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Chapter 46 Animal Sensory Systems and Movement 1 BLY122 A. Hunter from C. S. Major Chapter 46 Animal Sensory Systems and Movement I. How Do Sensory Organs Convey Information to the Brain? A. The type and sensitivity of sensory systems varies among different animals. 1. Moths mate at night under conditions in which it is difficult or impossible to see. a. Females emit pheromones. b. Males have large, feathery antennae that can detect even one molecule of pheromone. c. Males fly toward an increasing concentration of pheromone. 2. Bats are also active at night, hunting moths. a. Bats emit high-pitched sounds that echo off objects indicating the direction & shape of objects. b. Moths, detecting sounds of an onrushing bat, go into a chaotic escape flight to evade the moth. 3. Senses that humans don’t have a. Some aquatic predators detect electric fields in the muscles of passing prey. b. Many birds, sea turtles, and other animals detect magnetic fields. c. Biologists who work on these animals have the challenge of studying stimuli they cannot themselves detect. 4. Accurate sensory information is essential for guiding the movements of animals. B. Sensory Transduction 1. Each type of sensory information is detected by a sensory neuron or specialized receptor cell that synapses with a sensory neuron. a. The brain integrates information from sensory neurons of different types. b. Electrical impulses are sent to specific muscle groups. 2. Review of how nerve-impulse transmission works a. Electrical potential arises when charges across a cell membrane are separated, as when ion concentrations differ on either side. b. At rest, the inside of a neuron is more negative relative to the outside. c. Changes in electrical potential are recorded with microelectrodes. d. Ion flows that cause the interior of the neuron to become 3. Sensory receptors & neurons transduce the sensory information into changes in membrane polarization. a. Sensory stimuli cause ions to flow across the membrane. b. If a large change in potential occurs, an action potential is sent to the brain. c. If all types of sensory information are converted to electrical signals, how is it possible for the brain to interpret the information? C. Transmitting Information to the Brain 1. Receptor cells tend to be highly specialized. a. Each receptor in a human ear responds best to certain sound frequencies. b. The train of action potentials from a receptor cell contains information about 2. Each sensory neuron sends its information to a specific portion of the brain. 3. Different regions of the brain are specialized for interpreting different types of stimuli. II. Hearing A. Hearing is the ability to sense changes in pressure called sound. 1.
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