Prelim 2 Questions 1-10 Flashcards
What is the difference between sensation and perception?
What we perceive depends on assumptions our visual system makes and past learning
What is the visual transduction pathway without light?
Visual receptor cells (rods and cones) release neurotransmitters tonically (continuously) onto bipolar cells when NOT stimulated by light.
What is the visual transduction pathway with light?
Light stimulates rhodopsin (photopigment molecule) that causes a second messenger cascade resulting in Na+ channels closing and the receptor cells becoming hyper polarized. Stimulation by light source is indicated by stopping or reducing neurotransmitter release
What is the rod photoreceptor pathway?
Light acts on rhodopsin which changes shape of the overall molecule (retinal) causing 500 molecules of G protein transducin to be made. Each molecule of transducin causes GTP molecules to replace GDP. GTP complex then dissociates from retinal molecules and activates phosphodiesterase which causes active cGMP to turn into inactive GMP. cGMP was keeping Na+ channels open so Na+ channels close, so no positive ions coming in, hyper polarizes
Give an example of why adaptation is critical for vision (2)
Adaptation makes it possible for the retina to process light intensities that differ by more than a billion times.
Dark Adaptation- it takes time for photopigment to recombine after being split by light. The levels go up in the dark. If you want to be as sensitive as possible to dark, have to be in dark for 20-30 minutes to allow opsins to get to lowest level possible in rods
Why in peripheral vision do you have trouble coming up with details?
Cones help come up with details. In the retina, on the outside levels there are low compositions of cones and high compositions of rods and going inward there are high compositions of cones and low compositions of rods. In the middle the densely packed cones have high activity and good details, on the outsides the fewer cones and more rods cause low activity and good dim light. Trouble coming up with details.
Explain lateral inhibition.
Happens through horizontal cells. The first set of neurons send axonal projections to neighbor cells saying “shut up, I see light you don’t”. There is a whole network of inhibiting connections going side by side throughout the retina, each receptor is excited by light but inhibiting its neighbors through horizontal cells.
Explain the pathway between light, cones, and bipolar cells.
Light causes cones to be hyperpolarized and decreases the amount of glutamate that it is releasing. The released glutamate has opposite effects on the two kinds of bipolar cells because they have different glutamate receptors. Causes decreased inhibition on one bipolar cell which results in increased release of the NT glutamate at the synapse. This causes increases firing rate of (APs) to brain
For the other bipolar cells, light turns them off, hyperpolarized, decrease transmitter release, decrease APs
What is the difference between predator and prey receptive fields?
Predators have front eyes because they want to see what they are attacking, the majority of their receptive field is both eyes in the front and a little of side for each individual eye. Prey wants to be aware of movement all around them. They have side eyes and the majority of their receptive field is on the periphery.
Explain the relationship between visual field image, retinal image, and which side of the brain they go to.
The visual field is opposite to brain parts. Right visual field goes to the left brain and the left visual field goes to the right brain. The retinal image on the other hand is an inverted and reversed image of the visual field. Therefore the right half of the retina goes to the right side of the brain and the left half of the retina goes to the left side of the brain
Explain the relationship between cortical cells and higher order cells and what affects the APs of complex cells
Simple cortical cells are what make up the higher order cells. The simple cortical cells one after another are feed into a higher order cell, higher order neuron only has an AP if it gets sequential activation from one line after another (of simple cortical cells) or from a line that is moving not just standing still. The complex cells hold a larger location in the visual space sensitive to motion. Orientation and movement affect complex cell APs, if they have a line of correct orientation moving in the correct direction, lots of APs. If not correct orientation or not correct movement, won’t get lots of APs
