Section 29.3
• Students will be able to explain how the senses detect physical and
chemical stimuli.
KEY CONCEPT
The senses detect the internal and external environments.
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What is stimuli?
What are the five senses?
Bellringer
Write a short paragraph (3-4
sentences) explaining and giving
examples of how drugs alter your
brain chemistry.
▫ Use the vocabulary: addiction,
and tolerance, Stimulants or
depressants
• Addiction:
• physiological need for a substance
▫ Examples? What does the addiction lead a person to do?
• Tolerance:
• Takes larger doses of the drug to produce the same effect
▫ What is happening inside of their brain/body?
• Stimulants:
• are drugs that increase mental and physical functions
(increase neurotransmitter and electrical signals)
▫ Examples? Effects?
• Depressants:
• Cause fewer action potentials and decrease
neurotransmitter
▫ Examples? Effects ?
• If I blindfolded you and place you in the back of the
room would you reach the door?
• Your sensory organs and your brain allow you to
perceive stimuli as various sounds, sights, smells,
and tastes
Reactions to stimuli
Ex: Eyes react to bright or dim light by changing the
size of your pupils.
Ex: When your skin feels cold ________________.
Other examples?
The senses help to maintain homeostasis.
• Senses gather stimuli, and send
it to the nervous system.
• Nervous system responds to
stimuli.
▫ Pupils shrink when too much
light enters the eyes.
▫ Goose bumps when cold air
touches skin.
The senses detect physical and chemical stimuli.
• Humans have specialized sensory organs that
detect external stimuli. The information these
organs collect helps to make up the five senses:
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Vision
Hearing
Touch
Taste
Smell
Vision
• The eye contributes to
vision
• Humans rely on vision
more than any of the other
senses
• Eye contains about 70% of
all the sensory receptors in
the body
• Depends on the amount of
light available
“I can’t believe my eyes!”
Vision
• Specialized cells called rods and cones are the
photorecpetors.
• Rod cells: detect light intensity and are used in
black and white vision.
• Cone cells: detect color.
• Rod cells are sensitive to low amounts of light
and need bright light to function. This is why
you have a hard time seeing color when its dark.
Hearing
• The ear contributes to hearing.
– Collects vibrations- sound waves- from the air, amplifies them, and
converts them into nerve impulses that are interpreted in the brain as
sounds.
– Hair cells are specialized cells in the inner ear that contain
mechanoreceptors that detect vibrations.
– How do we rely on hearing?
Taste and Smell
• Taste and smell are closely
related.
• Your sense of taste is less sensitive when
your nose is stuffed up.
– Chemoreceptors detect chemicals
dissolved in fluid.
– In smell, small airborne chemicals enter
the nose.
– In taste, taste buds on tongue (bumps
called papillae) are the receptors that
detect the chemicals.
– How do we rely on taste and smell?
Touch, temperature, and pain
• The skin senses touch.
– detect pressure
– detect damaged tissue (pain)
– detect temperature
– How do we rely on touch
•Touch: mechanoreceptors that detect pressure,
movement, and tension.
•Temperature: thermoreceptors that detect heat and
cold.
•Pain: pain receptors that detect chemicals from
damaged cells.
The Stroop Effect Color Test
(YOU WILL BE DOING MORE ON YOUR OWN WITH YOUR PARTNER)
Directions:
•2 colors will be shown to you
•Say the COLOR of the word
shown
Red
Orange
• Remember say the
COLOR of the word
shown
Red
Gray
The Stroop Effect
• Psychologist John Stroop studied the
processing of words and how these thought
processes affected other mental tasks.
• He found that the brain must override an
automatic response when it receives
conflicting information, or interference
How much detail can you remember?
What can you remember?
• How many people were in the picture?
• 4
• What was the man reading the newspaper
wearing?
• Hat, green jacket
• How many of the men had sunglasses?
• 2- one wearing them, one hanging on shirt
• Describe the man on the left.
• Tan jacket, white shirt with a blue design,
had a beard, white, blue eyes
Why can’t you remember some of the
information?
Our brain distinguishes between
things that are important or not
important when interacting with the
environment.
3 composite sketches by three witnesses
Write down the first
picture you see in each
optical illusion.
MISTAKE?????
Nine hidden
ppl?
Why didn’t you see more than one
picture at first in the optical
illusion?
•Your brain is perceiving
individual sensory stimuli as a
meaningful whole.