Domain 2 Part 3Chapter 8Sensation

Sensation v. Perception

• Sensation: activation of our senses (eyes, ears, etc.)

• Perception: the process of understanding sensations

Absolute Threshold

• the weakest amount of a stimulus required to produce a sensation

Difference Threshold

• The smallest change in a physical stimulus that can be detected between two stimuli.

• Weber’s Law - The larger or stronger a stimulus, the larger the change required for a person to notice that anything has happened to it.

http://www.youtube.com/watch?v=wVhiezByMSU

Sensory Adaptation

• Decreased responsiveness to stimuli due to constant stimulation.

OUR SENSES

Our Most Dominant Sense

The most studied sense

Parts of the Eye

How the Eye Works

1. Light enters eye through pupil and reaches the lens.

2. The lens focuses the light on the retina.

3. Photoreceptors known as rods and cones turn the light energy into neuron impulses.

4. Neuron impulses travel along the optic nerve to the occipital lobe in the brain.

http://www.willseye.org/video/how-the-eye-works

Rods v. Cones

• Rods – Sensitive to low levels of

light – Basis of night vision – 75 to 150 million rods– See in black and white

• Cones – Require more light

before they begin to respond.

– Work best in daylight – 6 to 7 million cones – Sensitive to color

Color Deficiency

• Affects about 8% of American men and less than 1% American women

• It is a hereditary condition• Caused by cones not

functioning properly• Most people see some

colors• Very few people are totally

color-deficient

Hearing

Parts of the Ear

How the Ear Works1. Earflap directs sound waves down the auditory canal. 2. Sound waves vibrate the eardrum. 3. Hammer, anvil, and stirrup vibrate and push against

cochlea.4. Pressure against the cochlea makes the liquid inside

move. 5. Tiny hairs inside the cochlea pick up the motion and

turn the sound vibrations into neuron impulses. 6. The auditory nerve carries the impulses to the

cerebral cortex.

http://www.youtube.com/watch?v=dCyz8-eAs1I

Deafness

• Conduction deafness– Bones of the middle ear

become rigid and cannot carry sounds inward

– Hearing aids can usually help

• Sensorineural deafness – Cochlea, hair cells, or

auditory nerve is damaged.

– Need a cochlear implant needed to correct deafness.

Smell

– When gaseous molecules come into contact with smell receptors in your nose allow you to smell.

– The message is then sent through the olfactory nerve to the brain.

Taste

Taste + Smell = Flavor • The sensation of flavor is actually a combination of taste and

smell.

Touch and Pain• http://www.youtube.com/

watch?v=mQoS62jEvNA• Receptors located in our skin

provide information about pressure, warmth, cold, and pain.

• Different nerve endings respond to pressure, temperature and pain

• Our brain interprets the amount of change and the place of the change

• Gate Control Theory of Pain – lessen some pains by shifting our attention away from the pain impulses

http://www.youtube.com/watch?v=ZfWO2wciIUY

Vestibular Sense

• Tells us where our body is oriented in space.• Our sense of balance.• Hair cells within the semicircular canals relay

information of our body orientation. When you turn your head, these canals also move. Inertia causes the fluid in the canals to resist changes in motion, which bends receptor hair cells projecting into the fluid.

• Over stimulation of the vestibular sense by movements such as spinning, falling, and tilting can cause dizziness and motion sickness.

Kinesthetic Sense

• Tells us where our body parts are.• Receptors located in our muscles and

joints send information to our brain about our limbs.