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Neuro week 3
| Question | Answer |
|---|---|
| What structure allows us to see centrally? | Fovea, in area of the macula. |
| What are some optical factors affecting visual acuity? | pupil size, clarity of optical media (cataracts), refractive errors (myopia, astigmatism). |
| What is the difference between rods and cones? | Rods - night vision, scotopic, v sensitive, only one types, no colour vision, absent from fovea. Cones - day vision, photopic, less sensitive, three types, colour vision, densest in fovea. |
| Are rods or cones more prevalent? | Rods. |
| What are opsins and what do they bind to? | Protein photopigments that bind to Vitamin A. |
| What happens when retinal binds to an opsin? | Retinal goes from 11-cis to trans retinal, causing rhodopsin to change shape, cascade of events. |
| What do photoreceptors use as their NT? | glutamate |
| What happens to photoreceptors in dark? | cGMP gates a sodium channel causing continuous influx of sodium ions. Depolarisation |
| What happens to photoreceptors in light? | cGMP breaks down to GMP, cGMP no longer gates the sodium channels. Na flow ceases. Hyperpolarisation. |
| What does rhodopsin do in light? | Rhodopsin is activated. Initiates a cascade of events that ultimately leads to the closure of cGMP gated sodium channels. Rh -> transducin -> PDE -> breaks down cGMP. Hyperpolarisation |
| What are the "through" cells in retinal pathway called and what good are they? | Horizontal cells and amacrine cells. At 2 different points we have modulation, allowing us to see differences in visual scene. |
| What are bipolar cells important for? | spatial vision, colour vision. |
| Which cells are the output neurons of retina and release Glutamate? | Ganglion cells. also fire APs. |
| How do ganglion cells respond to light? | by either increasing or decreasing their action potential firing rate. |
| What is the receptive field of a ganglion cell? | The area of the retina that when stimulated with light changes the cell's membrane potential. |
| What is the significance of having many different GCs? | different responses - firing or decreased firing, transient or sustained repsonse. |
| What do horizontal cells do? | provide output onto photoreceptors, using GABA to inhibit (hyperpolarising) |
| What do amacrine cells do? | Inhibit laterally, release glycine and GABA, detect motion |
| Someone with tunnel vision would have what wrong with them? | rods dying, maybe genetic defect in rhodopsin, or proteins involved in phototransduction. |
| What do M ganglion and P ganglion cells do, respectively? | M - have large receptive fields so detect motion, flicker, and analyse gross features. P - small, more numerous, for visual acuity and colour. |
| What is the main target of ganglion cells? | lateral geniculate nucleus (thalamus) |
| What is the 'visual pathway'? | Nasal fibres cross at chiasm. Right visual hemifield viewed by left hemisphere. Left visual hemifield by the right hemisphere. |
| What are the layers of the Lateral Geniculate Nucleus? | Magnocellular 1, 2 (input from M ganglions); Parvocellular 3,4,5,6, (input from P ganglions). |
| Where is the primary visual cortex? | Area 17, occipital lobe, around calcarine fissure. |
| Define retinotopic organisation: | neighbouring cells within the retina project to neighbouring cells in the LGN &Vis cortex. |
| Where does input from LGN go into PVC? | layer 4C |
| Explain orientation selectivity: | neurons respond best to bars moving in a particular orientation, and form orientation columns. This means that if you look at imagine with a single-cell point of view, it's a deconstruction. |
| in which layers does mixing of information from each eye occur? | in layers IVB and layer III (both after layer 4C). M type input into layer 4Ca and P type cells into layer 4Cß. |
| If someone has a problem detecting movement, where is the deformity? | In dorsal stream, area MT - middle temporal lobe is an area specialised for processing object motion. Receives info from cortical areas including V2 & V3. Receives input from cells in layer IVB of primary cortex. (M type & LGN) |
| What does area V4 in the ventral stream do? | Receives input from blob and interblob regions of PVC via V2. Neurons in V4 have large receptive fields for orientation and colour. |
| What is Area IT for? | output of area V4. Neurons here respond to a wide variety of abstract shapes and colours. *visual memory and perception (especially faces). |
| Dorsal stream: ______, ventral stream:______? | Dorsal - where, ventral - what |
| Parameters related to sound? | Wavelength/pitch; amplitude/loudness; waveform/tone. |
| Which structure of the ear have a role in detecting motion in relation to gravity? | vestibular organs/semicicular canals. |
| What is the difference in roles of inner hair cells and outer hair cells? | inner - single row, do most of hearing. Outer aren't sensory but have a motor property --> cause stiffness to change in the organ of corti. (invovled with efferent fibres) |
| Describe the structure of the basilar membrane: | Not homogenous, made of short thick fibres that taper towards the end. |
| Where is there most displacement of the memebrane? | at base where most thick. |
| How do nerves know what frequency the sound is? | Due to location of movement of membrane. Mechanical system of 'spectral decomposition'. |
| Why is K+ used to depolarise hair cells? | Special cells, which K+ concentration higher outside of the cell. |
| briefly describe how difference in intensity is detected in the brainstem: | Whichever ear receives the most stimulation can also shut of the activity in the ascending pathway of the opposite ear/less stimulated ear. |
| Cortical representations are often topographically mapped to the: | contralateral periphery. |
| Cortical territory is unevenly magnified... | usually in proportin to peripheral receptor density |
| cortical territory is _____ | plastic |
Created by:
lmdavis97
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