Life Science 4.2 : Responding to the EnvironmentPresentation Transcript
Life Science 4.2 Responding to the Environment
Objectives: List four sensations that are detected by receptors in the skin. Describe how a feedback mechanism works. Describe how light relates to sight. Describe how the senses of hearing, taste, and smell work.
Sense of Touch Stimuli and Receptors Touch is what you feel when sensory receptors in the skin are stimulated. Each kind of receptor responds mainly to one kind of stimulus.
Responding to Sensory Messages Reflexes Immediate involuntary actions activated by pain receptors in your skin. Help you move quickly out of the way of danger. Feedback Mechanisms Cycles of events in which information from one step controls or affects a previous step. Example : Cooling of body
Sense of Sight Reacting to Light Your pupil is an opening that lets light enter the eye. The pupil is surrounded by the iris, a ring of muscle that controls the amount of light that enters the eye. Focusing the Light Light travels in straight lines until it passes through the cornea and the lens. Muscles in the eye change the shape of the lens in order to focus light onto the retina. Retina is packed with photoreceptors, which are special neurons that change light into electrical impulses. 2 photoreceptors are rods and cones Rods – sensitive to dim light – good for night vision Cones – sensitive to bright light – fine details and colors Impulses travel to axons in optic nerve – to the brain to be interpreted.
Parts of the Eye Common Vision Problems Convex lens – nearsightedness
Sense of Hearing Each ear has an outer, middle, and inner portion. Sound waves reaching the outer ear are funneled into the middle ear and then into the inner ear before being interpreted by the brain. Converted to electrical impulses by neurons in the fluid of the cochlea.
Sense of Taste Your tongue is covered with tiny bumps called papillae. Most papillae contain taste buds. Taste buds contain cluster of taste cells, or receptors for taste. Taste buds respond to sweetness, sourness, saltiness, and bitterness.
Sense of Smell Receptors for smell are located on olfactory cells in the upper part of your nasal cavity. An olfactory cell is a nerve cell that responds to chemical molecules in the air.