Three canals connected to the utricle detect movement and turning of the head in any direction because hair cells are organized in all directions and go into a cap called the cupula - When you spin quite a bit, the cupula becomes stationary as the body reaches equilibrium and stimulates the sense of dizziness Hearing and Equilibrium in Other Vertebrates - Fish do not have an ear that connects to the outside; instead vibrations travel along skeletal structures to their inner ear - Fish and aquatic amphibians have a lateral line system that goes along both sides of their body that detect the water movement against their body as they swim Concept 50.3 – Visual receptors in diverse animals depend on light-absorbing pigments - Although animals differ in how they sense light, there are similarities that indicate evolutionary origin Evolution of Visual Perception - All light detectors contain photoreceptors , cells that contain light- absorbing pigment molecules Light-Detecting Organs
- The simplest light-detecting organ consists of a pair of ocelli surrounded by darkly pigmented cells that block light so that light can be read only by the photoreceptors in the ocelli Compound Eyes - Insects and crustaceans and some worms have compound eyes - These consist of several thousand light detectors called ommatidia that have their own light-focusing lenses and each detect light from a tiny field - They are especially effective at detecting movement and can see different colors beyond the visual light range of humans Single-Lens Eyes - Single-lens eyes are found in jellies, some worms, spiders, and molluscs and work somewhat like a camera in that they have a small opening, the pupil , through which light enters and an iris that contracts and expands to function like aperture - All vertebrates have single-lens eyes The Vertebrate Visual System - Vision begins when photons of light enter the eye through the pupil and strike the rods and cones, where the energy is captured in the reconfiguration of a chemical bond in the retinal - Images are perceived in the brain, not the eye Sensory Transduction in the Eye - Chemical bonding sets off a chain reaction in the retinal that converts cis- retinal to trans-retinal - Once light has been converted, enzymes in the retinal change it back to cis-retinal, but this takes time and can blind you if changes in light occur drastically and suddenly Processing of Visual Information in the Retinal - Processing of visual information begins in the retinal, where cells depolarize or polarize in response to light - Sometimes information goes directly from the photoreceptors to bipolar cells to ganglion cells, or it may go through several sets of rods and cones, which enhances contrast in what is called lateral inhibition - The rods and cones that feed information to one ganglion cell are called a receptive field o A smaller receptive field results in a sharper image Processing of Visual Information in the Brain - The axons of ganglion cells form optic nerves that transmit information to
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- Atom, Chemical bond