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SENSATION It is the activity of the senses. A state of emotional excitement. TWO FACTORS IN ORDER FOR SENSATION TO OCCUR: 1. There must be a stimulus. 1. There must be receptors that are sensitive to the stimulus.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved KAGAN(1972) Defines a STIMULUS as any form of energy capable of exciting the nervous system like light waves, sound waves and chemical energy that causes the sensation of taste and smell. A RECEPTOR is a specialized nerve ending capable of responding to energy.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved SENSES The mechanisms which convert stimulus energy into neural energy 5 PRIMARY SENSES: 1. Vision 2. Hearing 3. Smell 4. Taste 5. Skin senses In addition, we have 6. Kinaesthetic 7. Sense of Equilibrium

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 35-5 Senses…… Special senses Sensory receptors located in head Nose – smell Tongue – taste Eyes – vision Ears – hearing and equilibrium Touch is a generalized sense Stimulus  nervous system  brain  response

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 35-6 Nose and Sense of Smell Olfactory receptors Chemoreceptors – respond to changes in chemical concentrations Chemicals must be dissolved in mucus Located in the olfactory organ

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 35-7 Nose and Sense of Smell (cont) Smell sensation that send the information along olfactory bulbs and tracts to different areas of the cerebrum; cerebrum interprets the information as a particular type of smell Activation of smell receptors  information sent to olfactory nerves

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 35-8 Nose and Sense of Smell (cont.) Sensory Adaptation Chemical can stimulate receptors for limited time Receptors fatigue and stop responding to chemical No longer smell odor

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 35-9 Tongue and Sense of Taste Gustatory receptors – located on taste buds Taste buds Location Papillae of the tongue Roof of mouth Walls of throat Tongue } fewer than on tongue

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste (cont.) Taste cells and supporting structures On taste buds Supporting structures fill in space Taste cells Chemoreceptors Chemicals in food and drink must be dissolved in saliva to activate Tongue

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste (cont.) Taste sensation 4 primary Sweet – tip Sour – sides Salty – tip and sides Bitter – back Unami 5 th basic taste Glutamic acid Spicy foods Activate pain receptors Interpreted by brain as “ spicy ” Tongue

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Tongue and Sense of Taste (cont.) Activation of taste cells Cranial nerves Gustatory cortex of cerebrum interprets information Taste sensation

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eye and Sense of Sight Vision system Eyes Optic nerves Vision centers in the brain Accessory structures Eye Processes light to produce images Three layers Two chambers Specialized parts

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eye and Sense of Sight (cont.) Outer – sclera White of the eye Protects the eye Sense receptors Cornea Front of eye “ Window ” that allows light into eye Bends light as it enters Eye

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eye and Sense of Sight (cont.) Middle – choroid Contains blood vessels Iris Colored part of eye Muscle that contracts and relaxes to open or close pupil Regulates the amount of light that enters the eye Lens Posterior to iris Focuses light on retina Accommodation Eye

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eye and Sense of Sight (cont.) Inner – retina Visual receptors Rods Sensitive to light Will function in dim light – “ limited ” night vision Do not provide sharp image or detect color Cones Function in bright light Sensitive to color and provide sharp images Optic disc – optic nerve enters retina Eye

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eye and Sense of Sight (cont.) Chambers of the eye Anterior chamber Front of lens Filled with aqueous humor – nourishes and bathes anterior eye Posterior chamber Behind lens Contains vitreous humor – maintains shape of eyeball and holds retina in place Eye

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Optic chiasm Eye and Sense of Sight: Visual Pathways Eye works like a camera Light enters the eye through the lens Refraction – cornea, lens, and fluids bend light to focus it on the retina Optic nerve Occipital lobe of cerebrum Retina converts light to nerve impulse Image upside down on retina Image turned right-side up

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Ear and the Senses of Hearing and Equilibrium: Structures External ear Auricle (pinna) Collects sound waves External auditory canal Guides sound wave to tympanic membrane Tympanic membrane Separates external canal and middle ear Vibrates when sound hits it Ear

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Eustachian tube Connects middle ear to throat Equalizes pressure on eardrum Oval window Separates middle ear from inner ear Ear Middle ear Ear ossicles Malleus Incus Stapes Ossicles vibrate in response to vibration of tympanic membrane The Ear and the Senses of Hearing and Equilibrium: Structures (cont.)

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Inner ear – labyrinth of communicating chambers Semicircular canals – detect balance of the body Vestibule – equilibrium Cochlea Hearing receptors Organ of Corti – organ of hearing Ear The Ear and the Senses of Hearing and Equilibrium: Structures (cont.)

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© 2009 The McGraw-Hill Companies, Inc. All rights reserved Equilibrium Head movement causes fluid in semicircular canals and vestibule to move Equilibrium receptors transmit information along vestibular nerves to cerebrum Cerebrum determines if body needs to make adjustments The Ear and the Senses of Hearing and Equilibrium: Structures (cont.)

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Sound waves collected Waves cause tympanic membrane to vibrate Ossicles amplify vibrations, which enter inner ear Movement of hairs lining cochlea trigger nerve impulses Impulses are transmitted by auditory nerve to the brain for interpretation The Ear and the Senses of Hearing and Equilibrium: Hearing Process

© 2009 The McGraw-Hill Companies, Inc. All rights reserved SKIN BODY’S LARGEST ORGAN.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Touch: The Skin Touch is to use your skin to have physical contact with something else. Nerves are like wires that relay messages to the brain Nerves in the skin send information about: –Pressure –Temperature –Pain –Vibration.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Touch Information from our skin travels up the spinal cord to the brain. Each nerve carries information from one part of the body.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Touch This sensory map shows that the brain touch area is dedicated to some body parts more than others.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved STIMULI OF SKIN: PRESSURE TEMPERATURE PAIN TEXTURE TOUCH

© 2009 The McGraw-Hill Companies, Inc. All rights reserved OUTERMOST LAYER OF THE SKIN: THIN FILM OF DEAD CELLS CONTAINING RECEPTORS

© 2009 The McGraw-Hill Companies, Inc. All rights reserved IMMEDIATELY BELOW THE DEAD LAYERS ARE THE FIRST RECEPTORS: LOOK LIKE GROUPS OF THREAD-LIKE HAIR EXTENSIONS

© 2009 The McGraw-Hill Companies, Inc. All rights reserved IN THE MIDDLE & FATTY LAYERS THERE ARE A VARIETY OF RECEPTORS WITH DIFFERENT SHAPES & FUNCTIONS.