1. Chapter 29 Sec 1-3
The Senses

2. Introduction Bats use echolocation to detect their environment.
Bats use echolocation to detect their environment.
High-pitched sounds are
produced in their larynges (singular, larynx) and
emitted from their mouths and noses.
Their brains process the time delay and spatial arrangement of the echoes to determine the size, shape, location, speed, and direction of objects in their environment.
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3. Introduction Marine mammals
Marine mammals
include dolphins, killer whales, and sperm whales,
produce ultrasonic clicking sounds in their nasal passages,
focus the sound by bouncing it off of skull bones and an oil-filled structure in their forehead, and
receive the echo in a narrow window of bone behind the jaw.
Echolocation has also been observed in some species of cave-dwelling birds and forest-dwelling shrews.
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4. Chapter 29: Big Ideas Sensory Reception Hearing and Balance Vision
Figure 29.0_1
Chapter 29: Big Ideas
Sensory Reception
Hearing and Balance
Figure 29.0_1 Chapter 29: Big Ideas
Vision
Taste and Smell 4

5. Figure 29.0_2
Figure 29.0_2 A bat (Plecotus auritus) navigating by echolocation 5

6. SENSORY RECEPTION
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7. 29.1 Sensory organs share a common cellular basis
All animal senses originate in sensory receptors, specialized cells or neurons that are tuned to the
conditions of the external world and
the internal organs.
All sensory receptors
trigger an action potential and
send information to the central nervous system.
Sensation depends on the part of the brain that receives the action potential.
Teaching Tips
You might want to ask your students to consider the uneven distribution of sensory receptors in the human body. Sensory receptors may be concentrated in regions where environmental inputs are focused, such as the eyes and ears, or spread more generally, such as skin or the walls of the digestive tract.
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8. Figure 29.1
Figure 29.1 A hammerhead shark hunting by electroreception 8

9. 29.2 Sensory receptors convert stimulus energy to action potentials
Sensory receptors detect stimuli.
All stimuli represent forms of energy.
In a process called sensory transduction, receptors
detect one type of signal (the stimulus) and
convert the signal to another type, an electrical signal.
Student Misconceptions and Concerns
The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help them make a connection. CD players, DVD recordings, and MP3 players rely upon electricity and signal conversions to store and generate sounds and images.
Teaching Tips
Students can better understand sensory adaptation by thinking about events in their lives. Perhaps they notice a distinct smell in the hallways and laboratories of the science facilities at your school. However, after a few minutes, we tend not to notice the smells as much. These experiences illustrate sensory adaptation.
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10. 29.2 Sensory receptors convert stimulus energy to action potentials
When a sensory receptor cell in a taste bud detects sugar molecules,
sugar molecules enter the taste bud,
sugar molecules bind to sweet receptors, specific protein molecules embedded in a taste receptor cell membrane, and
the binding triggers a signal transduction pathway that causes some ion channels in the membrane to close and others to open.
These changes in the flow of ions create a graded change in membrane potential called a receptor potential.
Student Misconceptions and Concerns
The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help them make a connection. CD players, DVD recordings, and MP3 players rely upon electricity and signal conversions to store and generate sounds and images.
Teaching Tips
Students can better understand sensory adaptation by thinking about events in their lives. Perhaps they notice a distinct smell in the hallways and laboratories of the science facilities at your school. However, after a few minutes, we tend not to notice the smells as much. These experiences illustrate sensory adaptation.
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11. Figure 29.2A Sensory transduction at a taste bud
pore
Sugar
molecule
Taste
bud 1
Sensory
receptor
cells
Sensory
neuron
Sweet
receptor
Sugar molecule
(stimulus) 2
Membrane
of a sensory
receptor cell
Signal
transduction
pathway 3
Ion
channels
Sensory
receptor
cell 4
Ion
Figure 29.2A Sensory transduction at a taste bud
Receptor
potential 5
Neurotransmitter
Sensory neuron
Action potential
to the brain mV
No sugar
Sugar present 6
Rates of action potentials 11

12. Sugar Taste molecule pore Taste bud Sensory receptor cells Sensory
Figure 29.2A_1
Sugar
molecule
Taste
pore 1
Taste
bud
Sensory
receptor
cells
Figure 29.2A_1 Sensory transduction at a taste bud (part 1)
Sensory
neuron 12

13. Sweet receptor Sugar molecule (stimulus) Membrane of a sensory
Figure 29.2A_2
Sweet
receptor
Sugar molecule
(stimulus) 2
Membrane
of a sensory
receptor cell
Signal
transduction
pathway 3
Ion
channels
Figure 29.2A_2 Sensory transduction at a taste bud (part 2) 4
Sensory
receptor
cell
Ion 13

14. Rates of action potentials
Figure 29.2A_3
Ion channels 4
Sensory
receptor
cell
Ion
Receptor
potential 5
Neurotransmitter
Sensory neuron
Action potential
to the brain
Figure 29.2A_3 Sensory transduction at a taste bud (part 3) mV
No sugar
Sugar present 6
Rates of action potentials 14

15. 29.2 Sensory receptors convert stimulus energy to action potentials
The stronger the stimulus,
the more neurotransmitter released by the receptor cell and
the more frequently the sensory neuron transmits action potentials to the brain.
Repeated stimuli may lead to sensory adaptation, the tendency of some sensory receptors to become less sensitive when they are stimulated repeatedly.
Student Misconceptions and Concerns
The concept of sensory transduction, as applied to any particular sense organ, is typically new to most students. Students’ familiarity with numerous forms of digital technology may help them make a connection. CD players, DVD recordings, and MP3 players rely upon electricity and signal conversions to store and generate sounds and images.
Teaching Tips
Students can better understand sensory adaptation by thinking about events in their lives. Perhaps they notice a distinct smell in the hallways and laboratories of the science facilities at your school. However, after a few minutes, we tend not to notice the smells as much. These experiences illustrate sensory adaptation.
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16. “Sugar” interneuron “Salt” interneuron Sugar receptor cell Salt
Figure 29.2B
“Sugar” interneuron
“Salt” interneuron
Sugar
receptor
cell
Salt
receptor
cell
Brain
Sensory
neurons
Taste
bud
Taste
bud
Figure 29.2B Action potentials transmitting different taste sensations
No sugar
No salt
Increasing sweetness
Increasing saltiness 16

17. 29.3 Specialized sensory receptors detect five categories of stimuli
There are five categories of sensory receptors.
1. Pain receptors detect dangerous stimuli including high heat and pressure.
2. Thermoreceptors detect heat or cold.
3. Mechanoreceptors respond to
mechanical energy,
touch,
pressure, and
sound.
Teaching Tips
In elementary school, students often learn that there are five senses (taste, smell, touch, sight, and hearing). Consider matching these five senses to the types of specialized sensory receptor described in Module 29.3.
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18. 29.3 Specialized sensory receptors detect five categories of stimuli
4. Chemoreceptors
include sensory receptors in our nose and taste buds and
respond to chemicals.
5. Electromagnetic receptors respond to
electricity,
magnetism, and
light (sensed by photoreceptors).
Teaching Tips
In elementary school, students often learn that there are five senses (taste, smell, touch, sight, and hearing). Consider matching these five senses to the types of specialized sensory receptor described in Module 29.3.
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19. Connective tissue Hair movement
Figure 29.3A
Heat
Light touch
Pain
Cold
Hair
Epidermis
Figure 29.3A Sensory receptors in the human skin
Dermis
Nerve
to brain
Connective
tissue
Hair
movement
Strong
pressure 19

20. Figure 29.3B Mechanoreception by a hair cell
“Hairs” of a
receptor cell
Fluid
movement
Fluid
movement
Neurotransmitter
at a synapse
More
neurotransmitter
molecules
Fewer
neurotransmitter
molecules
Sensory
neuron
Action
potentials
Action
potentials
Figure 29.3B Mechanoreception by a hair cell 1
Receptor cell at rest 2
Fluid moving in one direction 3
Fluid moving in the other direction 20

21. “Hairs” of a receptor cell Neurotransmitter at a synapse Sensory
Figure 29.3B_1
“Hairs” of a
receptor cell
Neurotransmitter
at a synapse
Sensory
neuron
Action
potentials
Action
potentials
Figure 29.3B_1 Mechanoreception by a hair cell (part 1) 1
Receptor cell at rest 21

22. Fluid moving in one direction
Figure 29.3B_2
Fluid
movement
More
neurotransmitter
molecules
Figure 29.3B_2 Mechanoreception by a hair cell (part 2) 2
Fluid moving in one direction 22

23. Fluid moving in the other direction
Figure 29.3B_3
Fluid
movement
Fewer
neurotransmitter
molecules
Figure 29.3B_3 Mechanoreception by a hair cell (part 3) 3
Fluid moving in the other direction 23

24. Figure 29.3C
Figure 29.3C Chemoreceptors on the antennae of a moth 24

25. Figure 29.3C_1
Figure 29.3C_1 Chemoreceptors on the antennae of a moth (part 1) 25

26. Figure 29.3C_2
Figure 29.3C_2 Chemoreceptors on the antennae of a moth (part 2) 26

27. Infrared receptor Figure 29.3D
Figure 29.3D Electromagnetic receptor organs in a snake
Infrared
receptor 27