chapter 9 part 1 Flashcards by Melinda Herceg

What do sensory receptors do?

transduce (convert) sensory energy (light) into neural signals

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What is the receptive field of a sensory receptor?

Specific part of the world to which a sensory receptor organ responds

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What does greater receptor density mean?

greater sensory sensitivities

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What are neural relays?

neuronal pathways that aid processing and integration of sensory info

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Describe the neural relay for visual system

Visual receptors –> thalamus –> cerebral cortex

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Describe the neural relay for auditory system

Auditory –> hindbrain –?>midbrain –> thalamus –> cerebral cortex

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Describe the neural relay for the somatosensory system

somatosensory receptors –> spinal cord –> brain stem –> thalamus –> cerebral cortex

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What is sensation?

Registration of physical stimuli from the environment by the sensory organs

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What is perception?

Subjective interpretation of sensations by the brain - influenced by context, emotion, experience

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What is the range for visible light?

400-700 nm

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What is the retina?

Light sensitive surface at the back of the eye that consists of neurons and photoreceptors

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What is the fovea?

Region at the center of the retina that is specialized for high acuity

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What is the orientation of the image on the eye?

Flipped upside down and reversed left to right

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Does the flipped orientation continue to V1?

Yes

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What does the fovea look like?

No rods and it is depressed so light can hit photoreceptors directly

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What size would letters have to be for us to see them in the center of vision vs the periphery?

Small in center and large in the periphery

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What is the blindspot?

Region of the retina where axons forming the optic nerve leave the eye and where blood vessels enter and leave

Has no photoreceptors

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What is another word for blind spot?

Optic disc

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Why don’t we notice our blindspot?

It is to the left of the fovea in the left eye and to the right of the fovea in the right eye so they can make up some of the missing info

Brain makes up for it

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How many rods and cones do we have

120 million rods and 6 million cones

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What are the characteristics of rods?

Sensitive to low levels of light
Used mainly for night vision
One type of pigment only
More numerous than cones
No rods in fovea

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What are the characteristics of cones?

Highly responsive to bright light
Specialized for colour and high visual acuity
Three types of pigments
Concentrated in fovea

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What are the three colours of cone pigments?

Blue (short), green (medium), rd (long)

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What is the distribution of different cone pigments?

equal numbers of red and green but fewer blue cones

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Where does rod sensitivity fall on the curve?

Between S and M cones

What do we use to test our photoreceptors?

Ishihara plates

What do photoreceptors do?

Transduce light into neural signa;s

What is the order of neurons in the retina?

Photoreceptors -- horizontal --- bipolar --- amacrine --- retinal ganglion cells (RGC)

What is the function of the horizontal cells?

links photoreceptors and bipolar cells

What is the function of bipolar cells?

receives input from photoreceptors

What is the function of amacrine cells?

Links bipolar and ganglion cells

What is the function of retinal ganglion cells?

axons give rise to optic nerve

What do Muller cells do?

help retina with homeostasis

What are the two main types of ganglion cells?

Magnocellular cells and parvocellular cells

Where do M-cells receive input from and what are they sensitive to? What size are they?

primarily from rods sensitive to light and moving stimuli (processing movement) Large

Where do P-cells receive stimuli from and what are they sensitive to? What size are they?

Primarily from cones Sensitive to colour and form Small

What is the third type of RGC?

Melanopsin retinal ganglion cells

What are melanopsin RGC for?

Sensitive to blue light and are for the sleep/wake cycle

Where does info from each visual field end up in each eye?

Right visual field = left side of each eye Left visual field = left side of each eye

Does each eye get info from both visual fields?

Yes

Where do the left and right visual fields end up in the brain?

Left visual field = right hemisphere Right visual field = left hemisphere

What are the inside and outerside of each eye called?

nasal = inside and temporal = outside

What is the optic chiasm?

Junction of the optic nerves from each eye

What happens at the optic chiasm?

Axons from nasal (inside) half of retina cross over Axons from temporal half remain on the same side

What are the three routes of of visual info in the brain?

Retinohypothalamic tract The Geniculostriate pathway Tectopulvinar pathway

Where does the retinohypothalamic tract synapse?

Synapses in the suprachiasmatic nucleus (in hypothalamus)

What is the retinohypothalamic tract for?

Role in circadian rhythms and pupillary reflex

What RGC cells send info to the geniculostriate system?

Mostly P cells and some M cells

What are the steps in the geniculostriate system?

LGN --> striate cortex (V1) to to other visual cortices

Which RGC send info to the tectopulvinar system?

M -cells

What are the steps in the tectopulvinar system?

Superior colliculus (midbrain) -- pulvinar (thalamus) -- other visual cortical areas

What is the tectopulvinar pathway for?

Detecting movement and location and orientating spatial attention

Which cells send their info to the retinohypothalamic tract?

Melanopsin RGC

How is information from the sides of each eye separated in the LGN?

Right LGN -- gets input from the right half of each eye Left LGN -- info from the left half of each eye

Do M and P RGC send separate projections to the LGN in the geniculostriate pathway?

Yes

Does the segregation of the LGN continue in V1

Yes

What are other names for the primary visual cortex?

V1, striate cortex

Which layer of the striate cortex does the LGN send its info to?

Layer 4

What do the two sub layers of layer 4 received info from?

4b --> layers 3-6 4a-- layers 1 and 2 of LGN

What are the two visual pathways from the striate cortex?

Dorsal visual stream (how) --> projects to parietal lobe Ventral visual stream (what) --> projects to temporal lobe

What does the tectopuvinar pathway do? Simple

provides info about location (where)

What are the two areas of the pulvinar (thalamus)?

Medial pulvinar Lateral pulvinar

Where does the medial pulvinar sends its connections to?

parietal lobe

Where does the lateral pulvinar send its connections to?

Temporal lobe

What is the disorder that the tectopulvinar pathway allows for?

Blind slight

What is blind sight?

People report not seeing anything due to damage to V1 but will avoid things when they walk They can use this pathway because it bypasses V1