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M2 Anatomy > Neuroscience Anat (CN II, III, IV, VI) > Flashcards

Neuroscience Anat (CN II, III, IV, VI) Flashcards

1
Q

VISION, state the
- sensory organ
- sensory receptors
- pathway

A

VISION, state the
- sensory organ = eye (retina)
- sensory receptors = rods and cones in retina
- pathwa: CN II (optic N) –> lateral geniculate nucleus (thalamus) –> primary visual cortex

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2
Q

VISION

State the structures in
1. outer
2. intermediate
3. innermost

A

VISION
1. outer (FIBROUS) - sclera and cornea
2. intermediate (VASCULAR AND PIGMENTED) - choroid, ciliary body, lens (suspensory ligaments), iris with dilator pupillae and sphincter pupillae
3. innermost (NERVOUS) - retina (outgrowth of brain into orbit)

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3
Q

State the 3 radially disposed sets and 2 tangential sets of structures in retina (nervous layer) and include their function.

A

RADIALLY DISPOSED SETS:
1. photoreceptors - receive and transduce light energy to action potential
2. bipolar cells - transmit information to ganglion cells
3. ganglion cells - project to thalamus and brainstem

TANGENTIAL SETS - integrate and modulate information
1. horizontal cell
2. amacrine cells

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4
Q

State the 8 layers of the retina from superficial to deep.

A
  1. pigment layer
  2. photoreceptor
  3. outer nuclear
  4. outer plexiform
  5. inner nuclear
  6. inner plexiform
  7. ganglion cell
  8. nerve fiber
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5
Q

State the funtions of photoreceptors and name the types of photoreceptors found.
State the difference between the types of photoreceptors.

A

PHOTORECEPTORS
- function = transduce light energy into chemical energy (action potential)
- types = rods and cones

RODS - CONES
sensitive to dim light - sensitive to bright light
no colour sense - colour sense and accurate detail
absent in fovea - most numerous in fovea

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6
Q

FOVEA
- located behind ____ and ____
- only contains ____, ____ are located more ____
- located within ____ (most ____ part of eye)

OPTIC DISC
- does not contain ____ or ____
- ____ ____ if light falls onto optic disc
- also where ____ N exits

A

FOVEA
- located behind PUPIL and LENS
- only contains CONES, RODS are located more PERIPHERALLY
- located within MACULA (most SENSITIVE part of eye)

OPTIC DISC
- does not contain RODS or CONES
- BLIND SPOT if light falls onto optic disc
- also where OPTIC N exits

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7
Q

IMPORTANT:

The visual image is ____ and ____ by the lens

____ of visual field is binocular
____ of visual field is monocular

A

The visual image is INVERTED and REVERSED by the lens

2/3 of visual field is binocular
1/6 (ON EACH SIDE) of visual field is monocular

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8
Q

Left hemisfield - supplied by ____ ____ and ____ ____
Right hemisfield - supplied by ____ ____ and ____ ____

A

Left hemisfield - supplied by LEFT NASAL HEMI-RETINA and RIGHT TEMPORAL HEMI-RETINA

Right hemisfield - supplied by RIGHT NASAL HEMI-RETINA and LEFT TEMPORAL HEMI-RETINA

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9
Q

State the pathway for the basic visual pathway from stimulus to effector

A
  1. light
  2. retina (receptor)
  3. optic nerve
  4. optic chiasma (partial decussation)
  5. optic tract
  6. lateral geniculate nucleus (thalamus)
  7. optic radiation
  8. primary visual cortex in occipital lobe
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10
Q

OPTIC RADIATION
- Connects the ____ ____ ____ to the ____ ____ ____
- Also known as ____ ____
- Is the collection of axons from relay neurons in ____ of thalamus carrying ____ information in the ____ ____
- ____ ____ is located within the optic radiation - has fibres representing the ____ retinal quadrants or ____ visual fields (____ fibres of optic radiation represent the ____ retinal quadrants/____ visual field)

A

OPTIC RADIATION
- Connects the LATERAL GENICULATE NUCLLEUS to the PRIMARY VISUAL CORTEX
- Also known as GENICULO-CALCARINE TRACT
- Is the collection of axons from relay neurons in LGN of thalamus carrying VISUAL information in the VISUAL CORTEX
- MEYER’S LOOP is located within the optic radiation - has fibres representing the INFERIOR retinal quadrants or SUPERIOR visual fields (UPPER fibres of optic radiation represent the SUPERIOR retinal quadrants/LOWER visual field)

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11
Q

State the 2 types of collateral fibres given off by optic tract

A
  1. SUPERIOR COLLICULUS (tectospinal tract) - EOM for visual reflexes
  2. PRETECTAL NUCLEUS - photopupillary and accommodation
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12
Q

Locate (1) Primary visual cortex (VC1) and (2) Visual associaton area (VC2)

A
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13
Q

State the function and pathway of
(1) VENTRAL VISUAL PATHWAY
(2) DORSAL VISUAL PATHWAY

A

(1) VENTRAL VISUAL PATHWAY - WHAT
- function = processing of form and colour information
- pathway = continues into cortex on under side of temporal lobe

(2) DORSAL VISUAL PATHWAY - WHERE, HOW
- function = processing of motion and spatial relationships
- pathway = continues into posterior parietal lobe

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14
Q

State the 4 common visual field defects

A
  1. monocular blindness - one-eyed blindness
  2. bitemporal hemianopia - lateral half of both eyes blind
  3. binasal hemianopia - medial half of both eyes blind
  4. homonymous hemianopia - letft/right half of both eyes blind
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15
Q

State the cause of each of the 4 common visual field defect.

A

(1) MONOCULAR BLINDNESS
- one-sided blindness
- cause = lesion in left/right optic N

(2) BITEMPORAL HEMIANOPIA
- lateral half of both eyes blind
- cause = lesion in optic chiasma of the nasal hemiretina

(3) BINASAL HEMIANOPIA
- medial half of both eyes blind
- cause = lesion in optic chiasma of the temporal hemiretina

(4) HOMONYMOUS HEMIANOPIA
- left/ right side of both eyes blind
- cause = lesion in left/right optic tract

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16
Q

State the 2 rarer (advanced) visual field defects

A
  1. quadrantopia (optic radiation) - blindness in the same quadrant of both eyes
  2. homonymous hemianopia with macular sparing - blindness in the same half of both eyes with macular sparing
17
Q

State the cause of each of the 2 rarer (advanced) visual field defect.

A

(1) QUADRANTOPIA
- blindness in the same quadrant of both eyes
- MEYER’S LOOP LESION
- left superior quadrantopia = lesion in lower fibres of right optic radiation that transmit information to the left upper visual quadrant
- left inferior quadrantopia = lesion in upper fibres of right optic radiation that transmit information to the left lower visual quadrant
- right superior quadrantopia = lesion in lower fibres of left optic radiation that transmit information to the right upper visual quadrant
- right inferior quadrantopia = lesion in upper fibres of left optic radiation that transmit information to the right lower visual quadrant

(2) HOMONYMOUS HEMIANOPIA WITH MACULAR SPARING
- blindness in the same half on both eyes
- vascular lesion affecting left or right visual cortex –> affects right or left (opposite) visual cortexes
- as the fovea and macula are supplied by MCA and PCA (2 arteries involved), one down, other compensate = macular sparing

18
Q

Recap:

State the
(1) intrinsic muscles of eye
(2) extrinsic muscles of eye

State any autonomic supply relevant.
State the pathways involved for autonomic supply.

A

(1) INTRINSIC MUSCLES OF EYE
- ciliary muscles (parasympathetic - sympathetic)
- sphincter pupillae (parasympathetic)
- dilator pupillae (sympathetic)

(2) EXTRINSIC MUSCLES OF EYE
- LR - CN6
- SO - CN4
- SR, IR, MR, IO - CN 3

PARASYMPATHETIC PATHWAY:
CN III - Edinger-Westphal Nc –> ciliary G –> muscle

SYMPATHETIC PATHWAY:
Superior cervical ganglion

19
Q

What axis is parallel to reti muscles?

A

axis of ORBIT

20
Q

Relate the
(1) 3 axis of movement
(2) 3 reference points
(3) 3 types of movement

A

(1) axis - (2) reference point - (3) movements

VERTICAL - PUPIL - elevation & depression
ANTERO-POSTERIOR - 12 O CLOCK - extorsion & intorsion
SIDE-TO-SIDE - PUPIL - abduction & adduction

21
Q

State the function of each extraocular muscle (EOM).

A
  1. medial rectus - adduction
  2. lateral rectus - abduction
  3. inferior oblique - elevation, abduction, extorsion
  4. superior oblique - depression, abduction, intorsion
  5. superior rectus - elevation, adduction, introsion
  6. inferior rectus - depression, adduction, extorsion
22
Q

State the course of the CN III, IV, VI
(1) motor nuclei
(2) intracranial course
(3) extracranial course

A

(1) MOTOR NUCLEI
- exits from brainstem in PCF

(2) INTRACRANIAL COURSE
- crosses over to MCF (cavernous sinus)

(3) EXTRACRANIAL COURSE
- enters orbit by superior orbital fissure

23
Q

CN VI - ABDUCENS N
(1) State the course of the nerve from orign to the EOM
(2) State effects of a lesion to CN VI

A

CN VI - ABDUCENS N

(1) COURSE
- Exits at pontomedullary junction
- Courses in PCF and enters into MCF via cavernous sinus
- Enters orbit by passing through the superior orbital fissure
- Innervates LR (lateral rectus)

(2) LESION TO CN VI
- no ptosis - LPS unaffected
- affected eye will be adducted due to unopposed adduction from paralysis of LR which is involved in abduction
- diplopia occurs on lateral gaze to side of affected eye

24
Q

CN IV - TROCHLEAR N
(1) State the course of the nerve from orign to the EOM
(2) State effects of a lesion to CN IV

A

CN IV - TROCHLEAR N

(1) COURSE
- Exits at midbrain level (inferior colliculis)
- Crosses midline before leaving PCF
- Wraps around the lateral aspect of the cerebral peduncle before entering MCF via cavernous sinus
- Enters orbit by superior orbital fissure
- Innervates SO (superior oblique)

(2) LESION TO CN IV
- no ptosis - LPS unaffected
- affected eye will be elevated due to paralysis of SO which acts to depress, abduct and intort eye
- elevation of affected eye is increased when head is tilted towards the affected side
- diplopia

25
Q

CN III - OCULOMOTOR N
(1) State the course of the nerve from orign to the EOM
(2) State effects of a lesion to CN III

A

CN III - OCULOMOTOR N

(1) COURSE
- Exits at midbrain level (superior colliculis)
- Travels ventrally leaving brainstem between the cerebral peduncles to MCF
- Enters cavernous sinuses
- Exits cranial cavity by superior orbital fissure to orbit
- Innervates IO, SR, IR, MR and LPS

(2) LESION TO CN III
- ptosis - LPS paralysed
- pupil dilated - sphincter pupillae paralysed unable to constrict pupil of affected eye
- affected eye laterally deviated because of unopposed action of LR (lateral rectus) which is not innervated by CN III
- diplopia present in all directions of gaze except lateral gaze of involved side

26
Q

EYE MOVEMENTS:
(1) Vergence = direct the 2 ____ at the same object
(2) Saccades = ____, darting ____ movement from one eye position to another
(3) Smooth pursuit = ____ ____ movement which allow tracking of a moving object
(4) Optokinetic reflex = combination of ____ and ____ to allow tracking of sequential moving targets
(5) Vestibulo-Ocular Reflex (VOR) = ____ smooth pursuit, coordinated by ____ ____ and does not require ____ input

A

EYE MOVEMENTS:
(1) Vergence = direct the 2 FOVEA at the same object
(2) Saccades = QUICK, darting CONJUGATE movement from one eye position to another
(3) Smooth pursuit = SLOWER CONJUGATE movement which allow tracking of a moving object
(4) Optokinetic reflex = combination of SACCADES and SMOOTH PURSUIT to allow tracking of sequential moving targets
(5) Vestibulo-Ocular Reflex (VOR) = REFLEXIVE smooth pursuit, coordinated by REFLEX ARC and does not require CORTICAL input

27
Q

Explain everything you know about the vestibulo-ocular reflex (VOR).

A

VESTIBULO-OCULAR REFLEX (VOR)
- function = stabilise image in retina during rotations of the head
- rotation of head detected –> triggers inhibitory signal to EOM on one side + excitatory signal to muscles on other side –> compensatory movement of the eyes
- pathway = rotational acceleration/deceleration of head –> receptors in semicircular canals –> vestibular nuclei –> ocular motor nuclei –> extraocular muscles

28
Q

State the 4 structures involved in central control of eye movement

A
  1. frontal eye field (FEF)
  2. paramedian pontine reticular formation (PPRF)
  3. superior colliculus
  4. medial longitudinal fasciculus (MLF)
29
Q

State the 3 visual reflexes.

A
  1. light - pupillary light reflex
  2. near objects - accommodation/convergence
  3. pain/emotional state - pupillary dilation
30
Q

Explain the pathway behind pupillary light reflex and consensual light reflex

A
31
Q

Explain the pathway for accommodation (near and far objects)

A

NEAR OBJECTS - require more focus power
- ciliary muscles contract –> suspensory ligaments relax –> lens thickening (parasympathetic)

FAR OBJECTS - require less focus power
- ciliary muscles relax –> suspensory ligaments contract –> lens thinning (sympathetic)

32
Q

Explain the pathway for pupillary dilation (in response to pain and emotion)

A

M2 Anatomy (11 decks)

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