1. Sensory Systems

2. Nerve cells identify particular stimuli, depending on their type. Neurons carry signal to brain where it is decoded. The brain uses information about which nerve cells are involved, the frequency of impulses (action potentials), and number of neurons in order to identify the stimulus. What is referred pain? For each sense specialized receptors sense the stimulus and transmit information to the brain: Skin – many types of receptors, including for pain, temperature, pressuree Taste and smell – chemical receptors Hearing – vibrations of hir cells Vision – rods and cones identify colored and b/w light, respectively Learning Objectives

3. SensorySystems Sensation – conscious awareness of a stimulus Perception – understanding of what that stimulus means

4. Sensory Mechanoreceptors: pressure, position, or acceleration Thermoreceptors: temperature Receptors Nocireceptors: damage tissue (pain) Chemoreceptors: chemicals Osmoreceptors: water volume Photoreceptors: visible toto light

5. Nerve impulses are allthe same – so how what’s going on? doesthebrainknow Which nerves are carrying the impulses? What is the frequency of the impulses? How many neurons responded to the stimulus?

6. Somatic Sensations (“of Touch, pressure, the body”) heat,heat,cold,pain,pain,movement Free nerve ending: “Naked” dendrites Encapsulated receptor: Enclosed in tissue

7. Nociceptors (pain receptors) are free nerve endings

8. Referred Pain Pain from internal organs may be wrongly projected to parts of skin surface

9. Taste Gustation = sense of taste

10. Smell Olfactory receptors: detect water-soluble or easily vaporized substances Communicate directly with olfactory bulbs brain in

11. Hearing Sounds are waves of compressed air

12. Detecting Sound Waves Pinnae Æ Ear Canal Æ Eardrum (vibrations) Æ Ear Bones Æ Oval Window Æ Cochlea

13. Cochlear duct Æ Organ of Corti (hair cells) Hair cells bend, release neurotransmitter to trigger action potential in auditory nerve

14. Progressive Deafness Hair cells are damaged with exposure to loud noises

15. Vision 3 layers of the eye: Outer Sclera (“white”): protection Cornea: focus light

16. 3layersoftheeyeeyecont. Middle Iris: regulate light Pupil: entrance for light Lens: focus light Ciliary Muscle: bend lens Inner Retina: light- sensitive tissue

17. Focusing of Light Cornea is curved – bends light rays Pattern on retina is upside-down & backwards

18. Signals criss-cross as they travel from the retina to the brain (corrects upside-down / backwards issue)

19. Fine-tuning the Focus Ciliary muscle adjusts the shape of the lens = accommodation

20. CommonVisionProblems Nearsightedness,Farsightedness,Astigmatism Nearsighted Farsighted

21. From visual signals to sight Photoreceptors with visual pigments found behind retina

22. Colorblindness If two kinds of cones missing = total color blindness Red-green colorblindness = lack most or all cones that respond to red or green