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Ocular Anatomy and Physiology > Week 4: Globe, EOM and Sclera > Flashcards

Week 4: Globe, EOM and Sclera Flashcards

1
Q

What are the peripheral nervous systems?

A
  1. Somatic nervous system

2. Autonomic nervous system

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2
Q

Explain what is somatic nervous system, its neurotransmitter and what it contains

A
  • Voluntary movement of the body
  • Covers skeletal muscles and sensory stimuli
  • Neurotransmitter: acetylcholine
    1. Afferent (signal travelling inwards): sensory - pressure, heat, pain
    2. Efferent (signal travelling outwards): motor: skeletal muscle
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3
Q

Explain what is autonomic nervous system, its neurotransmitters and what it contains

A
  • Involuntary movement of the body (e.g. heart rate, digestion)
  • Neurotransmitters: acetylcholine & norepinephrine
    1. Sympathetic nervous system
    2. Parasympathetic nervous system
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4
Q

What is sympathetic nervous system and what ocular innervations does it include?

A
  • Fight or flight response
  • Ocular innervation includes: iris dilator (pupil larger), ciliary muscle, superior tarsal muscle, lacrimal gland, choroidal & conjunctival blood vessels
  • Sympathetic ganglion is the Superior Cervical Ganglion
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5
Q

What is parasympathetic nervous system and what ocular innervations does it include?

A
  • Rest and digest response
  • Ocular innervations include: iris sphincter (pupils smaller), ciliary muscle, lacrimal gland
  • Parasympathetic Ganglion is the Ciliary Ganglion
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6
Q

What type of pathway is the optic nerve (CNII) and describe the pathway process

A
  • Sympathetic afferent pathway (going in)
  • Pathway:
    1. Retinal ganglion cells
    2. Cortical & sub-cortical visual centres in the brain
    3. RGC axons become myelinated in the optic nerve & sends message
  • Surrounded by cranial meninges
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7
Q

What type of pathway is the oculomotor nerve (CNIII) and explain its function and what it innervates

A
  • Efferent pathway (going out)
  • Function: eye movement
  • Innervation of:
    inferior rectus
    inferior oblique
    medial rectus
    superior rectus
    levator palpaebrae superioris
    iris sphincter (parasympathetic innervation)
    ciliary muscle (parasympathetic innervation)
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8
Q

What type of pathway is the trochlear nerve (CNIV) and explain its function, what it innervates and action of the EOM

A
  • Efferent pathway (going out)
  • Function: eye movement (intorsion, depression & abduction)
  • Innervation of: superior oblique
  • Action of SO is depression and adduction (eye will point down and in)
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9
Q

What type of pathway is the trigeminal nerve (CNV) and explain its function and its three divisions

A
  • Afferent pathway (going in)
  • Function: facial motor and sensory
  • Divisions: ophthalmic division (V1), Maxillary division (V2), mandibular division (V3)
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10
Q

What is the ophthalmic nerve function and its three main branches?

A
  • Most superior and smallest division
  • Function: sensory
  • Prior to entering the orbit, through the superior orbital fissure, it divides into 3 main branches: lacrimal nerve, frontal nerve & nasociliary nerve
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11
Q

Describe the lacrimal nerve

A
  • Sensory innervation of the lacrimal gland, upper eyelid and conjunctiva
  • Contains parasympathetic and sympathetic efferent to lacrimal gland
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12
Q

Describe the frontal nerve and what they divide into & what branches supply

A
  • Largest branch of ophthalmic nerve
  • Half way in the orbit, it divides into 2: large supraorbital branch & small supratrochlear branch
  • Supraorbital branch (supplies skin & conjunctiva of upper eyelid, skin of forehead & scalp, mucus membrane of frontal sinus)
  • small supratrochlear branch (supplies skin & conjunctiva of upper eyelid, skin of medial forhead)
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13
Q

Describe the nasociliary nerve, what they divide into & what they innervate

A
  • Short ciliary nerves
  • Two long ciliary nerves
  • Divides into: infratrochlear nerve & posterior ethmoid nerve
  • Infratrochlear nerve innervates conjunctiva of medial upper eyelid, medial canthus, lacrimal sac, caruncle & skin on bridge of nose
  • Posterior ethmoid nerve innervates mucosa of sphenoid & posterior ethmoidal sinuses
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14
Q

What is the maxillary nerve three main branches (elaborate)?

A
  • Infraorbital nerve: sensory fibers from cheek, upper lip, lower eyelid, lateral aspect of nose
  • Zygomatic nerve: sensory fibers from temporal region, cheek and lower eyelid
  • Posterior superior alveolar: sensory to teeth, maxillary sinus
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15
Q

What is the mandibular nerve functions and their sensory and motor?

A
  • Function: has sensory and a motor root
  • Sensory: teeth and gums of mandible, lower lip, lower part of face
  • Motor: chewing
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16
Q

What does the abducens nerve (CNVI) innervate and explain its function

A
  • Innervates: lateral rectus muscle
  • Function: eye movement (lateral rectus)
  • Has a long intracranial course exposing it to a high risk of dysfunction
17
Q

What does the facial nerve (CNVII) contain? (2 roots)

A
  • Large motor root: innervates facial muscles

- Smaller sensory root: from superior salivatory nucleus

18
Q

Explain the eye movement of abduction

A
  • Eye moves temporally

- LR contracts & MR relaxes

19
Q

Explain the eye movement of adduction

A
  • Eye moves nasally

- MR contracts & LR relaxes

20
Q

Explain the eye movement of elevation

A
  • Eye moves upwards

- SR contrats, IO contracts

21
Q

Explain the eye movement of depression

A
  • Eye moves downwards

- IR contracts & SO contracts

22
Q

Define version (binocularly)

A
  • Simultaneous movement of both eyes in same direction
23
Q

Define vergence (binocularly)

A
  • Simultaneous movement of both eyes in opposite directions
    1. Convergence (contract both MR)
    2. Divergence (contract both LR)
24
Q

Define position of gaze (binocularly)

A
  1. Primary: both eyes fixate a distant object directly ahead
  2. Secondary: up, down, left, right
  3. Tertiary: up-right, up-left, down-right, down-left
25
Q

Define agonist muscle (binocularly)

A
  • Main muscle that moves eye in a given direction
    1. Synergistic muscle: EOM in the same eye that achieve same eye movement as agonist
    2. Antagonist muscle: EOM in the same eye that achieve opposite eye movement as the agonist
    3. Yoked muscles: muscles in the two eyes that accomplish a given movement
26
Q

List the ductions and define them

A
  • Supraduction = elevation in one eye
  • Infraduction = depression in one eye
  • Incycloduction (intorsion) = nasal rotation in one eye
  • Excycloduction (extorsion) = temporal rotation in one eye
27
Q

List the conjugate (versions) and define them

A
  • Dextroversion = movement of both eyes to the right
  • Levoversion = movement of both eyes to the left
  • Supraversion = elevation of both eyes
  • Infraversion = depression of both eyes
28
Q

List the disconjugate (vergences)

A
  • Convergence (contract both MR)

- Divergence (contract both LR)

29
Q

List the measurement of the sclera and describe the colour of it

A
  • Posterior 5/6th if fibrous layer of the eyeball

Colour:

  • Opaque white in adults
  • Slightly bluish in children
  • Yellowish from fat deposition in elderly
30
Q

What is the connections for the sclera?

A
  • Connected by delicate connective tissue to the fascial sheath of the eye ball
  • Connected with EOMs at insertions
31
Q

List the structure/layers of the sclera and explain them in detail

A
  1. Episclera
    - Outermost layer
    - Loose connective tissue
  2. Sclera stroma (main body)
    - Dense fibrous tissue
  3. Lamina fusca
    - Inner most layer
    - Brown due to melanocytes
32
Q

List the types of EOM fibers and explain in detail

A
  1. Type A
    - Large diameter
    - Fast twitch (contracts quickly)
    - Used for saccadic movement
  2. Type B
    - Intermediate diameter
    - Slow twitch (contracts slowly)
    - Used for smooth pursuit movements
  3. Type C
    - Small diameter
    - Tonic contractions (sustained, slow, graded contractions)
    - Used to align right & left visual axes - fine tuning local contractions

Ocular Anatomy and Physiology (10 decks)

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