Download Answers to Mastering Concepts Questions

Answers to Mastering Concepts Questions
Chapter 29
29.1
1. The senses monitor internal and external stimuli, including blood pH, body temperature, levels
of ions and water in interstitial fluids, and a host of other physical and chemical conditions.
Information about these stimuli are transmitted to the central nervous system for processing and
may trigger hormonal, chemical, or behavioral adjustments that maintain homeostasis.
2. The major types of sensory receptors are chemo-, photo-, mechano-, thermo-, proprio-,
electro- and pain receptors.
3. A receptor potential is a graded potential that occurs in a sensory receptor. If the receptor
potential is large enough, it will generate an action potential in the sensory receptor.
4. Sensory adaptation is a reduced response to a stimulus, tuning out sensations that are the
equivalent of irrelevant “background noise.”
29.2
1. Mechanoreceptors in the skin provide the sense of touch. Some free nerve endings in the skin
are thermoreceptors, whereas other free nerve endings detect mechanical damage and produce
the sensation of pain.
2. Stretch receptors in muscles send nerve impulses when these muscles are stretched. The
brain integrates and interprets these impulses to tell the position of body parts.
29.3
1. The cerebral cortex distinguishes one odor from another based on the specific membranebound receptor proteins that have transmitted the impulse.
2. Pheromones are scent molecules made by one organism that carry information to another
individual of the same species and cause a response in that individual.
3. A taste bud is a cluster of taste receptor cells that have concentrations of chemoreceptors.
Each sends an action potential to sensory neurons that take the message to the medulla of the
brain for processing and integration.
4. The five taste sensations that impart a food’s flavor are sweet, bitter, salty, sour, and umami.
29.4
1. The parts of the vertebrate eye include the sclera, the choroids, and the retina. The sclera
includes the white of the eye and the cornea. The choroid includes blood vessels, lens, iris, and
pupil. The retina is a layer of photoreceptors at the back of the eye. Most of the eye’s volume is
filled with vitreous humor. Aqueous humor fills the space between the cornea, iris, and lens.
2. Rod cells and cone cells detect light. Rod cells provide black-and-white vision in dim light, and
cone cells provide color vision in bright light. Both cell types contain light-sensitive pigments that
absorb photons of light and trigger receptor potentials that are passed on to other neurons that
send action potentials to the brain.
3. In the retina, light sensitive pigments in rods and cones absorb light energy of different
wavelengths. In the presence of light, the pigment molecule changes shape and triggers a
receptor potential that stimulates the retina’s bipolar neurons. These send the message to the
ganglion cells. If they become depolarized, the ganglion cells send action potentials through the
visual pathway to the optic nerve. The optic nerve exits the eyeball, traveling from the retina to
the brain. Optic nerves first go to the thalamus. Then the visual information goes to neurons in the
primary visual cortex of the brain.
29.5
1. Mechanoreceptors detect sound waves and changes in body orientation, and they transmit this
information to processing centers in the brain.
2. The outer ear funnels sound waves into the auditory canal that ends in the eardrum. In
response to sound waves, the eardrum and bones of the middle ear move; their movements
jiggle the fluid of the cochlea. Vibration of the fluid in the cochlea causes cilia of hair cells to move
relative to the tectorial membrane. This movement, in turn, causes the hair cells to release a
neurotransmitter that triggers action potentials in the auditory nerve.
3. When body position changes, fluid in the three semicircular canals bends cilia of hair cells that
transmit action potentials to the nearby cranial nerve. The vestibule also has hair cells and is filled
with fluid that contains granules of calcium carbonate. As the head tilts, these granules land on
hair cells. When the cilia bend, the hair cells generate action potentials that the brain interprets
as a change in body position.