1. Sensation How the brain recognizes information from our senses

2. Characteristics of ALL senses Characteristics of ALL senses  Transduction: the process in which a sense organ changes, or transforms, physical energy into electrical signals that become neural impulses, which can then be sent to the brain for processing.  Adaptation: the decreasing response of the sense organs, the more they are exposed to a continuous level of stimulation.

3. Sensations vs. Perceptions  Sensations are relatively meaningless bits of information that result when the brain processes electrical signals that come from the sense organs.  Perceptions are meaningful sensory experiences that result after the brain combines hundreds of sensations.

4. Eye; Vision Structure and Function  Image reversed: All images seen by the eye are reflected upside down and somehow turned right side up by the brain.

5. Eye: Vision Structure and Function  Light waves: The eye light waves in the direction you are looking to reflect all things in your field of vision. The beams are brought into focus by the cornea and the lens… much like a camera focus.

6. Eye: Vision Structure and Function  Cornea: Rounded, transparent covering over the front of the eye.  Light passes through cornea; its curved surface bends, or focuses, the light waves into narrower beams.

7. Eye: Vision Structure and Function  Pupil: round opening at the front of your eye that allows light waves to pass into the eye’s interior.  The pupil grows larger or smaller because of a muscle called the iris.

8. Eye: Vision Structure and Function  Iris: circular muscle that surrounds the pupil and controls the amount of light entering the eye.  In dim light the iris relaxes, allowing more light to enter (pupil dilates).  In bright light the iris constricts, allowing less light to enter.  Contains pigment that gives your eye its color.

9. Eye: Vision Structure and Function  Lens: transparent, oval structure whose curved surface bends and focuses light waves into an even narrower beam.  Lens is attached to muscles that adjust the curve of the lens which adjusts the focusing.

10. Eye: Vision Structure and Function  Retina: located at the very back of the eyeball  Thin film that contains cells that are extremely sensitive to light.  These light sensitive cells, called photoreceptors, begin the process to transduction by absorbing light waves.

12. Ear: Audition  Sound waves are the stimuli for hearing (audition), resemble ripples of different sizes.  Amplitude: distance from bottom to top of sound wave. Measures loudness; large amp = loud, small amp = quiet  Frequency: speed in which sound waves occur. Measures pitch; fast = high pitch, slow = low pitch.

13. Measuring Sound Waves

14. Outer Ear  Three Parts: external ear, auditory canal, and tympanic membrane.

15. Outer Ear  The external ear is an oval shaped structure that protrudes from the side of the head.  The function of the external ear is to pick up sound waves and send them down a long, narrow tunnel called the auditory canal.

16. Outer Ear  Auditory Canal: long tube that funnels sound waves down its length so that the waves strike a thin, taut membrane (eardrum) or tympanic membrane.

17. Outer Ear  Tympanic Membrane: a taut, thin structure commonly known as the eardrum.  Sound waves strike the membrane and cause it to vibrate.  It then passes the vibrations on to the first of three small bones it is attached to.

18. Middle Ear  Bony cavity that is sealed at each end by membranes. The two membranes that seal the area is connected by three small bones which make up the middle ear.  Collectively, the three bones are known as the ossicles.  Because of their shape they are known as the hammer, anvil, and stirrup.  Together the ossicles serve as levers to greatly amplify sound waves and pass them on to the inner ear.

19. Inner Ear  Cochlea: has a bony coiled exterior that resembles a snail’s shell.  Contains receptors for hearing and its function is transduction (transforming) vibrations into nerve impulses that are sent to the brain for processing into auditory information.  The cochlea processes this information by using hair cells in the bottom called the basilar membrane.  The auditory nerve is a band of fibers that carry nerve impulses (electrical signals) to auditory cortex in the brain for processing.

20. Vestibular System  Located above the cochlea in the inner ear, includes three semicircular canals, resembling bony arches, which are set at different angles.  Each canal is filled with fluid that moves in response to movements in your head.  The functions of this system include sensing the position of the head, keeping the head upright, and maintaining balance.

21. Chemical Senses: Taste  Taste is called a chemical sense because the stimuli are various chemicals.  On the surface of the tongue are receptors, called taste buds, for four basic tastes… sweet, salty, sour, and bitter.  The function of the taste buds is to perform transduction, which is transforming chemical reactions into nerve impulses.

22. Taste Buds

23. Chemical Senses: Taste  Taste buds are physically shaped like tiny onions and are our only receptors for taste.  Chemicals dissolved in the saliva activate the taste buds, which produce nerve impulses that eventually reach areas in the brain’s parietal lobe.  Flavor: combined sensations of taste and smell.

24. Chemical Senses: Smell  Smell (Olfaction) is called a chemical sense because its stimuli are various chemicals that are carried by the air.  The upper part of the nose has a small area that contains receptor cells for olfaction… their function is transduction.  These olfactory cells dissolves molecules in the air with mucus which triggers the nerve impulses to the brain.

25. Touch  The sense of touch includes pressure, temperature, and pain.  Beneath the outer layer of skin are a half- dozen miniature sensors that are receptors.  The function of these receptors is to change mechanical pressure or changes in temperature into nerve impulses to the brain.

26. Receptors in the Skin  Skin: The body’s largest organ.  The outermost layer is a thin film of dead cells containing no receptors.  The first receptors are below the dead skin.  Middle and fatty layers of skin also have a variety of receptors.

27. Receptors in the Skin  Hair Receptors: hairs respond with fire or burst of activity when bent, however, when bent for a long time they cease to fire.  This is sensory adaption.

28. Receptors in the Skin  Free Nerve Endings: located near the bottom layer of skin  These receptors are what feel things such as pain and temperature.

29. Receptors in the Skin  Pacinian Corpuscle: Located in the fatty layer of skin… largest touch sensor  Has distinctive layers like an onion  Highly sensitive to touch, but adapts quickly.  Only receptor to respond to vibration.

30. Pain  Pain is an unpleasant sensory and emotional experience that may result from tissue damage, one’s thoughts or beliefs, or environmental stressors.  How it works: pain receptors in the body send nerve impulses to the somatosensory and limbic areas of the brain, where impulses are changes into pain sensations.  Pain helps us survive; it is our warning system.

31. Gate Control Theory of Pain  Theory that states that a human can create an imaginary gate the blocks pain messages to the brain by shifting attention.  Examples: Concentrate on other tasks, rubbing area, sleeping, exercise (releasing endorphins).