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Oct 20 2009 - Sensory Ecology BIEB 132 Lecture 8 I II III...

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Sensory ecology p. 1 of 7 Sensory Ecology BIEB 132: Lecture 8, 10/20/09 I. Sensory systems II. Mechanoreception III. Chemoreception IV. Electroreception V. Vision Reading: Levinton p. 52-53, 103-104 I. Sensory systems A. Types 1. 5 classic human senses – hearing, vision, taste, smell, touch 2. Sensory cues – sound, light, chemicals, pressure, position, heat, gravity, acceleration, electrical and magnetic fields B. Common themes of sensory systems 1. Detection – transduction, change from one energy form to another a) e.g., photoreceptor, membrane protein (GTP-binding protein), ion channel transduces the stimulus into a chemical or electrical signal 2. Amplification – receptor boosts signal during transduction process 3. Processing of signal – further filtering a) e.g., afferent nerves, second messengers b) higher order (brain) processing 4. Behavioral or physiological response 5. Adaptation to maintained stimulus – becomes less sensitive C. Sensory systems are not optimized 1. Sensory systems are not as good as they can be. They are as good as they need to be. II. Mechanoreception A. Detect gravity, pressure, water currents, sound and vibration (oscillatory motion of fluid particles) B. Acoustic energy transmitted very efficiently through water, persists over long range C. Mechanoreceptors – hair cells 1. Composed of many stereocilia (actin) and one kinocilium (microtubules) 2. Tip movement of only 0.1 nm sufficient to stimulate cells 3. Movement causes receptor potential based on flux of calcium into cells Figures: SEM of hair cells, Hair cell diagram
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Sensory ecology p. 2 of 7 4. Rapid transduction process –respond within 1-2 µ sec 5. Rapid adaptation – after 1 msec of deflection D. Statocysts – detecting gravity and acceleration in invertebrates 1. Statocyst – consists of statolith in contact with hair cells 2. Statolith usually consists of calcium carbonate, sand grains Figures: Idealized statocyst, Evolution of statocysts, Cnidarian statocyst, Squid statocysts, Statocysts in deep-sea shrimp Sergestes E. – Fish mechanoreception – ear and lateral line 1. Both use sensory hairs for transduction of vibration 2. Both respond to similar types of signals – separate central processing Ear Lateral line system Modality Sounds, vestibular senses (orientation) Net motion between fish and medium Frequency range < 50 Hz to > 2000 Hz 0 Hz (DC) to 200 Hz Detection range Far field Near field F. Lateral line system 1. Found in bony fish, cartilaginous fish, and aquatic amphibia 2. Consists of canals along the side of the body and over the head 3. Detects vibrations from the surrounding water a) Disturbances caused by other organisms b) Reflections of the animal’s disturbances off other objects c) Primitive form of echolocation 4. Neuromasts – receptors, groups of hair cells embedded in a gelatinous cupula a) Usually found in canals
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