Outline for Psychology 100 Lecture:
Sensation
I. Sensation: The process of detecting a physical stimulus from the environment
A. Sense:
B. Sensation vs. Perception:
C. Accessory Structure:
D. Receptors: specialized neurons that collect physical energy and perform transduction
E. Transduction:
F. Coding: translating physical properties of a stimulus into a neural code representing
those properties
1. Temporal Code:
2. Spatial Code: information is coded in terms of the locations of the firing neurons
G. The full sensory process (step-by-step):
H. Doctrine of Specific Nerve Energies: Stimulation of a sensory nerve codes for only
that sense, regardless of the source of stimulation
- Ex:
I. Sensation in your brain:
1. Information from each sense (except _____________) enters the:
2. Then goes to the:
3.
4. Density of nerves in a sense organ =
5.
6. After primary sensory cortex, areas of association cortex combine sensory info from
>1 sense.
II. Hearing
A. Sound: a repetitive fluctuation in the pressure of a medium, such as air.
1. Physical characteristics of sound:
a. Amplitude: difference between the peak and the baseline of a waveform. - It
is basically the INTENSITY of the sound.
b. Wavelength:
c. Frequency: number of complete waveforms, or cycles, that pass a given
point each second
2. Psychological dimensions of sound:
a. Loudness:
b. Pitch: How high/low a tone sounds.
- Depends on the frequency of sound waves.
c. Timbre:
3. The Ear and hearing:
a. Pinna: the visible outer part of our ear
b. Tympanic Membrane (eardrum) in the middle ear:
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c. Malleus (hammer), Incus (anvil) and Stapes (stirrup): amplify the
pressure changes that the original sound waves made in the air and focus them
onto the oval window
d. Cochlea:
i. Basilar Membrane:
ii. Organ of Corti: contains hair cells that connect with the auditory nerve
that goes to the brain, sending it a message about the amplitude (loudness)
and frequency (pitch) of the sound.
e. Auditory Nerve:
f. In the brain:
i. Auditory nerve takes sound info:
ii. From Thalamus, relayed to Primary Auditory Cortex:
- Location of sound determined by:
4. Deafness:
a. Conduction Deafness: when the 3 middle ear bones fuse together
b. Nerve Deafness:
III. Vision
A. Physical Stimulus for vision: Light Waves
1. Visible light:
2. Light intensity: how much energy the light contains
3. Color we see depends on:
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B. Parts of the Eye:
1. Cornea:
2. Lens:
a. Accommodation: ability of the lens to change shape to more clearly focus
images on the retina
3. Pupil:
a. Iris: the colored part of the eye; a ring of muscles that control the dilation of
the pupil
4. Retina:
5. Fovea: central area of the retina
C. How the parts of the eye work:
1. Light enters the eye through the cornea
2.
3.
4. Next goes to the lens:
5.
D. Inside the Retina:
1. Photoreceptors:
a. Contain Photopigments: chemicals that respond to light.
b. Dark Adaptation:
c. 2 types of Photoreceptors:
i. Rods:
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ii. Cones:
d. Details about Fovea:
i.
ii. High concentration of cones, no rods
iii.
IV. Interaction of Senses:
A. Synesthesia: An unusual interaction of the senses
a.) Examples:
b.) Neural basis:
V. The Chemical Senses: Smell & Taste:
A. Olfaction (Smell): detects chemicals that are airborne (“volatile”)
a.) Receptors:
b.) Olfactory bulb:
c.) Olfaction & Emotional Memory:
d.) Sensitivity to smell:
i. Pheromones: chemicals released by 1 animal & detected by another;
shape the 2nd animal’s behavior or physiology
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2. Gustation (Taste): detects chemicals in solution that come in contact with receptors
in the mouth
a.) Receptors:
b.) four main tastes: sweet, sour, bitter, salty
c.) “Supertasters”:
3. Smell, Taste & Flavor
a.) Anosmia:
b.) Flavor: smell & taste acting together as one system
- Capsaicin:
VI. Somatic Senses:
A. Touch:
a.) energy:
b.) Free Nerve Endings: receptors involved in the sense of touch
c.) Adaptation:
d.) We gather information about:
i. intensity: how heavy a stimulus is (firing rate, # of neurons
stimulated)
ii. location:
2. Temperature:
a.) 2 receptor types:
i. warm fibers: increase their firing rates when the temperature
changes in the range of about 95-115 degrees F
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ii. cold fibers:
3. Pain:
a.) 2 types of pain fibers:
i.) A-delta fibers: carry sharp, pricking pain; they are myelinated to
carry inputs quickly
ii.) C fibers:
b.) Emotional Aspects of pain:
c.) Gate-Control Theory: Sensation of pain is controlled by “gates” that open
& close in the spinal cord
i.) Analgesia:
- Natural Analgesics:
- Serotonin: can block pain pathways to brain
- Endorphins (natural opiates):
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