These light signals are transduced in our photoreceptors in the retina, and we actually have 2 types in the human eye, rods and these other types called cones that we'll get to in just a moment. Now, rods are photoreceptors that are capable of detecting lower levels of light. However, they're not capable of detecting the color of light. So these are sort of like our black and white receptors. They're usually found around the outer edges of the retina, and make up more of our peripheral vision. But that's not the case with all organisms. For example, cats tend to have lots of rods in their retinas, and not just on the outer edges, so that they can see better in the dark. Since, you know, they are, or they tend to be nocturnal hunters. Now, rhodopsin is the light-sensitive receptor protein that's actually going to, you know, do the phototransduction in rods, and it's composed of 2 components, retinol and opsin. Retinol is a light-absorbing molecule, it's actually a form of vitamin A, that's why. Another reason it's important to take your vitamins, and opsin is a light-sensitive protein. Now, what's going to happen is retinol will absorb light, and this is going to rearrange its structure and cause a conformational change in opsin. And, basically, it's going to act as a G protein receptor that will lead to the opening of sodium ion channels, and you can see a little model of that here. So, if light, and I'm just gonna use a sort of lightning bolt arrow, if light strikes rhodopsin it's going to cause, retinol to absorb it, and that's going to cause a change in the structure, and here you see they'll actually split, and the opsin will go and, you know ultimately act as a G protein to open this ion channel, and you can see what a rod looks like, sort of big picture wise over here. You know it's not your typical looking nerve cell, it has some weird structures. It does have, you know, a synaptic body, and you know, cell body with the nucleus that's kind of normal looking, but you know, then this stuff all up here is just bonkers. And the rhodopsin is going to actually be stored in this outer segment that has these, enfolded membranes all through here. That's what that pink line is, these enfolded membranes, and that's going to contain the rhodopsin and have it ready to go when light strikes. Now, cones are the photoreceptors that we use for color vision, and unlike rods that can pick up low levels of light, these really function best in bright light. And, they use different pigments to absorb different wavelengths of light. You can actually see a really nice chart right here that shows you the absorption of blue cones, green cones, and red cones, the 3 types of cones we have in our eyes, and you know, maybe if you've ever seen, a projector with the 3 different colored bulbs in it, you might have noticed that those are actually blue, green, and red bulbs. Now, you can also see rods absorption here, kind of in the middle, in the middle of all these. However, I do want you to note that it's going to be, you know picking up light in, you know, a range that has a decent amount of energy. That's the only thing I want to convey there. Now, the fovea is a special part of the retina. It's a little pit in the back, sort of in the center of the retina, and it's going to be packed with cones. And this is so that as light enters the eye, the center of our, you know our field of photoreceptors is going to have tons of these cones, and that's going to be the central point for light to be focused on, and so that's going to give us the clearest possible image, you know, when we translate all those signals in our brain. And you can see a cone structure here. It's not terribly similar to a rod's, but it has that same component of the outer segment with the enfolded membrane that's going to contain the photo pigment, or rather the pigment used for photoreception. However, of course its outer segment is shaped more like a cone, whereas the rod's outer segment is shaped more like a rod, and scientists just aren't very creative when it comes to naming most of the time. So with that, let's go ahead and turn the page.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
46. Sensory Systems
Sensory System
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