wnload Show email Explain the roles sympathetic and parasympathetic nervous syst
ID: 3483250 • Letter: W
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wnload Show email Explain the roles sympathetic and parasympathetic nervous systems with respect omeostatic cardiac functions. 8. What are Schwan cells? Explain the role of Schwan cells in myelin sheath degen-ratic . Explain how memories are created, stored, and recalled, and distinguish among the le consciousness and unconsciousness Specify the components of the afferent and efferent divisions of the nervous system, an 10. explain what is meant by the somatic nervous system. Describe representative examples of cranial reflexes that produce somatic responses to 11. specific stimuli. How are they relevant in clinical diagnosis, explain with one example 12. Explain the process of visual adaptation involving bleaching and regeneration of visual pigments. How is this different in night blindness condition? Explain why receptors respond to specific stimuli, and how the organization of a receptor 13. affects its sensitivity. 14. Summarize the effects of aging on the nervous system and give examples of interactions between the nervous system and other organ systemsExplanation / Answer
Rhodopsin, a biological pigment in the photoreceptors of the retina, which undergo photobleaches in response to light as it gets into the eye Visual Phototransduction starts with the isomerizing of the pigment chromophore from 11-cis to all-trans retinal.Then this pigment divides into free opsin and all-trans retinal. Dark adaptation of both rods and cones requires the regeneration of the visual pigment from opsin and 11-cis retinal.Therefore, the time required for dark adaptation and pigment regeneration is largely determined by the local concentration of 11-cis retinal and the rate at which then delivered to the opsin in the bleached rods.The reduction in calcium ion influx after channel closing causes phosphorylation of metarhodopsin II and catalysis up the cis-retinal to trans-retinal inactivation. Rods are more sensitive to light and so take longer to fully adapt to the change in light. Rods, whose photopigments regenerate more slowly, do not reach their maximum sensitivity for about half an hour.Cones take approximately 9–10 minutes to adapt to the dark.Both these have there different time setups . Sensitivity to light is regulated by changes in intracellular calcium ions and cyclic guanosine monophosphate.
The sensitivity of the rod pathway improves considerably within 5–10 minutes in the dark.
Factor affecting it .
1. Intensity and duration of the pre-adapting light
2 Size and location on the retina
3. Wavelength of Threshold light
4Rhodopsin regeneration
Insufficiency of adaptation most commonly presents as insufficient adaptation to dark environment is called night blindness.
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