Chapter 4 Self-test questions

. Which of the following behaviors is called 'positive phonotaxis'?

Orienting movement of a freely moving animal toward a light stimulus.

Orientation of a sessile animal toward a light stimulus.

Orienting movement of a freely moving animal toward an acoustic stimulus.

Orienting movement of a freely moving animal away from an acoustic stimulus.

. Which of the following statements concerning cilia is not correct?

Cilia are found in unicellular protists but are absent from metazoans.

Cilia are hair-like appendages, with a bundle of microtubules at their core.

The locomotion behavior of Paramecium is mediated by cilia.

Whereas cilia can be observed under the light microscope, an electron microscope is needed to view microtubules.

. Which of the following statements regarding the response of Paramecium to mechanical stimulation are correct? Please select all that apply.

Mechanical stimulation of the anterior end of Paramecium causes a reversal of the normal beat orientation of the cilia, resulting in a backward locomotion of the cell.

Mechanical stimulation of the anterior portion of the cell membrane of Paramecium leads to the activation of mechanosensitive calcium channels.

Activation of mechanosensitive calcium channels at the anterior end of Paramecium leads to an influx of Ca²⁺ ions into the cell, and thus to a depolarizing receptor potential.

Activation of mechanosensitive potassium channels, at the posterior end of Paramecium, leads to an influx of K⁺ ions into the cell, and thus, to a depolarizing receptor potential.

. Galvanotaxis in Paramecium involves an orienting movement towards the cathode of a DC electric field.

True

False

. Which of the following statements concerning galvanotaxis in Paramecium is correct?

Galvanotaxis is a behavioral response frequently exhibited by Paramecium under natural conditions.

Galvanotaxis in Paramecium is mediated by beating of the cilia in specific directions determined by the local membrane potential.

Galvanotaxis in Paramecium is mediated by beating, toward the posterior pole, of all cilia on the cell's membrane.

Exposure of Paramecium to a DC electric field triggers a strong depolarizing receptor potential, thus enhancing the beat rate of the cilia over the entire cell surface.

. Which of the following statements about the otolith organ of the inner ear of vertebrates are correct? Please select all that apply.

Geotaxis in vertebrates is mediated by the otolith organ of the inner ear.

In the otolith organ, bending of the stereocilia toward the row of the tallest stereocilia results in depolarization of the hair cells.

Hyperpolarization of the hair cells in the otolith organ results in a decrease of the firing rate in the afferent fibers of the vestibular nerve.

The function of the otolith organ depends on the pressure exerted by the otolith on the hair cells of the macula.

. The stereocilia of hair cells are, as the name implies, true cilia.

True

False

. Which of the following statements characterizes the composition of the hair-like projections at the apical surface of hair cells, in the vestibular system of vertebrates?

One stereocilium and a few dozen kinocilia.

A random mix of flagella, stereocilia, and kinocilia.

One kinocilium and a few dozen stereocilia.

Equal numbers of kinocilia and stereocilia.

. Finish this sentence correctly: In hair cells of the inner ear of vertebrates, transduction of the bending of the stereocilia into an electrical response is mediated by:

G-protein-coupled receptors.

mechanically sensitive channels.

cyclic nucleotide-gated channels.

sensory transient receptor potential family of cation channels.

Quiz Content