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 senzitivityto light“ http://www.slidesare.net/drpsdeb/presentations Rod/Conemembrane Depol.Hyperpol. + - Treshold Effect Darkness No light signal Tonic depolarization Glutamate release Bipolar cell - nothing Signalization Light signal Transient hyperpolarization Glutamate not released Bipolar cell depolarization Adaptation to darkness Membrane tonically hyperpolarized Adaptation to light Higher sensitivity to ligh Membrane tonically Depolarized more Lower sensitivity to ligh 77. The basic physiology of visual system – light detection vs. image formation, circadian rhythms Vision I29 • 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 I30 • 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)