1). All sensory receptors are able to initiate nerve impulses by opening or closing
a). voltage-gated ion channels.
d). stimulus-gated ion channels.
2). What type of stimulus triggers a response in nociceptors?
3). What is the function of baroreceptors?
a). They detect changes in blood pressure.
b). They detect muscle contractions and the movement of limbs.
c). They are exteroceptors.
d). They detect changes in blood chemistry.
4). Cilia from sensory cells that detect a body in motion are located within the
a). lateral line system.
c). semicircular canals.
d). pit organ.
5). Two senses that detect changes in chemical concentrations are
a). touch and pressure.
b). sight and smell.
c). hearing and balance.
d). taste and smell.
6). A person with defective otolith sensory receptors
a). is deaf.
b). has a difficult time maintaining balance.
c). cannot detect external temperature changes.
d). has a faulty sense of smell.
7). The ear detects sound by the movement of
a). the basilar membrane.
b). the tectorial membrane.
c). the cupula that surrounds the hair cells.
d). fluid in the semicircular canals.
8). Which of the following statements is incorrect?
a). Vertebrates focus the eye by changing the shape of the lens.
b). All vertebrate and invertebrate eyes use the same light-capturing molecule.
c). The vertebrate eye adjusts the amount of light entering the eye by contracting the ciliary muscles.
d). Fish focus the eye by moving the lens closer to or farther from the retina.
9). Most sensory receptors function by producing depolarizing potentials. Which of the following function by hyperpolarization rather depolarization?
c). olfactory receptors
d). rods and cones
10). Which of the following stimuli is not detected by fish?
a). infrared radiation
Test Your Visual Understanding
1). Corrective lenses are used to refocus the image correctly on the retina of the eye. Explain how each corrective lens in the figure modifies the refraction of the light from the image and why each is able to correct their respective eye problem.
Answer: In the top panel, nearsightedness is the condition where the eye can focus correctly on objects close up but the eye cannot focus correctly on objects far away. To correct this, a concave lens is used to spread the light from the image out more before entering the cornea. By doing this, the concave lens is able to make the light travel farther through the eye, allowing the focus point to fall on the retina, forming a clearer image.
In the lower panel, farsightedness is the condition where the eye can focus correctly on objects far away but the eye cannot focus correct on objects close up. To correct this, a convex lens is used to bend the light coming from the object inward before entering the cornea. By doing this, the convex lens is able to shorten the path of the light through the eye, allowing the focus point to fall on the retina, forming a clearer image.
Apply Your Knowledge
1). The human tongue contains about 10,000 taste buds, with each taste bud housing about 50 taste cells. Each taste cell has a life span of about 10 days. How many taste cells are replaced while you sleep (assume 7 hours of sleep)?
Answer: There are 10,000 taste buds with 50 taste cells in each for a total of 500,000 taste cells. If each taste cell is replaced every 10 days then:
500,000 cells / 10 days = 50,000 cells replaced per day (24 hours)
50,000 cells / 24 hours = 2,083.3 cells replaced per hour
2,083.3 cells x 7 hours = 14,583.1 taste cells replaced while you sleep.
2). How would the otolith organs of an astronaut in zero gravity behave? Would the astronaut still have a subjective impression of motion? Would the semicircular canals detect angular acceleration equally well at zero gravity?
Answer: Without gravity to force the otoliths down toward the hair cells, the otolith organ will not function properly. The otolith membrane would not rest upon the hair cells and would not move in response to movement of the body parallel or perpendicular to the pull of gravity. Consequently, the hair cell would not bend and so would not produce receptor potentials. Because the astronaut can see, they would have an impression of motion-they can see themselves move in relation to objects around them-but with their eye closed, they would not know if they were moving in relation to their surroundings. Because their proprioceptor would still function, they would be able to sense when they moved their arm or leg, but they would not have the sensation of their enter body moving through space.
The semicircular canals would not function equally well in zero gravity conditions. While the fluid in the semicircular canals is still able to move around, some sensation of angular movement would most likely occur, but the full function of the semicircular canals requires the force of gravity to aid in the directional movement of the fluid in the canals.