BIO PPT- External Stimuli

BIO PPT- External Stimuli - I Biological clocks a Circadian...

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Unformatted text preview: I. Biological clocks. a. Circadian rhythms. b. Circannual rhythms. II. Photoperiodism in plants. III. Sensory receptors in animals. a. General function. b. Photoreception. Detection of and Response to External Stimuli I. Biological clocks. w endogenous (internal). w genetic basis. w entrained (set) by exogenous signals. Rhythms w a. circadian w b. circannual a. circadian rhythms. w in plants, animals, and protists. w daily fluctuations. w most common entrainer (cue) is light. Earth's rotation 24hour period Constant environment: continuous light or dark w circadian rhythms deviate from a 24hour period. w freerunning period. Nocturnal flying squirrel b. circannual rhythms. migration of golden plover II. Photoperiodism in plants. w Photoperiodism = a physiological response to daylength. w Example in plants is flowering. Fig 39.20 Critical night length fig 39.22 3 sensations: nervous impulses III. Sensory receptors in animals. conveyed to the brain. 3 perceptions: the brain's interpretations of sensations. a. general function 3 respond to stimuli, e.g., heat, light, and pressure. 3 convert the energy of stimuli into nervous impulses. stimulus impulse 5 component processes: 1. reception. 2. transduction. 3. amplification. 4. transmission. 5. integration. 2 major categories 3 exteroreceptors: receive information from the outside world. 3 interoreceptors: provide information about the body's internal environment. Crossfiber patterning: degree of receptor activation can be very sensitive to one stimulus less sensitive to another Physiological adaptation: continued presence of same stimulus leads to decreased receptor activity Receptor adaptation to strength of stimuli b. Photoreception. Light-orienting eye (fig 49.16) imageforming eye invertebrates imageforming eye in invertebrates compound eye 49.17 imageforming eye in vertebrates 49.18 Hearing and equilibrium fig 49.8 ...
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