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(O) Anatomy > Reflexes of the Eye > Flashcards

Reflexes of the Eye Flashcards

1
Q

what is the one corneal reflex

A

blink

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2
Q

what does the blink reflex protect from

A

chemical and mechanical irritants

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3
Q

describe the blink reflex

A

corneal APs conducted along CN V1 to the trigeminal ganglion
CNS connections connect this to CN V and the AP travels to the pons
AP then conducted down CN VII to the obicularis oculi

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4
Q

how do we test the blink relfex

A

touching the patient’s sclera with a wisp of cotton wool

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5
Q

what is the vestibulo-ocular reflex

A

reflex stabilises eye sight and gaze on an object during head movement, turns the eyes in the opposite direction

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6
Q

through what nerves does the vestibulo-ocular reflex occur

A

CN connections between CN VIII and CN III, IV and VI

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7
Q

what is the oculocardiac reflex

A

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

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8
Q

describe the oculocardiac reflex pathway

A

AP travels down vagus to heart, slowing HR and relieving tension and pressure
CNS connections between CN V1 and CN X

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9
Q

what is the sympathetic reflex of the eyes

A

eyes open wider to allow more light in

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10
Q

what is the parasympathetic reflex of the eyes

A
  • the pupil allows less light into the eyes, to protect the retina from bright lights or during sleep
  • focus on near objects
  • reflex lacrimation to wash away foreign object/clean cornea
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11
Q

what type of muscles does the LPS contain

A

skeletal and smooth muscles

and Meullers muscle

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12
Q

what is Meuller’s muscle innervated by

A

sympathetic

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13
Q

how does LPS and Muellers muscle open the eyes

A

tonically contracted to maintain the opening o the eye

elevates the eyelid by an additional 2cm (usually in a sympathetic state)

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14
Q

how do postsynaptic sympathetic fibres to orbital structures

A
  • superior cervical sympathetic ganglion
  • internal carotid nerve
  • internal carotid plexus
  • axons carried on the ophthalmic artery
  • on ophthalmic artery branches to the orbital structures
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15
Q

what is the pupillary constriction reflex

A

parasympathetics constrict the pupil in response to bright light and rest and digest

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16
Q

what nerve controls the pupillary constriction reflex

A

CN III

17
Q

what happens during the pupillary constriction reflex

A

the sphincter pupillae fibres constrict decreasing the diameter of the pupil instantaneously

18
Q

what nerves control the pupillary dilation reflex

A

sympathetic

19
Q

what happens during the pupillary dilation reflex

A

the dilator pupillae muscles contract and pull on the sphincter dilating the pupils

20
Q

what is a mydriatic pupil

A

a non-physiologically enlarged pupil

21
Q

what is a mitotic pupil

A

a non-physiologically constricted pupil

22
Q

what nerve pathology is a fixed dilated pupil a sign of

A

CN III

23
Q

what is the pupillary light reflex

A

light detected by an ipsilateral optic nerve, but motor response is bilateral

24
Q

what nerve controls the pupillary light reflex

A

CN II

25
Q

what connects the lens to the ciliary body

A

suspensory ligaments

26
Q

what type of muscle is the ciliary body

A

smooth muscles, sphincter-like

27
Q

describe the process of seeing objects further away

A

ciliary body relaxes, ligaments tighten and the lens flattens to focus on the object

28
Q

what innervation controls the contraction of the ciliary body

A

parasympathetic

29
Q

describe the process of seeing objects close

A

the ciliary body contracts, the ligaments relax, and the lens becomes spherical to focus on the object

30
Q

what are the 3 components of clinically testing the near response reflex

A
  • bilateral pupil constriction
  • bilateral convergence of eyes to midline
  • Bilateral relaxation of the lens
31
Q

why are basal tears secreted

A

corneal health

32
Q

what is the function of basal tears

A

washed over the cornea during blinking to clear/nourish and hydrate the avascular cornea

33
Q

what enzyme do basal tears contain and what is its function

A

lysozyme

hydrolyses bacterial cell walls

34
Q

what are reflex tears produced in response to

A

mechanical or chemical stimulation

35
Q

what are the afferent and efferent limbs involved in reflex tears

A

afferent - CN V1 to the cornea/conjunctiva

efferent - CN VII parasympathetic axons

36
Q

describe the pathway of CN VII to the lacrimal glands

A
  • enters at the temporal bone
  • branches off the geniculate ganglion
  • passes through the medullcranial fossa
  • into pterygoid canal
  • pterygopalatine ganglion
  • sympathetic fibres form the internal carotid join the ganglion
  • both pass to lacrimal glanf following V1 and V2 fibres

(O) Anatomy (5 decks)

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