Final Exam: Chapter 9 Flashcards
Sensory receptors are designed to
respond only to a narrow band of energy—analogous to particles of certain sizes—such as the specific wavelengths of electromagnetic energy that form the basis of our vision.
Receptive field
A specific part of the world to which a sensory receptor organ reponds
Each photoreceptor cell (out of about 120 million) in the eye
points in a slightly different direction and so has a unique receptive field.
Sensory receptors are not —- across the body or its organs. For example, visual receptors are —–. This difference explains why —–
- evenly distributed
- more numerous in the center of our visual field than toward the edges
- our vision is sharper in the center than at the periphery.
All receptors connect to the cortex through
a sequence of intervening neurons
In the visual system, each of our two eyes has
a separate view of the world.
Explain how our seperate views from two eyes combine to produce one view
The information from the two views is combined in the thalamus such that the input from the left side or right side of each field is superimposed to produce two visual fields, one for the left and one for the right. At the next stage in the relay, V1, the brain begins to separate different aspects of the visual input such as shape and color.
Pathway for perception of movement
A second visual pathway that goes from the retina to the superior colliculus and then to the thalamus and cortex.
qualitative visual changes, such as from red to green, can be encoded by (2)
activity in different neurons or even by different levels of discharge in the same neuron
synesthesia (2)
What it is+ ex
- mixing of the senses
- ex: shivering when hearing music has “felt” sound
- hear in colour or identify smells by how the smells sound to them
All mammals have at least — primary cortical are for each sensory system
one
Perception
The subjective experience of sensation- how we interpret what we sense
Sensory receptors are
in terms of energy
energy filters that transduce incoming physical energy into neural activity
Receptor —- determines sensitivity to sensory stimulation.
Density
Our primary sensory experience is
visual
Explain to me how the eye works (4)
orient+bent+whats happens x2
- The cornea and lens of the eye like the lens of a camera, focus light rays to project a backward inverted image on a light-receptive surface
- As light enters the eye, it is bent first by the cornea, travels through pupil then bent again by the lens
- In the retina, light energy initiates neural activity which connects to optic nerve
- optic nerve conveys info from eye to brain
Fovea
Center of retina that has sharpest vision and denseted distribution of photoreceptors for colour
blind spot
AKA the optic disc, where blood vessels enter the eyes and the fibers leading from retinal neurons form the optic nerve leave the eye has no receptors and this forms a blind spot.
What alloes near or far images to be focused on the retina?
A web of muscles that adjust the shape of the eye’s lens to bend to greater or lesser degrees
The eye works correctly only when
sufficient light passes through the lens and is focused on the receptor surface- the retina in the eye
If the focal point of the light falls slightly in front of the receptor surface or slightly behind it….
a refractive error causes objects to appear blurry
Myopia (2)
What happens+eye structure
- Cannot bring distant objects into clear focus because focal point of light falls short of the retina
- Normally round eyeball being elongated
Hyperopia (2)
What happens+ eye structure
- People with hyperopia cannot focus on nearby objects beacyse the focal point of light falls beyonf the retina
- The hyperoptic eyeball is too short
Rod free area are most dense in the
fovea
Layer of cells in the retina
Ganglion cell, bipolar cell, cone/rod
The neurons lie —of the photoreceptor cells, but they — because —-
- in front
- do not prevent incoming light from being absorbed by those receptors
- the neurons are transparent and the photoreceptors are extremely sensitive to light.
retinal neurons are —- to lightand thus are unaffected by light passing through them en route to the light-sensitive photoreceptors.
insensitive
photoreceptors are more densely packed at the—-, in a region known as the
- center of the retina
- fovea
How is the blind spot corrected?
Your optic disc is in a different location in each eye. The optic disc is lateral to the fovea in each eye, which means that it is to the left of the fovea in the left eye and to the right of the fovea in the right eye. Because the two eyes’ visual fields overlap, the right eye can see the left eye’s blind spot and vice versa.
Explain to me the two ways of optic nerve swelling and the consequence (3)
- Intracranial pressure increases due to tumor or brain abscence (infection) can cause optic disc swelling. This is because optic nerve is currounded by CSF.
- Optic neuritis- inflammation of optic nerve
Swollen optic disc usually causes loss of vision
Explain the energy change in vision
Light produces chemical energy
Explain auditory energy changes
Air pressure produces mechanical energy
Somatosensory
mechanical energy
Taste and olfaction energy changes
Chemical molecules
Neural relay for visual receptors
Neural relay for auditory receptors
Neural relay for somatosensory receptors
Sensation
Registration of physical stimuli from the environment by the sensory organs
Rods (5)
shape+abundance+sensitivity+function for+pigment
- longer then cones and cylindrical at one end
- more numerous than cones
- sensitive to low levels of brightness
- function for night vision
- One type of pigment
Cones (4)
Shape+light+mediate+pigment
- Tapered end
- do not respond to dim light but highly responsive to bright light
- mediate colour vision and our ability to see fine detail
- 3 types of pigments
Retina
- light sensitive surface at the back of the eye consists of neurons and photoreceptor cells
the three cone pigments and their range of wavelengths
- short (bluish)
- medium (greenish)
- long (reddish)
**
Photoreceptors are connected to
*Not optic nerve
two layers of retinal neurons
cThe first layer of of retinal neuron photoceptors contains
- bipolar, horizontal, and
amacrine
Horizontal cells link
photorecptors with bipolar cells
Second neural layer that connects with photoreceptors
retinal ganglion cells
amacrine cells link
link bipolar cells with retinal ganglion cells
retinal ganglion cells (RGCs) 2
axons+ sesnsitve
- axons collect in a bundle at the optic disc and leave the eye to form the optic nerve
- sensitive to increased intraocular pressure
Glaucoma
- a group of eye diseases damaging the optic nerve due to high intraocular pressure
Retinitis pigmentosa+ recovery techniques (3)
- Death of retinal (photoreceptors) cells
- Implat proshetic devide in eye to convert light to electrical signals and pass it to RGGs
- Introduce light sensitive ion gated channels to repair the receptors
Retinal ganglion cells fall into 2 major categories:
- magnocellular cells
- parvocellular cells
Magnocellular cell
receive from+ found
- receive info from rods and are sensitive to light but not colour
- Found throughout the retina, includig the periphery where we are sensitive to movement but not colour or fine detail
parvocellular cells (3)
size+ receive input+found largely in
- Smaller
- receive input from cones so are sensitive to colour
- found largely in the region of the fovea where we are sensitive to colour and fine detail
As we follow the ganglion cell axons into the brain, you will see that these two categories of RGCs
maintain their distinctiveness throughout the visual pathways
A tiny subset of retinal ganglion cells (around 1 percent) contain melanopsin, a light-sensitive protein, and thus form a third type of photoreceptor in the eye. These photoreceptors function to
synchronize circadian rhythms, regulate pupil size, and regulate melatonin release.
Crossing the optic chiasm
So we begin with the optic nerves, one exiting from each eye. Just before entering the brain, the optic nerves partly cross from the optic chiasm. About half the fibers from each eye cross in such a way that the left half of each optic nerve goes to the left side of the brain, and the right half goes to the brain’s right side.
the nasal retina
- medial path of each retina crosses to the opposite site in the brain
Temporal retina
The lateral path travels straight back on the same size
Information from the right side of the visual field (blue) moves from –, ending in the —-.
- the two left halves of the retinas
- left hemisphere
What is the 2 main pathways that lead to the visual cortex in the occipital lobe and what do they do? (2)
- The geniculostriate pathway for porecessing the object’s image
- Tectopulvinar pathway for directing rapid eye movements
Geniculostriate system
On entering the brain, the RGC axons separate, forming two distinct pathways. All of the P ganglion axons and some of the M ganglion axons form a pathway called the geniculostriate system. This pathway goes from the retina to the lateral geniculate nucleus (LGN) of the thalamus and then to layer IV of the primary visual cortex in the occipital lobe. From there, the axon pathway divides and one route goes to vision related regions of the parietal lobe and the other to the temporal lobe
P and M layers in the thalamus layer (LG)
Layer 1,2 are magnocellular and 3-6 is parvocellular
Tectopulvinar system
formed by+ runs+bypass
runs from the eye through the midbrain superior colliculus to the pulvinar. The pulvinar sends connections to the parietal and temporal lobes, bypassing the occipital visual areas
Formed by axons of the remaining M gaglion cell
Retinohypothalamic tract
synchronize our clock
dorsal and ventral stream (direction only)
Information from the ipsilateral side (same side in eye) goes to layers —— in the thalamus (LG)
2,3,5
Information from the contralateral side (diffme side in eye) goes to layers —— in the thalamus (LG)
1,4,6
there are — layers in the thalamic LGN as well as the striate cortex
six
Tell me about the P/M cell route from the thalamus to the visual coretx/striate
Layer 4 of the visual cortex is the main afferent (incomming) layer of the cortex. Layer 4 has several layers more prominent the IVCalpha and IVCbeta. LGN layers 1/2 goes to the alpha and layer 3-6 to beta.
cortical columns
strips of occipital cortex
Information from each eye travels to adjacent regions in cortical layer IV. Right: A horizontal plane through striate cortex shows a zebralike effect of alternating left and right eye regions
In the tectopulvinar pathway, the medial pulvinar sends connections to the
parietal lobe
In the tectopulvinar pathway, the lateral pulvinar sends connections to the
temporal lobe
extrastriate (secondary visual) cortex
The remaining ociptal visual areas other then V1 in the occipital lobe.
V2-V5
Neurons in the blobs take part in —; neurons in the interblobs participate in perception of —-.
- color perception
- form and motion
Input from the right visual field goes to the — hemisphere, and input from the left visual field goes to the — hemisphere
- left
- right
Within region V1, then, input arriving from the P cell and M cell pathways of the geniculostriate system is segregated into three separate types of information:
color, form, and motion
All three types of information move from region V1 to the adjoining region —
V2
Region V2 has a pattern of thick and thin stripes intermixed with pale zones. The thick stripes receive input from the —- in region V1; the thin stripes receive input from V1’s —; and the pale zones receive input from V1’s —.
- movementsensitive neurons
- color-sensitive neurons
- form-sensitive neurons
Ventral stream helps with
object recognition
Dorsal stream
control form+motion
Begins in region V1 and flows through V2 to the other occipital areas and finally to the parietal cortex, ending in area PG
Right LGN: input from the— half of each retina
Left LGN: input from the — half of each retina
- right
- left
Information at the top of the visual field stimulates ganglion cells on the — of the retina
bottom
The receptive field of a ganglion cell
the position light falls on+ type
In the receptive field of an RGC with an oncenter and off-surround, a spot of light shining on the center excites the neuron, but a spot of light in the surround inhibits it. When the light in the surround is turned off, firing rate increases briefly—an offset response. In the receptive field of a RCG with an off-center and on-surround, a light shining in both the center and the surround (periphery), light in the center produces inhibition, light on the surround produces excitation, and light across the entire field produces weak inhibition.
Receptive Fields for Simple V1 Cells
a complex cell in V1 shows the same response throughout its
circular receptive field, responding best to bars of light moving at a particular angle. The response is reduced or absent with the bar of light at other orientations.
Receptive Field of a Hypercomplex Cell V1
A hypercomplex cell in V1 responds to a moving bar of light in a particular orientation (e.g., horizontal) anywhere in the excitatory (ON) part of its receptive field. If most of the bar extends into the inhibitory area (OFF), however, the response is inhibited.
A V1 cell responds to—- in a particular orientation on the retina.
- a row of ganglion cells
Receptive Fields for Simple V1 Cells
Simple cells respond to a bar of light in a particular orientation, such as (A) horizontal or (B) oblique. The position of the bar in the visual field is important because the cell either responds (ON) or does not respond (OFF) to light in adjacent visual field regions.
The connectivity pattern in a column is
vertical
Intrinsically Photosensitive
Melanopsin Ganglion Cells (ipRGCs)
●In response to light, ipRGCs are capable of depolarizing without any synaptic input from other photoreceptors (intrinsically photosensitive)
