9 Vision I Vision I2 Light Vision I3 ✓ Electromagnetic radiation with wavelengths in range of 400 – 700 nm https://upload.wikimedia.org/wikipedia/commons/f/f1/EM_spectrum.svg Color mixing Vision I4 http://www.indiana.edu/~jkmedia/classes/images/colormodes.jpg Photoreceptive organ Vision I5 ✓Light detection ✓Image formation Light detection Vision I6 • Circadian activity – Both prokaryotes and eukaryotes – Day/night cycle is the most influential and the most stable biorhythm – Oscillation with a period of aprox. 24 hours even without signals from environment – Environmental signals synchronize circadian activity • Seasonal activity https://www.pointsdevue.com/article/good-blue-and-chronobiology-light-and-non-visual-functions Light detection Vision I7 • Circadian activity – Both prokaryotes and eukaryotes – Day/night cycle is the most influential and the most stable biorhythm – Oscillation with a period of aprox. 24 hours even without signals from environment – Environmental signals synchronize circadian activity • Seasonal activity https://www.pointsdevue.com/article/good-blue-and-chronobiology-light-and-non-visual-functions Light detection Vision I8 • Circadian activity – Both prokaryotes and eukaryotes – Day/night cycle is the most influential and the most stable biorhythm – Oscillation with a period of aprox. 24 hours even without signals from environment – Environmental signals synchronize circadian activity • Seasonal activity https://www.pointsdevue.com/article/good-blue-and-chronobiology-light-and-non-visual-functions Circadian activity Vision I9 https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Biological_clock_human.svg/2000px-Biological_clock_human.svg.png Biological clock Vision I10 • Cellular level – Group of proteins rhythmically expressed creating interconnected feedback loops (about 24hours) • Peripheral Clock protein expression • Tissue level – Peripheral oscillators – Adrenal gland, lung, liver, pancreas, skin – Influenced by neurohumoral factors and also by light • Central pacemaker – Hypothalamus (nucleus suprachiasmaticus) • Central clock protein expression • Information about illumination from retina (specialized ganglion cells) – synchronization of central pacemaker ➢ Pineal gland - melatonin ➢ Autonomnic nervous system – adreanl gland - cortisol http://slideplayer.com/slide/7013288/ Biological clock Vision I11 • Cellular level – Group of proteins rhythmically expressed creating interconnected feedback loops (about 24hours) • Peripheral Clock protein expression • Tissue level – Peripheral oscillators – Adrenal gland, lung, liver, pancreas, skin – Influenced by neurohumoral factors and also by light • Central pacemaker – Hypothalamus (nucleus suprachiasmaticus) • Central clock protein expression • Information about illumination from retina (specialized ganglion cells) – synchronization of central pacemaker ➢ Pineal gland - melatonin ➢ Autonomnic nervous system – adreanl gland - cortisol http://slideplayer.com/slide/7013288/ Biological clock Vision I12 • Cellular level – Group of proteins rhythmically expressed creating interconnected feedback loops (about 24hours) • Peripheral Clock protein expression • Tissue level – Peripheral oscillators – Adrenal gland, lung, liver, pancreas, skin – Influenced by neurohumoral factors and also by light • Central pacemaker – Hypothalamus (nucleus suprachiasmaticus) • Central clock protein expression • Information about illumination from retina (specialized ganglion cells) – synchronization of central pacemaker ➢ Pineal gland - melatonin ➢ Autonomnic nervous system – adreanl gland - cortisol http://slideplayer.com/slide/7013288/ Biological clock Vision I13 • Cellular level – Group of proteins rhythmically expressed creating interconnected feedback loops (about 24hours) • Peripheral Clock protein expression • Tissue level – Peripheral oscillators – Adrenal gland, lung, liver, pancreas, skin – Influenced by neurohumoral factors and also by light • Central pacemaker – Hypothalamus (nucleus suprachiasmaticus) • Central clock protein expression • Information about illumination from retina (specialized ganglion cells) – synchronization of central pacemaker ➢ Pineal gland - melatonin ➢ Autonomnic nervous system – adreanl gland - cortisol http://slideplayer.com/slide/7013288/ Central pacemaker synchronization Vision I14 Wahl S, Engelhardt M, Schaupp P, Lappe C, Ivanov IV. The inner clock-Blue light sets the human rhythm. J Biophotonics. 2019; e201900102. (1% of ganglion cells) Image formation Vision I15 https://www.fotoskoda.cz/images/manufacturers/camera_obscura.png Image formation Vision I16 https://www.fotoskoda.cz/images/manufacturers/camera_obscura.png http://de.academic.ru/pictures/meyers/large/030717c.jpg Image formation Vision I17 http://www.slideshare.net/CsillaEgri/presentations Image formation Vision I18 ➢ Shape ➢ Color ➢ Localization ➢ Movement ➢ Image interpretation - CNS http://www.slideshare.net/CsillaEgri/presentations Image formation Vision I19 http://www.slideshare.net/drpsdeb/presentations Vision I20 http://www.slideshare.net/drpsdeb/presentations Photopigment of rods Vision I21 Rhodopsin • Opsin – G – protein • Retinal – Retinol aldehyde (vit. A) http://www.slideshare.net/CsillaEgri/presentations Photopigments of cones Vision I 22 • 3 types of cones - 3 types of photopigment – Blue(420nm) – Green (530nm) – Red (560nm) • Color is interpreted by ratio of cone stimulation – Orange (580nm) • Blue: 0% • Green: 42% • Red:99% Rod http://www.slideshare.net/CsillaEgri/presentations Photopigments of cones Vision I 23 • 3 types of cones - 3 types of photopigment – Blue(420nm) – Green (530nm) – Red (560nm) • Color is interpreted by ratio of cone stimulation – Orange (580nm) • Blue: 0% • Green: 42% • Red:99% Rod http://www.slideshare.net/CsillaEgri/presentations Phototransduction Vision I 24 • Photoreceptors continuously release neurotransmitter (glutamate) in darkness • In response to the light, the membrane hyperpolarizes and release less neurotransmitter http://www.slideshare.net/drpsdeb/presentations Phototransduction - darkness Vision I 25 • Guanylate cyklase – cGMP • cGMP-gated Na+ channels – Na+ influx • Voltage gated Ca2+ channels – Release of glutamate • The balance is kept by – K+ efflux – Na+/K+ exchanger • Resting membrane potential: – 40mV http://www.slideshare.net/drpsdeb/presentations Phototransduction - light Vision I 26 • Photon is absorbed by photopigment • Isomerization of retinal • Cascade of reactions result in cGMP phosphodiesterase – cGMP levels decreased • Deactivation of cGMP gated Na+ channels • K+ efflux continues • Membrane hyperpolarization – Deactivation of voltage Ca2+ channels – Decrease in glutamate release http://www.slideshare.net/drpsdeb/presentations Adaptation to the light/darkness Vision I 27 • Optic adaptation – Constriction of pupils • Photoreceptor adaptation – Ca2+ inhibits guanylate cyclase – cGMP gated Na+ channels... – Darkness • Higher Ca2+ levels → cGMP decreased → membrane more hyperpolarized → „higher sensitivity to light“ – Light • Lower Ca2+ levels → cGMP increased → membrane more depolraized → „lower senzitivity to light“ http://www.slidesare.net/drpsdeb/presentations 77. The basic physiology of visual system – light detection vs. image formation, circadian rhythms Vision I28 • Brief characterization of light • Light detection (LD) vs. image formation (IF) • LD - almost all the living organisms - one of the oldest functions - mainly for circadian activity synchronization • IF - Functional overview of eye anatomy (camera obscura with a lens) • Circadian rhythms • Definition + importance • Biological clock (cellular level, tissue level, central pacemaker) • Brief overview of circadian rhytms in humans (“active”hours, “rest” hours, physiological changes, associated hormone oscilations…) 78. The basic physiology of visual system – rods and cones function, on/off receptive field, nervus opticus vs. tractus opticus Vision I29 • Rods and cons function • Characterization and comparison • Phototransduction mechanism and adaptation • Brief overview of retina organization (retina process receptor potential – analog, AP is generated in ganglion cells) • Receptive field organization • On/off receptive fields • Magnocellular system (BW) • Parvocellular system (Color) • Nervus opticus vs. tractus opticus • Projections from tractus opticus (Main centers in the brain involved in visual signals processing)