Life: The Science of Biology

David Sadava, David M. Hills, H. Craig Heller

Chapter 46

Sensory Systems - all with Video Answers

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Chapter Questions

Problem 1

Which statement about sensory systems is not true?
a. Sensory transduction involves the conversion (direct or indirect) of a physical or chemical stimulus into changes in membrane potentials.
b. In general, a stimulus causes a change in the flow of ions across the plasma membrane of a sensory receptor cell.
c. The term "adaptation" refers to the process by which a sensory system becomes insensitive to a continuing source of stimulation.
d. The more intense a stimulus, the greater the magnitude of each action potential fired by a sensory neuron.
e. Sensory adaptation plays a role in the ability of organisms to discriminate between important and unimportant information.

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Problem 2

Which statement about olfaction is not true?
a. In general, mammals depend more on vision than on olfaction as their dominant sensory modality.
b. Olfactory stimuli are recognized by the interaction between odorant molecules and receptor proteins on olfactory hairs.
c. The more odorant molecules that bind to receptors, the more action potentials are generated.
d. The greater the number of action potentials generated by an olfactory receptor, the greater the intensity of the perceived smell.
e. The perception of different smells results from the activation of different combinations of olfactory receptors.

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Problem 3

The membrane most directly responsible for the ability to discriminate different pitches of sound is the
a. round window.
b. oval window.
c. tympanic membrane.
d. tectorial membrane.
e. basilar membrane.

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Problem 4

Which statement is not true?
a. The transmembrane potential of a rod cell becomes more negative when the rod cell is exposed to light.
b. A photoreceptor releases the most neurotransmitter when in total darkness.
c. Whereas in vision the intensity of a stimulus is encoded by the degree of hyperpolarization of photoreceptors, in hearing the intensity of a stimulus is encoded by changes in firing rates of sensory neurons.
d. Stiffening of the ossicles in the middle ear can lead to deafness.
e. The interaction among hammer (malleus), anvil (incus), and stirrup (stapes) conducts sound waves across the fluid-filled middle ear.

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Problem 5

Which of the following statements about information flow in the vertebrate visual system is true?
a. Action potentials in bipolar cells cause the release of neurotransmitter onto ganglion cells.
b. Amacrine cells integrate the activity of neighboring rod and cone cells.
c. When photons of light enter the eye, the first cells they encounter in the retina are ganglion cells.
d. The highest density of rod cells in the human retina is centrally located in the fovea, resulting in high-acuity dim-light vision.
e. Pigmented epithelial cells at the back of the retina provide information about the level of ambient light for contrast adjustments.

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Problem 6

What are the similarities and differences in the functioning of olfactory receptors and taste receptors? How do these sensory cells enable the central nervous system to discriminate between an apple and an orange?

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Problem 7

If you were blindfolded and sitting in a wheeled chair, how would you know if you were being pushed forward or backward?

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Problem 8

To human ears, sounds are louder underwater than in air. Why is this so?

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Problem 9

Fish have fluid-filled channels called lateral line canals running down the sides of their bodies. These canals contain hair cells, as illustrated below. Describe what you think the functions of these lateral-line hair cells are.

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Problem 10

An owl can capture a mouse scurrying across a forest floor in total darkness. What sensory information do you think the owl uses, and how does it get directional information from that sensory information?

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