The Senses
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The Senses Chapter 8-2
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The Senses. Chapter 8-2. From A Second Way of Knowing: The Riddle of Human Perception by Edmund Blair Bolles , 1991. Seeing in the Dark - PowerPoint PPT Presentation
Transcript of The Senses
The Senses
Chapter 8-2
From A Second Way of Knowing: The Riddle of Human Perception by Edmund Blair Bolles, 1991
Seeing in the Dark
Sit yourself in total darkness, a space so dark you cannot see your hand before your face. Now hold your hand before your face and move it from side to side. You see your hand in motion.
vision
• Most studied sense
Vision Parts
• Pupil• Lens• Retina• Optic nerve
pupil
• The opening in the iris that regulates the amount of light entering the eye
lens
• A flexible, transparent structure in the eye that changes its shape to focus light on the retina
retina
• The innermost coating of the back of the eye, containing the light-sensitive receptor cells
• Light sensitive receptor cells:– Rods
• Better for night vision• 75-150 million in the eye
– Cones • Better in daylight• 6-7 million in the eye• See color
Optic nerve
• The nerve that carries impulses from the retina to the brain
vision
How it works:1. Light enters the eye through the pupil2. Light reaches the lens3. The lens focuses the light onto the retina4. The retina’s rods and cones change the light
energy into neuronal impulses5. Impulses travel over the optic nerve to the brain
and into the occipital lobe
light
• Form of electromagnetic radiation• Colors are different wavelengths of light• We see color after light hits objects and
bounce back to us at different speeds/frequencies
The Electromagnetic Spectrum
Color deficiency
• When some or all of a person’s cones do not function properly
• Affects 8% of American men, less than 1% of women• Hereditary
– Carried in female genes
Ex.• Hard to tell the difference between red and green• Hard to tell the difference between yellow and green• Color blind (see in black and white and shades of grey)
Binocular Fusion
• The process of combining the images received from the two eyes into a single, fused image
• 2 eyes get two messages/images, the brain makes both of these messages/images into one
Retinal disparity
• The difference between the images stimulating each eye
• Each eye has a slightly different view of things
• Important for depth perception– If there is a large retinal disparity, the object is close– If there is a small retinal disparity, the object is far
away
Nearsightedness & farsightedness
• Perfect shaped eyeballs = perfect vision
• Little too long eyeballs = nearsighted– Close clear– Far away blurry
• Too short eyeball = farsighted– Close blurry– Far away clear
hearing• Depends on vibrations of the air (sound waves)
How it works:1. Sound waves pass through various bones2. Sound waves reach the inner ear3. Tiny hairs in the inner ear move back and forth4. Tiny hairs change sound vibrations into neuronal signals5. Neuronal signals travel through the auditory nerve to
the brain
Auditory nerve
• The nerve that carries impulses from the inner ear to the brain, resulting in the sensation of sound
loudness
• Determined by the amplitude (height) of sound waves
• Higher the amplitude, the louder the sound
decibels
• The strength or sound pressure energy measurement
• Decibel range: 0-140 decibels
pitch
• Sound-wave frequency – rate of the vibration of the medium through which the sound wave is transmitted
• Low frequencies = bass sounds• High frequencies = shrill squeaks
Locating sound
• In both ears, but in the closer ear first
The pathway of sound
• Outer ear – receives sound waves– Earflap directs sound down the auditory canal (a
short tube)– Air in the canal vibrates and makes the eardrum
vibrate
The pathway of sound
• Middle ear – Air filled cavity– Has 3 tiny bones• Hammer• Anvil• Stirrup• Vibrate and push the cochlea
The pathway of sound
• Inner ear – Cochlea– Bony tube that contains fluids and neurons– Pressure against the cochlea makes the liquid
inside the cochlea move– Tiny hairs inside the cochlea feel the motion– The hairs are attached to sensory cells– Sensory cells turn the sound vibrations into
neuronal impulses
Deafness
Types:• Conduction– When anything hinders the physical motion of the
ear– Hearing aids can work
• Sensorineural – Damage to the cochlea, hair cells, or the auditory
neurons– Cochlear implants can work
balance
• Regulated by the vestibular system in the inner ear
Vestibular system
• three semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve
• Hair cells project into the fluid in each canal• When you turn your head, canals move, and
fluid will move and bend the hairs
Smell & Taste
• Chemical senses
Smell
How it works:1. Chemical molecules come into contact with
the smell receptors in your nose2. Molecules enter in vapors that reach a
special membrane in the upper part of the nasal passage where the small receptors are
3. Receptors send messages about smells through the olfactory nerve to the brain
Olfactory nerve
• The nerve that carries smell impulses from the nose to the brain
• Caries messages about smell
Taste • Chemicals stimulate receptors in the taste buds on your tongue• Taste information is sent to the brain as well as information
about texture & temperature• Flavor = combining taste, smell and tactile sensations• Relies heavily on smell
• 4 primary tastes:– Sour– Salty– Bitter– sweet
Skin Senses
• Skin receptors provide at least 4 types of information:– Pressure– Warmth– Cold – Pain
• Where there are more receptors, there is more feeling
Perceptions of Pain
• Pain comes from many different stimuli
• Types of pain:– Sharp – localized pain you may feel immediately
after an injury– Dull – generalized pain you may feel later
Gate Control Theory of Pain
• We can lessen some pains by shifting our attention away from the pain impulses OR by sending other signals to compete with the pain signal
Body Senses
• Kinesthesis – the sense of boy movement and body position
• Works with vestibular and visual senses to maintain posture and balance
