Chapter 29- The Senses Accommodation Aqueous humor Astigmatism Auditory canal Basilar membrane Blind spot Chemoreceptors Choroid Cochlea Compound eye Cones Conjunctiva Cornea Eardrum Electromagnetic receptors Eustachian tube Eye cup Farsightedness Fovea Hair cells Inner ear Iris Lens Mechanoreceptors Middle ear Nearsightedness Ommatidia Organ of Corti Outer ear Oval window Pain receptors Perception Photopsins Photoreceptors Pinna Pupil Receptor potential Retina Rhodopsin Rods Saccule Sclera Semicircular canals Sensation Sensory adaptation Sensory transduction Single-lens eye Stretch receptors Thermoreceptors Utricle Visual acuity Vitreous humor

Sensory input Sensations- awareness of sensory stimuli Sensory info moves from receptors via action potentials to CNS Body takes sensation and forms perception- meaningful interpretation of sensory data

Sensory transduction Converting stimulus into electrical signal –Change in membrane potential (receptor potential) –Potentials vary- stronger the stimulus- larger the receptor potential Sensory adaptation- tendency of sensory receptors to become less sensitive –Triggers fewer action potentials –Keeps body from reacting to background stimuli

5 types of sensory receptors 1 - Pain- respond to excess heat, cold, pressure, chemicals –All parts of human body except brain 2-Thermoreceptors- detect heat or cold on skin, others deep in body monitor blood temp –Messages get sent to hypothalamus which regulates body temp 3-Mechanoreceptors- highly diverse (touch, pressure, stretch, motion, sound) –Stretch receptors in muscle- monitor body position –Hair cells- detect sound waves and movement in air or water

5 types of sensory receptors 4- Chemoreceptors- develops potentials in response to chemicals –In nose, mouth and arteries (amount of O 2 in blood) 5- Electromagnetic- can detect various wavelengths –Ex: fish send out electric current and use receptors to detect food/obstacles –Some org’s are thought to detect Earth’s magnetic field –Photoreceptors (including eyes)- most common electromagnetic receptor

3 types of eyes Eye cup- (in flat worms)- provide info on intensity and direction of light, brain compares info from each eye and sends signal to move away Compound eye- have lens, focus and form images by ommatidia- light detecting units having lens and photoreceptor cells Single-lens eye- similar to a camera and vertebrate single lens eye

Vertebrate eye Detects color, form images, respond to light E –Sclera- outer surface of eye, whitish CT and clear in front, cornea –Choroid- underneath sclera, iris in front of eye Iris- colored part of eye Pupil- opening- lets in light –Lens- held in position by ligaments, focuses images onto retina (layer inside choroid) –Photoreceptors on retina pass action potentials via sensory neurons to optic nerve –Fovea- retina’s center of focus –Humors- fluid in eye –Conjunctiva- mucous membrane lining eyelid

Focusing –Fish and squid- rigid lens- muscles move lens back and forth –Mammals- change lens shape- accommodation

Photoreceptor cells Rods- sensitive to light, shades of gray- night vision Cones- stimulated by bright light, distinguish color –3 types- blue, green, yellow –Colorblindness- cone deficiency When rods and cones absorb light  membrane permeability changes

The Ear Converts air pressure waves to action potential that’s perceived as sound –To hear and maintain balance – by stimulating cilia like projections on hair cells

3 regions of the ear Outer- pinna and auditory canal –Collect sound waves and channel them to middle ear Middle- –Eardrum- separates outer from middle ear –When sound waves strike drum  passed to hammer, anvil and stirrup  sending vibrations to inner ear –Eustachian tube- conducts air between inner ear and back of throat  keeps pressure equal on either side of drum Inner- fluid-filled channels in bones –Sound waves & movement  set fluid in motion –Cochlea- contains hearing organ  organ of Corti –Hair cells in Corti  ear receptor cells –Regions of basilar membrane in organ can determine types of sounds

Organs of balance Semicircular canals- detect head motion– 3 canals are all perpendicular to each other to detect all directions Utricle and saccule- detect head position with respect to gravity –Motion sickness- conflict between what ear says and eyes say

Smell and Taste Dependent on chemoreceptors Nose receptor can detect up to 50 odors Some insects have chemoreceptors in feet * works same way all senses do converting stimuli to action potentials