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JMP Y2S1 > Week 41- Vision and Cranial Nerves > Flashcards

Week 41- Vision and Cranial Nerves Flashcards

1
Q

What causes the rotation of the eyeball?

A

Extraocular muscles

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2
Q

Where are the nuclei located that innervate the eye muscles?

A

Within the brainstem

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3
Q

What are the three nerves that innervate the ocular muscles?

A

Oculomotor nerve III
Trochlear nerve IV
Abducens nerve VI
3,4,6

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4
Q

What nuclei/nerve innervates the lateral rectus muscles?

A

Abducens nerve (cranial nerve 6, VI)

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5
Q

What nuclei/nerve innervates the superior oblique muscles?

A

Trochlear nerve (cranial nerve 4, IV)

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6
Q

What nerve innervates all other extraocular muscles?

A

Oculomotor nerve (cranial nerve 3, III)

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7
Q

What is convergence in the eyes?

A

Bringing optical axes together to allow for binocular vision of close objects

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8
Q

What muscle allows the eyes to converge in convergence?

A

Medial rectus muscle –> innervated by the oculomotor nerve

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9
Q

What does convergence mean practically?

A

When we focus on a point –> the convergence of the eyes allows the point to fall on identical portions of the retina of each eye (fovea)

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10
Q

What are the two main muscles that control the pupil diameter?

A

Dilator (M. dilator pupillae)

Sphincter (M. sphincter pupillae)

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11
Q

What direction is the dilator fibres for pupil control?

A

Radial direction

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12
Q

What direction is the sphincter fibres in for pupil control?

A

Circular

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13
Q

What is the pupil affects of contraction of the dilator muscles vs sphincter muscles?

A

Dilators –> causes pupil dilation (midriasis)

Sphincters –> decrease in pupil diameter (myosis)

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14
Q

What is the difference in innervation of the dilators vs sphincter muscles for pupils?

A

Dilators –> sympathetically innervated

Sphincters –> parasympathetically dilated

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15
Q

What is the pupillary reflex?

A

Activated by bright light –> the pupil reduces its diameter –> reduces light entering the eye

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16
Q

What is the mechanism steps behind the pupil reflex?

A

Light is shined through one eye e.g right
Action potentials from right eye reach both right and left pretectal nuclei
The pretectal nuclei stimulate both sides of the Eddinger-Westphal nucleus even if light was only perceived in only the right eye
Right and left sides of the Eddinger-Westphal nucleus generate action potentials through the right and left oculomotor nerves –> causing pupil constriction

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17
Q

What are cataracts?

A

Opacity of a normally clear lens –> stops the entry of light into the eye and to the retina

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18
Q

What is refraction?

A

The changing of light direction when interfacing between two medias with different refraction indices

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19
Q

How does the lens function in the eye?

A

Functions as a prism to refract light and direct it onto the retina

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20
Q

What is focal length?

A

The distance which it takes the light rays to be brought to focus by the lens

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21
Q

What is larger in short focal lengths?

A

The optical refractive power is larger

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22
Q

How is optical refractive power (optical power) measured?

A

Dioptres –> 1 diaopters is the optical power of a lens that converges parallel rays at a focal length of 1m

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23
Q

What structure in the eye provides the most optic power?

A

The anterior surface of the cornea

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24
Q

What is the total refractive power of the eye?

A

59 diopters

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25
Q

What is accommodation?

A

The movement of the lens shape (more or less convex) to change the focal power to get a clear focus of light on the retina –> brain adjusts accommodation in concert with convergence

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26
Q

What is the default shape of the lens without externally directed tension?

A

Spherical shape

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27
Q

What causes the lens to flatten?

A

Tension from the suspensory ligaments

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28
Q

What causes the lens to increase its curvature?

A

Both meridional and circular fibres of the ciliary muscles –> reduces tension by ligaments

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29
Q

What kind of innervation is ciliary muscles controlled by?

A

Parasympathetic

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30
Q

What is the term for a less elastic lens which makes accommodation difficult/impossible?

A

Presbyopia

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31
Q

How many layers are in the retina?

A

4 layers:
Pigmented Epithelium
Photosensitive cells (rods and cones)
Two layers of neurons (bipolar cells and ganglion cells)

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32
Q

What neuron layer forms the optic nerve?

A

Axons of the ganglion cells

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33
Q

What is the purpose of the outer Pigmented epithelium layer?

A

Prevents the reflection of light

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34
Q

What is the Fovea?

A

It lies in the macule area –> small depression in the retina of the eye where visual acuity is highest.
The centre of the field of vision is focused in this region

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35
Q

What is most concentrated at the fovea?

A

retinal cones are particularly concentrated

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36
Q

What are the main structural differences between the fovea and the retinal periphery?

A

High ratio of rods to cones
Higher ratio of photoreceptors to ganglion cells
More sensitive to low light

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37
Q

Why is central vision the most accurate (high acuity vision)?

A

Fovea has less internal cellular layers –> means less light dissipation before hitting photoreceptors
Cones are much smaller and tightly packed with a 1:1 convergence on bipolar cells

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38
Q

What are the two types of photoreceptors?

A

Rods and cones

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39
Q

What is the role of photoreceptors?

A

Electromagnetic radiation (light) into neural signals

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40
Q

What is the general structure of rods?

A

Long, cylindrical outer segment with many disks

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41
Q

What is the general structure of cones?

A

Shorter, tapering outer segment with fewer disks

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42
Q

Which photoreceptor is more sensitive to light?

A

Rods are 1000 times more sensitive

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43
Q

Why is peripheral vision better at night?

A

Central vision is the work of the macule –> high density of cones –> cones not sensitive to low intensity light
Peripheral vision has more rods –> which are much more sensitive to low intensity light

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44
Q

What is the mechanism of phototransduction in rods?

A

Light energy interacts with photopigment
Produces change in membrane potential
Causes a change in second messenger (similar to G-protein-coupled neurotransmitter receptor) but instead of increasing second messenger it decreases second messenger

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45
Q

What is the ion channel response to phototransduction?

A

Decrease Na+ conductance –> photoreceptor hyperpolarizes

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46
Q

What state is a photoreceptor in during the dark vs light?

A

Depolarised in dark

Hyperpolarised in light

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47
Q

What is the molecule that absorbs photons of visible light?

A

Rhodopsin

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48
Q

What is the role of the retina?

A

Conversion of light stimulus at the inputs (rods and cones) to neuronal discharge of ganglion cells at output

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49
Q

What is the basis for colour vision?

A

There is different opsins (molecules that absorb visible light and act like G-protein coupled receptors)

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50
Q

What are the three different opsins needed for colour vision?

A

Red (long wavelength)
Green (medium wavelength)
Blue (short wavelength)

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51
Q

What is the term for normal colour vision?

A

Trichromats

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52
Q

What is the term for lacking one type of cone/colour in vision?

A

Dichromats

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53
Q

What chromosome is Rhodopsin on?

A

Chromosome 3

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54
Q

What chromosome is the blue cone on?

A

Chromosome 7

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55
Q

What chromosome is red and green cones on?

A

X chromosome –> why males are affected more often

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56
Q

Where do most of the ganglion cell axons from the retina project to?

A

The lateral geniculate nucleus (LGN) in the thalamus

57
Q

From the thalamus where do neurons project?

A

Via optic radiations –> to the occipital cortex

58
Q

In humans where do the axons of the LGN neurons synapse with the cortical neurons in the primary visual cortex?

A

Area 17 –> in the occipital lobe –> mainly around the medial surface around the calcarine fissure

59
Q

What happens to axons at the optic chiasm?

A

Axons from nasal side of the retina –> decussate (cross over)
Axons from the temporal side of the retina –> don’t cross over

60
Q

What is the affect of axons crossing over/ nor crossing over at the optic chiasm?

A

Nasal side –> cross over –> project on contralateral side of the brain (opposite side)
Temporal side –> don’t cross over –> project on ipsilateral side of brain (same side)

61
Q

What is the effects of decussation on vision?

A

Each half of the binocular vision is detected by the opposite side of the brain

62
Q

What does bitemporal hemianopsia appear like and what can cause it?

A

Person only sees straight ahead without peripheral vision –> caused by an issue in signals from the nasal sides of the retina –> can be caused by pituitary adenoma

63
Q

What are some factors in dark adaption?

A

Dilation of pupils
Regeneration of unbleached rhodopsin
Adjustment of functional circuitry

64
Q

How are photoreceptors adapted going from dark to bright light?

A

Initially bright light is glary to dark adapted eye

Adaption increases dynamic range of cones by about 1000 times

65
Q

What does the adaption mechanisms of the photoreceptors rely on?

A

cGMP gated Na+ channels in photoreceptor are also Ca2+ permeable
Ca2+ inhibits the enzyme guanylyl cyclase
Intracellular Ca2+ is pumped out by a membrane exchange pump (4Na+ in –> Ca2+ + K+ out)

66
Q

Slow adaption of photoreceptors in bright light mechanism:

A
  1. cGMP levels in outer segment initially fall to very low level
  2. All cGMP gated Na+ channels close – causing maximal hyperpolarization (to -70 mV). Photoreceptor is now saturated.
  3. Ca++ influx stops
  4. Intracellular Ca++ level slowly falls
  5. Guanylyl cyclase activity increases
  6. cGMP levels rise
  7. More cGMP dependent Na+ channels open
  8. Photoreceptor depolarizes – no longer saturated
67
Q

What is the term for an eye with no refractive defects?

A

Emmetropia

68
Q

What are the two common refractive abnormalities?

A

Myopia

Hyperopia

69
Q

What is the problem with myopia?

A

The lens refracts the light too powerfully and it focuses too early and misses the retina

70
Q

What is the problem with Hyperopia?

A

The lens refracts too little and the light focuses on a point behind or past the retina

71
Q

What kind of lens is required to correct myopia?

A

A diverging lens

72
Q

What kind of lens is needed to correct Hyperopia?

A

Converging lens

73
Q

What is the normal optical power across the meridians of the eye?

A

The same across

74
Q

What is astigmatism?

A

A refractive abnormality where there is a difference in optical power in different meridians of the eyes lens (normally) –> can cause distorted or blurred vision

75
Q

What is the various axis’s that may be affected by astigmatism?

A

Vertical, horizontal or anywhere in between

76
Q

What produces intraocular fluid?

A

Within the cilia of the ciliary bodies

77
Q

What is a normal value for intraocular pressure?

A

12-20mmHg

78
Q

What is glaucoma?

A

Elevated intraocular pressure (up to 70mmHg) –> causes optic nerve issues –> may lead to blindness

79
Q

How is intraocular pressure measured?

A

Through non-contact tonometer

80
Q

What are the cranial nerves pneumonic?

A

Oh oh oh to touch and feel virgin girls vaginas ah heaven

81
Q

What are all the cranial nerves?

A 
O --> olfactory nerve
O --> optic nerve
O --> oculomotor
T -> trochlear 
T --> trigeminal 
A --> abducens
F --> facial
V --> vestibular 
G --> glossopharyngeal
V --> Vagus
A --> accessory
H --> Hypoglossal
82
Q

What is the function of the olfactory nerve?

A

It relays sensory data to the brain, and it is responsible for the sense of smell.

83
Q

What is the function of the optic nerve?

A

The job of theoptic nerveis to transfer sensory visual information from the retina to the vision centres of the brain via electrical impulses.

84
Q

What is the function of the oculomotor nerve?

A

Innervation to the pupil and lens (autonomic, parasympathetic) Innervation to the upper eyelid (somatic) Innervation of the eyemusclesthat allow for visual tracking and gaze fixation (somatic)

85
Q

What is the function of the trochlear nerve?

A

Thetrochlear nerveis a motornerve, and it controls the superior oblique muscle of the eye. The superior oblique muscle controls the downward movement of the eyeball and, in part, keeps the eyeball from rolling upward into the orbit (eye socket).

86
Q

What is the function of the trigeminal nerve?

A

Its mainfunctionis transmitting sensory information to the skin, sinuses, and mucous membranes in the face. It also stimulates movement in the jaw muscles.

87
Q

What is the function of the abducens nerve?

A

that controls the movement of the lateral rectus muscle, responsible for outward gaze. It is a somatic efferentnerve.

88
Q

What is the function of the facial nerve?

A

controls the muscles offacialexpression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue.

89
Q

What is the function of the vestibular nerve?

A

responsible for both hearing and balance and brings information from the inner ear to the brain

90
Q

What is the function of the glossopharyngeal nerve?

A

It receives general somatic sensory fibres (ventral trigeminothalamic tract) from the tonsils, the pharynx, the middle ear and the posterior 1/3 of the tongue. It receives special visceral sensory fibres (taste) from the posterior 1/3 of the tongue.

91
Q

What is the function of the Vagus nerve?

A

helps to regulate many critical aspects of human physiology, including the heart rate, blood pressure, sweating, digestion, and even speaking.

92
Q

What is the function of the accessory nerve?

A

supplies thesternocleidomastoid andtrapezius muscles. The sternocleidomastoid muscle tilts and rotates the head, while the trapezius muscle, connecting to thescapula, acts to shrug the shoulder.

93
Q

What is the function of the hypoglossal nerve?

A

motor control of the extrinsic muscles of the tongue: genioglossus, hyoglossus, styloglossus, and the intrinsic muscles of the tongue.

94
Q

What is eyesight?

A

An ability of a person to see clearly without any corrective lenses (visual acuity)

95
Q

What is visual field?

A

The area that can be seen by the eye when it is directed forward –> including peripheral vision

96
Q

How is eyesight tested clinically?

A

An eye chart

97
Q

How is visual field tested clinically?

A

Examiner directly across from patient
Hands, fingers, or instrument used to move around patients field of view –> essentially comparing field of view to your own

98
Q

What are the terms for refractive error in the eyes?

A

Myopia –> light focused in front of retina

Hyperopia –> light focuses behind the retina

99
Q

What is the normal anatomy of the pituitary gland?

A

Pea sized –> sits behind bridge of the nose –> has 3 lobes:
Anterior
Posterior
Intermediate –> less important

100
Q

What is the functions of the pituitary gland?

A

Regulate function of endocrine glands

Master gland –> controls –> thyroid, adrenal, ovaries, testes

101
Q

What are some hormones of the Anterior lobe of the pituitary gland?

A 
Adrenocorticotropic hormone (ACTH)
Follicle stimulating hormone (FSH)
Growth hormone (GH)
Luteinizing hormone (LH)
Prolactin 
Thyroid stimulating hormone (TSH)
102
Q

What are some hormones of the posterior lobe of the pituitary gland?

A

Anti-diuretic hormone (ADH)

Oxytocin

103
Q

Why can pituitary tumours cause visual field disturbances?

A

Pushes on the optic chiasm –> disturb optic nerve signals

104
Q

What are the two main categories of headache?

A

Primary –> not a symptom for another disease –> headache from headache (benign)
Secondary –> symptom of another disease –> needs to be ruled out

105
Q

When is a primary headache diagnosed?

A

When a secondary headache is ruled out

106
Q

Common causes of primary headaches?

A 
Alcohol
Changes in sleep
Poor posture
Skipped meals
Stress
107
Q

What is believed to be the cause of migraine?

A

The pain nucleus of the trigeminal nerve becomes spontaneously active; pain is felt in the head or upper neck and blood flow in the face and scalp increases reflexly. Noradrenaline is released from the adrenal gland and causes the platelets to release serotonin. Serotonin in the circulation is thought to reflect levels of this neurotransmitter in the brain.
The brainstem nuclei of one side have a reciprocal effect on those of the other side; their effects may alternate, causing cortical changes on one side and headache on the other, or causing the headache itself to change from side to side.
–> essentially caused by brain interactions with the cranial blood vessels

108
Q

Who are Torres straight islanders?

A

are the Indigenous peoples of theTorres Strait Islands, which are part of the state of Queensland, Australia. Ethnically distinct from the Aboriginal people of the rest of Australia, they are often grouped with them as Indigenous Australians

109
Q

Which cranial nerve controls pupil diameter?

A

Cranial nerve 3 –> oculomotor

110
Q

What is mydriasis?

A

It is the opening of the pupil in response to low light

111
Q

What is Miosis?

A

The constriction of the pupil in bright light

112
Q

What kind of innervation constricts the pupils?

A

Parasympathetic –> circular muscle constriction

113
Q

What kind of innervation dilates the pupils?

A

Sympathetic –> radial muscles contract

114
Q

What movement would be impaired if CN4 was compressed?

A

Superior oblique movement

115
Q

How would a patient present with CN4 compression?

A

Diplopia
Head tilt away from lesion
Double vision when going down stairs

116
Q

What would infection of CN6 impair?

A

Lateral rectus muscle –> eye abduction

117
Q

Which way does the eye deviate in CN6 issues?

A

Will adduct –> move towards the nasal side

118
Q

What pattern of visual loss is expected in Homonymous hemianopia?

A

Half of vision gone in both eyes –> can be nasal or temporal side

119
Q

What is the consensual reflex in pupils?

A

Light in one eye –> other eye constricts

120
Q

What is the direct pupil reflex?

A

Light in a eye –> and that eye constricts

121
Q

What pattern of visual loss is expected in macula degeneration?

A

Blurry vision in centre of eye

122
Q

What pattern of visual loss is expected in bitemporal hemianopia?

A

Both temporal sides on each eye lost –> peripheral vision loss

123
Q

What pattern of visual loss is expected in right optic nerve ischaemia?

A

Vision loss on the right side

124
Q

Where would the lesion be with one upper quarter vision loss on the right ride?

A

R upper quadrant loss is from issue with upper L optic radiations

125
Q

What happens to the image as it passes the LGN?

A

Flips Horizontal to vertical

126
Q

Where does the upper quadrant visual info get processed?

A

Temporal

127
Q

Where does the lower quadrant visual info get processed?

A

Parietal

128
Q

What cranial nerve closes the eyelid by relaxing the muscle??

A

Facial nerve

129
Q

Where is the cranial nerve 3 nucleus?

A

Brainstem –> midbrain

130
Q

small visual field loss on nasal side of left eye –> what side of the retina has a deficit?

A

Temporal side of retina

131
Q

Flashing lights –> like I had cobwebs over the eye –> what does this point to diagnostically?

A

Retinal detachment

132
Q

What is bells palsy?

A

temporary weakness or paralysis of the muscles in the face. It can occur when the nerve that controls your facial muscles becomes inflamed, swollen, or compressed.

133
Q

Why is important if the forehead affected by a facial droop?

A

Upper vs Lower motor neuron issue
If they can move forehead –> upper issue –> increases stroke risk
If they cant –> lower motor neuron issue –> more likely bells palsy

134
Q

What cranial nerve is important for bells palsy and facial movement?

A

Cranial nerve 7 –> facial nerve

135
Q

What causes bell’s palsy?

A

It’s believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of your face. Or it might be a reaction that occurs after a viral infection.

136
Q

What is the nerve controlling the sensory part of the corneal reflex?

A

Cranial nerve 5 –> V1

137
Q

What is the nerve controlling the motor part of the corneal reflex?

A

Cranial nerve 7

138
Q

Where do you poke someone for the corneal reflex?

A

Gently poke cotton in the lower middle eye

JMP Y2S1 (24 decks)

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