries sympathetic axons into the orbit
describe the route taken by parasympathetic ganglions to reach the organs of the body/head & neck (in general)
All parasympathetic axons leave the CNS via cranial nerves III, VII, IX & X and via sacral spinal nerves
Craniosacral outflow
Internal organs, not body wall
Vagus nerve supplies organs of the neck, chest and abdomen as far as the mid-gut
Sacral spinal nerves ‘carry’ parasympathetic axons to the hindgut, pelvis and perineum
Describe the route taken by parasympathetic axons to reach the smooth muscle/ arterioles/ lacrimal gland of the orbit (in particular)
All parasympathetic axons leave the CNS via cranial nerves III, VII, IX & X (and via the spinal nerves)
Parasympathetic ganglia in head – to eye, lacrimal gland and salivary glands
where does the oculomotor nerve connect with the CNS? where does it pass through?
at junction between midline and pons.
Passes through cavernous sinus
Exits via superior orbital fissure
what does CN III supply
Somatic motor to superior (SR), medial (MR) & inferior rectus (IR) and inferior oblique (IO)
Somatic motor to levator palpebrae superioris (LPS)
CN III has presynaptic parasympathetic axons to the ciliary ganglion (superior and inferior) - which innervates what?
Superior division:
SR and LPS
Inferior division:
MR, IR, IO and ciliary ganglion
what do the ciliary nerves do?
supply autonomic axons to control diameter of iris & refractive shape of lens
what forms the first part of the blink reflex?
Long ciliary nerves
what do the long and short ciliary nerve consist of?
Long ciliary nerves:
sympathetic
somatic sensory
Short ciliary nerves:
sympathetic
parasympathetic
name some autonomic reflexes of the eye
maximal eyelid elevation / wide eye opening of fight or flight
pupillary dilation/constriction adjusting light entry: (pupillary) light reflex
focussing lens far & near vision: accommodation reflex
lacrimation reflex tear production
vestibulo-ocular reflex
oculocardiac reflex
what is the oculocardiac reflex
reflex bradycardia in response to tension on extraocular muscles or pressure on eye
CNS connections between CN V1 & CN X
what is the vestibulo-ocular reflex?
turns the eyes in the opposite direction to a head movement
stabilises gaze on an object during head movement
CNS connections between CN VIII & CNs
III, IV & VI
what are the sympathetic functions concerning the eye
opens eyes WIDER
gets MORE LIGHT in
focus on FAR OBJECTS
(?emotional lacrimation)
what are the parasympathetic functions concerning the eye
allow orbicular oculi to work
get less light into eyes (to protect the retina from bright light or when asleep
focus on near objects
reflex lacrimation (to wash away the stimulant foreign body & clean the cornea)
what opens eyes wider?
levator palpebrae superioris contains skeletal PLUS smooth muscle
how to the postsynaptic sympathetic fibres reach levator palpebrae superioris?
superior cervical sympathetic ganglion → internal carotid nerve → internal carotid plexus → axons carried on the ophthalmic artery… → and on its branches to the orbital structures
what dilates the pupil? when?
sympathetics
dim light or flight/fight
non-physiologically enlarged pupil is called what?
mydriatic pupil
mydriatic drugs induce dilation of the pupil
how does the dilator pupillae work? (dilates pupil)
Fibres run radially
around the external circumference of iris – fixed
insert around the internal circumference of iris - mobile
parasympathetics do what to the pupil? when?
constrict
in bright light and “rest & digest”
non-physiologically constricted pupil is called?
miotic pupil
component of Horner’s syndrome
what does a fixed “Pin point” pupil mean?
serious pathological sign
e.g. opiate drugs
what does a “fixed-dilated” (“blown”) pupil indicate
serious pathological sign
e.g. of CN III pathology
where do the sphincter pupillae fibres encircle the pupil? (constricts pupil)
around the internal circumference of iris
what is the special sensory (afferent) limb of the pupillary reflex
ipsilateral CNII - optic nerve
what is the motor (efferent) limb of the pupillary reflex
bilateral via CNs III -
oculomotor nerves
what is the pupillary light reflex
direct light reflex occurs in the stimulated eye
a consensual light reflex occurs in the non-stimulated eye
describe the pupillary light reflex?
1st neurones: retinal ganglion cells pass via ipsilateral optic nerve decussate in optic chiasm synapse in pretectal nucleus in midbrain
2nd neurones (bilateral): located entirely within midbrain & connect pretectal nucleus to next synapse in Edinger-Westphal nucleus (location of cell bodies of parasympathetic axons of CN III)
3rd neurones (bilateral): pass from EW nucleus, via CN III then its inferior division, to synapse in ciliary ganglion
4th neurones (bilateral): course in short ciliary nerves to sphincter pupillae muscles
how is the lens controlled?
suspensory ligament of lens connects the circumferences of the lens & the ciliary body
ciliary body
muscular and vascular
smooth muscle like a sphincter around circumference - ciliary muscle controls lens
how does the lens focus on “far away objects”
no parasympathetics
ligament tightens & lens flattens to focus on an object in the distance
the ciliary muscle contracts in “near vision”
parasympathetic
ligament relaxes & lens becomes spherical to focus on near objects
what is the accommodation reflex
response to ‘near’ (and far)
what are the 3 components of the accommodation reflex
bilateral pupillary constriction
bilateral convergence of both eyes towards midline
bilateral relaxation of the lens
what controls the bilateral pupillary constriction in the accommodation reflex
parasympathetic constriction of sphincter pupillae
CNs III
what controls the bilateral relaxation of the lens in the accommodation reflex
the lens becomes spherical due to contraction of the ciliary muscles
CNs III
what controls the bilateral convergence of both eyes towards midline in the accommodation reflex
medial rectus
CNs III
lacrimation two types of tears?
basal
reflex
what are basal tears in lacrimation? what do they do?
important in corneal health
clean/nourish & hydrate the avascular cornea
contain lysozyme: - enzyme that hydrolyses bacterial
cell walls
what are reflex tears in lacrimation? innervation?
extra tears in response to mechanical or chemical stimulation
afferent limb is CN V1 from cornea/conjunctiva
efferent limb is parasympathetic axons originating from CN VII
(emotional tears included)
what causes the lacrimal gland to produce tears
branch CNVII, parasympathetic innervation
what is Horner’s syndrome
Impaired sympathetic innervation to head and neck
symptoms of Horner’s syndrome
miosis
ptosis
reduced sweating (anhydrosis)
increased warmth and redness
what are the cause of Horner’s syndrome
- root of neck trauma
- carotid dissection
- internal jugular vein engorgement
- deep cervical node metastases
- pancoast tumour (lung apex)
