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Ophthalmology Week 1 > Anatomy - Important Reflexes of the Orbital Region > Flashcards

Anatomy - Important Reflexes of the Orbital Region Flashcards

1
Q

where does the suspensory ligament of the eye attach between?

A

the zygoma and the lacrimal bone

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2
Q

what is the function of the suspensory ligament of the eye?

A

holds the eye just above the floor of the orbit

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3
Q

in which direction does a fractured zygoma tend to rotate?

A

medially towards the floor of the orbit

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4
Q

how can a fractured zygoma cause double vision?

A

the suspensory ligament attaches laterally to the zygoma so if they zygoma is fractured it tends to rotate medially towards the floor of the orbit and the ligament cannot do its job so the eye can be lowered to towards the orbital floor, which causes the eyes to no longer be on the same vertical position

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5
Q

what else can be injured, other than the suspensory ligament, in a fractured zygoma?

A

the infraorbital neurovascular bundle

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6
Q

if there is damage to the infraorbital NVB, what does this result in?

A

general sensory deficit of the facial skin

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7
Q

what does CN V1 supply?

A

the upper eyelid, the cornea, all the conjuctiva, the skin of the root/bridge/tip of the nose

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8
Q

what does CN V2 supply?

A

the skin of the lower eyelid, the skin over the maxilla, the skin of the ala of the nose, the skin/mucosa of the upper lip

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9
Q

what does CN V3 supply?

A

the skin over the mandible and TMJ joint

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10
Q

what area of the mandible is not supplied by CN V3? and what does supply it?

A

the angle of the mandible- supplied by C2,3 spinal nerves

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11
Q

what is the name of the branch that supplies the angle of the mandible?

A

great oricular nerve

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12
Q

what are the 2 components of the blink reflex?

A

the afferent (sensory) limb and the efferent (motor) lim

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13
Q

how do you assess the blink reflex in clinical practice?

A

use a sterile point of cotton wool and gently touch the cornea

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14
Q

when the cotton wool touches the cornea, what is the pathway in which AP are conducted to the brain?

A

via CN V1 to the trigeminal ganglion then in the trigeminal nerve (CN V) to the pons

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15
Q

once the APs reach the pons, how is the motor limb of the blink reflex brought about?

A

there is CNS connections between CN V and CN VII, action potentials are conducted to the eyelid part of orbicularis oculi to bring about the blink

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16
Q

where do presynaptic sympathetic axons from the CNS (to supply the head and neck) exit the spinal cord?

A

in T1 spinal nerve

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17
Q

after a presynaptic sympathetic axon exits the spinal cord in T1 spinal nerve, what does it ascend within and where does it synapse?

A

ascends within sympathetic trunk and then synapses in the superior cervical sympathetic ganglion

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18
Q

when a presynpatic sympathetic axon synapses at the superior cervical ganglion, what does it release?

A

acetylcholine

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19
Q

where do the postsynaptic sympathetic axons enter after synapsing in the superior cervical ganglion?

A

the internal carotid nerve and external carotid nerve

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20
Q

once the postsynaptic sympathetic axons have entered the internal and external carotid nerve, what do they do?

A

pass onto the surface of the internal and external carotid arteries to be carried to organs of the head

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21
Q

what artery carries sympathetic axons into the orbit?

A

the ophthalmic artery - branch of internal carotid

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22
Q

what forms the stellate ganglion?

A

the inferior cervical and 1st thoracic ganglia often fuse to form the stellate ganglion

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23
Q

what does the postsynaptic sympathetic axon release to stimulate the target organ?

A

noradrenaline

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24
Q

where are the ganglions for parasympathetic axons?

A

located within the organ

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25
Q

what do the presynaptic parasympathetic axons release when they synapse in the parasympathetic ganglion?

A

acetylcholine

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26
Q

what does the postsynaptic parasympathetic axon release to stimulate the organ?

A

acetylcholine

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27
Q

what are the CNs that can carry presynaptic parasympathic axons?

A

CN III, VII, IX and X

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28
Q

what spinal nerves can carry presynaptic parasympathetic axons?

A

sacral spinal nerves

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29
Q

what is the parasympathetic ganglion in the orbit called?

A

the ciliary ganglion

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30
Q

what muscles of the eye receive their somatic motor innervation from occulomotor nerves?

A

superior, medial and inferior rectus, inferior oblique and levator palpebrae superioris

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31
Q

what nerve gives presynaptic parasympathetic axons to the ciliary ganglion?

A

occulumotor CN III

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32
Q

where does the oculomotor nerves connect with the CNS?

A

near the midline at the junction between the midbrain and the pons

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33
Q

what are the 2 branches of the occulumotor nerve?

A

superior branch and inferior branch

34
Q

what muscles does the superior branch of the occulomotor nerve supply?

A

the superior rectus and levator palpebrae superioris

35
Q

what does the inferior branch of the occulomotor supply in the orbit?

A

medial rectus, inferior rectus, inferior oblique and the ciliary ganglion

36
Q

what do the ciliary nerves supply and what does this control?

A

autonomic axons to control the diameter of the iris and the refractive shape of the lens

37
Q

what type of fibres does the long ciliary nerve have?

A

sympathetic and somatic sensory

38
Q

what type of fibres does the short ciliary nerve have?

A

somatic sensory, parasympathetic and sympathetic

39
Q

what nerve forms the first part of the afferent limb of the blink reflex?

A

long ciliary nerve

40
Q

what are the 4 autonomic reflexes of the eye?

A
  • maximal eyelid elevation
  • pupillary dilation/constriction: the pupillary light reflex
  • focussing the lens: the accomodation reflex
  • lacrimation
41
Q

what does the vestibulo-ocular reflex do?

A

turns the eyes in the opposite direction to a head movement

42
Q

what is the oculocardiac reflex?

A

reflex bradycardia in response to tension on the extraocular muscles or pressure on the eye

43
Q

what type of innervation is responsible for opening the eyes wider and focusing on far away objects?

A

sympathetic system

44
Q

what system allows the orbicularis oculi to work to get less light into the eye?

A

parasympathetic

45
Q

what system controls reflex lacrimation?

A

parasympathetic

46
Q

what system controls emotional lacrimation?

A

sympathetic

47
Q

what type of muscle does levator palpebrae superioris contain?

A

both skeletal and smooth muscle

48
Q

how does the postsynaptic sympathetic fibres reach the levator palpebrae superioris?

A

via superior cervical sympathetic ganglion, to the internal carotid nerve, into the internal carotid plexus, axons carried on the ophthalmic artery and its branches to reach orbital structures

49
Q

what is a non-physiological enlarged pupil called?

A

mydriatic pupil

50
Q

what do mydriatic drugs induce?

A

dilation of the pupil

51
Q

what is arranged radially around the iris that controls pupillary dilation?

A

dilator pupillae fibres

52
Q

where is the mobile insertion of the dilator pupillae fibres?

A

around the internal circumference of the iris

53
Q

where is the fixed origin of the dilator pupillae fibres?

A

around the external circumference of the iris

54
Q

in the eye, what is often a sign of serious pathology eg opiate drugs?

A

a fixed ‘pin point’ pupil

55
Q

what is a non-physiological constricted pupil called?

A

a miotic pupil

56
Q

what syndrome can a miotic pupil be a feature of?

A

Horner’s Syndrome

57
Q

what is a fixed-dilated (blown) pupil often a sign of?

A

a serious pathology e.g CN III pathology

58
Q

how are the sphincter pupillae fibres arranged internal circumference of the iris?

A

they encircle it - like a donut

59
Q

what is the only part of the pupillary light reflex that is unilateral?

A

the special sensory (afferent) limb of the reflex

60
Q

what is meant by the direct light reflex?

A

the reflex in the eye that is stimulated with light

61
Q

what is meant by the consensual light reflex?

A

the reflex in the non-stimulated eye

62
Q

how is the light reflex the same in both eyes even though its only one eye being stimulated?

A

there is CNS connections in the thalamus which brings above the motor limb of the reflex in both eyes

63
Q

what nerve is responsible for the light reflex?

A

CN III

64
Q

how many neurone chains are involved in the light reflex?

A

4 neurone chain

65
Q

what happens in the 1st neurones in the light reflex?

A

the retinal ganglion cells pass via ipsilateral optic nerve to decussate in the optic chiasm then synapse in the pretectal nucleus in the midbrain

66
Q

where is the second neurones located and what happens here in the light reflex?

A

located within the midbrain and connect the pretectal nucleus to the next synapse in the Edinger Westphal nucleus

67
Q

what is the Edinger Westphal nucleus?

A

the location of the cell bodies of the parasympathetic axons of CN III

68
Q

in the 3rd neurones, the neurones pass from the edinger westphal nucleus via CN III inferior division to where and to do what? (in light reflex)

A

to synpase in the ciliary ganglion

69
Q

what happens in the 4 neurones in the light reflex?

A

course bilaterally in the short ciliary nerves to the sphincter pupillae muscles

70
Q

what does the suspensory ligament of the lens do?

A

connects the circumference of the lens and the ciliary body

71
Q

how is the smooth ciliary muscle positioned?

A

like a sphincter all around the circumference of the ciliary body

72
Q

what controls the refractive shape of the lens?

A

the ciliary muscles

73
Q

to see something in the distance, what does the ciliary muscle and ligament do? and what affect does this have on the lens?

A

the ciliary muscle relaxes, the ligament tightens and the lens flattens to focus on something far away

74
Q

how does the ciliary muscle and ligament act to change the lens when using “near vision” eg reading a book

A

the ciliary muscle contracts, the ligament relaxes and the lens becomes spherical

75
Q

how do you clinically asses all 3 components of the accommodation reflex?

A
  1. bilateral pupillary constriction
  2. bilateral convergence
  3. bilateral relaxation of the lens
76
Q

what is the purpose of basal tears?

A

clean/nourish and hydrate the avascular cornea

77
Q

basal tears contains lysozyme, what does this do?

A

that hydrolyse bacterial cell walls

78
Q

what are reflex tears?

A

extra tears in response to mechanical or chemical stimulation

79
Q

what nerve is responsible for the afferent limb of the reflex tears reflex?

A

CN V1

80
Q

what nerve is responsible for the efferent limb of the reflex tears?

A

parasympathetic axons originating from CN VII

81
Q

what is the 3rd type of tears (not basal or reflex)?

A

emotional tears

Ophthalmology Week 1 (6 decks)

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