Lecture_21_Sensory_Systems.pptx

GENERAL BIOLOGY II Lecture 21: Sensory Systems Chapter: 36 Sensory Systems Sensory Systems Taste and Smell (chemosensory systems) Touch, Hearing, and Balance (mechanoreceptor systems) Sight (electromagnetic receptor systems) Sensory Receptor Cells Rely on membrane receptors Imbedded in cells that co...

GENERAL BIOLOGY II Lecture 21: Sensory Systems Chapter: 36 Sensory Systems Sensory Systems Taste and Smell (chemosensory systems) Touch, Hearing, and Balance (mechanoreceptor systems) Sight (electromagnetic receptor systems) Sensory Receptor Cells Rely on membrane receptors Imbedded in cells that communicate with neurons (taste and sight) Or membrane receptors are embedded directly in neuron membranes (smell) In most multicellular animals, the receptor cells are organized into sensory organs. Sensory Transduction Conversion of physical or chemical stimuli into nerve impulse Initial transformation at the sensory receptor Sensory Transduction Stimulated membrane sensory receptor causes ion channels in the plasma membrane to open Sensory receptors then either fire action potentials themselves or synapse with neurons that do Signals interpreted in the CNS (Perception) Sensory Transduction Chemoreceptors Provide the sense of smell and taste Respond to molecules in the environment (or our mouth) that bind to receptors in the cell membrane Chemoreceptors Smell – chemosensitive projections of neurons extend into the mucus that line the upper part of our nasal passage Taste – taste buds on our tongue are specialized cells that synapse with sensory neurons Mechanorecpetors Respond to physical deformation of the plasma membrane Opens a Na+ ion channel, causing an action potential to fire Responsible for our sense of touch Mechanorecpetors Merkel’s disks respond to light touch. Meissner’s corpuscles respond to touch and lowfrequency vibration. Ruffini endings detect stretch, deformation within joints, and warmth. Pacinian corpuscles detect transient pressure and highfrequency vibration. Mechanorecpetors Sense of hearing and balance are dependent on Hair Cells Specialized mechanoreceptors that sense mechanical vibration using Stereocilia on their surface Do not fire action potentials, but do synapse with neurons Stimulation of hail cells alters the rate at which neurons fire Mechanorecpetors Hair cells that are responsible for hearing in vertebrates are contained in the cochlea Sound vibrations enter outer ear and vibrate the tympanic membrane. The tympanic membrane then moves the bones in the middle ear (incus, malleus, and stapes) Middle ear bones then vibrate the oval window in the cochlea Mechanorecpetors Sense of hearing and balance are dependent on Hair Cells Specialized mechanoreceptors that sense mechanical vibration using Stereocilia on their surface Do not fire action potentials, but do synapse with neurons Stimulation of hail cells alters the rate at which neurons fire Mechanorecpetors Hair cells are also used to sense balance relative body orientation to the environment (balance) The vestibular system in the inner ear detects gravity, acceleration, and deceleration using 3 semicircular canals Each semicircular canal detects angular momentum in one plane that the head can turn (nodding up-down, turning left or right, or moving side to side) When the body moves, fluid in the canals move hair cells, and the hair cell movement is converted into nerve impulses Mechanorecpetors Electromagnetic Receptors Respond to electrical, magnetic, and light stimuli Photoreceptors are the most common Opsin – light-sensitive protein that converts light energy into electrical signals Electromagnetic Receptors Each opsin protein contains a pigment called Retinal When light energy strike retinal, it shifts from a cisto trans- isomer configuration This shift in configuration opens Na+ channels to depolarize the cell Electromagnetic Receptors While all animals use the same mechanism to change light into electrical signals, animal eye configuration and anatomy varies widely Eyecups Compound Eyes Single-lens Eyes Electromagnetic Receptors Electromagnetic Receptors Eyecups – only detect light intensity and direction Compound Eyes – each lens is called an ommatidium. The more ommatidia, the greater the visual resolution. Predatory insects have far more than herbivores. Electromagnetic Receptors Single lens eyes – focus an inverted image on the retina, a thin, photoreactive tissue in the back of the eye Rod cells – blue-green sensitive; the brain interprets this as black-and-white vision Cone cells – provide color vision For Next Class Complete the Quiz on CANVAS Read Chapter 38: Musculoskeletal System