6.2 Systems in the NS, Sensory I - VISUAL SYSTEM and upper cranial nerves (HARC) Flashcards
the WALLS of the EYEBALL are DIVIDED into 3 LAYERS:
- OUTER FIBROUS
- MIDDLE VASCULAR
- INNER (RETINA)
OUTER FIBROUS LAYER of the eye consists of which parts:
SCLERA (the WHITE of the eye)
CORNEA
the SCLERE covers which parts of the EYEBALL
POSTERIOR and LATERAL PARTS
5/6th of eyeball
Cornea is CONTINUOUS with it ANTERIORLY
(1/6th)
what is the SCLERA of the Outer Fibrous layer PIERCED by
the OPTIC NERVE
Colour of SCLERA and CORNEA
SCLERA - OPAQUE, WHITE (dense connective tissue)
CORNEA - TRANSPARENT
how is BLOOD SUPPLY to the CORNEA
NONE
- AVASCULAR
receives its nutrients by diffusion
what is the CORNEA RESPONSIBLE FOR
REFRACTION OF LIGHT entering the eye
parts of the MIDDLE VASCULAR LAYER of the eyeball
- CHOROID
- CILLIARY BODY -> CILLIARY MUSCLE, CILLIARY PROCESS
- IRIS
what is LOOSELY ATTACHED to the CHOROID
SCLERA of the outer fibrous layer
CHOROID is FIRMLY ATTACHED to the..
RETINA
CHOROID is composed of 2 LAYERS
outer:
inner:
OUTER: HIGHLY PIGMENTED layer that ABSORBS LIGHT
INNER: HIGHLY VASCULAR LAYER
CILLIARY BODY is CONTINUOUS with the CHOROID and how is it around the EYEBALL
forms a COMPLETE RING AROUND it
what is the CILIARY MUSLCE part of the CILIARY BODY
SMOOTH MUSCLE (Longitudinal, Circular, Radial) that are controlled by PARASYMPATHETICS of the OCCULOMOTOR
- ATTACHES to the LENS via the CILLIARY PROCESS
what is the CILIARY PROCESS part of the CILIARY BODY
- what is it attached to
it is ATTACHED to ZONAL FIBRES suspending / attached to the LENS
what does CONTRACTION of the CILIARY MUSCLE do
DECREASES SIZE of the RING
-> REDUCES TENSION on the LENS
which is more RELAXED for NEAR VISION
CILIARY MUSCLE CONTROLLED by which NERVOUS SYSTEM and which NERVE
PARASYMPATHETIC NERVOUS SYSTEM
by OCCULOMOTOR
CONTRACTION of CILIARY MUSCLE has what EFFECT on the LENS
RELAXATION
IRIS is the COLOURED PART of the EYE.
it is the CIRCULAR STRUCTURE that PROJECTS from the…
CILIARY BODY
CENTRAL OPENING of the IRIS is the..
PUPIL
IRIS consists of which SMOOTH MUSCLES:
- SPHINCTER PUPILLAE
- DILATOR PUPILLAE
which IRIS SMOOTH MUSCLE CONSTRICTS the PUPILLARY OPENING (smaller pupil)
SPHINCTER PUPILLAE
- PARASYMPATHETIC OCCULOMOTOR
which IRIS SMOOTH MUSCLE has RADIALLY ARRANGED FIBRES that DILATE the PUPIL
DILATOR PUPILLAE
- SYMPATHETIC
which LAYER of the CHOROID (middle vascular) is HIGHLY VASCULAR
INNER
how are FIBRES of the DILATOR PUPILLAE ARRANGED
RADIALLY
DILATION of PUPIL is via which NERVOUS SYSTEM
SYMPATHETIC
CONSTRICTION of PUPIL is via which NERVOUS SYSTEM
PARASYMPATHETIC
what is the INNER LAYER of the EYEBALL
the RETINA
RETINA has OUTER and INNER LAYERS:
OUTER PIGMENTED layer
INNER NEURAL layer
which LAYER of the RETINA is FIRMLY ATTACHED to the CHOROID
OUTER PIGMENTED LAYER
PIGMENTED (outer) LAYER of RETINA CONTINUES …. over the INNER SURFACE of the…
ANTERIORLY
OVER inner surface of the CILIARY BODY & IRIS
- ORA SERRATA (NON-VISUAL PART)
NEURAL (inner) LAYER of RETINA SUBDIVIDES into NEURAL COMPONENTS / 3 LAYERS of CELLS:
- PHOTORECEPTOR CELL LAYER (RODS & CONES)
- GANGLION CELL LAYER
- BIPOLAR CELL LAYER
RETINA - INNER NEURAL layer is ATTACHED to the OUTER PIGMENTED layer AROUND THE..
OPTIC NERVE & ORA SERRATA
what is the ORA SERRATA
the NON-VISUAL end part of RETINA
as light does’t hit there
- JUNCTION between the RETINA and CILIARY BODY
PHOTORECEPTORS (RODS&CONES) are important to ORIENTATE the PATH OF LIGHT and the PATH OF ACTIVATION
they have SPECIALISED NEURONS that are capable of..
PHOTOTRANSDUCTION
- CONVERSION of LIGHT into a CHANGE IN ELECTRCAL POTENTIAL across the cell membrane
(convert light into electrical signal)
as LIGHT falls o n the RETINA it ACTIVATES the RODS & CONES. this ACTIVATION SPREADS to the… to ….
BIPOLAR CELLS
to the GANGLION CELLS
GANGLION CELLS CONVERGE to FORM the..
OPTIC NERVE
are there MORE RODS or MORE CONES?
MORE RODS - 130 million
cones: 7 MILLION
Which PHOTORECEPTOR is for COLOUR VISION
CONES
RODS: BLACK & WHTIE
Which PHOTORECEPTOR is for COLOUR VISION
CONES
RODS: BLACK & WHITE
which PHOTORECEPTOR are responsible for VISION at LOW LIGHT / can still ACTIVATE at LOW LIGHT LEVELS
- SCOTOPIC VISION
RODS
which PHOTORECEPTOR has HIGH SPACIAL ACUITY (ability to discriminate 2 stimuli that are close together) therefore more FOCUSED
CONES
which PHOTORECEPTOR has 3 TYPES: SHORT, MIDDLE, LONG-WAVELENGTH SENSITIVE
CONES
characteristics of RODS
- 130 million, more ABUNDANT
- LOW LIGHT LEVELS vision (scotopic vision)
- BLACK & WHITE, do not mediate colour vision
- LOW SPATIAL ACUITY
characteristics of CONES
- 7 million (less)
- ACTIVE at HIGHER LIGHT LEVELS (PHOTOPIC VISION)
- capable of COLOUR vision
- HIGH SPATIAL ACUITY
- 3 types: SHORT, MIDDLE, LONG
WAVELENGTH SENSITIVE
what does LIGHT HIT FIRST, BEFORE RODS/CONES
PIGMENT EPITHELIUM
HORIZONTAL CELLS can be found BETWEEN BIPOLAR CELLS
what are they responsible for
RECEIVE INPUT from multiple PHOTORECEPTOR cells and MAKE ADJUSTMENTS (whether want more activation or not) and REGULATE ACTIVITY in the photo receptor cells
AMACRINE CELLS RECEIVE SIGNALS from..
BIPOLAR CELS
what do AMACRINE CELLS do after they RECEIVE SIGNALS from Bipolar cells
involved in REGULATION and INTEGRATION of ACTIVTY in BIPOLAR & GANGLION CELS
HORIZONTAL CELLS RECEIVE INPUT from which cells
PHOTORECEPTOR CELLS
RETINAL GANGLION CELLS have 2 FIELDS shaped as 2 CONCENTRIC CIRCLES: CENTRE & SURROUND
what are the 2 CATEGORIES for them
- ON CENTRE, OFF SURROUND
- OFF CENTRE, ON SURROUND
(if centre switched on then surround is switched off, vice versa)
if LIGHT hits on the CENTRE ONLY of an ON CENTRE, OFF SURROUND ganglion cell,
Is it inhibited or activated
ACTIVATED
- FIRES RAPIDLY
if LIGHT hits on the CENTRE ONLY of an OFF CENTRE, ON SURROUND ganglion cell,
Is it inhibited or activated
INHIBITED
ganglion cell does not fire
if LIGHT hits on the SURROUND ONLY of an ON CENTRE, OFF SURROUND ganglion cell,
Is it inhibited or activated
INHIBITED
if LIGHT hits on the SURROUND ONLY of an OFF CENTRE, ON SURROUND ganglion cell,
Is it inhibited or activated
ACTIVATED
- Fires rapidly
what happens if LIGHT spot Expands and hits BOTH the CENTRE and SURROUND (off or on)
WEAK RESPONSE
- low frequency firing / SLOW
how is FIRING of the GANGLION CELL when there is NO LIGHT Stimulus
eg on centre, off surround
at a BASELINE RATE
if a LIGHT SPOT coincides with an ON CENTRE how is the FIRING RATE
MAXIMUM
there are 2 TYPES of BIPOLARCELLS that SIGNAL to RETINAL GANGLION CELLS:
- OFF BIPOLAR CELLS
- ON BIPOLAR CELLS
an OFF BIPLOAR CELL does what to the stimulus and what happens to the cell by light
PRESERVES the sign of the cone / allows stimulus to pass on as it is
and is HYPERPOLARISED
an ON BIPLOAR CELL does what to the stimulus and what happens to the cell by light
REVERSES the sign of the cone
and is DEPOLARISED by light
HORIZONTAL CELLS receive signals from Photoreceptors and send … FEEDBACK
INHIBITORY FEEDBACK
what is the Point on the RETINA called where the OPTIC NERVE LEAVES it
OPTIC DISC
- branches from the retinal artery spread from here
what structure is the BLIND SPOT and why
the OPTIC DISC as it has NO LIGHT SENSITIVE RECEPTOR CELLS
what is the name of the YELLOWISH COLOURATION and the THINNEST PART of the RETINA
MACULA LUTEA
CENTRAL DEPRESSION of the MACULA LUTEA (on retina) is called the..
FOVEA CENTRALIS
where are ALMOST ALL and the CONES CONTAINED
in the MACULA LUTEA
- therefore has HIGHEST LEVEL OF ACUITY
(has very few Rods)
what is the name of the WHITE OF THE EYE
the SCLERA
(OUTER FIBROUS LAYER of eye)
the CHOROID is in which part of the EYE
VASCULAR (middle) LAYER
CONTRACTION of the CILIARY MUSCLE allows for far or near vision?
NEAR VISION
- Reduces tension of the Lens so more Relaxed
what structure of the eye is PIERCED by the OPTIC NERVE
SCLERA
(outer fibrous)
which IRIS MUSCLE is under SYMPATHETIC CONTROL
DILATOR PUPILLAE
which CELLS Make ADJUSTMENTS to input from PHOTORECEPTOR CELLS and REGULATE their ACTIVITY
HORIZONTAL CELLS
where is the HIGHEST LEVEL of SPATIAL ACUITY in the eye
MACULA LUTEA of the Retina
which part of the RETINA has NO LIGHT SENSITIVE RECEPTOR CELLS
OPTIC DISC
- BLIND SPOT
which cells allow PHOTOPIC VISION
CONES
- activate at HIGH LIGHT LEVELS
which Cells cause INHIBITORY FEEDBACK for Photoreceptor cells
HORIZONTAL CELLS
LIGHT PATHWAY as it enters the eye:
- PIGMENT EPITHELIUM
- RODS / CONES
- BIPOLAR CELLS
- GANGLION CELLS
- Optic Nerve Fibres
- OPTIC NERVE
- OPTIC CHIASM
- OPTIC TRACT
-> LATERAL GENICULATE BODY (THALAMUS)
-> OPTIC RADIATION
-> OCCIPITAL LOBE primary/secondary visual cortex
what has an OUTER PIGMENTED LAYER and INNER NEURAL LAYER
The RETINA
what part of the eye is AVASCULAR
CORNEA
CILLIAR PROCESS attaches to which FIBRES suspending the LENS
ZONAL FIBRES
which IRIS MUSCLE is under PARASYMPATHETIC CONTROL
SPHINCTER PUPILLAE
- CONSTRICTS eyelids
which cells are involved in the REGULATION and INTEGRATION of ACTIVITY in BIPOLAR AND GANGLION CELLS
AMACRINE CELLS
which BIPOLAR CELLS are HYPERPOLARISED by LIGHT
those switched OFF
what is the FOVEA CENTREALIS
CENTRAL DEPRESSION in the MACULA LUTEA of the Retina
what is the THINNEST AREA of the RETINA
MACULA LUTEA
which BIPOLAR CELLS are DEPOLARISED by LIGHT
those switched ON
- REVERSE the sign of the cone
VISUAL AXIS of eye
- AXIS of each ORBIT FACES which DIRECTION
ANTEROLATERALLY
how many AXIS of the EYE
3
the A-P AXIS (anterior-posterior) allows what movement
LATERAL-MEDIAL ROTATION
the TRANSVERSE AXIS allows what movement
ELEVATION - DEPRESSION
(facing upwards/downwards)
the VERTICAL AXIS allows what movement
ABDUCTION-ADDUCTION
which EYE AXIS is used for LOOKING UP / DOWN
TRANSVERSE AXIS
- Elevation - Depression
which EYE AXIS is used for ABDUCTION and ADDUCTION
VERTICAL AXIS
which EYE AXIS allows for LATERAL-MEDIAL ROTATION
A-P AXIS
